ALBERT

Description: Publication date: September 2015 Source: Journal of Hydrology: Regional Studies, Volume 4, Part B Author(s): Alberto Pistocchi, Costanza Calzolari, Francesco Malucelli, Fabrizio Ungaro Study region The plains of Emilia Romagna, Italy. Study focus Urban expansion is among the main causes of increase in flood frequency and intensity in small rural catchments in Europe, and our study region is paradigmatic in this respect. We present here a regional screening-level assessment of soil sealing impacts in terms of increased flood peak discharges and flooding volumes on the secondary drainage network of the plains. We estimate flood peak discharges and flooding volumes through a simple kinematic model with runoff coefficients for the land use of 2008 and 1976. Additionally, we calculate an equivalent compensatory flood detention volume that would enable preserving flood peak discharges as prior to soil sealing (principle of “hydraulic invariance”). The proposed approach is simple and readily applicable to any region facing similar issues, for screening-level assessment of flood hazards over an extended stream network. New hydrological insights for the region The analysis highlights a significant increase in flood hazards throughout the secondary stream network. The impact. Widespread and relatively uniform, is more apparent in smaller catchments and in the case of more permeable soils. This demands retrofitting of the majority of the drainage network and/or significantly higher costs from flooding damages. The analysis suggests that costs of additional flooding after soil sealing may be higher than those of soil sealing impacts compensation through flood detention (hydraulic invariance).

Description: Publication date: September 2015 Source: Journal of Hydrology: Regional Studies, Volume 4, Part B Author(s): M.A. Sarr, O. Seidou, Y. Tramblay, S. El Adlouni Study region The study considers six precipitation stations located in Senegal, West Africa. Senegal is located in the Sahel, an area that is threatened by climate variability and change. Both droughts and extreme rainfall have been an issue in recent years. Study focus Two different statistical downscaling techniques were applied to the outputs of four regional climate models at six selected precipitation stations in Senegal. First, the delta-change method was applied to the mean annual precipitation as well as the 5, 10, 20, 50 and 100-year return period daily precipitation events. Second, a quantile–quantile transformation (QQ) was used to downscale the monthly distributions of precipitation simulated by regional climate models (RCMs). The 5, 10, 20, 50 and 100-year daily precipitation events were afterward calculated. All extreme events were calculated assuming that maximum annual daily precipitations follow the generalized extreme value (GEV) distribution. The two-sided Kolmogorov–Smirnov (KS) test was finally used to assess the performance of the quantile–quantile transformation as well as the GEV distribution fit for the annual maximum daily precipitation. New hydrological insights for the region Results show that the two downscaling techniques generally agree on the direction of the change when applied to the outputs of same RCM, but some cases lead to very different projections of the direction and magnitude of the change. Projected changes indicate a decline in mean precipitation except for one RCM over one region in Senegal. Projected changes in extreme precipitations are not consistent across stations and return periods. The choice of the downscaling technique has more effect on the estimation of extreme daily precipitations of return period equal or greater than ten years than the choice of the climate models.

Description: Publication date: September 2015 Source: Journal of Hydrology: Regional Studies, Volume 4, Part B Author(s): J.S. Lessels, T.F.A. Bishop Study region South eastern Australia. Study focus This region is characterised with rainfall events that are associated with large exports of nutrients and sediments. Many water quality monitoring schemes use a form of event-based sampling to quantify these exports. Previous water quality studies that have evaluated different sampling schemes often rely on continuously monitored water quality data. However, many catchment authorities only have access to limited historical data which consists of event-based and monthly routine samples. Therefore there is a need to develop a method that assesses the importance of sampling events using information from limited historical data. This work presents a simulation based approach using unconditional simulation based on historical stream discharge. Such an approach offers site-specific information on optimal sampling schemes. A linear mixed model is used to model the relationship between total phosphorus and stream discharge and the auto-correlation of total phosphorus. New hydrological insights for the region The inclusion of event-based sampling improved annual load estimates of all sites with a maximum RMSE difference of 16.11 tonnes between event-based and routine sampling. Based on the accuracy of annual loads, event-based sampling was found to be more important in catchments with a large relief and high annual rainfall in this region. Using this approach, different sampling schemes can be compared based on limited historical data.

Description: Publication date: September 2015 Source: Journal of Hydrology: Regional Studies, Volume 4, Part B Author(s): Hayet Chihi, Ghislain de Marsily, Habib Belayouni, Houcine Yahyaoui Study region “Jeffara de Medenine” aquifer system in south-eastern Tunisia. Study focus This study investigates the role of fault structures in the distribution of hydrogeochemical facies and groundwater compartmentalization for the aquifer system. New hydrological insights for the region The proposed methodology, including seismic structural study, hierarchical cluster analysis and geostatistical methods, allowed an efficient multi-element characterization of the spatial patterns of the structural elements in the aquifers and of the hydrogeological parameters used in a spatial cross-correlation to explore the dependence of the geochemical properties in each “geochemical population” on the hosting structural compartment to delineate the different geochemical compartments. The tectonic studies showed that the lateral extent of the aquifers is controlled by normal faults. The multivariate statistical analysis revealed a strong spatial coherence between hydrogeochemical facies clustering and the reservoir compartments at both large and small scales. The kriged maps of major-ion concentrations and of total dissolved solids in the aquifers were then analyzed and compared with the reservoir facies distribution for each compartment, the geometric characteristics of the aquifer, and the piezometric level trends. This allowed to characterize the hydraulic behavior of the Medenine fault and to understand the underlying physical and chemical processes having led to the spatial distribution of the geochemical properties, and thus, the hydrogeochemical functioning of the aquifers.

Description: Publication date: September 2015 Source: Journal of Hydrology: Regional Studies, Volume 4, Part B Author(s): Marnie L. Atkins, Isaac R. Santos, Damien T. Maher Study region This study investigates dissolved methane distribution in groundwater from the Richmond River Catchment (New South Wales, Australia) before proposed coal seam gas (CSG, or coal bed methane) development. Study focus Unconventional gas exploration has rapidly expanded in recent years. However, the impact of these operations on groundwater systems is poorly understood. A total of 91 groundwater samples were analyzed from 6 geological units. Our observations act as regional baseline research prior to CSG extraction and may assist with long term impact assessment. New hydrological insights for the region Methane was found in all geological units ranging between 0.26 and 4427 μg L −1 (median 10.68 μg L −1 ). Median methane concentrations were highest in chloride-type groundwater (13.26 μg L −1 , n = 58) while bicarbonate-type groundwater had lower concentrations (3.71 μg L −1 ). Groundwater from alluvial sediments had significantly higher median methane concentrations (91.46 μg L −1 ) than groundwater from both the basalt aquifers (0.7 μg L −1 ) and bedrock aquifers (4.63 μg L −1 ); indicating geology was a major driver of methane distribution. Methane carbon stable isotope ratios ranged from –90.9‰ to –29.5‰, suggesting a biogenic origin with some methane oxidation. No significant correlations were observed between methane concentrations and redox indicators (nitrate, manganese, iron and sulphate) except between iron and methane in the Lismore Basalt ( r 2 = 0.66, p 〈 0.001), implying redox conditions were not the main predictor of methane distribution.

Description: Publication date: September 2015 Source: Journal of Hydrology: Regional Studies, Volume 4, Part B Author(s): Z. Zomlot, B. Verbeiren, M. Huysmans, O. Batelaan Study focus Groundwater is of strategic importance. The accurate estimation of groundwater recharge and assessing the fundamental controlling factors are therefore of utmost importance to protect groundwater systems. We used the spatially-distributed water-balance model WetSpass to estimate long-term average recharge in Flanders. We validated recharge rates with base flow estimates of 67 daily stream flow records using the hydrograph analyses. To this end we performed principal component analysis, multiple linear regression analysis and relative importance analysis to assess the controlling factors of the spatial variation of recharge and base flow with the influencing watershed characteristics. New hydrological insights for the region The average resulting recharge is 235 mm/year and occurs mainly in winter. The overall moderate correlation between base flow estimates and modeled recharge rates indicates that base flow is a reasonable proxy of recharge. Groundwater recharge variation was explained in order of importance by precipitation, soil texture and vegetation cover; while base flow variation was strongly controlled by vegetation cover and groundwater depth. The results of this study highlight the important role of spatial variables in estimation of recharge and base flow. In addition, the prominent role of vegetation makes clear the potential importance of land-use changes on recharge and hence the need to include a proper strategy for land-use change in sustainable management of groundwater resources.

Description: Publication date: September 2015 Source: Journal of Hydrology: Regional Studies, Volume 4, Part B Author(s): B. Ibrahim, D. Wisser, B. Barry, T. Fowe, A. Aduna Study region Hydrological observation networks in the West African region are not dense and reliable. Furthermore, the few available discharge data often present significant gaps. The Volta basin, the second largest transboundary basin in the region, is a typical example of a basin with inadequate hydrological networks. Study focus In this study, a prediction approach to determine monthly discharge in ungauged watersheds is developed. The approach is based on the calibration of two conceptual models for gauged watersheds and an estimation of models’ parameters from the physical and climatic characteristics of the watersheds. The models’ parameters were determined for each ungauged watershed through two different methods: the multiple linear regressions and the kriging method. The two methods were first validated on five gauged watersheds and then applied to the three ungauged watersheds. New hydrological insights for the region The application of the two hydrological models on the eight watersheds helped to produce relevant monthly runoff and to establish the annual hydrological balances from 1970 to 2000 for both gauged and ungauged watersheds. The developed method in this study could therefore help estimate runoff time series, which are of crucial importance when it comes to design hydraulic structures such as small reservoirs.

Description: Publication date: Available online 14 August 2015 Source: Journal of Hydrology: Regional Studies Author(s): Mayank Shekhar, Amalava Bhattacharyya Study region Zemu Chuu (river), Lachen, North Sikkim, Eastern Himalaya India. Study focus Using tree-ring data of fir ( Abies densa ) the temporal variation of 222 years January–April mean discharge of Zemu Chuu, upper reaches of the Teesta River at Lachen, North Sikkim Eastern Himalaya was investigated. This was based on linear regression reconstruction model which explained variance of 50.1% during calibration period (AD 1976–1996). The model was verified by reduction of error (RE), sign test (ST), product mean test (Pmt), root mean square error (RMSE) and Durbin–Watson test (DW). The RE never falls below zero suggesting the model had explanatory power over the entire period of reconstruction. New hydrological insights for the region The explored strong relationship between tree ring records and instrumental data enable to develop mean January–April months (premonsoon) river discharge of Zemu Chuu from remote area of Sikkim. Reconstructed data reveals high stream-flow when it is more than the mean plus one standard deviation and as low when flow is less than the mean minus one standard deviation. There were such 23 high discharge and 21 extremely low years over the past AD 1775–1996. This premonsoon reconstruction of river flow would be of great significance when scarcity of water is acute in the North East Himalaya.

Description: Publication date: September 2015 Source: Journal of Hydrology: Regional Studies, Volume 4, Part B Author(s): Jonathan A. Warrick, John M. Melack, Blair M. Goodridge Study region Coastal watersheds of southern California, United States. Study focus We sought to better understand the rates and variability of suspended-sediment discharge from small coastal watersheds (〈100 km 2 ) of California. Suspended-sediment concentrations and stream discharge were measured with automated samplers near the mouths of four small watersheds (10–56 km 2 ). New hydrological insights for the region The watersheds were found to have suspended-sediment concentrations that extended over five orders of magnitude (1 to over 100,000 mg L −1 ). Sediment concentrations were weakly correlated with discharge ( r 2 = 0.10–0.25), and four types of hysteresis patterns were observed during high flow events (clockwise, counterclockwise, no hysteresis, and complex). Annual sediment yields varied by 400-fold across the four watersheds (e.g., 5–2100 t km −2 yr −1 during the 2003–2006 water years), and sediment discharge was measurably elevated in one watershed that was partially burned by a late summer wildfire. Dozens of high flow events provided evidence that suspended-sediment yields were generally related to peak stream discharge and event-based precipitation, although these relationships were not consistent across the watersheds. This suggests that watersheds smaller than 100 km 2 can provide large – and therefore important – fluxes of sediment to the coast, but that simple techniques to estimate sediment loads, such as sediment rating curves, hydrologic regressions, and extrapolation using global sediment yield relationships that include watershed area as a primary factor, may provide poor results. Graphical abstract

Description: Publication date: September 2015 Source: Journal of Hydrology: Regional Studies, Volume 4, Part B Author(s): Chris C. Gianfagna, Chris E. Johnson, David G. Chandler, Charlie Hofmann Study region The Catskills region of New York State is largely forested and dominated hydrologically by stream watersheds with few natural lakes. The area experiences intensive water resources management and ecosystem monitoring due to its strategic role as the principal water supply for New York City. Study focus We analyzed average daily flows in nested and non-nested pairs of gaged watersheds in the Catskills to assess whether daily flow in ungaged watersheds can be calculated based on watershed area ratios. New hydrological insights for the region Watershed area ratio was the most important basin parameter for estimating flow at upstream sites based on downstream flow. The area ratio alone explained 93% of the variance in the slopes of relationships between upstream and downstream flows. Regression analysis indicated that flow at any upstream point can be estimated by multiplying the flow at a downstream reference gage by the watershed area ratio. This method accurately predicted upstream flows at area ratios as low as 0.005. We also observed a very strong relationship ( R 2 = 0.79) between area ratio and flow–flow slopes in non-nested catchments. Our results indicate that a simple flow estimation method based on watershed area ratios is justifiable, and indeed preferred, for the estimation of daily streamflow in ungaged watersheds in the Catskills region.

Description: Publication date: September 2015 Source: Journal of Hydrology: Regional Studies, Volume 4, Part B Author(s): Alfonso Rivera Study region Canada–USA border. Study focus Since 2005, Canada has followed international developments in transboundary groundwater issues in cooperation with its southern neighbor the United States (USA) within the Internationally Shared Aquifer Resources Management Initiative (ISARM) of UNESCO. As a result, 10 Transboundary Aquifer Systems (TAS) were identified along the border between Canada and the USA. This study is an extensive review of the current state of the 10 TAS. Documentation of scientifically-based knowledge on TAS is an important step in identifying potential issues in policies that might be adopted to address shared water-resource issues. New hydrological insights for the region This analysis emphasizes the need for more scientific data, widespread education and training, and a more clearly defined governments’ role to manage groundwater at the international level. The study reviews the current legal framework and summarises the current scientific knowledge for the TAS with respect to the hydrologic and geologic framework as well as some of the major drivers for supply and demand. It also describes the links, approach and relevance of studies on the TAS to the UN Law of Transboundary Aquifers and on how these might fit in the regional strategy for the assessment and management of the TAS. Clear communication, shared knowledge and common objectives in the management of TAS will prepare the countries for future negotiations and cooperative binational programs.

Description: Publication date: September 2015 Source: Journal of Hydrology: Regional Studies, Volume 4, Part B Author(s): Brioch Hemmings, Daren Gooddy, Fiona Whitaker, W. George Darling, Alia Jasim, Joachim Gottsmann Study region Montserrat, Lesser Antilles, Caribbean. Study focus Analysis of δ 2 H and δ 18 O isotopes, and chlorofluorocarbon (CFC) anthropogenic tracers in Montserrat groundwater provides insights into the age and provenance of the spring waters. New hydrological insights δ 2 H and δ 18 O analysis indicates uniform recharge elevations for groundwaters on Montserrat. CFC-11 and CFC-12 analysis reveals age differences between isotopically similar, high elevation springs and low elevation aquifer waters. Low CFC concentrations within a confined low elevation aquifer suggest water ages of ∼45 years. High CFC concentrations in the northern and western springs are explained by rapid infiltration of cool (high CFC concentration) rainfall into saturated compartments, with flow through the vadose zone to the phreatic zone dominated by compartment flow. Lower CFC concentrations in a number of aligned warmer springs suggest a contribution from older, warmer waters from depth. Temperatures and CFC concentrations indicate older component supply rates of up to 8 L/s to the highest yielding spring on Centre Hills, with contributions of up to 75% in the warmest spring waters.

Description: Publication date: March 2015 Source: Journal of Hydrology: Regional Studies, Volume 3, Supplement 1

Description: Publication date: March 2015 Source: Journal of Hydrology: Regional Studies, Volume 3, Supplement 1

Description: Publication date: March 2015 Source: Journal of Hydrology: Regional Studies, Volume 3, Supplement 1

Description: Publication date: March 2015 Source: Journal of Hydrology: Regional Studies, Volume 3, Supplement 1

Description: Publication date: Available online 3 April 2015 Source: Journal of Hydrology: Regional Studies Author(s): A. Shahul Hameed , T.R. Resmi , S. Suraj , C. Unnikrishnan Warrier , M. Sudheesh , R.D. Deshpande Study region The Chaliyar river basin, Kerala State, India. Study focus Detailed understanding about spatio-temporal variation in the interaction and exchange of water between surface and sub-surface reservoirs is important for effective watershed management. Spatio-temporal variations in the oxygen isotopic composition ( δ 18 O) were used to understand the interaction between groundwater and river water, and to estimate the groundwater recharge from river water in the Chaliyar river basin. New hydrological insights for the region Based on the spatio-temporal variation in δ 18 O values of river and groundwater and fluctuation in ground water levels, following important inferences are made: (1) estimated river water contribution to post-monsoon groundwater recharge is ∼16% in the lowland coastal area of the Chaliyar river basin and 29% in midland region; (2) northeast winter monsoon rains contribute to the groundwater of Chaliyar river basin only in an insignificant manner, and with a delayed response; (3) unlike river water samples which exhibit both seasonal and spatial variation of more than 3‰, the groundwater samples vary only marginally (∼1‰) between the seasons and across the physiographic zones; (4) groundwater samples exhibit inverse altitude gradient in δ 18 O values in the highland zone, in all the three seasons. This may be due to flow of the isotopically depleted groundwater down the gradient and evaporation of residual water in the upper reaches of the basin.

Description: Publication date: March 2015 Source: Journal of Hydrology: Regional Studies, Volume 3, Supplement 1 Author(s): Ashish Sharma

Description: Publication date: Available online 16 May 2015 Source: Journal of Hydrology: Regional Studies Author(s): E.H. Elias , A. Rango , C.M. Steele , J.F. Mejia , R. Smith Study region Upper Rio Grande, Colorado and New Mexico, USA. Study focus Climate change is predicted to further limit the water availability of the arid southwestern U.S. We use the snowmelt runoff model to evaluate impacts of climate change on snow covered area (SCA), streamflow timing and runoff volume. Simulations investigate four future conditions using models downscaled to existing climate stations. Twenty-four subbasins of the Upper Rio Grande containing appreciable snowmelt and a long-term gauging station are simulated. New hydrological insights for the region Future annual volume is 193–204 million m 3 more to 448–476 million m 3 less than the pre-climate change value of 2688 million m 3 . There is disparity between increased volume in wetter simulations (+7%) and decreased volume (−18%) in drier simulations. SCA on 1 April reduced by approximately 50% in all but the warmer/wetter climate. Peak flow is 14–24 days early in the future climates. Among the 24 subbasins there is considerable range in mean melt season SCA (−40% to −100%), total volume change (−30% to +57%) and runoff timing advancement indicating that climate change is best evaluated at the subbasin scale. Daily hydrographs show higher streamflow in March and April, but less from mid-May until the end of the water year. The large decrease in volume in May, June and July will compound water management challenges in the region.

Description: Publication date: March 2015 Source: Journal of Hydrology: Regional Studies, Volume 3, Supplement 1 Author(s): Mohammad Kamruzzaman

Description: Publication date: March 2015 Source: Journal of Hydrology: Regional Studies, Volume 3, Supplement 1

Description: Publication date: March 2015 Source: Journal of Hydrology: Regional Studies, Volume 3, Supplement 1

Description: Publication date: March 2015 Source: Journal of Hydrology: Regional Studies, Volume 3 Author(s): Jean-Michel Lemieux , Jalil Hassaoui , John Molson , René Therrien , Pierre Therrien , Michel Chouteau , Michel Ouellet Study region This study is conducted in the Magdalen Islands (Québec, Canada), a small archipelago located in the Gulf of St. Lawrence. Study focus This work was undertaken to support the design of a long-term groundwater monitoring network and for the sustainable management of groundwater resources. This study relies mostly on the compilation of existing data, but additional field work has also been carried out, allowing for the first time in the Magdalen Islands, direct observation of the depth and shape of the transition zone between freshwater and seawater under natural conditions. Simulations were conducted along a 2D cross-section on Grande Entrée Island in order to assess the individual and combined impacts of sea-level rise, coastal erosion and decreased groundwater recharge on the position of the saltwater–freshwater interface. The simulations were performed considering variable-density flow and solute transport under saturated-unsaturated conditions. The model was driven by observed and projected climate change scenarios to 2040 for the Magdalen Islands. New hydrological insights for the region The simulation results show that among the three impacts considered, the most important is sea-level rise, followed by decreasing groundwater recharge and coastal erosion. When combined, these impacts cause the saltwater–freshwater interface to migrate inland over a distance of 37 m and to rise by 6.5 m near the coast to 3.1 m further inland, over a 28-year period.

Description: Publication date: March 2015 Source: Journal of Hydrology: Regional Studies, Volume 3 Author(s): M.A. Pascolini-Campbell , Richard Seager , David S. Gutzler , Benjamin I. Cook , Daniel Griffin Study region The Gila River, New Mexico, is characterized by two peaks in streamflow: one in the winter–spring (December–May), and summer (August–September). The region is influenced both by Pacific SST variability as well as the North American Monsoon. Study focus The mechanisms responsible for the variability of the winter–spring and summer streamflow peaks are investigated by correlation of streamflow with precipitation and sea surface temperature for 1928–2012. Decadal variability in the flow record is examined for a longer term perspective on Gila River streamflow using tree ring-based reconstructions of the Palmer Drought Severity Index (PDSI) and the Standardized Precipitation Index (SPI). New hydrological insights for the region Results indicate a strong influence of winter–spring precipitation and Pacific SST anomalies on the winter–spring streamflow, with El Niño conditions in the Pacific causing increased precipitation and streamflow. Decadal Pacific variability helps explain the transition from high winter flow in the late 20th century to lower flows in the most recent decade. The summer streamflow has a somewhat weaker correlation with precipitation and Pacific SST than the winter–spring streamflow. Its variability is more likely influenced by local North American Monsoon precipitation variability. PDSI and SPI reconstructions indicate much more severe and extended periods of droughts and pluvials in past centuries as well as periods of concurrent winter and summer drought.

Description: Publication date: March 2015 Source: Journal of Hydrology: Regional Studies, Volume 3 Author(s): Tsou Jaw , Jialun Li , Kuo-lin Hsu , Soroosh Sorooshian , Fatima Driouech Study region Morocco (excluding Western Sahara). Study focus This study evaluated Moroccan precipitation, dynamically downscaled (0.18-degree) from three runs of the studied GCM ECHAM5/MPI-OM, under the present-day (1971–2000/20C3M) and future (2036–2065/A1B) climate scenarios. The spatial and quantitative properties of the downscaled precipitation were evaluated by a verified, fine-resolution reference. The effectiveness of the hydrologic responses, driven by the downscaled precipitation, was further evaluated for the study region over the upstream watershed of Oum er Rbia River located in Central Morocco. New hydrological insights for the region The raw downscaling runs reasonably featured the spatial properties but quantitatively misrepresented the mean and extreme intensities of present-day precipitation. Two proposed bias correction approaches, namely stationary Quantile-Mapping (QM) and non-stationary Equidistant CDF Matching model (EDCDFm), successfully reduced the system biases existing in the raw downscaling runs. However, both raw and corrected runs projected great diversity in terms of the quantity of future precipitation. Hydrologic simulations performed by a well-calibrated Variable Infiltration Capacity model successfully reproduced the present-day streamflow. The driven flows were identified highly correlated with the effectiveness of the downscaled precipitation. The future flows were projected to be markedly diverse, mainly due to the varied precipitation projections. Two of the three flow simulation runs projected slight to severe drying scenarios, while another projected an opposite trend for the evaluated future period.

Description: Publication date: March 2015 Source: Journal of Hydrology: Regional Studies, Volume 3 Author(s): Megersa Olumana Dinka , Willibald Loiskandl , Julius Musyoka Ndambuki Study region The Matahara region is located in the East Showa zone of Oromiya regional state (Ethiopia). Matahra Sugar Estate and Lake Basaka (highly saline, alkaline and sodic lake) are situated within the flat plains of Matahara region. The area is vulnerable to the occurrences of various tectonic and volcanic activities due to its location in the upper most part of the Main Ethiopian Rift Valley region. Study focus In this study, the hydrochemical properties of different surface water and groundwater bodies available at Matahara region have been characterized for quality compositions. Water samples were collected from different water sources and analyzed for important major quality parameters following standard test procedures. Other chemical indices were derived from the measured quality parameters. The potential sources of minerals were suggested for each of the considered water sources based on their quality characteristics. New hydrological insights for the region Overall, the study result elucidates that the chemical composition of different water bodies are due to natural processes and/or anthropogenic activities within the region. The local anthropogenic processes could be discharges from factory, domestic sewage and farming activities. Some of the water types are found to have relatively higher concentration of dissolved constituents. Irrigation waters have almost equal chemical compositions, indicating their hydrochemical sources are almost the same. Most of the concentrations are relatively high in Lake Basaka, groundwater and hot springs. It is easy to imagine the potential damaging effects of such quality waters on crop production, soil properties and environment of the region.

Description: Publication date: March 2015 Source: Journal of Hydrology: Regional Studies, Volume 3 Author(s): Julianne Hagarty , David Azanu , Bernadette Atosona , Ray Voegborlo , Erica A.H. Smithwick , Kamini Singha Study region Buruli ulcer, an emerging disease caused by Mycobacterium ulcerans , largely affects poor rural populations in tropical countries. The environmental niche that supports this necrotizing bacterium is unclear. Here, water samples were collected from five communities within Ghana in the rainy season in 2011: four in the southern part of Ghana (three disease-endemic communities: Pokukrom, Betenase, and Ayanfuri, and one control: Kedadwen) and one non-endemic community (Nangruma) in the north. Study focus Past studies of Buruli ulcer conclude that water quality is, in some way, closely related to the transmission of this disease. This work serves as a first step to explore links between Buruli ulcer incidence and water quality. More broadly, this research works toward identifying the environmental niche for M. ulcerans , providing characterization of water bodies hazardous to human health in at-risk communities. New hydrological insights Trace metals, thought to aid in the preferential growth of M. ulcerans , are present in higher concentrations in mining pits and stagnant pools than in other tested water bodies. Arsenic in particular could serve as a double threat for BU incidence: it could support the growth of M. ulcerans while suppressing immune systems, making the population more susceptible to disease. Few other differences between endemic and non-endemic communities exist, implying other variables such as human behavior may also control the onset of Buruli ulcer.

Description: Publication date: Available online 18 April 2015 Source: Journal of Hydrology: Regional Studies Author(s): Fabrice Papa , Frédéric Frappart , Yoann Malbeteau , Mohammad Shamsudduha , Venugopal Vuruputur , Muddu Sekhar , Guillaume Ramillien , Catherine Prigent , Filipe Aires , Rajesh Kumar Pandey , Sujit Bala , Stephane Calmant Study region The Ganges–Brahmaputra (GB), a major river basin of the Indian Sub-Continent (ISC), is the host of more than 700 millions people. Study focus In addition to monsoons and strong climate variability, GB is facing growing demands for freshwater availability by a continually growing population and rapidly developing of agricultural and industrial sectors. The management of water resources is thus of highest priority and, in the context of current over-abstraction of groundwater, accurate estimates of terrestrial freshwater storage are essential. We propose a multi-satellite approach to estimate surface freshwater storage (SWS) and subsurface water storage (SSWS, groundwater + soil moisture) variations over GB. New hydrological insights Basin-scale monthly SWS variations for the period 2003–2007 show a mean annual amplitude of ∼410 km 3 , contributing to about 45% of the Gravity Recovery And Climate Experiment (GRACE)-derived total water storage variations (TWS). During the drought-like conditions in 2006, we estimate that the SWS deficit over the entire GB basin in July–August–September was about 30% as compared to other years. The SWS variations are then used to decompose the GB GRACE-derived TWS and isolate the variations of SSWS whose mean annual amplitude is estimated to be ∼550 km 3 . This new dataset of water storage variations represent an unprecedented source of information for hydrological and climate modeling studies of the ISC.

Description: Publication date: Available online 7 April 2015 Source: Journal of Hydrology: Regional Studies Author(s): Swati Verma , Abhijit Mukherjee , Runti Choudhury , Chandan Mahanta Study region Brahmaputra River basin, India. Study focus The present study deciphers the groundwater solute chemistry and arsenic (As) enrichment in the shallow aquifers of the study region. Four different geomorphologic units, e.g. piedmont (PD), older alluvium of river Brahmaputra and its tributaries (OA), active alluvium of river Brahmaputra and its tributaries (YA) and river channel deposits (RCD) were identified. More than 62% of all groundwater samples collected have dissolved As >0.01 mg/L, whereas about 87% of groundwater samples in OA terrain are enriched with As, which draws a distinct difference from the adjoining Gangetic aquifers. New hydrological insights for the region Most groundwater solutes of RCD and YA terrains were derived from both silicate weathering and carbonate dissolution, while silicate weathering process dominates the solute contribution in OA groundwater. Groundwater samples from all terrains are postoxic with mean pe values between Fe(III) and As(V)–As(III) reductive transition. While, reductive dissolution of (Fe–Mn)OOH is the dominant mechanism of As mobilization in RCD and YA aquifers, As in OA and PD aquifers could be mobilized by combined effect of pH dependent sorption and competitive ion exchange. The present study focuses on the major ion chemistry as well as the chemistry of the redox sensitive solutes of the groundwater in different geomorphic settings and their links to arsenic mobilization in groundwater.

Description: Publication date: Available online 11 March 2015 Source: Journal of Hydrology: Regional Studies Author(s): B.M. Hallett , H.A. Dharmagunawardhane , S. Atal , E. Valsami-Jones , S. Ahmed , W.G. Burgess Study region The Maheshwaram and Waipally catchments of Andhra Pradesh, India, and the Plonnaruwa catchment of north-central Sri Lanka. Study focus The distribution of F across eight crystalline phases and between the bedrock and the regolith at eleven sites in three catchments is documented. Mineral contributions to F release during weathering and regolith development are quantified. New hydrological insights for the region An estimate of weathering duration for the in situ regolith in Andhra Pradesh, 250–380 Ka, is close to a previous estimate for southern India. Partial or total destruction of the primary F-bearing bedrock minerals and consistent depletion of F in the remnant minerals result in a much reduced total F content in the regolith. Leaching experiments and field relationships, however, indicate a greater potential for F mobilisation to groundwater from the regolith than the bedrock. Schemes for managed aquifer recharge should beware the risk of mobilising additional F to groundwater.

Description: Publication date: March 2015 Source: Journal of Hydrology: Regional Studies, Volume 3, Supplement 1 Author(s): Salah Er-Raki

Description: Publication date: Available online 8 May 2016 Source: Journal of Hydrology: Regional Studies Author(s): Yeshewatesfa Hundecha, Berit Arheimer, Chantal Donnelly, Ilias Pechlivanidis Study region Europe. Study focus A semi-distributed continuous hydrological model, HYPE, was applied to model daily stream flows in more than 35,000 subcatchments across Europe. A stepwise regionalization approach was implemented to estimate different groups of model parameters. HRU based parameters were estimated first for each soil and landuse class, respectively. Lake and reservoir parameters were estimated separately. Catchments were grouped based on similarity of their characteristics and model parameters defined at a catchment scale were then regionalized for each group as functions of the catchment characteristics by simultaneously calibrating the model for a number of catchments to concurrently optimize the overall model performance and the functional relationships between the parameters and the catchment characteristics. Calibration was performed at 115 discharge stations and the approach was validated at 538 independent stations. New hydrological insights for the region Parameters could be linked to catchment descriptors with good transferability, with median NSE of 0.54 and 0.53, and median volume error of −1.6% and 1.3% in the calibration and validation stations, respectively. Although regionalizing parameters for different groups of catchments separately yielded a better performance in some groups, the overall gain in performance against regionalization using a single set of regional relationships across the entire domain was marginal. The benefits of separate regionalization were substantial in catchments with considerable proportion of agricultural landuse and higher mean annual temperature.

Description: Publication date: June 2016 Source: Journal of Hydrology: Regional Studies, Volume 6 Author(s): Haiyun Shi, Tiejian Li, Jiahua Wei, Wang Fu, Guangqian Wang Study region Three-River Headwaters (TRH) region, China. Study focus Precipitation is regarded as the basic component of the global hydrological cycle. This study investigated the spatial and temporal characteristics of precipitation over the TRH region during 1961–2014, based on the observed data of 29 meteorological stations. New hydrological insights for the region The results showed that: (1) temporally, the TRH region has experienced a significant increasing trend in the annual precipitation ( p 〈 0.1) during 1961–2014, especially in the dry season ( p 〈 0.01). (2) Spatially, the mean annual precipitation (MAP) in the TRH region showed the southeast-to-northwest decreasing trend and the annual precipitation recorded at most stations (i.e., 26 in 29) presented the increasing trends. (3) A close correlation of the MAP with elevation was found, that is, a low-to-high increasing trend below 3800 m but an inverse correlation above 3800 m; in addition, statistical equations to estimate precipitation with high R 2 values were established based on longitude, latitude and elevation. (4) Characteristics of related meteorological variables and possible impact of precipitation on runoff were analyzed and discussed. These results would be valuable for the researchers to better understand the changing characteristics of precipitation and for the managers to make better decisions in the future.

Description: Publication date: March 2016 Source: Journal of Hydrology: Regional Studies, Volume 5 Author(s): Eric Nicolini, Karyne Rogers, Delphine Rakowski Study region Lifou Island, near the main island of New Caledonia. Study focus Stable oxygen and hydrogen isotopes of groundwater and rainfall were used to characterise baseline values for the main fresh water aquifer of Lifou Island and describe its recharge. Other stable isotope parameters (nitrates and DIC) were used to investigate the interaction between surface water (rainfall) and groundwater, including anthropogenic effects from human activities. New hydrological insights for the region This study represents the first baseline isotopic characterisation of Lifou Island’s groundwater aquifer composition and provides a reference for future investigative studies on groundwater quality and security. Groundwater sampled in June and October 2012 had nearly identical isotopic composition. Tap water sampled monthly between February 2012 and January 2014 also had a constant isotopic composition similar to the groundwater. Groundwater recharge was found to occur when monthly precipitation exceeded 140 mm, with the recharge cycle representing 20–30% of the annual rainfall. Relationships between HCO 3 2− content, pH, soil δ 13 C DIC and satellite photo interpretation suggests a variance of soil pCO 2 , which is explained by different vegetation cover and higher water use efficiencies in forested areas (high pCO 2 , more negative δ 13 C isotope values). The δ 15 N NO3 values for most groundwater indicate they are uncontaminated with anthropogenic nitrates, although some samples taken in October (dry season) showed a slight denitrification, possibly of natural origin.

Description: Publication date: December 2016 Source: Journal of Hydrology: Regional Studies, Volume 5, Supplement 1 Author(s): Anonymous

Description: Publication date: Available online 10 December 2015 Source: Journal of Hydrology: Regional Studies Author(s): Tatsuya Utsunomiya, Masaki Hata, Ryo Sugimoto, Hisami Honda, Shiho Kobayashi, Yoji Miyata, Makoto Yamada, Osamu Tominaga, Jun Shoji, Makoto Taniguchi Study focus There have been far more studies on how the variability in surface water discharge affects production of animal communities in aquatic ecosystems while less information has been accumulated on the mechanisms of how the groundwater supply works. Study region Physical and biological surveys were conducted to test the hypothesis that high level of submarine ground water discharge enhances species richness, abundance and biomass of fishes and invertebrates in coastal waters of Obama Bay, Japan, where a high contribution of nutrients (ca. 65% of phosphorus) to total provided through all freshwater has been reported. Survey for horizontal distribution of radon-222 ( 222 Rn) concentration showed high levels of submarine groundwater discharge in the west part of survey area. Fish and invertebrate communities were compared within a relatively small spatial scale (ca. 100 m) in relation to level of submarine groundwater discharge. New hydrological insights Species richness, abundance and biomass of fishes and abundance and biomass of turban snail and hermit crab were significantly higher in the area with high 222 Rn concentration. Abundance of gammarids, the most major prey item of the fishes, was 18 times higher in the area with high 222 Rn concentration. Since the turban snail, hermit crab and gammarids feed on producers (phytoplankton and benthic microalgae), submarine groundwater are concluded to increase species richness and production of fishes and invertebrates through providing nutrients and enhancing primary production.

Description: Publication date: March 2016 Source: Journal of Hydrology: Regional Studies, Volume 5 Author(s): A.C. de la Casa, G.G. Ovando Study region Changes in reference evapotranspiration (ET o ) may have important consequences for agricultural suitability in the central region of Argentina. Annual ET o variation was assessed, in terms of both territory and time, for the 7 decades between 1941 and 2010, analyzing the behavior of the 4 atmospheric variables which determine it: temperature, vapor pressure, wind speed and cloud cover. Study focus The influence of each variable on ET o was evaluated from a multiple regression model and a simple correlation analysis, using climate data from the observation network, and repeating this analysis using interpolated variables. In this grid scheme, linear relationships were determined between ET o and the different key atmospheric variables, plus precipitation (PP), and the t test was applied to establish the statistically significant sectors ( P 〈 0.1). Then, those areas with a significant trend change ( P 〈 0.1) were determined by the Mann–Kendall test. Finally, the interception of the grids was performed to establish their joint occurrence. New hydrological insights for the region Most of the region analyzed (>91%) presents a non-significant variation of ET o over time, with a mostly non-significant change of each driving variable, regarding both its relationship with ET o and its own trend of change. The beneficial change in agricultural suitability reported for this water-limited region was found to be produced almost exclusively by increasing PP. Graphical abstract

Description: Publication date: Available online 11 December 2015 Source: Journal of Hydrology: Regional Studies Author(s): Makoto Taniguchi, Naoki Masuhara, Kimberly Burnett Security measures of three resources; water, energy and food are analyzed for thirty two countries in the Asia Pacific region which are faced to Pacific Ocean, in terms of amounts of the resource, self-production, and diversity of sources of each resource. Diversity for all the three resources is also analyzed using surface water and groundwater for water sources; hydro power, geothermal power, solar, and biomass for energy; and cereals, vegetable, fruit, meat, and fish for food. We see high diversity of sources of water in the US and the Philippines, and a low diversity of sources of food in the US, Canada, and Indonesia. These security measures including water security show new hydrological insight for Asia-Pacific region.

Description: Publication date: Available online 10 December 2015 Source: Journal of Hydrology: Regional Studies Author(s): Aiko Endo, Izumi Tsurita, Kimberly Burnett, Pedcris M. Orencio Study region Asia, Europe, Oceania, North America, South America, Middle East and Africa. Study focus The purpose of this paper is to review and analyze the water, energy, and food nexus and regions of study, nexus keywords and stakeholders in order to understand the current state of nexus research. New hydrological insights Through selected 37 projects, four types of nexus research were identified including water–food, water–energy–food, water–energy, and climate related. Among them, six projects (16%) had a close linkage with water–food, 11 (30%) with water–energy–food, 12 (32%) with water–energy, and eight (22%) with climate. The regions were divided into Asia, Europe, Oceania, North America, South America, Middle East and Africa. North America and Oceania had a tendency to focus on a specific nexus type, water–energy (46%) and climate (43%), while Africa had less focus on water–energy (7%). Regarding keywords, out of 37 nexus projects, 16 projects listed keywords in their articles. There were 84 keywords in total, which were categorized by the author team depending on its relevance to water, food, energy, climate, and combination of water–food–energy–climate, and 40 out of 84 keywords were linked with water and only 4 were linked with climate. As for stakeholders, 77 out of 137 organizations were related to research and only two organizations had a role in media.

Description: Publication date: March 2016 Source: Journal of Hydrology: Regional Studies, Volume 5 Author(s): Shilpa M. Asokan, Peter Rogberg, Arvid Bring, Jerker Jarsjö, Georgia Destouni Study region The large semi-arid Aral Region in Central Asia and the smaller tropical Mahanadi River Basin (MRB) in India. Study focus Few studies have so far evaluated the performance of the latest generation of global climate models on hydrological basin scales. We here investigate the performance and projections of the global climate models in the Coupled Model Intercomparison Project, Phase 5 (CMIP5) for freshwater fluxes and their changes in two regional hydrological basins, which are both irrigated but of different scale and with different climate. New hydrological insights for the region For precipitation in both regions, model accuracy relative to observations has remained the same or decreased in successive climate model generations until and including CMIP5. No single climate model out-performs other models across all key freshwater variables in any of the investigated basins. Scale effects are not evident from global model application directly to freshwater assessment for the two basins of widely different size. Overall, model results are less accurate and more uncertain for freshwater fluxes than for temperature, and particularly so for model-implied water storage changes. Also, the monsoon-driven runoff seasonality in MRB is not accurately reproduced. Model projections agree on evapotranspiration increase in both regions until the climatic period 2070–2099. This increase is fed by precipitation increase in MRB and by runoff water (thereby decreasing runoff) in the Aral Region.

Description: Publication date: March 2016 Source: Journal of Hydrology: Regional Studies, Volume 5 Author(s): Justin A. Schulte, Raymond G. Najjar, Ming Li Study region The Mid-Atlantic region of the United States. Study focus An understanding of past streamflow variability is necessary for developing future management practices that will help mitigate the impacts of extreme events such as drought or floods on agriculture and other human activities. To better understand mechanisms driving streamflow variability at all timescales, annual to multi-decadal streamflow variability of three major rivers in the Mid-Atlantic region of the United States (the Susquehanna, Delaware, and Hudson Rivers) was studied in the context of climate modes using correlation and wavelet analyses. New hydrological insights for the region Results from the correlation analysis detected statistically significant relationships between climate indices and streamflow that were similar for the three rivers. The results from the wavelet analysis showed that 18- and 26-year periodicities were embedded in the streamflow time series. Decadal variability of streamflow was coherent with the El-Niño Southern Oscillation (SO) and the Pacific Decadal Oscillation (PDO). The time series for the PDO and SO indices and precipitation were found to be synchronized to the decadal variability of a global circulation pattern consisting of a Rossby wave train emanating from the North Pacific. The SO explained 37–54% of the 1960s drought, 33–49% of the 1970s pluvial, and 19–50% of the 2000s pluvial in the three river basins.

Description: Publication date: December 2016 Source: Journal of Hydrology: Regional Studies, Volume 5, Supplement 1 Author(s): Anonymous

Description: Publication date: Available online 5 January 2016 Source: Journal of Hydrology: Regional Studies Author(s): Daniel J. Hoover, Kingsley O. Odigie, Peter W. Swarzenski, Patrick Barnard Study region The study region spans coastal California, USA, and focuses on three primary sites: Arcata, Stinson Beach, and Malibu Lagoon. Study focus 1 m and 2 m sea-level rise (SLR) projections were used to assess vulnerability to SLR-driven groundwater emergence and shoaling at select low-lying, coastal sites in California. Separate and combined inundation scenarios for SLR and groundwater emergence were developed using digital elevation models of study site topography and groundwater surfaces constructed from well data or published groundwater level contours. New hydrological insights for the region SLR impacts are a serious concern in coastal California which has a long (∼1800 km) and populous coastline. Information on the possible importance of SLR-driven groundwater inundation in California is limited. In this study, the potential for SLR-driven groundwater inundation at three sites (Arcata, Stinson Beach, and Malibu Lagoon) was investigated under 1 m and 2 m SLR scenarios. These sites provide insight into the vulnerability of Northern California coastal plains, coastal developments built on beach sand or sand spits, and developed areas around coastal lagoons associated with seasonal streams and berms. Northern California coastal plains with abundant shallow groundwater likely will see significant and widespread groundwater emergence, while impacts along the much drier central and southern California coast may be less severe due to the absence of shallow groundwater in many areas. Vulnerability analysis is hampered by the lack of data on shallow coastal aquifers, which commonly are not studied because they are not suitable for domestic or agricultural use. Shallow saline aquifers may be present in many areas along coastal California, which would dramatically increase vulnerability to SLR-driven groundwater emergence and shoaling. Improved understanding of the extent and response of California coastal aquifers to SLR will help in preparing for mitigation and adaptation.

Description: Publication date: June 2016 Source: Journal of Hydrology: Regional Studies, Volume 6 Author(s): Bogdan Ozga-Zielinski, Maurycy Ciupak, Jan Adamowski, Bahaa Khalil, Julien Malard Study region Narew River in Northeastern Poland. Study focus Three methods for frequency analysis of snowmelt floods were compared. Two dimensional (2D) normal distribution and copula-based 2D probability distributions were applied to statistically describe floods with two parameters (flood peak Q max,f and flood volume V f ). Two copula functions from different classes – the elliptical Gaussian copula and Archimedean 1-parameter Gumbel–Hougaard copula – were evaluated based on measurements. New hydrological insights for the region The results indicated that the 2D normal probability distribution model gives a better probabilistic description of snowmelt floods characterized by the 2-dimensional random variable ( Q max,f , V f ) compared to the elliptical Gaussian copula and Archimedean 1-parameter Gumbel–Hougaard copula models, in particular from the view point of probability of exceedance as well as complexity and time of computation. Nevertheless, the copula approach offers a new perspective in estimating the 2D probability distribution for multidimensional random variables. Results showed that the 2D model for snowmelt floods built using the Gumbel–Hougaard copula is much better than the model built using the Gaussian copula.

Description: Publication date: Available online 1 April 2016 Source: Journal of Hydrology: Regional Studies Author(s): Demetris Koutsoyiannis, Günter Blöschl, András Bárdossy, Christophe Cudennec, Denis Hughes, Alberto Montanari, Insa Neuweiler, Hubert Savenije

Description: 〈p〉Publication date: August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Hydrology: Regional Studies, Volume 24〈/p〉 〈p〉Author(s): Johnson U. Kitheka〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉 〈h6〉Study region〈/h6〉 〈p〉This study was undertaken in the Athi-Sabaki river basin in Kenya in East Africa.〈/p〉 〈/div〉 〈div〉 〈h6〉Study focus〈/h6〉 〈p〉The study focused on the determination of the influence of streamflow variability on salt fluxes. This involved monitoring of river discharge and river salinity in the period between 2012 and 2018.〈/p〉 〈/div〉 〈div〉 〈h6〉New hydrological insights〈/h6〉 〈p〉: This study demonstrates that Athi-Sabaki river discharges significant quantity of salt to the sea. There are significant seasonal and inter-annual variations in salt fluxes that are due to variations in river discharge and rainfall in the basin. The relationship between streamflow variations and variations of salinity in the river was inverse with highest salinity concentrations and fluxes occurring during low flow conditions. The river salinity and TDS concentrations decreased with an increase in river discharge due to dilution effect and flushing of salt from the river. The highly polluted sub-basins draining through the City of Nairobi exhibited relatively higher salinity and salt fluxes as compared to non-polluted ones draining rural areas. The total salt flux in the basin ranged between 29 × 10〈sup〉3〈/sup〉 and 261 × 10〈sup〉3〈/sup〉 tons year〈sup〉−1〈/sup〉. The relatively high salinity and salt fluxes were attributed to the discharge of wastewaters, seepage of groundwater and irrigation return flows. The study calls for water pollution control, sustainable irrigation and landuse practices in the basin.〈/p〉 〈/div〉

Description: 〈p〉Publication date: August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Hydrology: Regional Studies, Volume 24〈/p〉 〈p〉Author(s): Dagnachew Daniel Molla, Tenalem Ayenew Tegaye, Christopher G. Fletcher〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉 〈h6〉Study region〈/h6〉 〈p〉The volcano-tectonic lakes basin of Abaya-Chamo is part of the Main Ethiopian Rift system and exhibits large variations in geomorphology, physiography and climate between the rift floor and the plateau.〈/p〉 〈/div〉 〈div〉 〈h6〉Study focus〈/h6〉 〈p〉Despite the importance of streamflow for water resources management and planning in the basin, many of the rivers there are ungauged. To make quantitative estimates of streamflow for spatially resolved water availability in such a highly heterogeneous environment, therefore, requires numerical modeling. This study is the first to quantify the surface and shallow groundwater resources in Abaya-Chamo, and to validate the physically fully distributed hydrologic model WetSpass under highly data-limited conditions, in a complex two-lake environment.〈/p〉 〈/div〉 〈div〉 〈h6〉New hydrological insights〈/h6〉 〈p〉Simulated total river flow and estimated baseflow were verified at 15 gauging stations, with a good agreement. The WetSpass model is shown to be suitable for such a complex setting with a correlation coefficient of 0.95 and 0.97 for total flow and baseflow respectively at a statistically significant level (p-value 〈 0.05). The simulated annual water budget reveals that 74.6% of the 22.1 billion lit/yr in total precipitation in the basin is lost through evapotranspiration, 15.7% through surface runoff, and only 9.7% recharges the groundwater system. The simulations also revealed the surface runoff and groundwater recharge are the most sensitive to soil textural class, while evapotranspiration depends more strongly on land use.〈/p〉 〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S2214581818302623-ga1.jpg" width="159" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Hydrology: Regional Studies, Volume 24〈/p〉 〈p〉Author(s): Zeinab Mohammadi Raigani, Kazem Nosrati, Adrian L. Collins〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉 〈h6〉Study region〈/h6〉 〈p〉The Kamish River catchment (308 km〈sup〉2〈/sup〉); a mountainous agricultural catchment under dry-land and rangeland farming located in Kermanshah province, in western Iran.〈/p〉 〈/div〉 〈div〉 〈h6〉Study focus〈/h6〉 〈p〉The main objective of this study was to apportion sub-basin spatial source relative contributions to target channel bed sediment samples using a composite fingerprinting procedure including a Bayesian un-mixing model. In total, thirty-four geochemical tracers, eleven elemental ratios and different weathering indices were measured or estimated for 43 tributary sediment samples collected to characterise three sub-basin spatial sediment sources and eleven target bed sediment samples collected at the outlet of the main basin. Statistical analysis was used to select three different composite signatures.〈/p〉 〈/div〉 〈div〉 〈h6〉New hydrological insights for the region〈/h6〉 〈p〉Using a composite signature based on KW-H and DFA, the respective relative contributions (with uncertainty ranges) from tributary sub-basins 1, 2 and 3 were estimated as 54.3% (47.8–62.0), 11.4% (4.2–18.7) and 34.3% (27.6–39.9), compared to 72.0% (61.6–82.7), 13.6% (9.0–18.5) and 14.2% (3.1–25.4) using a combination of KW-H and data mining, and 50.8% (42.8–59.9), 28.7% (20.2–37.3) and 20.3% (12.7–27.2) using a fingerprint selected by KW-H and PCCA. The root mean square difference between these source estimates highlighted sensitivity to the composite signatures. Evaluation of the un-mixing model predictions using virtual mixture tests confirmed agreement between modelled and known source proportions.〈/p〉 〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S2214581819301247-ga1.jpg" width="500" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Hydrology: Regional Studies, Volume 25〈/p〉 〈p〉Author(s): Thushara De Silva M., George M. Hornberger〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉 〈h6〉Study region〈/h6〉 〈p〉The Mahaweli multipurpose water resources system of Sri Lanka, spread across 25,500 km〈sup〉2〈/sup〉, incorporates the Mahaweli, Kala Oya, Malwatu Oya, Kantale Oya and Maduru Oya river basins.〈/p〉 〈/div〉 〈div〉 〈h6〉Study focus〈/h6〉 〈p〉We developed a model that can be used to assess water resources management alternatives of reservoir cascade operation to fulfill diverse and often conflicting water demands. The Mahaweli project is mainly operated for hydropower generation and irrigated agriculture. This study quantifies performances of water management alternatives considering trade-offs between hydropower and agricultural yield. Reliability, resilience, and vulnerability are other considerations that we explore.〈/p〉 〈/div〉 〈div〉 〈h6〉New hydrological insights for the region〈/h6〉 〈p〉In the Mahaweli reservoir system, water is used primarily for paddy irrigation and hydropower generation. Increasing water diversions for paddy irrigation leads to decreases in hydropower so in times of limited water availability, decisions about trade-offs are required. In addition to diversions, decisions about how much arable land to cultivate during times of water shortage affect measures of risk related to paddy yield. Our results show that existing infrastructure places a constraint on how much water diverted for irrigation can be used productively and also leads to spatial variability in improvements in risk measures at the expense of reductions in expected yield across the basin.〈/p〉 〈/div〉

Description: 〈p〉Publication date: October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Hydrology: Regional Studies, Volume 25〈/p〉 〈p〉Author(s): Luis Angel Espinosa, Maria Manuela Portela, Rui Rodrigues〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉 〈h6〉Study region〈/h6〉 〈p〉Madeira Island, Portugal (a small island of the North Atlantic Ocean).〈/p〉 〈/div〉 〈div〉 〈h6〉Study focus〈/h6〉 〈p〉Droughts from January 1937 to December 2016, were studied using monthly rainfall at 41 rain gauges covering most of the island. The gaps of the original rainfall data were filled by Multiple Imputation by Chained Equations (MICE). The drought conditions were assessed by means of the Standardized Precipitation Index (SPI), specifically the SPI6. To study the drought variability, some clustering techniques and principal components analysis (PCA) were applied to the SPI field.〈/p〉 〈/div〉 〈div〉 〈h6〉New hydrological insights for the region〈/h6〉 〈p〉Three homogeneous regions (northern slope, southern slope, and central region), each of them with different temporal climatic variability may be identified. Furthermore, for each region, the droughts were characterized in terms of magnitude and duration, and based on a kernel occurrence rate estimator (KORE) as well as on frequency of the drought periods. Finally, two climatic drivers, namely the El Niño-Southern Oscillation (ENSO) and the North Atlantic Oscillation (NAO) were teleconnected to the drought variability at the identified homogeneous regions for the period under study. It was not possible to establish a clear relationship between ENSO/NAO and drought occurrence. Nevertheless, the results showed that the spatio-temporal drought variability in Madeira Island has been subjected to noticeable changes in recent years (2001–2016) with a considerable higher number of periods under drought conditions than in the past.〈/p〉 〈/div〉

Description: 〈p〉Publication date: October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Hydrology: Regional Studies, Volume 25〈/p〉 〈p〉Author(s): Xiao-feng Zhang, Hao-chen Yan, Yao Yue, Quan-xi Xu〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉 〈h6〉Study region〈/h6〉 〈p〉The middle and lower reaches of the Jinsha River Basin (MLJRB).〈/p〉 〈/div〉 〈div〉 〈h6〉Study focus〈/h6〉 〈p〉The main objective is to evaluate the impact of climate change and anthropogenic activities to the water and sediment resources of the studied region in 1960—2015. The variation of runoff and suspended sediment load is first analyzed with regard to their trends and abrupt change. Different factors attributable to the variation are then quantitatively separated.〈/p〉 〈/div〉 〈div〉 〈h6〉New hydrological insights for the region〈/h6〉 〈p〉The annual runoff and sediment load across the MLJRB both decreased abruptly and coincidently in the recent two decades, with the transitional years detected to be 2006 and 2002, respectively. Comparing the post-transition period to the pre-transition period, runoff decreased 14.7% and sediment load decreased 63%. Climate change is the major contribution for the decrease in runoff, which explains 56.3% of the reduction, and impoundment of large reservoirs and water consumption contributed 18.6% and 2.7% respectively. The other 22.5% was ascribed to water-soil conservation and other factors. In contrast to water resources, human activities were dominant in sediment reduction, including 44.9% caused by large reservoirs, 1% from increased water consumption and 35% by conservation measures and other potential factors. Remarkably, almost 90% of the sediment load can be trapped as the direct consequence of the construction and operation of two huge dams, Xiluodu and Xiangjiaba, since 2013.〈/p〉 〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S2214581819300102-ga1.jpg" width="378" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Hydrology: Regional Studies, Volume 25〈/p〉 〈p〉Author(s): Achamyeleh G. Mengistu, Leon D. van Rensburg, Yali E. Woyessa〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉 〈h6〉Study region〈/h6〉 〈p〉This study was conducted in Soutloop River Catchment, Northern Cape, South Africa.〈/p〉 〈/div〉 〈div〉 〈h6〉Study focus〈/h6〉 〈p〉Although hydrologic models play a critical role in the management of natural resources in arid areas, their application is challenged by the scarcity of data for calibration and validation. Therefore, this study aimed at to configure, calibrate and validate SWAT model in a data-scarce catchment by using the regionalization with physical similarity approach. This approach uses dual calibration and validation procedure, 〈em〉i.e.〈/em〉, one in the donor catchment (by using SWAT-CUP (SWAT Calibration and Uncertainty Programs) and the other on the study catchment (by manual calibration and verification).〈/p〉 〈/div〉 〈div〉 〈h6〉New hydrological insights for the region〈/h6〉 〈p〉Based on the sensitivity analysis, sixteen parameters were calibrated by SWAT-CUP. The result from the uncertainty analysis indicated acceptable values of both the R-factor (0.8〈sup〉**〈/sup〉) and P-factor (0.7**). The model performance evaluation also showed acceptable ranges of values (〈em〉e.g.〈/em〉, NS was 0.76** and R〈sup〉2〈/sup〉 was 0.78**). However, the main calibration and validation process was conducted outside the target catchment, though it was assumed that the donor and target catchments have similar hydrological responses. Therefore, the study suggested further inspection methods to minimize the model uncertainty in the study catchment. This study enables researchers to exploit the river eco-regional classifications of South Africa to apply hydrologic models to estimate the components of water balance in arid/semi-arid catchments.〈/p〉 〈/div〉

Description: 〈p〉Publication date: October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Hydrology: Regional Studies, Volume 25〈/p〉 〈p〉Author(s): Mohammad Zendehbad, Peter Cepuder, Willibald Loiskandl, Christine Stumpp〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉 〈h6〉Study region〈/h6〉 〈p〉Urban aquifer of Mashhad city, northeastern Iran.〈/p〉 〈/div〉 〈div〉 〈h6〉Study focus〈/h6〉 〈p〉Measuring the ratios of the stable nitrate isotopes and hydrogeochemistry of major components in order to specify the origin of nitrate contamination and potential transformation processes in the aquifer.〈/p〉 〈/div〉 〈div〉 〈h6〉New hydrological insights for the region〈/h6〉 〈p〉This study represents the first isotopic characterization of groundwater nitrate to identify the sources of excessive nitrate in the urban aquifer and provides a reference for the potential implementation of executive programs on groundwater quality and protection. Nitrate concentration exceeded the limits for nitrate in drinking water in most of the wells (110 out of 261). Isotopic composition of the oxygen and nitrogen of NO〈sub〉3〈/sub〉〈sup〉−〈/sup〉 in groundwater indicated sewage as the primary source of nitrate contamination. Denitrification was identified as a non-significant process in the aquifer. Concentrations of anions (Cl〈sup〉−〈/sup〉, SO〈sub〉4〈/sub〉〈sup〉2−〈/sup〉 and PO〈sub〉4〈/sub〉〈sup〉3−〈/sup〉) and NO〈sub〉3〈/sub〉〈sup〉−〈/sup〉 showed strong correlations confirming potential wastewater influence. Most of the groundwater was weakly acidic, and the chemistry of the groundwater was rather affected by urbanization and land-use than by aquifer rock interactions. The absence of a reliable sewer collecting system, particularly in the central and southern parts of the study area, directly resulted in the poor water quality. Considering the lack of natural attenuation processes in the groundwater, management options need to be considered for reducing nitrogen input into groundwater.〈/p〉 〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S221458181930062X-ga1.jpg" width="499" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: October 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Hydrology: Regional Studies, Volume 19〈/p〉 〈p〉Author(s): José Bandeira Brasil, Eunice Maia de Andrade, Helba Araújo de Queiroz Palácio, Pedro Henrique Augusto Medeiros, Julio Cesar Neves dos Santos〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉 〈h6〉Study region〈/h6〉 〈p〉Iguatu Experimental Basin, located in the semi-arid region of northeastern Brazil.〈/p〉 〈/div〉 〈div〉 〈h6〉Study focus〈/h6〉 〈p〉The aim of this study was to investigate the influence of rainfall characteristics on throughfall, stemflow and interception loss in a deciduous forest of a tropical semi-arid region, from a data series of eight consecutive years. The data were collected from 2010 to 2017, comprising a total of 225 events.〈/p〉 〈/div〉 〈div〉 〈h6〉New hydrological insights for the region〈/h6〉 〈p〉Among the variables used to characterize rainfall, the maximum 30-min intensity (〈em〉I30〈/em〉) best explained the interception losses, which is also well correlated to rainfall depth and event average intensity. The predominant events (67% of the total) are characterised by low rainfall depth, low 〈em〉I30〈/em〉 and higher interception loss (18% of the gross rainfall). In addition, there is a threshold between rainfall characteristics and the interception process: for rainfall and 〈em〉I30〈/em〉 lower than 20 mm and 15 mm/h respectively, and rainfall duration lower than 100 min, interception losses are usually higher than 30%, reaching up to 74%. For the remaining events, interception losses are mostly within the range of 10–20% of rainfall. The data and information on the interception process, presented in this study, helps the comprehension of the overall water balance in dry environments and improve the capacity for parameterization of hydrological models, contributing to a more efficient water and environmental management.〈/p〉 〈/div〉

Description: 〈p〉Publication date: June 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Hydrology: Regional Studies, Volume 23〈/p〉 〈p〉Author(s): D.A. Hughes〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉 〈h6〉Study region〈/h6〉 〈p〉Sub-Saharan Africa.〈/p〉 〈/div〉 〈div〉 〈h6〉Study focus〈/h6〉 〈p〉Water resources availability assessments are highly uncertain due to inadequate observation networks, and this is expected to get worse into the future. This uncertainty is expected to increase in the future due to climate, environmental, population and other socio-economic development changes.〈/p〉 〈/div〉 〈div〉 〈h6〉New hydrological insights for this region〈/h6〉 〈p〉This paper argues for a coordinated effort to provide improved water resources information by water scientists both within the region and from outside. It further proposes a unified approach based on hydrological modelling that incorporates realistic measures of uncertainty and that can be applied to the region as a whole using a common methodology. The concept is designed to make the best use of all available data sets, including local observations as well as emerging global data. The suggested approach has scientific credibility (based on previous studies), is technically feasible and offers a range of long-term benefits. The overall conclusion is that without a project of this type, water resources planning and management decisions in the region will continue to be based on inadequate information and unquantified uncertainties.〈/p〉 〈/div〉

Description: 〈p〉Publication date: February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Hydrology: Regional Studies, Volume 21〈/p〉 〈p〉Author(s): L. Myeni, M.E. Moeletsi, A.D. Clulow〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Soil moisture is the key parameter that governs the partitioning of the mass and energy fluxes between land and atmosphere through its influence on surface evaporation, runoff, albedo and emissivity. Therefore, accurate quantification of soil moisture is critical in the study of the soil-plant-atmosphere continuum as well as in hydrology and climate change studies. However, soil moisture remains a challenging hydrometeorological variable to monitor and interpret over high temporal and spatial resolution. The cost of setting up, operating and maintaining dense soil moisture networks across different agro-climatic zones of the African regions is currently financially unattainable due to high competition for resources. Consequently, soil moisture is often estimated indirectly, using both remote sensing and hydrological models, which provide periodic updates and valuable estimates at lower cost over African continent thus far. In recent years, huge efforts have been undertaken to install in situ soil moisture monitoring networks to support the satellite retrievals, satellite product improvement and modelling in Africa. However, the lack of large and representative in situ soil moisture monitoring networks across different agro-climatic zones of the African regions still hinders evaluation and verification of the most promising remote sensing products and hydrological models to estimate soil moisture. Consequently, the need for accurate and continuous real-time in situ soil moisture measurements covering a wide range of agro-climatic zones of the African continent is indisputable.〈/p〉〈/div〉

Description: 〈p〉Publication date: February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Hydrology: Regional Studies, Volume 21〈/p〉 〈p〉Author(s): Johanna Ngula Niipele, Jianping Chen〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉 〈h6〉Study region〈/h6〉 〈p〉The study area is the Iishana sub-basin located in north-central Namibia. The basin is characterised by low-lying interconnected ephemeral drainage networks locally known as Iishana. In the past decade, the basin has experienced frequent droughts and flooding events due to recent weather anomalies possibly enhanced by the sprawling urban development.〈/p〉 〈/div〉 〈div〉 〈h6〉Study focus〈/h6〉 〈p〉Although extensive studies have been conducted on water availability in the basin, no attempts have been made to update existing hydrological maps which provide limited information on the impacts of geo-hydrological dynamics in the area. The aim of this study was to test the effectiveness of the Advanced Land Observing Satellite Digital Elevation Model (ALOS DEM) for drainage network extraction. ArcHydro tools were used for drainage feature extraction. Validation of extracted networks was based on field observations and delineated networks from earth observation data and Normalized Difference Wetness Index (NDWI). The accuracy of extracted drainage networks was assessed through visual observation of data overlay and the coefficient of line correspondence (CLC).〈/p〉 〈/div〉 〈div〉 〈h6〉New hydrological insights〈/h6〉 〈p〉The resulting drainage networks will be used to update the current hydrographic map of the area which will aid in the development of flood and drought mitigating measures for environmental management. The CLC computed metric obtained a 0.91 match between extracted and delineated drainage networks. The results show that ALOS DEM is capable of extracting drainage networks within the Iishana sub-basin.〈/p〉 〈/div〉

Description: 〈p〉Publication date: February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Hydrology: Regional Studies, Volume 21〈/p〉 〈p〉Author(s): Ameer Muhammad, Grey R. Evenson, Tricia A. Stadnyk, Alaba Boluwade, Sanjeev Kumar Jha, Paulin Coulibaly〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉 〈h6〉Study region〈/h6〉 〈p〉Prairie Pothole Region of Canada.〈/p〉 〈/div〉 〈div〉 〈h6〉Study focus〈/h6〉 〈p〉The Prairie region spans across approximately 870,000 km〈sup〉2〈/sup〉 of the Great Plains region of Canada (80%) and the United States (20%). The presence of a large number of depressional wetlands (potholes) results in dynamic surface-water and stream connectivity during wet and dry year necessitating an improved understanding of watershed-scale interactions of the Prairie Potholes. The Soil Water Assessment Tool (SWAT) hydrological model with three structural variants is utilized to assess the degree of accuracy associated with increasing model complexity and its impact on the model calibration of the Upper Assiniboine River Basin at Kamsack.〈/p〉 〈/div〉 〈div〉 〈h6〉New hydrologic insight for the region〈/h6〉 〈p〉The SWAT model was calibrated and verified with three different structural arrangements in 1) lumped pothole, 2) semi discretized pothole, 3) and fully discretized pothole representation. The fully discretized pothole version of the SWAT reflected streamflow best (KGE of 0.78) but with greater uncertainty, larger data and computational resource requirements. The fully discretized (modified) model, however, was able to capture the high flow and the fill-and-spill processes, which is a defining characteristic of the Prairie Pothole Region (PPR). Significant improvements to the predictive ability of SWAT in the case of the modified model was observed, thus allowing an enhanced understanding of the aggregate effect of potholes in this watershed.〈/p〉 〈/div〉

Description: 〈p〉Publication date: February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Hydrology: Regional Studies, Volume 21〈/p〉 〈p〉Author(s): Ann W. Kamamia, Hosea M. Mwangi, Karl-Heinz Feger, Stefan Julich〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉 〈h6〉Study region〈/h6〉 〈p〉Nyangores catchment, Mara catchment, Kenya.〈/p〉 〈/div〉 〈div〉 〈h6〉Study focus〈/h6〉 〈p〉Hydrologic models are widely used tools in watershed management to assist in decision making by representing catchment functions under alternative scenarios. This study focused on the evaluation of the 5 segment Flow Duration Curve based calibration procedure (5FDC) for the period 1975–1978 using the Soil Water Assessment Tool (SWAT). The Normal Calibration Procedure (NCP) based on the hydrograph was compared to the 5FDC. Two separate ensembles each containing 10 Pareto calibration runs were obtained individually from each method and evaluated based on their goodness-of-fit. A final Combined Procedure (CP), which was an intersection of 5FDC and NCP was executed. With this supplementary analysis, the parameter distribution and water component balance were analyzed and compared.〈/p〉 〈/div〉 〈div〉 〈h6〉New hydrological insights for the region〈/h6〉 〈p〉The comparison of 5FDC and NCP shows that the 5FDC provides a better representation of the low and mid-level section of the flow duration curve as compared to the NCP, which greatly overestimates these flows. This method also closely matches the observed runoff ratios. This indicates that the 5FDC calibration may be well suited for water resource applications focused on low flows. The CP combines the advantages of both procedures by improving parameter identifiability, leading to better representation of high and low flows.〈/p〉 〈/div〉

Description: 〈p〉Publication date: February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Hydrology: Regional Studies, Volume 21〈/p〉 〈p〉Author(s): Makoto Higashino, Heinz G. Stefan〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉 〈h6〉Study region〈/h6〉 〈p〉The Banjo River basin on Kyushu Island in the southwest of Japan.〈/p〉 〈/div〉 〈div〉 〈h6〉Study focus〈/h6〉 〈p〉This study focuses on the impact of local and/or large scale climate change on the river flow in the small and steep river basin. The variability, trend, correlation and change of extreme and mean precipitation and river (flood) runoff are investigated.〈/p〉 〈/div〉 〈div〉 〈h6〉New hydrological insights〈/h6〉 〈p〉In the small and steep river basins of Japan, the maximum annual flood runoff which occurs in the wet season, is well correlated with maximum precipitation on a daily time scale. Daily flow and precipitation data recorded in the basin from 1960 to 2015, have a correlation coefficient R〈sup〉2〈/sup〉 = 0.72. A high variability of the maximum and mean annual flows, and significant rising trends in daily extreme precipitation and river (flood) flows were also found in the data analysis. The maximum annual flood has increased on average by 5.98 m〈sup〉3〈/sup〉/s per year from 330 m〈sup〉3〈/sup〉/s in 1960; this increase is fully accounted for by the trend in observed maximum annual precipitation which is 1.1 mm/day per year. On an annual timescale maximum precipitation and maximum flood discharges have become substantially higher in phase with the ENSO (El Nino-Southern Oscillation) in the Pacific Ocean. Time frequency analyses revealed that a periodic component of the annual maximum flood flow in the Banjo River basin with a period of about 6 to 8 years has become significant since the beginning of the 21 st century. The number of days with more than 100, 200, 300, 400 and 500 m〈sup〉3〈/sup〉/s flows has increased, which is important for flood control planning.〈/p〉 〈/div〉

Description: 〈p〉Publication date: February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Hydrology: Regional Studies, Volume 21〈/p〉 〈p〉Author(s): J.J. Gibson, S.J. Birks, M. Moncur〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉 〈h6〉Study region〈/h6〉 〈p〉Surveys of stable isotopes of water in 121 lakes were conducted between 2007 and 2009 to assist in characterizing baseline hydrology of the South Athabasca Oil Sands area, Alberta, a 35,000 km〈sup〉2〈/sup〉 boreal forest region with subdued relief, about 70% wetland cover, and a mosaic of lakes, rivers and buried channel networks. The region, currently under rapid development for in-situ oil sands, was close to baseline conditions at the time of survey.〈/p〉 〈/div〉 〈div〉 〈h6〉Study focus〈/h6〉 〈p〉Using an isotope mass balance approach, isotope data were applied to estimate water yield to lakes across the region. High-resolution maps were created to illustrate the spatial distribution of water yield and to compare observed patterns to geologic and physiographic features.〈/p〉 〈/div〉 〈div〉 〈h6〉New hydrological insights for the region〈/h6〉 〈p〉Site-specific differences in water yield were found in relation to geologic and physiographic features. Notably, high water yields were found in lakes underlain by Colorado shale, lower runoff was found in proximity to incised and buried channels. Consistent patterns from year-to-year reveal zones of low runoff which may be more susceptible to development-related impacts including changes in surface/groundwater interaction and pressurization or depressurization of aquifers or formations. The approach may be helpful for informing design of new monitoring programs to ensure runoff variability is considered. Periodic reassessments are recommended to capture potential development and/or climatic change impacts on the water cycle.〈/p〉 〈/div〉

Description: 〈p〉Publication date: February 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Hydrology: Regional Studies, Volume 27〈/p〉 〈p〉Author(s): GZ Ndhlovu, YE Woyessa〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉 〈h6〉Study Region〈/h6〉 〈p〉The Kabompo River Basin (KRB) in Zambia is one of the 13 basins found in the Zambezi River Basin in Southern African region.〈/p〉 〈/div〉 〈div〉 〈h6〉Study Focus〈/h6〉 〈p〉Global Climate Model (GCMs) projections have spatial resolution of up to several hundred kilometres, which may not be adequate for capturing local details mostly needed for impact assessment at local and regional scale. Downscaling techniques developed to improve the detail include; regional climate modelling and statistical techniques linking climate information at GCM resolution with that at local scale. This paper deals with evaluation and assessment of the impact of climate change on water balance for the KRB. In order to evaluate climate change impact, six bias–corrected and downscaled GCM outputs were acquired and used as inputs for hydrological modelling with the SWAT model to determine the impact under two future climate scenarios.〈/p〉 〈/div〉 〈div〉 〈h6〉New Hydrological Insights for the Region〈/h6〉 〈p〉The results indicate that the future catchment water balance for KRB under RCP4.5 will have insignificant variation from the current catchment water balance as annual statistics show that rainfall will reduce by 1 % while water yield and runoff will increase by 5 % and 6 % respectively. Meanwhile under RCP8.5, annual statistics show that rainfall will increase by 19 % while water yield and runoff will increase by 40 % and 65 % respectively and resulting in a significant increase in catchment water balance.〈/p〉 〈/div〉

Description: 〈p〉Publication date: February 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Hydrology: Regional Studies, Volume 27〈/p〉 〈p〉Author(s): Eniola Damilola Ashaolu〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉 〈h6〉Study region〈/h6〉 〈p〉Osun Drainage Basin, Nigeria.〈/p〉 〈/div〉 〈div〉 〈h6〉Study focus〈/h6〉 〈p〉Estimating spatial and temporal patterns of recharge is important for sustainable groundwater resources management. This is especially true for data poor regions, such as the Basement Complex in Nigeria, which has shallow aquifers, a proliferation of wells and no efficient groundwater monitoring network. This study evaluates the performance of a spatially distributed monthly water balance model (WetSpass-M) in estimating groundwater recharge. The WetSpass-M model has moderate data demands, which allows for comprehensive assessment of recharge.〈/p〉 〈/div〉 〈div〉 〈h6〉New hydrological insights for the region〈/h6〉 〈p〉27 % of the rainfall in Osun drainage basin becomes recharge, while the remaining is lost through evapotranspiration (43 %), surface runoff (21 %) and interception (9 %). September is the month with highest recharge, ranging between 0 and 73 mm in the north and 129 up to 213 mm in the south and northeast of the basin. The study revealed the significance of the applied water balance model in understanding the spatial and temporal status of recharge. Therefore, the spatial and temporal patterns of recharge should be taken into consideration in preparing a sustainable groundwater resources management plan for the Osun drainage basin. Artificial recharge might be adopted to store storm water runoff during wet periods to improve the groundwater supply in dry months. Also, monthly groundwater withdrawals should be regulated in relation to spatial and temporal recharge patterns.〈/p〉 〈/div〉

Description: 〈p〉Publication date: February 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Hydrology: Regional Studies, Volume 27〈/p〉 〈p〉Author(s): Enoch Bessah, Abdulganiy O. Raji, Olalekan J. Taiwo, Sampson K. Agodzo, Olusola O. Ololade, Alexandre Strapasson〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉 〈h6〉Study Region〈/h6〉 〈p〉Pra River Basin, Ghana.〈/p〉 〈/div〉 〈div〉 〈h6〉Study Focus〈/h6〉 〈p〉The study modelled the changes in water yield using regional, sub-regional and local climate conditions from modelling outputs at spatial resolutions of 44 km, 12 km and 0.002 km respectively to drive the Integrated Valuation of Ecosystem Services and Trade-offs model at three time periods of land use land cover (LULC). Changes in historical water yield (simulated for 1986, 2002 & 2018 LULC using the mean climatic parameters from 1981-2010) and future scenario (simulated for 2018 LULC using the mean climatic parameters from 2020-2049) for annual, seasonal and monthly periods were assessed.〈/p〉 〈/div〉 〈div〉 〈h6〉New Hydrological Insights for the Region〈/h6〉 〈p〉The results show that future annual water yield could change by -46%, -48%, +44% and -35% under the regional, sub-regional, local and ensemble mean of the climate scenarios respectively. Seasonal water yield from the ensemble mean of the future climate scenario was projected to decrease between 2-16 mm, with a mean decrease of 33.39% during the December–February season. There was no directional effect of spatial resolution on water yield. The future period could be impacted by both drought and flood. We recommend that re/afforestation should be encouraged to improve infiltration and reduce deforestation which was 2.27% per annum in the assessed period to prevent flood causing runoffs, while irrigation technology will help to improve resilience to drought.〈/p〉 〈/div〉

Description: 〈p〉Publication date: April 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Hydrology: Regional Studies, Volume 22〈/p〉 〈p〉Author(s): Sitotaw Haile Erena, Hailu Worku〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉 〈h6〉Study region〈/h6〉 〈p〉This study was conducted in Dire Dawa city, Ethiopia.〈/p〉 〈/div〉 〈div〉 〈h6〉Study focus〈/h6〉 〈p〉This study aims to explore the hydrological impacts of land use land cover changes using rational method. As to perform land use analysis, four decade based satellite imagery were analyzed using ERDAS imagine. The hydrological effect of land cover change and respective surface runoff was calculated using rational method.〈/p〉 〈/div〉 〈div〉 〈h6〉New hydrological insights for the region〈/h6〉 〈p〉The trend of land use land cover analysis shows that the city has been experiencing significant decrease in forest land with continuous concomitant increases in bare land and settlements through the study period. In response of land use changes, the trend of surface runoff showed continuous increasing trend. The result of focus group discussion confirms that land use change has significantly affected the trend of surface runoff generation. The study also found out that the amount of surface runoff was positively sensitive to forest land and negatively to bare land and settlement classes. To demonstrate the future effect of surface runoff, the study developed worst and best case scenarios. The worst case showed that if the current land use continuous in the coming years, the watershed could receive more surface runoff that threaten the existence of the city. The best case scenario suggested rehabilitation of bare land cover and rooftop rainwater harvesting as promising condition to drop the amount of surface runoff. The output of the study provides environmental friendly surface runoff mitigation strategies that can be adopted at household and community levels.〈/p〉 〈/div〉

Description: 〈p〉Publication date: April 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Hydrology: Regional Studies, Volume 22〈/p〉 〈p〉Author(s): Olga V.O. Gomes, Eduardo D. Marques, Vinicius T. Kütter, José R. Aires, Yves Travi, Emmanoel V. Silva-Filho〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉 〈h6〉Study Region〈/h6〉 〈p〉Porous aquifer system of Northeastern Guanabara Bay, Rio de Janeiro, Brazil.〈/p〉 〈/div〉 〈div〉 〈h6〉Study Focus〈/h6〉 〈p〉The present work aimed to comprehend the geochemical processes responsible for the considerable range of salinity (48 to 5651 μS. cm〈sup〉−1〈/sup〉) through chemical composition of groundwater (hydrogeochemical modeling through PHREEQC) allied to chemical ratios (Cl/Br ratio) and stable isotopes data (δ〈sup〉18〈/sup〉O and δ〈sup〉2〈/sup〉H).〈/p〉 〈/div〉 〈div〉 〈h6〉New hydrological insights for the region〈/h6〉 〈p〉The PHREEQC modeling showed that high pH and low pe values conditioning the main processes controlling the hydrogeochemical evolution of groundwater in that region. The salinity origins should be explained by 4 hypotheses: 1) a group related to recharge zones, close to the basin headboard or connected to the fractured aquifers from the basement rocks (low Cl/Br ratio and predominance of light δ〈sup〉18〈/sup〉O and δ〈sup〉2〈/sup〉H isotopes; 2) a group formed by groundwater with high Cl/Br ratio and predominance of heavy δ〈sup〉18〈/sup〉O and δ〈sup〉2〈/sup〉H isotopes, associated to dissolution processes of Tertiary brackish water environment sediments; 3) a group formed by groundwater with low Cl/Br ratio, high Cl〈sup〉−〈/sup〉 concentrations and low δ〈sup〉18〈/sup〉O and δ〈sup〉2〈/sup〉H, related to groundwater under influence of Caceribu River (high content of domestic effluents); and 4) a group composed by groundwater with high salinity, high Cl〈sup〉−〈/sup〉 concentrations and enrichment of δ〈sup〉18〈/sup〉O and δ〈sup〉2〈/sup〉H, located at a mangrove area, where the influence of seawater intrusion in the aquifer is recognized.〈/p〉 〈/div〉

Description: 〈p〉Publication date: April 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Hydrology: Regional Studies, Volume 22〈/p〉 〈p〉Author(s): Johannes Christoph Haas, Steffen Birk〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉 〈h6〉Study region〈/h6〉 〈p〉Austria.〈/p〉 〈/div〉 〈div〉 〈h6〉Study focus〈/h6〉 〈p〉Using publicly available data for the main components of the hydrological cycle we use standardization to calculate countrywide and regional averages of groundwater levels, stream stages and precipitation. These averages get analyzed for the occurrence of trends, compared with each other and the Austrian water use over time.〈/p〉 〈/div〉 〈div〉 〈h6〉New hydrological insights for the region〈/h6〉 〈p〉It is shown that groundwater levels trend downwards until the 1980s, from whereon they recover. Precipitation follows this track, but the downward trend is much less severe. River stages lack data for the downward trending period, but follow the upward trend too. The trend in groundwater is a reverse of the trends observed in water use and we hypothesize that the discrepancy between average precipitation and average groundwater pre 1980s could be caused by the increasing water use in this period, especially since Austrias water demands are mostly sourced from groundwater.〈/p〉 〈/div〉

Description: 〈p〉Publication date: April 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Hydrology: Regional Studies, Volume 22〈/p〉 〈p〉Author(s): Anna Malagó, Fayçal Bouraoui, Bruna Grizzetti, Ad De Roo〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉 〈h6〉Study region〈/h6〉 〈p〉Mediterranean River Basins.〈/p〉 〈/div〉 〈div〉 〈h6〉Study focus〈/h6〉 〈p〉Human activities and consequent pollution have put the freshwater and marine ecosystems of the Mediterranean region under pressure, with high risk of eutrophication phenomena. In this study, an extended version of the Geospatial Regression Equation for European Nutrient losses model (GREEN), originally developed for estimating nutrient loads from diffuse and point sources in Europe, was extended to include additional nutrient sources using a grid cell discretization. The spatial resolution is 5 arc minute and the model inputs consist of the latest and best available global data.〈/p〉 〈/div〉 〈div〉 〈h6〉New hydrological insights for the region〈/h6〉 〈p〉The results of this study show that during 2003–2007 (baseline), 1.87 Tg/y of total nitrogen (TN), 1.22 Tg/y of nitrates (N-NO〈sub〉3〈/sub〉), 0.11 Tg/y of total phosphorus (TP) and 0.03 Tg/y of orthophosphate (P-PO〈sub〉4〈/sub〉) were discharged in the Mediterranean Sea. The source apportionment analysis showed that the main contributor to total nitrogen and nitrate loads is agriculture followed by natural background, while for orthophosphate dominant sources include wastewater and scattered dwellings. Two scenarios were investigated to assess sustainable water and nutrient management options, showing that the reduction of 50% of nitrogen surplus leads to a significant reduction of nitrogen emission in regions characterized by high intensity agriculture, while the upgrading of wastewater treatment plants to tertiary level was more efficient for TP reduction.〈/p〉 〈/div〉

Description: 〈p〉Publication date: June 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Hydrology: Regional Studies, Volume 23〈/p〉 〈p〉Author(s): Le Thi Thanh Thuy, Seiki Kawagoe, Ranjan Sarukkalige〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉 〈h6〉Study region〈/h6〉 〈p〉In this study, three provinces in Northeast Vietnam including Bac Kan, Thai Nguyen, and Tuyen Quang are examined to determine the precipitation variation characteristics.〈/p〉 〈/div〉 〈div〉 〈h6〉Study focus〈/h6〉 〈p〉The average yearly temperature during the last two decades in Northeast Vietnam has increased by 0.72 °C when compared to the period 1962–1990. The Clausius Clapeyron (CC) relation indicates that a warmer atmosphere can result in higher moisture-holding capacity; hence, there is the possibility of increased extreme rainfall with respect to the rise in temperature. We evaluate the relationship between the average 24-hour temperature and rainfall extremes using the binning method. The estimation of the 24-hour probable maximum precipitation (PMP) is then implemented based on the moisture maximization and Hershfield statistical methods.〈/p〉 〈/div〉 〈div〉 〈h6〉New hydrological insights for the region〈/h6〉 〈p〉The 99.9〈sup〉th〈/sup〉 percentiles of 24-hour precipitation are close to the super CC scaling up to peak points of 22.6–25.6 °C and decrease at higher temperatures. The Hershfield method produces 24-hour PMP results ranging from 232 mm to 895 mm. PMP outputs using the moisture maximization method based on the 100-year dew point are higher than those results generated from the statistical method except for Chiem Hoa station. Considering possible changes in future relative humidity under a warming climate from GCMs and RCM projections for two RCP scenarios, RCP 8.5 indicates the possible rise in probable extreme precipitation.〈/p〉 〈/div〉

Description: Publication date: March 2015 Source: Journal of Hydrology: Regional Studies, Volume 3, Supplement 1

Description: Publication date: March 2015 Source: Journal of Hydrology: Regional Studies, Volume 3, Supplement 1

Description: Publication date: March 2015 Source: Journal of Hydrology: Regional Studies, Volume 3, Supplement 1

Description: Publication date: March 2015 Source: Journal of Hydrology: Regional Studies, Volume 3, Supplement 1

Description: Publication date: September 2015 Source: Journal of Hydrology: Regional Studies, Volume 4, Part B Author(s): Abdouramane Gado Djibo , Ousmane Seidou , Harouna Karambiri , Ketevera Sittichok , Jean Emmanuel Paturel , Hadiza Moussa Saley Study region The Sirba watershed, Niger and Burkina Faso countries, West Africa. Study focus Water resources management in the Sahel region, West Africa, is extremely difficult because of high inter-annual rainfall variability. Unexpected floods and droughts often lead to severe humanitarian crises. Seasonal rainfall forecasting is one possible way to increase resilience to climate variability by providing information in advance about the amount of rainfall expected in each upcoming rainy season. Rainfall forecasting models often arbitrarily assume that rainfall is linked to predictors by a multiple linear regression with parameters that are independent of time and of predictor magnitude. Two probabilistic methods based on change point detection that allow the relationship to change according to time or rainfall magnitude were developed in this paper using normalized Bayes factors. Each method uses one of the following predictors: sea level pressure, air temperature and relative humidity. Method M1 allows for change in model parameters according to annual rainfall magnitude, while M2 allows for changes in model parameters with time. M1 and M2 were compared to the classical linear model with constant parameters (M3) and to the climatology (M4). New hydrological insights for the region The model that allows a change in the predictor–predictand relationship according to rainfall amplitude (M1) and uses air temperature as predictor is the best model for seasonal rainfall forecasting in the study area.

Description: Publication date: September 2015 Source: Journal of Hydrology: Regional Studies, Volume 4, Part B Author(s): Frank Joseph Wambura, Preksedis Marco Ndomba, Victor Kongo, Siza Donald Tumbo Study Region The Wami River sub-basin is among the river sub-basins with a vital ecosystem in Tanzania. It comprises the Saadani National park and it has the very great potential of irrigation and rain fed agriculture. Study Focus The objective of this study was to evaluate the uncertainty of future streamflow in respect of increasing water demands and uncertain projected climate inputs, General Circulation Models (GCMs). The water demands were projected to the year 2039 and GCM precipitation was selected as the changing climatic variable. The CMIP5-GCMs were evaluated for their skills and those with the minimum skill scores above 75% were downscaled and used in projection of scenario RCP 8.5 precipitation. Then uncertainties of RCP 8.5 precipitation were estimated using a fuzzy extension principle and finally used to simulate uncertainties of future runoff using a rainfall-runoff model, Soil and Water Assessment Tool (SWAT). New Hydrological Insights for the Region The results of projected streamflow shows that the baseline annual climatology flow (ACF) is 98 m 3 /s and for the future, the median ACF is projected to be 81 m 3 /s. At 100% uncertainty of skilled projections, the ACF from the sub-basin is projected to range between −47% and +36% from the baseline ACF. However, the midstream of the sub-basin shows reliable water availability for foreseen water uses expansion up to the year 2039.

Description: Publication date: September 2015 Source: Journal of Hydrology: Regional Studies, Volume 4, Part B Author(s): Fernando Mainardi Fan , Dirk Schwanenberg , Walter Collischonn , Albrecht Weerts Study region This paper describes a major ensemble-forecasts verification effort for inflows of three large-scale river basins of Brazil: Upper São Francisco, Doce, and Tocantins Rivers. Study focus In experimental scenarios, inflow forecasts were generated forcing one hydrological model with quantitative precipitation forecasts (QPF) from three selected models of the TIGGE database. This study provides information on the regional ensemble performance and also evaluates how different QPF models respond for the different basins and what happens with the use of combined QPF in a greater ensemble. New hydrological insights for the region This work presents one of the first extensive efforts to evaluate ensemble forecasts for large-scale basins in South America using TIGGE archive data. Results from these scenarios provide validation criteria and confirm that ensemble forecasts depend on the particular EPS used to run the hydrological model and on the basin studied. Furthermore, the use of the Super Ensemble seems to be a good strategy in terms of performance and robustness. The importance of the TIGGE database is also highlighted.

Description: Publication date: Available online 17 December 2015 Source: Journal of Hydrology: Regional Studies Author(s): Jun Nishijima, Kento Naritomi Study region The area of the Beppu geothermal field is located in southeast Japan (33°15′ to 20′ N, 131°27′ to 32′ E). Study focus The Beppu geothermal field, which is one of the largest hot-spring resorts, is located in the eastern end of the Beppu-Shimabara Graben, in central Kyushu, Japan. Details of the subsurface structure are necessary for hydrothermal modeling and numerical simulation. This study aims to delineate the shallow underground fault and basement structure using gravity analysis. New hydrological insights for the region A high Bouguer anomaly is detected in the southern part of this area, which corresponds to the distribution of the Kankaiji andesite. The results of the edge-detection filter of gravity data indicate that the northern edge of the high Bouguer anomaly corresponds to the Asamigawa Fault in the southern part of the study area, but deviates 1 km southeast of the Kankaiji hot spring to the north. In this area of high value, which indicates the fault, three hot spring areas, Horita, Kankaiji and Hamawaki, are located. The distribution of the depths of the three-dimensional gravity basement enables the delineation of the interface between the volcanic basement rocks and the fan deposit. The conspicuous, steep slope of the gravity basement is detected along the Asamigawa Fault and the southern hot-spring area. However, the northern hot-spring area is distributed on the uplift of the gravity basement. The results of the gravity analysis indicate that the structure of the hot-spring water path differs between the southern and northern hot-spring areas.

Description: Publication date: March 2016 Source: Journal of Hydrology: Regional Studies, Volume 5 Author(s): Ningfang Yang, Zhixiong Shen, Saugata Datta, Karen H. Johannesson Study region The Mississippi Delta in southern Louisiana, United States. Study focus The probable role that microbial respiration plays in As release from the shallow aquifer sediments. New hydrological insights for the region Shallow groundwaters in southern Louisiana have been reported to contain elevated As concentrations, whereas mechanisms responsible for As release from sediments have rarely been studied in this region. Microbial respiration is generally considered the main mechanism controlling As release in reducing anoxic aquifers such as the shallow aquifers in southern Louisiana and those of the Bengal basin. This study investigates the role microbial respiration plays in As release from shallow aquifer sediments in southern Louisiana through sediment incubation experiments and porewater analysis. Arsenic concentrations were the lowest in the sterilized control experiments, slightly higher in the un-amended experiments, and the highest in the experiments amended with acetate, and especially those amended with both acetate and AQDS (9,10-anthraquinone-2,6-disulfonic acid). Although Fe and Mn generally decreased at the beginning of all the experiments, they did follow a similar trend to As after the decrease. Porewater analysis showed that As and Fe concentrations were generally positively correlated and were higher in the coarse-grained sediments than in the fine-grained sediments. Results of the investigation are consistent with microbial respiration playing a key role in As release from the shallow aquifers sediments in southern Louisiana.

Description: Publication date: September 2016 Source: Journal of Hydrology: Regional Studies, Volume 7 Author(s): Donizete dos R. Pereira, Mauro A. Martinez, Fernando F. Pruski, Demetrius D. da Silva Study region The study was developed for fhe Pomba River Basin, which is located in southeast region of Brazil in the continent of South America. Study focus This study aimed to (a) calibrate and validate the SWAT model for a sub-basin of Pomba River Basin, (b) validate it for use with upstream and downstream control sections and (c) validate it for sub-basins other than the one where calibration was performed. This was done with the goal of having a model that can be used for the estimation of water availability and the planning of soil use and occupation. The model was calibrated by trial and error during the period from January 1996 through December 1999, while validation was conducted during the period from January 2000 through December 2004. Estimated the maximum, average and minimum annual daily streamflows were evaluated based on the paired t -test and linear regression analysis. New hydrological insights The SWAT model was qualified for simulating the Pomba River sub-basin in the sites where rainfall representation was reasonable to good. The model can be used in the simulation of maximum, average and minimum annual daily streamflow based on the paired t -test, contributing with the water resources management of region, although the model still needs to be improved, mainly in the representativeness of rainfall, to give better estimates of extreme values. Graphical abstract

Description: Publication date: September 2016 Source: Journal of Hydrology: Regional Studies, Volume 7 Author(s): Eliot A. Atekwana, Loago Molwalefhe, Oratile Kgaodi, Anna M. Cruse Study region Okavango Delta, Middle Kalahari, NW Botswana. Study focus We investigated the effect of evapotranspiration on the evolution of dissolved inorganic carbon (DIC) and stable carbon isotopes of DIC (δ 13 C DIC ) in the Okavango River. We measured the DIC concentrations and the δ 13 C DIC for samples collected over a 400 km reach of the river in the Okavango Delta during flood conditions and non-flood conditions. In addition, we incubated river samples collected from the proximal portion (Mohembo) and the distal portion (Maun) of the Delta and subsequently evaporated the samples by ∼90% under ambient conditions. New hydrological insights We found a 379% and 500% increase in the DIC concentrations and a δ 13 C DIC increase of 3.9‰ and 6.1‰ in the river during the flood non-flood conditions, respectively. The DIC concentrations of evaporated river samples increased by 535% for the Mohembo and by 850% for the Maun samples. The increase in the δ 13 C DIC of the evaporated river samples resulted from CO 2(g) loss during chemical equilibrium with atmospheric CO 2(g) followed by carbon exchange between DIC and atmospheric CO 2(g) . Although the δ 13 C DIC increased spatially for the Okavango River, it never reached the value of ∼0‰ expected for equilibration of river DIC with atmospheric CO 2(g) . The results of the evaporated river samples suggest that isotopic enrichment from equilibration in Okavango River was balanced by respiration and photo-oxidation of carbon-depleted dissolved organic matter.

Description: Publication date: Available online 24 March 2015 Source: Journal of Hydrology: Regional Studies Author(s): Jonathan Spinoni , Gustavo Naumann , Jürgen V. Vogt , Paulo Barbosa Study region Europe, including European Russia, but excluding Greenland, the Canary Islands, the Azores, and Madeira. Study focus Drought is a complex climate-related phenomenon that can affect different sectors causing economic, social, and environmental impacts. We focus on meteorological and hydrological droughts, defined as shortage of precipitation over several months and we discuss the biggest drought events in 1950–2012. To define such drought events we computed three drought indicators, the Standardized Precipitation Index, the Standardized Precipitation Evapotranspiration Index, and the Reconnaissance Drought Index and we merged them into a combined indicator at 3-month scale for meteorological and 12-month for hydrological droughts. The indicators have been calculated using the E-OBS gridded data (0.25° × 0.25°). New hydrological insights for the region Europe has been subdivided into thirteen regions and for each region we determined a list of drought events. The events have been characterized by the time, duration, severity, average area involved, peak month, and area involved at the peak month. We computed time series of the combined indicators for each region and country to determine the twenty-two biggest drought events in 1950–2012. Northern Europe and Russia show the highest drought frequency, duration, and severity in the 1950s and 1960s, where this is for the 1970s in Central Europe and the British Islands, and the 1990s and 2000s for the Mediterranean area and Baltic Republics.

Description: Publication date: March 2015 Source: Journal of Hydrology: Regional Studies, Volume 3, Supplement 1 Author(s): Hossein Tabari

Description: Publication date: March 2015 Source: Journal of Hydrology: Regional Studies, Volume 3, Supplement 1

Description: Publication date: March 2015 Source: Journal of Hydrology: Regional Studies, Volume 3, Supplement 1 Author(s): Huade Guan

Description: Publication date: March 2015 Source: Journal of Hydrology: Regional Studies, Volume 3, Supplement 1 Author(s): Luca Brocca

Description: Publication date: March 2015 Source: Journal of Hydrology: Regional Studies, Volume 3 Author(s): Ferdinand Beck , András Bárdossy , Jochen Seidel , Thomas Müller , Elvira Fernandez Sanchis , Andreas Hauser Study region The study was conducted with data from the city state of Singapore, a densely populated and highly urbanized island state close to the equator. Study focus The study provides a basic statistical characterization of Singapore's precipitation regime. It quantifies the effects of daily and yearly cycles and the connections to the El Niño Southern Oscillation and Sea Surface Temperature on hourly rainfall amounts. A regional regression analysis was applied to detect trends in hourly and daily precipitation extremes. New hydrological insights for the region • Rainfall events in the early morning and in the afternoon exhibit different spatio-temporal characteristics. • Singapore's precipitation activity is influenced by the El Niño Southern Oscillation, but not during the North-East Monsoon season. During the La Niña phase, seasonal precipitation totals are higher and the arrival of the most intense precipitation events is shifted towards morning hours. • The rainfall regime has been changing during the investigation period from 1981 to 2010. Rainfall totals as well as hourly and daily extremes increased. The increase in daily extremes was the fastest, changing the temporal scaling of the extremes. • The predicted changes in precipitation scaling towards higher daily sums have implications for the management of stormwater run-off.

Description: Publication date: March 2015 Source: Journal of Hydrology: Regional Studies, Volume 3 Author(s): Theresa M. Modrick , Konstantine P. Georgakakos Study region Small watersheds (O[25 km 2 ]) in the mountain regions of southern California comprise the study region. Study focus This paper examines changes in flash flood occurrence in southern California resulting from projected climatic change. The methodology synthesizes elements of meteorological modeling, hydrology and geomorphology into an integrated modeling approach to define flash flood occurrence in a systematic and consistent way on a regional basis with high spatial and temporal resolution appropriate for flash flooding. A single climate model with three-dimensional atmospheric detail was used as input to drive simulations for historical and future periods. New hydrological insights for the region Results indicate an increase in flash flood occurrence for the study region. For two distributed hydrologic models employed, the increase in flash flood occurrence frequency is on average between 30% and 40%. Regional flash flood occurrence is characterized by near saturation of the upper soil layer, and wider ranges in lower soil layer saturation and in precipitation. Overall, a decrease in the total number of precipitation events was found, although with increased precipitation intensity, increased event duration, and higher soil saturation conditions for the 21st century. This combination could signify more hazardous conditions, with fewer precipitation events but higher rainfall intensity and over soils with higher initial soil moisture saturation, leading to more frequent occurrence of flash floods.

Description: Publication date: March 2015 Source: Journal of Hydrology: Regional Studies, Volume 3 Author(s): M. Kopytkovskiy , M. Geza , J.E. McCray Study region The Upper Colorado River Basin (UCRB), comprised of the Colorado and Gunnison River basins, is the prime water source for much of the western United States. Study focus Future climate change models were used to drive a hydrologic model of the UCRB to evaluate future water resources and hydropower potential of the basin, using three different climate projections. The Intergovernmental Panel on Climate Change (IPCC) emission scenarios, the A2-business as usual, and the B1-reduced emissions scenarios were evaluated. More than 4500 water diversions and 17 reservoirs were incorporated into the hydrologic model. New hydrological insights for the region Precipitation projections from climate models vary up to 16%; flow projections revealed greater differences, up to 50%. The climate models projected increase in temperature at low elevations with extreme seasonality at high elevations, although summer temperatures increased at all elevations. The models projected a 60% decline in precipitation at lower elevations and a 74% increase at high elevations, although precipitation declined during the summer months at all elevations. Using the A2 scenario an overall decrease in annual flow was predicted, attributed to a reduction in precipitation and increasing temperature trends; however, this was not consistent during the winter months, which showed an increase in precipitation at high elevations and a modest temperature increase during the winter and resulted in an increase in stream flow. The responses to climate change on reservoir levels varied basin-wide due to variability in precipitation, evapotranspiration, and stream flow. Simulations indicated that water levels in Blue Mesa Reservoir (the largest reservoir in the UCRB) would decline by more than 70% with increasing annual temperatures. Reservoirs with smaller surface areas to the volume ratio were not significantly impacted by evapotranspiration. Our results indicate that hydropower management strategies in the UCRB must adapt to potential climate change, but the required adaptations are dependent on several factors including reservoir size and location.

Description: Publication date: Available online 2 April 2015 Source: Journal of Hydrology: Regional Studies Author(s): Shashank Shekhar , Roger S.K. Mao , Esther B. Imchen Study region North district of Delhi, India. Study focus The North district of Delhi has mostly shallow water levels and is a groundwater surplus region in contrast to the over-exploited aquifers of the region. The surface runoff and flood waters during monsoon season in the district either causes water logging in lower elevation areas or they join drains and rivers as rejected recharge. This study aims to understand groundwater dynamics of the region in perspective of the aquifer architecture and proposes groundwater management options to meet local water requirements. New hydrological insights in the region Three distinct hydrogeological domains are identified with subtle differences in groundwater occurrence. Insights are obtained in stream–aquifer interaction and baseflow to the Yamuna River is quantified. The salinity enrichment in groundwater has been attributed to water logging in clay rich formations under semi arid condition. The viability of limited dewatering of shallow aquifers and its replenishment by enhanced recharge from surface runoff and flood waters during the monsoon period have been established.

Description: Publication date: March 2015 Source: Journal of Hydrology: Regional Studies, Volume 3 Author(s): G. Seiller , I. Hajji , F. Anctil Study region Twenty diversified U.S. watersheds. Study focus Identifying optimal parameter sets for hydrological modeling on a specific catchment remains an important challenge for numerous applied and research projects. This is particularly the case when working under contrasted climate conditions that question the temporal transposability of the parameters. Methodologies exist, mainly based on Differential Split Sample Tests, to examine this concern. This work assesses the improved temporal transposability of a multimodel implementation, based on twenty dissimilar lumped conceptual structures and on twenty U.S. watersheds, over the performance of the individual models. New hydrological insights for the region Individual and collective temporal transposabilities are analyzed and compared on the twenty studied watersheds. Results show that individual models performances on contrasted climate conditions are very dissimilar depending on test period and watershed, without the possibility to identify a best solution in all circumstances. They also confirm that performance and robustness are clearly enhanced using an ensemble of rainfall-runoff models instead of individual ones. The use of (calibrated) weight averaged multimodels further improves temporal transposability over simple averaged ensemble, in most instances, confirming added-value of this approach but also the need to evaluate how individual models compensate each other errors.

Description: Publication date: March 2015 Source: Journal of Hydrology: Regional Studies, Volume 3 Author(s): Ibrahim Nourein Mohammed , Arne Bomblies , Beverley C. Wemple Study region Lake Champlain Basin, northwestern New England, USA. Study focus Our study uses regional hydrologic analyses and modeling to examine alternative possibilities that might emerge in the Lake Champlain Basin streamflow regime for various climate scenarios. Climate data as well as spatial data were processed to calibrate the Regional Hydro-Ecological Simulation System (RHESSys) model runoff simulations. The 21st century runoff simulations were obtained by driving the RHESSys model with climate data from the Coupled Model Intercomparison Project phase 5 (CMIP5) for representative concentration pathways RCP 4.5 and 8.5. New hydrological insights for the region Our analyses suggest that most of CMIP5 ensembles fail to capture both the trends and variability observed in historical precipitation when run in hindcast. This raises concerns of using such products in driving hydrologic models for the purpose of obtaining reliable runoff projections that can aid researchers in regional planning. A subset of five climate models among the CMIP5 ensembles have shown statistically significant trends in precipitation, but the magnitude of these trends is not adequately representative of those seen in observed annual precipitation. Adjusted precipitation forecasts project a streamflow regime described by an increase of about 30% in seven-day maximum flow, a four days increase in flooded days, a three orders of magnitude increase in base flow index, and a 60% increase in runoff predictability (Colwell index).

Description: Publication date: Available online 17 April 2015 Source: Journal of Hydrology: Regional Studies Author(s): Abhijit Mukherjee , Dipankar Saha , Charles F. Harvey , Richard G. Taylor , Kazi Matin Ahmed , Soumendra N. Bhanja The Indian Sub-Continent is one of the most densely populated regions of the world, hosting ∼23% of the global population within only ∼3% of the world's land area. It encompasses some of the world's largest fluvial systems in the world (River Brahmaputra, Ganges and Indus Basins), which hosts some of the highest yielding aquifers in the world. The distribution of usable groundwater in the region varies considerably and the continued availability of safe water from many of these aquifers (e.g. Bengal Basin) is constrained by the presence of natural contaminants. Further, the trans-boundary nature of the aquifers in the Indian Sub-Continent makes groundwater resource a potentially politically sensitive issue, particularly since this region is the largest user of groundwater resources in the world. Indeed, there is considerable concern regarding dwindling well yield and declining groundwater levels, even for the highly productive aquifers. Though irrigation already accounts for >85% of the total ground water extraction of the region, there is a mounting pressure on aquifers for food security of the region. Highly variable precipitation, hydrogeological conditions and predicted, impending climate change effects provide substantial challenges to groundwater management. The observed presence of natural groundwater contaminants together with the growing demand for irrigated food production and predicted climate change further complicate the development of strategies for using groundwater resources sustainably. We provide an introduction and overview of 11 articles, collated in this special issue, which describe the current condition of vulnerable groundwater resources across the Indian Sub-Continent.

Description: Publication date: September 2015 Source: Journal of Hydrology: Regional Studies, Volume 4, Part B Author(s): S.H.P.W. Gamage , G.A. Hewa , S. Beecham Study region The study is based on unregulated catchments located in Mt. Lofty, Northern and Yorke regions of South Australia (SA). Study focus Hydrological losses, which are frequently used in design flood estimation, have a wide range of spatial and temporal variability. However, the current practice for many design applications is to use a single loss value. Adopting a single representative value for loss is likely to introduce a high degree of uncertainty and potential bias. This paper identifies the relationships between losses and other parameters that can be incorporated in hydrological models to make reasonably accurate estimates of the losses. This paper assesses the variability of losses and identifies a method that can model initial loss (IL) using the parameters total rainfall (TR), rainfall duration ( D ) and antecedent wetness (AW). This study is based on 1162 rainfall events from the selected catchments. New hydrological insights for the region This paper introduces two nomographs, TR– D and TR–AW, which are implemented using k-colour maps and a central tendency method. The developed methods are then validated using the rainfall runoff model, Water Bound Network Model (WBNM). This study will yield improvements to existing loss models by utilising rainfall and antecedent data, instead of using representative values to generalise real situations.

Description: Publication date: September 2015 Source: Journal of Hydrology: Regional Studies, Volume 4, Part B Author(s): Christine A. Rumsey , Matthew P. Miller , David D. Susong , Fred D. Tillman , David W. Anning Study region The study region encompasses the Upper Colorado River Basin (UCRB), which provides water for 40 million people and is a vital part of the water supply in the western U.S. Study focus Groundwater and surface water can be considered a single water resource and thus it is important to understand groundwater contributions to streamflow, or baseflow, within a region. Previously, quantification of baseflow using chemical mass balance at large numbers of sites was not possible because of data limitations. A new method using regression-derived daily specific conductance values with conductivity mass balance hydrograph separation allows for baseflow estimation at sites across large regions. This method was applied to estimate baseflow discharge at 229 sites across the UCRB. Subsequently, climate, soil, topography, and land cover characteristics were statistically evaluated using principal component analysis (PCA) to determine their influence on baseflow discharge. New hydrological insights for the region Results suggest that approximately half of the streamflow in the UCRB is baseflow derived from groundwater discharge to streams. Higher baseflow yields typically occur in upper elevation areas of the UCRB. PCA identified precipitation, snow, sand content of soils, elevation, land surface slope, percent grasslands, and percent natural barren lands as being positively correlated with baseflow yield; whereas temperature, potential evapotranspiration, silt and clay content of soils, percent agriculture, and percent shrublands were negatively correlated with baseflow yield.

Description: Publication date: March 2015 Source: Journal of Hydrology: Regional Studies, Volume 3, Supplement 1