ALBERT

Description: 〈b〉A General Analytical Model for Head Response to Oscillatory Pumping in Unconfined Aquifers: Consider the Effects of Delayed Gravity Drainage and Initial Condition〈/b〉〈br〉 Ching-Sheng Huang, Ya-Hsin Tsai, Hund-Der Yeh, and Tao Yang〈br〉 Hydrol. Earth Syst. Sci. Discuss., https//doi.org/10.5194/hess-2018-482,2018〈br〉 〈b〉Manuscript under review for HESS〈/b〉 (discussion: open, 2 comments)〈br〉 This study develops a new model describing head fluctuation induced by oscillatory pumping test (OPT) in unconfined aquifer with the effects of delayed gravity drainage (DGD) and initial condition regarding the hydraulic head prior to OPT. The DGD reduces to instantaneous gravity drainage when a dimensionless parameter exceeds 500. A pseudo-steady state model excluding initial condition causes a time shift from the actual transient model in predicting simple harmonic motion of head fluctuation.

Description: 〈b〉Direct or indirect recharge on groundwater in the middle-latitude desert of Otindag, China?〈/b〉〈br〉 Bing-Qi Zhu, Xiao-Zong Ren, and Patrick Rioual〈br〉 Hydrol. Earth Syst. Sci. Discuss., https//doi.org/10.5194/hess-2018-395,2018〈br〉 〈b〉Manuscript under review for HESS〈/b〉 (discussion: open, 0 comments)〈br〉 Although rainfall is scarce in global deserts, the Otindag Desert is abundant of water resources (mainly groundwater). To understand the water origin in this desert, stable and radioactive isotopes and hydrochemistry of natural waters were investigated. The groundwaters in the desert were young but not of meteoric origin, i.e., out of control by the modern and palaeo- direct recharge. The tectonic control, but not the climate control, is essentially responsible for the water origin there.

Description: 〈b〉Stochastic hydrogeology's biggest hurdles analyzed and its big blind spot〈/b〉〈br〉 Yoram Rubin, Ching-Fu Chang, Jiancong Chen, Karina Cucchi, Bradley Harken, Falk Heße, and Heather Savoy〈br〉 Hydrol. Earth Syst. Sci., 22, 5675-5695, https://doi.org/10.5194/hess-22-5675-2018, 2018〈br〉 This paper addresses questions related to the adoption of stochastic methods in hydrogeology, looking at factors such as environmental regulations, financial incentives, higher education, and the collective feedback loop involving these factors. We show that stochastic hydrogeology's blind spot is in focusing on risk while ignoring uncertainty, to the detriment of its potential clients. The imbalance between the treatments of risk and uncertainty is shown to be common to multiple disciplines.

Description: 〈b〉Monitoring Groundwater Storage Depletion Using Gravity Recovery and Climate Experiment (GRACE) Data in the Semi-Arid Catchments〈/b〉〈br〉 Nizar Abou Zaki, Ali Torabi Haghighi, Pekka M. Rossi, Mohammad J. Tourian, and Bjørn Klove〈br〉 Hydrol. Earth Syst. Sci. Discuss., https//doi.org/10.5194/hess-2018-471,2018〈br〉 〈b〉Manuscript under review for HESS〈/b〉 (discussion: open, 0 comments)〈br〉 Groundwater is considered a main source of fresh water in semi-arid climatic zones, especially for agricultural usage. This study compares in-situ groundwater volume variation measurements with GRACE derived water mass data. The study concludes the possibility of using GRACE data to monitor groundwater depletion in catchments that lack measured data. GRACE data can here help in drawing general conclusions for integrated water resources management, and sustainable usage of this resources.

Description: 〈b〉Evaluation of soil moisture from CCAM-CABLE simulation, satellite based models estimates and satellite observations: Skukuza and Malopeni flux towers regional case study〈/b〉〈br〉 Floyd Vukosi Khosa, Mohau Jacob Mateyisi, Martina Reynita van Der Merwe, Gregor Timothy Feig, Francois Alwyn Engelbrecht, and Michael John Savage〈br〉 Hydrol. Earth Syst. Sci. Discuss., https//doi.org/10.5194/hess-2018-546,2018〈br〉 〈b〉Manuscript under review for HESS〈/b〉 (discussion: open, 0 comments)〈br〉 The paper evaluates soil moisture outputs from three structurally distinct models against in situ data. Our goal is to find how site and region representative the model outputs are. This is a question of interest as some of the models have a specific regional focus on their inceptions. Much focus is placed on how the models capture the soil moisture signal. We find that there is agreement on seasonal patterns between the models and observations with a tolerable level of model uncertainty.

Description: 〈b〉HESS Opinions: Incubating deep-learning-powered hydrologic science advances as a community〈/b〉〈br〉 Chaopeng Shen, Eric Laloy, Amin Elshorbagy, Adrian Albert, Jerad Bales, Fi-John Chang, Sangram Ganguly, Kuo-Lin Hsu, Daniel Kifer, Zheng Fang, Kuai Fang, Dongfeng Li, Xiaodong Li, and Wen-Ping Tsai〈br〉 Hydrol. Earth Syst. Sci., 22, 5639-5656, https://doi.org/10.5194/hess-22-5639-2018, 2018〈br〉 Recently, deep learning (DL) has emerged as a revolutionary tool for transforming industries and scientific disciplines. We argue that DL can offer a complementary avenue toward advancing hydrology. New methods are being developed to interpret the knowledge learned by deep networks. We argue that open competitions, integrating DL and process-based models, more data sharing, data collection from citizen scientists, and improved education will be needed to incubate advances in hydrology.

Description: 〈b〉Challenges to implementing bottom-up flood risk decision analysis frameworks: how strong are social networks of flooding professionals?〈/b〉〈br〉 James O. Knighton, Osamu Tsuda, Rebecca Elliott, and M. Todd Walter〈br〉 Hydrol. Earth Syst. Sci., 22, 5657-5673, https://doi.org/10.5194/hess-22-5657-2018, 2018〈br〉 Decision-making for flood risk management is often the collective effort of professionals within government, NGOs, private practice, and advocacy groups. Our research investigates differences among flood experts within Tompkins County, New York (USA). We explore how they differ in their perceptions of flooding risk, desired project outcomes, and knowledge. We observe substantial differences among experts, and recommend formally acknowledging these perceptions when engaging in flood management.

Description: 〈b〉Hess Opinions: Socio-economic and ecological trade-offs of flood management – benefits of a transdisciplinary approach〈/b〉〈br〉 Karl Auerswald, Peter Moyle, Simon Paul Seibert, and Juergen Geist〈br〉 Hydrol. Earth Syst. Sci. Discuss., https//doi.org/10.5194/hess-2018-544,2018〈br〉 〈b〉Manuscript under review for HESS〈/b〉 (discussion: open, 0 comments)〈br〉 The demand for flood protection often results in the construction of more and bigger levees along rivers. We highlight that such technical solutions often result in undesired socioeconomic and ecological consequences such as increased downstream flooding risk, changes of groundwater levels and a loss of aquatic and terrestrial biodiversity. We propose a transdisciplinary approach of integrated flood management and green infrastructure instead of reliance on technical protection measures.

Description: 〈b〉Quantification of seasonal variabilities in groundwater discharge in an extensive irrigation watershed using H, O, and Sr isotopes〈/b〉〈br〉 Takeo Yoshida, Takanori Nakano, Ki-cheol Shin, Takeo Tsuchihara, Hiroki Minakawa, Susumu Miyazu, and Tomijiro Kubota〈br〉 Hydrol. Earth Syst. Sci. Discuss., https//doi.org/10.5194/hess-2018-551,2018〈br〉 〈b〉Manuscript under review for HESS〈/b〉 (discussion: open, 0 comments)〈br〉 Irrigation for rice paddy accounts a large part of water use in watersheds, especially in the Asian countries. Although irrigation water is lost through vaporization by plants, some portion of the irrigation water recharge local aquifers and return to the original streams through subsurface pathways. However, quantifying the amount of water returning to the stream is not an easy task. We quantified the amount of return flow using 〈q〉colors of water〈/q〉, or environmental tracers dissolved in water.

Description: 〈b〉Climate change effects on the hydrology of the headwaters of the Tagus River: implications for the management of the Tagus–Segura transfer〈/b〉〈br〉 Francisco Pellicer-Martínez and José Miguel Martínez-Paz〈br〉 Hydrol. Earth Syst. Sci., 22, 6473-6491, https://doi.org/10.5194/hess-22-6473-2018, 2018〈br〉 Effects that climate change could have on the Tajo–Segura transfer are evaluated. To that, water resources that would be in the donor basin are estimated by hydrological modelling if the last climatic projections are accomplished. For these water resources, the exploitation of the transfer is simulated using a decision support system, providing volumes that could be transferred to the Segura basin according to its operating rule.

Description: 〈b〉Assessing the Added Value of the Intermediate Complexity Atmospheric Research Model (ICAR) for Precipitation in Complex Topography〈/b〉〈br〉 Johannes Horak, Marlis Hofer, Fabien Maussion, Ethan Gutmann, Alexander Gohm, and Mathias W. Rotach〈br〉 Hydrol. Earth Syst. Sci. Discuss., https//doi.org/10.5194/hess-2018-612,2018〈br〉 〈b〉Manuscript under review for HESS〈/b〉 (discussion: open, 1 comment)〈br〉 This study presents the first in-depth evaluation of the Intermediate Complexity Atmospheric Research model (ICAR) for high resolution precipitation fields. The model is evaluated with data from weather stations located in the Southern Alps of New Zealand. While ICAR underestimates rainfall amounts, it clearly improves over a coarser global model and shows the potential to generate precipitation fields for long-term impact studies focused on the local impact of a changing global climate.

Description: 〈b〉Numerical study on the response of the largest lake in China to climate change〈/b〉〈br〉 Dongsheng Su, Xiuqing Hu, Lijuan Wen, Lin Zhao, Zhaoguo Li, Juan Du, and Georgiy Kirillin〈br〉 Hydrol. Earth Syst. Sci. Discuss., https//doi.org/10.5194/hess-2018-583,2018〈br〉 〈b〉Manuscript under review for HESS〈/b〉 (discussion: open, 0 comments)〈br〉 In this study, Freshwater Lake Model simulation results, verified by satellite and buoy observation data, were used to quantify the recent climate change effects on the thermal regime of the largest lake in China. Results indicate that the FLake model can nicely reproduce the lake thermal pattern. The lake surface is warming while the lake bottom has no significant trend. The climate change also caused an earlier ice off and later ice on, lead to an obvious change on the energy balance of lake.

Description: 〈b〉Caffeine vs. carbamazepine as indicators of wastewater pollution in a karst aquifer〈/b〉〈br〉 Noam Zach Dvory, Yakov Livshitz, Michael Kuznetsov, Eilon Adar, Guy Gasser, Irena Pankratov, Ovadia Lev, and Alexander Yakirevich〈br〉 Hydrol. Earth Syst. Sci., 22, 6371-6381, https://doi.org/10.5194/hess-22-6371-2018, 2018〈br〉 This research is paramount given the significance of karst aquifers as essential drinking water sources. While CBZ is considered conservative, CAF is subject to sorption and degradation, and therefore each of these two pollutants can be considered effective tracers for specific assessment of aquifer contamination. The model presented in this paper shows how each of the mentioned contaminants could serve as a better tool for aquifer contamination characterization and its treatment.

Description: 〈b〉Large-scale ERT surveys for investigating shallow regolith properties and architecture〈/b〉〈br〉 Laurent Gourdol, Rémi Clément, Jérôme Juilleret, Laurent Pfister, and Christophe Hissler〈br〉 Hydrol. Earth Syst. Sci. Discuss., https//doi.org/10.5194/hess-2018-519,2018〈br〉 〈b〉Manuscript under review for HESS〈/b〉 (discussion: open, 0 comments)〈br〉 Electrical Resistivity Tomography (ERT) is a remarkable tool for characterizing the geometry and properties of the regolith. However, its use for large horizontal surveys remains cumbersome to characterize shallow subsurface structures due to the requirement of small electrode spacing increments. Here we propose a new approach to overcome this limitation. We demonstrate that our protocol significantly improves the accuracy of ERT profiles when using large electrode spacing increments.

Description: 〈b〉A propensity index for surface runoff on a karst plateau〈/b〉〈br〉 Christian Reszler, Jürgen Komma, Hermann Stadler, Elmar Strobl, and Günter Blöschl〈br〉 Hydrol. Earth Syst. Sci., 22, 6147-6161, https://doi.org/10.5194/hess-22-6147-2018, 2018〈br〉 Karst aquifers are vulnerable to pollution due to the typically short particle travel times. As the rainwater runs off on the surface it may collect contamination before infiltrating. This paper proposes a new field-mapping method for the ability of the landscape to produce and convey surface runoff. The method is based on local data collection in the field, and a visual assessment of surface runoff traces from a distance, which makes it suitable for larger areas than traditional field mapping.

Description: 〈b〉Analysis of combined and isolated effects of land-use and land-cover changes and climate change on the upper Blue Nile River basin's streamflow〈/b〉〈br〉 Dagnenet Fenta Mekonnen, Zheng Duan, Tom Rientjes, and Markus Disse〈br〉 Hydrol. Earth Syst. Sci., 22, 6187-6207, https://doi.org/10.5194/hess-22-6187-2018, 2018〈br〉 Understanding responses by changes in land use and land cover (LULC) and climate over the past decades on streamflow in the upper Blue Nile River basin is important for water management and water resource planning. Streamflow in the UBNRB has shown an increasing trend over the last 40 years, while rainfall has shown no trend change. LULC change detection findings indicate increases in cultivated land and decreases in forest coverage prior to 1995.

Description: 〈b〉Controls of fluorescent tracer retention by soils and sediments〈/b〉〈br〉 Marcus Bork, Jens Lange, Markus Graf-Rosenfellner, and Friederike Lang〈br〉 Hydrol. Earth Syst. Sci. Discuss., https//doi.org/10.5194/hess-2018-549,2018〈br〉 〈b〉Manuscript under review for HESS〈/b〉 (discussion: open, 0 comments)〈br〉 Fluorescent tracers such as uranine and sulforhodamine B are useful tools to gain knowledge about water and solute fluxes in aquatic and terrestrial ecosystems. In batch experiments, we investigated systematically the influence of pH, organic carbon and texture on tracer adsorption on soils and sediments and quantified their impact and possible interactions. Overall, the investigated controls determine if the respective tracer shows more conservative or more non-conservative transport behaviour.

Description: 〈b〉Toward a conceptual framework of hyporheic exchange across spatial scales〈/b〉〈br〉 Chiara Magliozzi, Robert C. Grabowski, Aaron I. Packman, and Stefan Krause〈br〉 Hydrol. Earth Syst. Sci., 22, 6163-6185, https://doi.org/10.5194/hess-22-6163-2018, 2018〈br〉 The hyporheic zone is the area below riverbeds where surfacewater and groundwater mix. Hyporheic flow is linked to river processes and functions, but research to date has not sufficiently addressed how factors operating at different scales in time and space drive hyporheic flow variations at reach and larger scales. This review presents the scale-specific processes and interactions that control hyporheic flow, and a case study showing how valley factors affect its expression at the reach scale.

Description: 〈b〉How does initial soil moisture influence the hydrological response? A case study from southern France〈/b〉〈br〉 Magdalena Uber, Jean-Pierre Vandervaere, Isabella Zin, Isabelle Braud, Maik Heistermann, Cédric Legoût, Gilles Molinié, and Guillaume Nord〈br〉 Hydrol. Earth Syst. Sci., 22, 6127-6146, https://doi.org/10.5194/hess-22-6127-2018, 2018〈br〉 We investigate how rivers in a flash-flood-prone region in southern France respond to rainfall depending on initial soil moisture. Therefore, high-resolution data of rainfall, river discharge and soil moisture were used. We find that during dry initial conditions, the rivers hardly respond even for heavy rain events, but for wet initial conditions, the response remains unpredictable: for some rain events almost all rainfall is transformed to discharge, whereas this is not the case for others.

Description: 〈b〉Dynamic responses of DOC and DIC transport to different flow regimes in a subtropical small mountainous river〈/b〉〈br〉 Yu-Ting Shih, Pei-Hao Chen, Li-Chin Lee, Chien-Sen Liao, Shih-Hao Jien, Fuh-Kwo Shiah, Tsung-Yu Lee, Thomas Hein, Franz Zehetner, Chung-Te Chang, and Jr-Chuan Huang〈br〉 Hydrol. Earth Syst. Sci., 22, 6579-6590, https://doi.org/10.5194/hess-22-6579-2018, 2018〈br〉 DOC and DIC export in Taiwan shows that the annual DOC and DIC fluxes were 2.7–4.8 and 48.4–54.3 ton C km〈sup〉2〈/sup〉 yr〈sup〉1〈/sup〉, respectively, which were approximately 2 and 20 times higher than the global means of 1.4 and 2.6 ton C km〈sup〉2〈/sup〉 yr〈sup〉1〈/sup〉, respectively.

Description: 〈b〉Modeling experiments on seasonal lake ice mass and energy balance in Qinghai-Tibet Plateau: A case study〈/b〉〈br〉 Wenfeng Huang, Bin Cheng, Jinrong Zhang, Zheng Zhang, Timo Vihma, Zhijun Li, and Fujun Niu〈br〉 Hydrol. Earth Syst. Sci. Discuss., https//doi.org/10.5194/hess-2018-616,2018〈br〉 〈b〉Manuscript under review for HESS〈/b〉 (discussion: open, 0 comments)〈br〉 Up to now, little is known on ice thermodynamics and lake-atmosphere interaction over Tibetan Plateau during ice-covered seasons due to a lack of field data. In this study, model experiments on ice thermodynamics were conducted in a shallow lake using HIGHTSI. Water-ice heat flux was a major source of uncertainty for lake ice thickness. Heat and mass budgets were estimated within the vertical air-ice-water system. Strong ice sublimation occurred and was responsible for water loss during winter.

Description: 〈b〉Evaluation of drought representation and propagation in Regional Climate Model simulations over Spain〈/b〉〈br〉 Anaïs Barella-Ortiz and Pere Quintana-Seguí〈br〉 Hydrol. Earth Syst. Sci. Discuss., https//doi.org/10.5194/hess-2018-603,2018〈br〉 〈b〉Manuscript under review for HESS〈/b〉 (discussion: open, 0 comments)〈br〉 Drought is an important climatic risk. Its representation and propagation by regional climate models from Med-CORDEX simulations is analysed using standardized indices. Results show that these models improve meteorological drought representation, but large uncertainties are identified in its propagation and the way soil moisture and hydrological droughts are characterised. These are mainly due to model formulation, making necessary further improvements in land surface modelling.

Description: 〈b〉On the uncertainty of initial condition and initialization approaches in variably saturated flow modeling〈/b〉〈br〉 Danyang Yu, Jinzhong Yang, Liangsheng Shi, Qiuru Zhang, Kai Huang, Yuanhao Fang, and Yuanyuan Zha〈br〉 Hydrol. Earth Syst. Sci. Discuss., https//doi.org/10.5194/hess-2018-557,2018〈br〉 〈b〉Manuscript under review for HESS〈/b〉 (discussion: open, 0 comments)〈br〉 Soil water movement is quite important due to its direct effects on environment, agriculture and hydrology. Simulation of soil water movement requires accurate determination of model parameters as well as initial and boundary conditions. However, it is difficult to obtain the accurate initial soil moisture/matric potential profile at the beginning of simulation time, making it necessary to run the simulation model from arbitrary initial condition until the uncertainty of initial condition (UIC) is diminished. The behavior of this process is usually defined as “warming up”. In this paper, two common methods in quantifying the UIC (one is based on running a single simulation recursively across multiple hydrological years, and the other is based on Monte-Carlo simulations with various initial condition) are compared and the required “warm-up” time twu (minimum time required for model to warm up to eliminate the UIC) is identified with different soil textures, meteorological conditions, and soil profile lengths. Then we analyze the effects of different initial conditions on parameter estimation within two data assimilation frameworks (i.e, ensemble Kalman filter and iterative ensemble smoother), and assess several existing model initializing methods to obtain initial condition based on the availability of data related to the retrieval of initial soil moisture profile. Results reveal that Monte-Carlo simulations and the recursive simulation over many years can both demonstrate the temporal behavior of UIC and a common threshold is recommended to determine the warm-up time for both methods. Besides, the relationship between warm-up time for variably saturated flow modeling and the model settings (soil textures, meteorological conditions and soil profile length) are quantitatively identified. In addition, we propose a “warm-up” period before assimilating data in order to obtain a better performance of parameter and state estimation.

Description: 〈b〉Observation operators for assimilation of satellite observations in fluvial inundation forecasting〈/b〉〈br〉 Elizabeth S. Cooper, Sarah L. Dance, Javier García-Pintado, Nancy K. Nichols, and Polly Smith〈br〉 Hydrol. Earth Syst. Sci. Discuss., https//doi.org/10.5194/hess-2018-589,2018〈br〉 〈b〉Manuscript under review for HESS〈/b〉 (discussion: open, 0 comments)〈br〉 Flooding from rivers is a huge and costly problem worldwide. Computer simulations can help to warn people if and when they are likely to be affected by river flood water, but such predictions are not always accurate or reliable. Information about flood extent from satellites can help keep these forecasts on track. Here we investigate different ways of using information from satellite images, and look at the effect on computer predictions. This will help to develop flood warning systems.

Description: 〈b〉Estimating radar precipitation in cold climates: the role of air temperature within a non-parametric framework〈/b〉〈br〉 Kuganesan Sivasubramaniam, Ashish Sharma, and Knut Alfredsen〈br〉 Hydrol. Earth Syst. Sci., 22, 6533-6546, https://doi.org/10.5194/hess-22-6533-2018, 2018〈br〉 This study investigates the use of gauge precipitation and air temperature observations to ascertain radar precipitation in cold climates. The use of air temperature as an additional variable in a non-parametric model improved the estimation of radar precipitation significantly. Further, it was found that the temperature effects became insignificant when air temperature was above 10 °C. The findings from this study could be important for using radar precipitation for hydrological applications.

Description: 〈b〉Modelling the high-resolution dynamic exposure to flood in city-region〈/b〉〈br〉 Xuehong Zhu, Qiang Dai, Dawei Han, Lu Zhuo, Shaonan Zhu, and Shuliang Zhang〈br〉 Hydrol. Earth Syst. Sci. Discuss., https//doi.org/10.5194/hess-2018-590,2018〈br〉 〈b〉Manuscript under review for HESS〈/b〉 (discussion: open, 0 comments)〈br〉 Urban flooding exposure is generally investigated with the assumption of stationary disasters and disaster-bearing bodies within an event, and thus cannot satisfy the increasingly elaborative modelling and management of urban flood. In this study, a comprehensive method was developed to simulate dynamic exposure to urban flooding considering residents’ travel behavior. Several scenarios, including diverse flooding types and various responses of residents to flooding, were considered.

Description: 〈b〉Developing a drought-monitoring index for the contiguous US using SMAP〈/b〉〈br〉 Sara Sadri, Eric F. Wood, and Ming Pan〈br〉 Hydrol. Earth Syst. Sci., 22, 6611-6626, https://doi.org/10.5194/hess-22-6611-2018, 2018〈br〉 Of particular interest to NASA's SMAP-based agricultural applications is a monitoring product that assesses near-surface soil moisture in terms of probability percentiles for dry and wet conditions. However, the short SMAP record length poses a statistical challenge for the meaningful assessment of its indices. This study presents initial insights about using SMAP Level 3 and Level 4 for monitoring drought and pluvial regions with a first application over the contiguous United States (CONUS).

Description: 〈b〉A review of methods for measuring groundwater–surface water exchange in braided rivers〈/b〉〈br〉 Katie Coluccio and Leanne Kaye Morgan〈br〉 Hydrol. Earth Syst. Sci. Discuss., https//doi.org/10.5194/hess-2018-566,2018〈br〉 〈b〉Manuscript under review for HESS〈/b〉 (discussion: open, 0 comments)〈br〉 Braided rivers are uncommon internationally but are important freshwater resources. However, there is limited understanding of how characteristics unique to braided rivers affect groundwater–surface water flow paths. This article reviews prior studies that have investigated groundwater–surface water interactions in these rivers and their associated aquifers to provide guidance on methodologies most suitable for future work in braided rivers and highlight gaps in current knowledge.

Description: 〈b〉The probability distribution of daily precipitation at the point and catchment scales in the United States〈/b〉〈br〉 Lei Ye, Lars S. Hanson, Pengqi Ding, Dingbao Wang, and Richard M. Vogel〈br〉 Hydrol. Earth Syst. Sci., 22, 6519-6531, https://doi.org/10.5194/hess-22-6519-2018, 2018〈br〉 〈p〉Choosing a probability distribution to represent daily precipitation depths is important for precipitation frequency analysis, stochastic precipitation modeling and in climate trend assessments. Early studies identified the two-parameter gamma (G2) distribution as a suitable distribution for wet-day precipitation based on the traditional goodness-of-fit tests. Here, probability plot correlation coefficients and L-moment diagrams are used to examine distributional alternatives for the wet-day series of daily precipitation for hundreds of stations at the point and catchment scales in the United States. Importantly, both Pearson Type-III (P3) and kappa (KAP) distributions perform very well, particularly for point rainfall. Our analysis indicates that the KAP distribution best describes the distribution of wet-day precipitation at the point scale, whereas the performance of G2 and P3 distributions are comparable for wet-day precipitation at the catchment scale, with P3 generally providing the improved goodness of fit over G2. Since the G2 distribution is currently the most widely used probability density function, our findings could be considerably important, especially within the context of climate change investigations.〈/p〉

Description: 〈b〉On the skill of raw and post-processed ensemble seasonal meteorological forecasts in Denmark〈/b〉〈br〉 Diana Lucatero, Henrik Madsen, Jens C. Refsgaard, Jacob Kidmose, and Karsten H. Jensen〈br〉 Hydrol. Earth Syst. Sci., 22, 6591-6609, https://doi.org/10.5194/hess-22-6591-2018, 2018〈br〉 The present study evaluates the skill of a seasonal forecasting system for hydrological relevant variables in Denmark. Linear scaling and quantile mapping were used to correct the forecasts. Uncorrected forecasts tend to be more skillful than climatology, in general, for the first month lead time only. Corrected forecasts show a reduced bias in the mean; are more consistent; and show a level of accuracy that is closer to, although no higher than, that of ensemble climatology, in general.

Description: 〈b〉A new probability density function for spatial distribution of soil water storage capacity leads to the SCS curve number method〈/b〉〈br〉 Dingbao Wang〈br〉 Hydrol. Earth Syst. Sci., 22, 6567-6578, https://doi.org/10.5194/hess-22-6567-2018, 2018〈br〉 A novel distribution function is proposed for describing the spatial distribution of soil water storage capacity, and then the classical and empirical hydrologic model (the SCS curve number method) is derived as when the initial soil water storage is zero. This distribution function unifies the SCS curve number method and probability-distributed models such as the VIC and Xinanjiang models. The unified model provides a better way for modeling surface runoff.

Description: 〈b〉Locality-based 3-D multiple-point statistics reconstruction using 2-D geological cross sections〈/b〉〈br〉 Qiyu Chen, Gregoire Mariethoz, Gang Liu, Alessandro Comunian, and Xiaogang Ma〈br〉 Hydrol. Earth Syst. Sci., 22, 6547-6566, https://doi.org/10.5194/hess-22-6547-2018, 2018〈br〉 One of the critical issues in MPS simulation is the difficulty in obtaining a credible 3-D training image. We propose an MPS-based 3-D reconstruction method on the basis of 2-D cross sections, making 3-D training images unnecessary. The main advantages of this approach are the high computational efficiency and a relaxation of the stationarity assumption. The results, in comparison with previous MPS methods, show better performance in portraying anisotropy characteristics and in CPU cost.

Description: 〈b〉Application of an improved global-scale groundwater model for water table estimation across New Zealand〈/b〉〈br〉 Rogier Westerhoff, Paul White, and Gonzalo Miguez-Macho〈br〉 Hydrol. Earth Syst. Sci., 22, 6449-6472, https://doi.org/10.5194/hess-22-6449-2018, 2018〈br〉 Our study improved a global-scale groundwater model to build the first nationwide estimate of the water table surface in New Zealand. By identifying the main alluvial aquifers with high spatial detail, we showed that this model can help better delineate aquifer boundaries. In catchment studies we demonstrated excellent correlation with ground observations and provided water table estimates where data were sparse and across regions, which could help solve trans-boundary issues between catchments.

Description: 〈b〉Spatial variability of mean daily estimates of actual evaporation from remotely sensed imagery and surface reference data〈/b〉〈br〉 Robert N. Armstrong, John W. Pomeroy, and Lawrence W. Martz〈br〉 Hydrol. Earth Syst. Sci. Discuss., https//doi.org/10.5194/hess-2018-600,2018〈br〉 〈b〉Manuscript under review for HESS〈/b〉 (discussion: open, 0 comments)〈br〉 Digital and thermal images taken near midday were used to scale daily point observations of key factors driving actual evaporation estimates across a complex Canadian prairie landscape. Point estimates of actual evaporation agreed well with observed values via eddy covariance. Impacts of spatial variations on areal estimates were minor and no covariance was found between model parameters driving the energy term. The methods can be applied further to improve land surface parameterisations.

Description: 〈b〉Copula and ARMA based study of controlled outflow at Farakka barrage〈/b〉〈br〉 Uttam Singh, Venkappayya R. Desai, Pramod K. Sharma, and Chandra S. P. Ojha〈br〉 Hydrol. Earth Syst. Sci. Discuss., https//doi.org/10.5194/hess-2018-380,2018〈br〉 〈b〉Manuscript under review for HESS〈/b〉 (discussion: open, 0 comments)〈br〉 In this study, 25 years mean monthly out flow discharge data of Farakka barrage was used (i.e., from 1949 to 1968). Farakka barrage is located between on Ganga River. Spatial and temporal variation in flow rate for any particular area is very common due to various meteorological and other factors existing in nature.

Description: 〈b〉Redressing the balance: quantifying net intercatchment groundwater flows〈/b〉〈br〉 Laurène Bouaziz, Albrecht Weerts, Jaap Schellekens, Eric Sprokkereef, Jasper Stam, Hubert Savenije, and Markus Hrachowitz〈br〉 Hydrol. Earth Syst. Sci., 22, 6415-6434, https://doi.org/10.5194/hess-22-6415-2018, 2018〈br〉 We quantify net intercatchment groundwater flows in the Meuse basin in a complementary three-step approach through (1) water budget accounting, (2) testing a set of conceptual hydrological models and (3) evaluating against remote sensing actual evaporation data. We show that net intercatchment groundwater flows can make up as much as 25 % of mean annual precipitation in the headwaters and should therefore be accounted for in conceptual models to prevent overestimating actual evaporation rates.

Description: 〈b〉Multi-model approach to quantify groundwater level prediction uncertainty using an ensemble of global climate models and multiple abstraction scenarios〈/b〉〈br〉 Syed M. Touhidul Mustafa, M. Moudud Hasan, Ajoy Kumar Saha, Rahena Parvin Rannu, Els Van Uytven, Patrick Willems, and Marijke Huysmans〈br〉 Hydrol. Earth Syst. Sci. Discuss., https//doi.org/10.5194/hess-2018-580,2018〈br〉 〈b〉Manuscript under review for HESS〈/b〉 (discussion: open, 0 comments)〈br〉 〈p〉Worldwide, groundwater resources are under a constant threat of overexploitation and pollution due to anthropogenic and climatic pressures. For sustainable management and policy making a reliable prediction of groundwater levels for different future scenarios is necessary. Uncertainties are present in these groundwater level predictions and originate from greenhouse gas scenarios, climate models, conceptual hydro(geo)logical models (CHMs) and groundwater abstraction scenarios. The aim of this study is to quantify the individual uncertainty contributions using an ensemble of 2 greenhouse gas scenarios (representative concentration pathway 4.5 and 8.5), 22 global climate models, 15 alternative CHMs and 5 groundwater abstraction scenarios. This multi-model ensemble approach was applied to a drought prone study area in Bangladesh. Findings of this study, firstly, point at the strong dependence of the groundwater levels on the CHMs considered. All groundwater abstraction scenarios showed a significant decrease in groundwater levels. If the current groundwater abstraction trend continues, the groundwater level is predicted to decline about 5 to 6 times faster for the future period 2026–2047 compared to the baseline period (1985–2006). Even with a 30 % lower groundwater abstraction rate, the mean monthly groundwater level would decrease by up to 14 m in the southwestern part of the study area. The groundwater abstraction in the northwestern part of Bangladesh has to reduce by 60 % of the current abstraction to ensure sustainable use of groundwater. Finally, the difference in abstraction scenarios was identified as the dominant uncertainty source. CHM uncertainty contributed about 23 % of total uncertainty. The alternative CHM uncertainty contribution is higher than the recharge scenario uncertainty contribution, including the greenhouse gas scenario and climate model uncertainty contributions. It is recommended that future groundwater level prediction studies should use multi-model and multiple climate and abstraction scenarios.〈/p〉

Description: 〈b〉An assessment of trends and potential future changes in groundwater-baseflow drought based on catchment response times〈/b〉〈br〉 Jost Hellwig and Kerstin Stahl〈br〉 Hydrol. Earth Syst. Sci., 22, 6209-6224, https://doi.org/10.5194/hess-22-6209-2018, 2018〈br〉 Due to the lack of long-term observations, insights into changes of groundwater resources are obscured. In this paper we assess past and potential future changes in groundwater drought in headwater catchments using a baseflow approach. There are a few past trends which are highly dependent on the period of analysis. Catchments with short response times are found to have a higher sensitivity to projected seasonal precipitation shifts, urging for a local management based on response times.

Description: 〈b〉Rainfall–runoff modelling using Long Short-Term Memory (LSTM) networks〈/b〉〈br〉 Frederik Kratzert, Daniel Klotz, Claire Brenner, Karsten Schulz, and Mathew Herrnegger〈br〉 Hydrol. Earth Syst. Sci., 22, 6005-6022, https://doi.org/10.5194/hess-22-6005-2018, 2018〈br〉 In this paper, we propose a novel data-driven approach for rainfall–runoff modelling, using the long short-term memory (LSTM) network, a special type of recurrent neural network. We show in three different experiments that this network is able to learn to predict the discharge purely from meteorological input parameters (such as precipitation or temperature) as accurately as (or better than) the well-established Sacramento Soil Moisture Accounting model, coupled with the Snow-17 snow model.

Description: 〈b〉Technical note: Mapping surface-saturation dynamics with thermal infrared imagery〈/b〉〈br〉 Barbara Glaser, Marta Antonelli, Marco Chini, Laurent Pfister, and Julian Klaus〈br〉 Hydrol. Earth Syst. Sci., 22, 5987-6003, https://doi.org/10.5194/hess-22-5987-2018, 2018〈br〉 We demonstrate how thermal infrared images can be used for mapping the appearance and disappearance of water at the surface. The use of thermal infrared images allows for mapping this appearance and disappearance for various temporal and spatial resolutions, and the images can be understood intuitively. We explain the necessary steps in detail, from image acquisition to final processing, by relying on image examples and experience from an 18-month mapping campaign.

Description: 〈b〉Inundation mapping based on reach-scale effective geometry〈/b〉〈br〉 Cédric Rebolho, Vazken Andréassian, and Nicolas Le Moine〈br〉 Hydrol. Earth Syst. Sci., 22, 5967-5985, https://doi.org/10.5194/hess-22-5967-2018, 2018〈br〉 Inundation models are useful for hazard management and prevention. They are traditionally based on hydraulic partial differential equations (with satisfying results but large data and computational requirements). This study presents a simplified approach combining reach-scale geometric properties with steady uniform flow equations. The model shows promising results overall, although difficulties persist in the most complex urbanised reaches.

Description: 〈b〉The effect of input data resolution and complexity on the uncertainty of hydrological predictions in a humid vegetated watershed〈/b〉〈br〉 Linh Hoang, Rajith Mukundan, Karen E. B. Moore, Emmet M. Owens, and Tammo S. Steenhuis〈br〉 Hydrol. Earth Syst. Sci., 22, 5947-5965, https://doi.org/10.5194/hess-22-5947-2018, 2018〈br〉 The paper analyzes the effect of two input data (DEMs and the combination of soil and land use data) with different resolution and complexity on the uncertainty of model outputs (the predictions of streamflow and saturated areas) and parameter uncertainty using SWAT-HS. Results showed that DEM resolution has significant effect on the spatial pattern of saturated areas and using complex soil and land use data may not necessarily improve model performance or reduce model uncertainty.

Description: 〈b〉Exploring seasonal and regional relationships between the Evaporative Stress Index and surface weather and soil moisture anomalies across the United States〈/b〉〈br〉 Jason A. Otkin, Yafang Zhong, David Lorenz, Martha C. Anderson, and Christopher Hain〈br〉 Hydrol. Earth Syst. Sci., 22, 5373-5386, https://doi.org/10.5194/hess-22-5373-2018, 2018〈br〉 Correlation analyses were used to explore relationships between the Evaporative Stress Index (ESI) – which depicts anomalies in evapotranspiration (ET) – and various land and atmospheric variables that impact ET. The results revealed that the ESI is more strongly correlated to anomalies in soil moisture and near-surface vapor pressure deficit than to precipitation and temperature anomalies. Large regional and seasonal dependencies in the strengths of the correlations were also observed.

Description: 〈b〉Global downscaling of remotely sensed soil moisture using neural networks〈/b〉〈br〉 Seyed Hamed Alemohammad, Jana Kolassa, Catherine Prigent, Filipe Aires, and Pierre Gentine〈br〉 Hydrol. Earth Syst. Sci., 22, 5341-5356, https://doi.org/10.5194/hess-22-5341-2018, 2018〈br〉 A new machine learning algorithm is developed to downscale satellite-based soil moisture estimates from their native spatial scale of 9 km to 2.25 km.

Description: 〈b〉Hydrological modelling and future runoff of the Damma Glacier CZO watershed using SWAT. Validation of the model in the greater area of the Göscheneralpsee, Switzerland〈/b〉〈br〉 Maria Andrianaki, Juna Shrestha, Florian Kobierska, Nikolaos P. Nikolaidis, and Stefano M. Bernasconi〈br〉 Hydrol. Earth Syst. Sci. Discuss., https//doi.org/10.5194/hess-2018-493,2018〈br〉 〈b〉Manuscript under review for HESS〈/b〉 (discussion: open, 0 comments)〈br〉 We studied the hydrology of the Damma glacier watershed and the impact of climate change, by applying the model SWAT. Climate change scenarios showed that runoff will change significantly in the future. Future daily runoff in May and June, is predicted to increase. However, future runoff from July to October is significantly decreased. These results proved that SWAT can be used for a glacierised watershed and can be a useful tool for water managers and policy makers.

Description: 〈b〉Discharge hydrograph estimation at upstream-ungauged sections by coupling a Bayesian methodology and a 2-D GPU shallow water model〈/b〉〈br〉 Alessia Ferrari, Marco D'Oria, Renato Vacondio, Alessandro Dal Palù, Paolo Mignosa, and Maria Giovanna Tanda〈br〉 Hydrol. Earth Syst. Sci., 22, 5299-5316, https://doi.org/10.5194/hess-22-5299-2018, 2018〈br〉 The knowledge of discharge hydrographs is useful for flood modelling purposes, water resource management, and the design of hydraulic structures. This paper presents a novel methodology to estimate the unknown discharge hydrograph in an ungauged river section using only water level information recorded downstream. A Bayesian procedure is coupled with a 2-D hydraulic model parallelized for GPUs. Finally, the proposed procedure has been applied to estimate inflow hydrographs in real river reaches.

Description: 〈b〉Using a multi-hypothesis framework to improve the understanding of flow dynamics during flash floods〈/b〉〈br〉 Audrey Douinot, Hélène Roux, Pierre-André Garambois, and Denis Dartus〈br〉 Hydrol. Earth Syst. Sci., 22, 5317-5340, https://doi.org/10.5194/hess-22-5317-2018, 2018〈br〉 The distributed, process-oriented model, MARINE, was used to test several hypotheses of flow dynamics in soils during flash flood events in the Mediterranean area. Results show that the most realistic hypothesis for each catchment is consistent with existing in situ observations and measurements. The study also highlights the potential of distributed modelling and spatial observations in hydrology, especially in dealing with equifinality issues.

Description: 〈b〉Value of uncertain streamflow observations for hydrological modelling〈/b〉〈br〉 Simon Etter, Barbara Strobl, Jan Seibert, and H. J. Ilja van Meerveld〈br〉 Hydrol. Earth Syst. Sci., 22, 5243-5257, https://doi.org/10.5194/hess-22-5243-2018, 2018〈br〉 To evaluate the potential value of streamflow estimates for hydrological model calibration, we created synthetic streamflow datasets in various temporal resolutions based on the errors in streamflow estimates of 136 citizens. Our results show that streamflow estimates of untrained citizens are too inaccurate to be useful for model calibration. If, however, the errors can be reduced by training or filtering, the estimates become useful if also a sufficient number of estimates are available.

Description: 〈b〉Estimation of Evapotranspiration and Other Soil Water Budget Components in an Irrigated Agricultural Field of a Desert Oasis, Using Soil Moisture Measurements〈/b〉〈br〉 Zhongkai Li, Hu Liu, Wenzhi Zhao, Qiyue Yang, Rong Yang, and Jintao Liu〈br〉 Hydrol. Earth Syst. Sci. Discuss., https//doi.org/10.5194/hess-2018-518,2018〈br〉 〈b〉Manuscript under review for HESS〈/b〉 (discussion: open, 1 comment)〈br〉 A database of soil moisture measurements was used to test the potential of a soil moisture database in estimating the SWBCs. Although the planting of the past decade have significantly increased the soils' water-holding ability, the magnitude of increase in most of the parameters was independent of the treatments. Significant variances were observed among the plots in both the cumulative irrigation volumes and deep drainages, and the ET demands for all the plots behaved pretty much the same.

Description: 〈b〉Rainfall disaggregation for hydrological modeling: is there a need for spatial consistence?〈/b〉〈br〉 Hannes Müller-Thomy, Markus Wallner, and Kristian Förster〈br〉 Hydrol. Earth Syst. Sci., 22, 5259-5280, https://doi.org/10.5194/hess-22-5259-2018, 2018〈br〉 Rainfall time series are disaggregated from daily to hourly values to be used for rainfall–runoff modeling of mesoscale catchments. Spatial rainfall consistency is implemented afterwards using simulated annealing. With the calibration process applied, observed runoff statistics (e.g., summer and winter peak flows) are represented well. However, rainfall datasets with under- or over-estimation of spatial consistency lead to similar results, so the need for a good representation can be questioned.

Description: 〈b〉The importance of small artificial water bodies as sources of methane emissions in Queensland, Australia〈/b〉〈br〉 Alistair Grinham, Simon Albert, Nathaniel Deering, Matthew Dunbabin, David Bastviken, Bradford Sherman, Catherine E. Lovelock, and Christopher D. Evans〈br〉 Hydrol. Earth Syst. Sci., 22, 5281-5298, https://doi.org/10.5194/hess-22-5281-2018, 2018〈br〉 Artificial water bodies are a major source of methane and an important contributor to flooded land greenhouse gas emissions. Past studies focussed on large water supply or hydropower reservoirs with small artificial water bodies (ponds) almost completely ignored. This regional study demonstrated ponds accounted for one-third of flooded land surface area and emitted over 1.6 million t CO〈sub〉2〈/sub〉 eq. yr〈sup〉−1〈/sup〉 (10 % of land use sector emissions). Ponds should be included in regional GHG inventories.

Description: 〈b〉Numerical modeling of flow and transport in the Bari industrial area by means of rough walled parallel plate and random walk models〈/b〉〈br〉 Claudia Cherubini, Nicola Pastore, Dimitra Rapti, and Concetta I. Giasi〈br〉 Hydrol. Earth Syst. Sci., 22, 5211-5225, https://doi.org/10.5194/hess-22-5211-2018, 2018〈br〉 The present study investigates the hotspots of groundwater contamination in the industrial area of Modugno (Bari – southern Italy) where the limestone aquifer has a fractured and karstic nature. The characterization of the dynamics of fluid flow and solute transport in fractured aquifers is of broad concern worldwide, especially when considered in relation to water resource exploitation, because fractured aquifers serve as the primary source of drinking water for many areas of the world.

Description: 〈b〉Technical note: Analytical sensitivity analysis and uncertainty estimation of a two-component hydrograph separation method which uses conductivity as a tracer〈/b〉〈br〉 Weifei Yang, Changlai Xiao, and Xiujuan Liang〈br〉 Hydrol. Earth Syst. Sci. Discuss., https//doi.org/10.5194/hess-2018-492,2018〈br〉 〈b〉Manuscript under review for HESS〈/b〉 (discussion: open, 0 comments)〈br〉 This paper analyzed the sensitivity of the baseflow index to the parameters of the conductivity two-component hydrograph separation method. The results indicated that the baseflow index is more sensitive to the conductivity of baseflow, and the separation method may be more suitable for the long time series in a small watershed. And after considering the mutual offset of the measurement errors of conductivity and streamflow, the uncertainty of baseflow index was reduced by half.

Description: 〈b〉Multimodel assessments of human and climate impacts on mean annual streamflow in China〈/b〉〈br〉 Xingcai Liu, Wenfeng Liu, Hong Yang, Qiuhong Tang, Martina Flörke, Yoshimitsu Masaki, Hannes Müller Schmied, Sebastian Ostberg, Yadu Pokhrel, Yusuke Satoh, and Yoshihide Wada〈br〉 Hydrol. Earth Syst. Sci. Discuss., https//doi.org/10.5194/hess-2018-525,2018〈br〉 〈b〉Manuscript under review for HESS〈/b〉 (discussion: open, 0 comments)〈br〉 Due to the population growth and economic development, human activities associated with water resources management have significantly increased in China during the past decades. This assessment helps us understand how streamflow has been affected by climate and human in China. Our analyses indicate that climate change dominated streamflow changes in most areas and human activities have increasingly decreased streamflow in northern basins of China which are vulnerable to future climate change.

Description: 〈b〉Assessment of spatial uncertainty of heavy local rainfall using a dense gauge network〈/b〉〈br〉 Sungmin O and Ulrich Foelsche〈br〉 Hydrol. Earth Syst. Sci. Discuss., https//doi.org/10.5194/hess-2018-517,2018〈br〉 〈b〉Manuscript under review for HESS〈/b〉 (discussion: open, 0 comments)〈br〉 We analyse heavy local rainfall to address questions regarding the spatial uncertainty due to the approximation of areal rainfall using point measurements. 10-years rainfall data from a dense network of 150 rain gauges in southeastern Austria are employed, which permits robust examination of small-scale rainfall at various horizontal resolutions. Quantitative uncertainty information from this study can guide both data users and producers to estimate uncertainty in their own rainfall datasets.

Description: 〈b〉Land cover effects on hydrologic services under a precipitation gradient〈/b〉〈br〉 Ane Zabaleta, Eneko Garmendia, Petr Mariel, Ibon Tamayo, and Iñaki Antigüedad〈br〉 Hydrol. Earth Syst. Sci., 22, 5227-5241, https://doi.org/10.5194/hess-22-5227-2018, 2018〈br〉 This study establishes relationships between land cover and river discharge. Using discharge data from 20 catchments of the Bay of Biscay findings showed the influence of land cover on discharge changes with the amount of precipitation, with lower annual water resources associated with the greater presence of forests. Results obtained illustrate the relevance of land planning to the management of water resources and the opportunity to consider it in future climate-change adaptation strategies.

Description: 〈b〉Vulnerability of tourism development to salt karst hazards along the Jordanian Dead Sea shore〈/b〉〈br〉 Najib Abou Karaki, Simone Fiaschi, Killian Paenen, Mohammad Al-Awabdeh, and Damien Closson〈br〉 Hydrol. Earth Syst. Sci. Discuss., https//doi.org/10.5194/hess-2018-479,2018〈br〉 〈b〉Manuscript under review for HESS〈/b〉 (discussion: open, 4 comments)〈br〉 The Dead Sea shore is a dynamic karst system. It started developing in the 1960s, when its water resources were diverted. The Dead Sea water level is lowering (at approximately 1.4 m/yr in 2018), causing disequilibrium between the underground fresh waters and the base level. Remote sensing techniques combined with repeated field observations provide an early warning system against resulting hydrogeological hazards, limiting or preventing possible disastrous consequences related to subsidence.

Description: 〈b〉Implementation of salt-induced freezing point depression function into CoupModel_v5 for improvement of modelling seasonally frozen soils〈/b〉〈br〉 Mousong Wu, Per-Erik Jansson, Jingwei Wu, Xiao Tan, Kang Wang, Peng Chen, and Jiesheng Huang〈br〉 Hydrol. Earth Syst. Sci. Discuss., https//doi.org/10.5194/hess-2018-466,2018〈br〉 〈b〉Manuscript under review for HESS〈/b〉 (discussion: open, 0 comments)〈br〉 〈p〉Soil freezing/thawing is important for soil hydrology and water management in cold regions. Salt in agricultural field impacts soil freezing/thawing characteristics and therefore soil hydrologic process. In this context, we conducted field experiments on soil water, heat and salt dynamics in two seasonally frozen agricultural regions of northern China to understand influences of salt on cold regions hydrology. We developed CoupModel by implementing impacts of salt on freezing point depression. We employed a Monte-Carlo sampling method to calibrate the new model with field observations. The new model improved soil temperature mean error (ME) by 16 % to 77 % when new freezing point equations were implemented into CoupModel. Nevertheless, we found that parameters related to energy balance and soil freezing characteristics in the new model were sensitive to soil heat and water transport at both sites. However, a systematic model sensitivity and calibration has shown to be able to improve model performance, with mean values of R〈sup〉2〈/sup〉 from behavioral simulations for soil temperature at 5 cm depth as high as 0.87 and 0.90, and mean value of R〈sup〉2〈/sup〉 for simulated soil water (liquid or total water contents at 5 cm depth) of 0.31 and 0.80 at site Qianguo and site Yonglian, respectively. This study provided a new approach considering influences of salt on soil freezing/thawing in numerical models and highlighted the importance of salt in soil hydrology of seasonally frozen agricultural soils.〈/p〉

Description: 〈b〉Impact of glacier loss on annual basin water yields〈/b〉〈br〉 Evan Carnahan, Jason M. Amundson, and Eran Hood〈br〉 Hydrol. Earth Syst. Sci. Discuss., https//doi.org/10.5194/hess-2018-509,2018〈br〉 〈b〉Manuscript under review for HESS〈/b〉 (discussion: open, 0 comments)〈br〉 We model the effects of glacier dynamics, climate, and plant succession on annual streamflow during glacier retreat. Streamflow initially increases as the glacier melts but eventually decreases to below preretreat levels due to increases in evapotranspiration. Glacier dynamics largely controls early variations in streamflow, whereas plant succession plays a progressively larger roll throughout. We show that glacier dynamics and landscape evolution are equally important in predicting streamflow.

Description: 〈b〉Spatial Relationship between Precipitation and Runoff in Africa〈/b〉〈br〉 Fidele Karamage, Yuanbo Liu, Xingwang Fan, Meta Francis Justine, Guiping Wu, Yongwei Liu, Han Zhou, and Ruonan Wang〈br〉 Hydrol. Earth Syst. Sci. Discuss., https//doi.org/10.5194/hess-2018-424,2018〈br〉 〈b〉Manuscript under review for HESS〈/b〉 (discussion: open, 2 comments)〈br〉 〈p〉Lack of sufficient and reliable hydrological information is a key hindrance to water resource planning and management in Africa. Hence, the objective of this research is to examine the relationship between precipitation and runoff at three spatial scales, including the whole continent, 25 major basins and 55 countries. For this purpose, the long-term monthly runoff coefficient (R〈sub〉c〈/sub〉) was estimated using the long-term monthly runoff data (R) calculated from the Global Runoff Data Centre (GRDC) streamflow records and Global Precipitation Climatology Centre (GPCC) precipitation datasets for the period of time spanning from 1901 to 2017. Subsequently, the observed R〈sub〉c〈/sub〉 data were interpolated in order to estimate R〈sub〉c〈/sub〉 over the ungauged basins under guidance of key runoff controlling factors, including the land-surface temperature (T), precipitation (P) and potential runoff coefficient (C〈sub〉o〈/sub〉) inferred from the land use and land cover, slope and soil texture information. The results show that 16 % of the annual mean precipitation (672.52 mm) becomes runoff (105.72 mm), with a runoff coefficient of 0.16, and the remaining 84 % (566.80 mm) evapotranspirates over the continent during 1901–2017. Spatial analysis reveals that the precipitation–runoff relationship varies significantly among different basins and countries, mainly dependent on climatic conditions and its inter-annual variability. Generally, high runoff depths and runoff coefficients are observed over humid tropical basins and countries with high precipitation intensity compared to those located in subtropical and temperate drylands.〈/p〉

Description: 〈b〉Design water demand of irrigation for a large region using a high-dimensional Gaussian copula〈/b〉〈br〉 Xinjun Tu, Yiliang Du, Vijay P. Singh, Xiaohong Chen, Kairong Lin, and Haiou Wu〈br〉 Hydrol. Earth Syst. Sci., 22, 5175-5189, https://doi.org/10.5194/hess-22-5175-2018, 2018〈br〉 For given frequencies of precipitation of a large region, design water demands of irrigation of the entire region among three methods, i.e., equalized frequency, typical year and most-likely weight function, slightly differed, but their alterations in sub-regions were complicated. A design procedure using the most-likely weight function in association with a high-dimensional copula, which built a linkage between regional frequency and sub-regional frequency of precipitation, is recommended.

Description: 〈b〉Breeze effects at a large artificial lake: summer case study〈/b〉〈br〉 Maksim Iakunin, Rui Salgado, and Miguel Potes〈br〉 Hydrol. Earth Syst. Sci., 22, 5191-5210, https://doi.org/10.5194/hess-22-5191-2018, 2018〈br〉 Lakes and reservoirs can affect local weather regimes but usually it is difficult to trace and assess it. In this work we used the Meso-NH atmospheric model to study the impact of the Alqueva reservoir, one of the largest artificial lakes in western Europe, located in the southeast of Portugal, on meteorological parameters and the formation of a lake breeze system. The magnitude of this impact as well as the intensity of the breeze are shown in the paper.

Description: 〈b〉The El Niño event of 2015–16: Climate anomalies and their impact on groundwater resources in East and Southern Africa〈/b〉〈br〉 Seshagiri Rao Kolusu, Mohammad Shamsudduha, Martin C. Todd, Richard G. Taylor, David Seddon, Japhet J. Kashaigili, Girma Y. Ebrahim, Mark O. Cuthbert, James P. R. Sorensen, Karen G. Villholth, Alan M. MacDonald, and Dave A. MacLeod〈br〉 Hydrol. Earth Syst. Sci. Discuss., https//doi.org/10.5194/hess-2018-516,2018〈br〉 〈b〉Manuscript under review for HESS〈/b〉 (discussion: open, 1 comment)〈br〉 〈p〉The impact of climate variability on groundwater storage has received limited attention despite widespread dependence on groundwater as a resource for drinking water, agriculture and industry. Here, we assess the climate anomalies that occurred over Southern Africa (SA) and East Africa, south of the equator (EASE), during the major El Niño event of 2015–16, and their associated impacts on groundwater storage, across scales, through analysis of in situ groundwater piezometry and GRACE satellite data. At the continental scale, the El Niño of 2015–16 was associated with a pronounced dipole of opposing rainfall anomalies over EASE and Southern Africa, north/south of ~12° S, a characteristic pattern of ENSO. Over Southern Africa the most intense drought event in the historical record occurred, based on an analysis of the cross-scale areal intensity of surface water balance anomalies (as represented by the Standardised Precipitation-Evapotranspiration Index, SPEI), with an estimated return period of at least 200 years and a best estimate of 260 years. Climate risks are changing and we estimate that anthropogenic warming only (ignoring changes to other climate variables e.g. precipitation) has approximately doubled the risk of such an extreme SPEI drought event. These surface water balance deficits suppressed groundwater recharge, leading to a substantial groundwater storage decline indicated by both GRACE satellite and piezometric data in the Limpopo basin. Conversely, over EASE during the 2015–16 El Niño event, anomalously wet conditions were observed with an estimated return period of ~10 years, likely moderated by the absence of a strongly positive Indian Ocean Zonal Mode phase. The strong but not extreme rainy season increased groundwater storage as shown by satellite GRACE data and rising groundwater levels observed at a site in central Tanzania. We note substantial uncertainties in separating groundwater from total water storage in GRACE data and show that consistency between GRACE and piezometric estimates of groundwater storage is apparent when spatial averaging scales are comparable. These results have implications for sustainable and climate-resilient groundwater resource management, including the potential for adaptive strategies, such as managed aquifer recharge during episodic recharge events.〈/p〉

Description: 〈b〉Hess Opinions: An interdisciplinary research agenda to explore the unintended consequences of structural flood protection〈/b〉〈br〉 Giuliano Di Baldassarre, Heidi Kreibich, Sergiy Vorogushyn, Jeroen Aerts, Karsten Arnbjerg-Nielsen, Marlies Barendrecht, Paul Bates, Marco Borga, Wouter Botzen, Philip Bubeck, Bruna De Marchi, Carmen Llasat, Maurizio Mazzoleni, Daniela Molinari, Elena Mondino, Johanna Mård, Olga Petrucci, Anna Scolobig, Alberto Viglione, and Philip J. Ward〈br〉 Hydrol. Earth Syst. Sci., 22, 5629-5637, https://doi.org/10.5194/hess-22-5629-2018, 2018〈br〉 One common approach to cope with floods is the implementation of structural flood protection measures, such as levees. Numerous scholars have problematized this approach and shown that increasing levels of flood protection can generate a false sense of security and attract more people to the risky areas. We briefly review the literature on this topic and then propose a research agenda to explore the unintended consequences of structural flood protection.

Description: 〈b〉A small-volume multiplexed pumping system for automated, high-frequency water chemistry measurements in volume-limited applications〈/b〉〈br〉 Bryan M. Maxwell, François Birgand, Brad Smith, and Kyle Aveni-Deforge〈br〉 Hydrol. Earth Syst. Sci., 22, 5615-5628, https://doi.org/10.5194/hess-22-5615-2018, 2018〈br〉 A multiplexed pumping system (MPS) for obtaining continuous water quality data at multiple locations was previously reported. The existing design was not practical for sampling water in volume-limited applications such as small mesocosms or porewater sampling. This paper discusses the design and performance of a small-volume MPS and illustrates two applications, showing spatial variability in replicate in situ mesocosms and short-circuiting in a woodchip bioreactor using porewater sampling.

Description: 〈b〉Submarine groundwater discharge site in the First Salpausselkä ice-marginal formation, south Finland〈/b〉〈br〉 Joonas J. Virtasalo, Jan F. Schröder, Samrit Luoma, Juha Majaniemi, Juha Mursu, and Jan Scholten〈br〉 Hydrol. Earth Syst. Sci. Discuss., https//doi.org/10.5194/hess-2018-507,2018〈br〉 〈b〉Manuscript under review for HESS〈/b〉 (discussion: open, 0 comments)〈br〉 Submarine groundwater discharge (SGD) is a significant source of nutrients and other potentially harmful substances to coastal sea. We analyse a rich dataset of offshore seismic sub-bottom profiles, multibeam and sidescan sonar images of seafloor, and onshore ground-penetrating radar profiles to establish the geometry of an SGD site in south Finland. The SGD takes place through meter scale pits (pockmarks) on the seafloor, confirmed by elevated radon concentrations in the overlying water.

Description: 〈b〉Quantifying streamflow and active groundwater storage in response to climate warming in an alpine catchment on the Tibetan Plateau〈/b〉〈br〉 Lu Lin, Man Gao, Jintao Liu, Xi Chen, and Hu Liu〈br〉 Hydrol. Earth Syst. Sci. Discuss., https//doi.org/10.5194/hess-2018-541,2018〈br〉 〈b〉Manuscript under review for HESS〈/b〉 (discussion: open, 0 comments)〈br〉 In the paper, recession flow analysis assuming nonlinearized outflow from aquifers into streams was used to quantify active groundwater storage in a headwater catchment with larger glacierization and large-scale frozen ground on the Tibetan Plateau, which provides a perspective to clarify the way of glacial retreat and frozen ground degradation on hydrological processes. We are very grateful to all editors and reviewers for their efforts to help us improve the quality of the manuscript.

Description: 〈b〉A 50-year analysis of hydrological trends and processes in a Mediterranean catchment〈/b〉〈br〉 Nathalie Folton, Eric Martin, Patrick Arnaud, Pierre L'Hermite, and Mathieu Tolsa〈br〉 Hydrol. Earth Syst. Sci. Discuss., https//doi.org/10.5194/hess-2018-547,2018〈br〉 〈b〉Manuscript under review for HESS〈/b〉 (discussion: open, 0 comments)〈br〉 The long-term study of precipitation, flows, flood or drought mechanisms, in the Réal Collobrier research Watershed, located in South-East France, in the Mediterranean forest, improves knowledge of the water cycle and is unique tool for understanding of how catchments function. This study shows a small decrease in rainfall and a tendency marked towards a decrease in the water resources of the catchment in response to climate trends, with a consistent increase in drought severity and duration.

Description: 〈b〉Using Snowfall Intensity to Improve the Correction of Wind-Induced Undercatch in Solid Precipitation Measurements〈/b〉〈br〉 Matteo Colli, Mattia Stagnaro, Luca Lanza, Roy Rasmussen, and Julie M. Thériault〈br〉 Hydrol. Earth Syst. Sci. Discuss., https//doi.org/10.5194/hess-2018-447,2018〈br〉 〈b〉Manuscript under review for HESS〈/b〉 (discussion: open, 0 comments)〈br〉 Our results provide geoscience scientists, meteorological and hydrological services with an improved method to correct the snow measurements from its main source of uncertainty (the wind-induced undercatch of snow particles). The correction builds upon existing approaches developed during the WMO SPICE program and proposes the use of the snowfall intensity variable. The analysis takes advantage of both field datasets provided by SPICE and results of computational fluid-dynamics simulations.

Description: 〈b〉Seasonal drought predictability and forecast skill in the semi-arid endorheic Heihe River basin in northwestern China〈/b〉〈br〉 Feng Ma, Lifeng Luo, Aizhong Ye, and Qingyun Duan〈br〉 Hydrol. Earth Syst. Sci., 22, 5697-5709, https://doi.org/10.5194/hess-22-5697-2018, 2018〈br〉 Predicting meteorological droughts more than 2 months in advance became difficult due to low predictability, leading to weak skill for hydrological droughts in wet seasons. Hydrological drought forecasts showed skills up to 3–6 lead months due to the memory of initial hydrologic conditions in dry seasons. Human activities have increased hydrological predictability during wet seasons in the MHRB. This fills gaps in understanding drought and predictability predictions in endorheic and arid basins.

Description: 〈b〉Seasonal origins of soil water used by trees〈/b〉〈br〉 Scott T. Allen, James W. Kirchner, Sabine Braun, Rolf T. W. Siegwolf, and Gregory R. Goldsmith〈br〉 Hydrol. Earth Syst. Sci. Discuss., https//doi.org/10.5194/hess-2018-554,2018〈br〉 〈b〉Manuscript under review for HESS〈/b〉 (discussion: open, 0 comments)〈br〉 We used stable isotopes of xylem water to study differences in the seasonal origin of water in more than 900 individual trees from three dominant species in 182 Swiss forested sites. We discovered that, surprisingly, mid-summer transpiration was mostly supplied by winter precipitation across diverse humid climates. Our findings provide new insights into tree vulnerability to droughts, transport of water (and thus solutes) in soils, and the climatic information conveyed by plant-tissue isotopes.

Description: 〈b〉Spatial and temporal variability of groundwater recharge in a sandstone aquifer in a semi-arid region〈/b〉〈br〉 Ferdinando Manna, Steven Murray, Daron Abbey, Paul Martin, John Cherry, and Beth Parker〈br〉 Hydrol. Earth Syst. Sci. Discuss., https//doi.org/10.5194/hess-2018-531,2018〈br〉 〈b〉Manuscript under review for HESS〈/b〉 (discussion: open, 0 comments)〈br〉 〈p〉With the aim to understand the spatial and temporal variability of groundwater recharge, a high-resolution, spatially-distributed numerical model (MIKE SHE) representing surface water and groundwater was used to simulate responses to precipitation in a 2.16 km〈sup〉2〈/sup〉 upland catchment on fractured sandstone near Los Angeles, California. Exceptionally high temporal and spatial resolution was used for this catchment modeling: an hourly time-step, a 20 × 20 meter grid in the horizontal plane and 240 numerical layers distributed vertically within the thick vadose zone and in the upper part of the groundwater zone. The finest-practical spatial and temporal resolution were selected to accommodate the large degree of surface and subsurface variability of catchment features. Physical property values for the different lithologies were assigned based on previous on-site investigations whereas the parameters controlling streamflow and evapotranspiration were derived from literature information. The calibration of streamflow at the outfall and of transient and average hydraulic head provided confidence in the reasonableness of these input values and in the ability of the model to reproduce observed processes. Confidence in the calibrated model was enhanced by validation through, (i) comparison of simulated average recharge to estimates based on the applications of the chloride mass-balance method from data from the groundwater and vadose zones within and beyond the catchment (Manna et al., 2016; Manna et al., 2017) and, (ii) comparison of the water isotope signature (〈sup〉18〈/sup〉O and 〈sup〉2〈/sup〉H) in shallow groundwater to the variability of isotope signatures for precipitation events over an annual cycle. The average simulated recharge across the catchment for the period 1995–2014 is 16 mm y〈sup〉−1〈/sup〉 (4 % of the average annual precipitation), which is consistent with previous estimates obtained by using the chloride mass balance method (4.2 % of the average precipitation). However, one of the most unexpected results was that local recharge was simulated to vary from 0 to 〉 1000 mm y〈sup〉−1〈/sup〉 due to episodic precipitation and overland runoff effects. This recharge occurs episodically with the major flux events at the bottom of the evapotranspiration zone, as simulated by MIKE SHE and confirmed by the isotope signatures, occurring only at the end of the rainy season. This is the first study that combines MIKE SHE simulations with the analysis of water isotopes in groundwater and rainfall to determine the timing of recharge processes in semi-arid regions. The study advances the understanding of recharge and unsaturated flow processes in semi-arid regions and enhances our ability to predict the effects of surface and subsurface features on recharge rates. This is crucial in highly heterogeneous contaminated sites because different contaminant source areas have widely varying recharge and, hence, groundwater fluxes impacting their mobility.〈/p〉

Description: 〈b〉Contrasting rainfall-runoff characteristics of floods in Desert and Mediterranean basins〈/b〉〈br〉 Davide Zoccatelli, Francesco Marra, Moshe Armon, Yair Rinat, James A. Smith, and Efrat Morin〈br〉 Hydrol. Earth Syst. Sci. Discuss., https//doi.org/10.5194/hess-2018-550,2018〈br〉 〈b〉Manuscript under review for HESS〈/b〉 (discussion: open, 0 comments)〈br〉 This study presents a comparison of flood properties over multiple Mediterranean and Desert catchments. While in Mediterranean areas floods are related with rainfall amount, in Deserts we observed a strong connection with the characteristics of the more intense part of storms. Because of the different mechanisms involved, despite having significantly shorter and more localized storms, Deserts are able to produce floods with magnitude comparable to Mediterranean areas.

Description: 〈b〉The value of satellite remote sensing soil moisture data and the DISPATCH algorithm in irrigation fields〈/b〉〈br〉 Mireia Fontanet, Daniel Fernàndez-Garcia, and Francesc Ferrer〈br〉 Hydrol. Earth Syst. Sci., 22, 5889-5900, https://doi.org/10.5194/hess-22-5889-2018, 2018〈br〉 One of the main objectives of remote sensing methodology is to downscale soil moisture to improve irrigation management. The DISPATCH algorithm is able to measure soil moisture at 1 km resolution using SMOS and MODIS data. In this work DISPATCH has been evaluated with soil moisture sensors, under heterogeneous conditions where local irrigation is applied. Results show that DISPATCH is not sensitive when local irrigation is applied even at low resolution.

Description: 〈b〉Do users benefit from additional information in support of operational drought management decisions in the Ebro basin?〈/b〉〈br〉 Clara Linés, Ana Iglesias, Luis Garrote, Vicente Sotés, and Micha Werner〈br〉 Hydrol. Earth Syst. Sci., 22, 5901-5917, https://doi.org/10.5194/hess-22-5901-2018, 2018〈br〉 In this paper we follow a user-based approach to examine operational drought management decisions and how the role of information on them can be assessed. The approach combines a stakeholder consultation and a decision model representing the interrelated decisions of the irrigation association and farmers. The decision model was extended to include information on snow cover from satellite. This contributed to better decisions in the simulation and ultimately higher benefits for the farmers.

Description: 〈b〉Hydrological functioning of western African inland valleys explored with a critical zone model〈/b〉〈br〉 Basile Hector, Jean-Martial Cohard, Luc Séguis, Sylvie Galle, and Christophe Peugeot〈br〉 Hydrol. Earth Syst. Sci., 22, 5867-5888, https://doi.org/10.5194/hess-22-5867-2018, 2018〈br〉 The hydrological functioning of western African headwater wetlands remains poorly understood, despite their potential for small-scale farming and their role in streamflow production. We found that land cover changes significantly affect water budgets, and pedo-geological features control dry season baseflow. These are the results of virtual experiments with a physically based critical zone model evaluated against streamflow, evapotranspiration, soil moisture, water table and water storage data.

Description: 〈b〉Global phosphorus recovery from wastewater for agricultural reuse〈/b〉〈br〉 Dirk-Jan D. Kok, Saket Pande, Jules B. van Lier, Angela R. C. Ortigara, Hubert Savenije, and Stefan Uhlenbrook〈br〉 Hydrol. Earth Syst. Sci., 22, 5781-5799, https://doi.org/10.5194/hess-22-5781-2018, 2018〈br〉 Phosphorus (P) is important to global food security. Thus it is concerning that natural P reserves are predicted to deplete within the century. Here we explore the potential of P recovery from wastewater (WW) at global scale. We identify high production and demand sites to determine optimal market prices and trade flows. We show that 20% of the agricultural demand can be met, yet only 4 % can be met economically. Nonetheless, this recovery stimulates circular economic development in WW treatment.

Description: 〈b〉Assimilation of passive microwave AMSR-2 satellite observations in a snowpack evolution model over northeastern Canada〈/b〉〈br〉 Fanny Larue, Alain Royer, Danielle De Sève, Alexandre Roy, and Emmanuel Cosme〈br〉 Hydrol. Earth Syst. Sci., 22, 5711-5734, https://doi.org/10.5194/hess-22-5711-2018, 2018〈br〉 A data assimilation scheme was developed to improve snow water equivalent (SWE) simulations by updating meteorological forcings and snowpack states using passive microwave satellite observations. A chain of models was first calibrated to simulate satellite observations over northeastern Canada. The assimilation was then validated over 12 stations where daily SWE measurements were acquired during 4 winters (2012–2016). The overall SWE bias is reduced by 68 % compared to original SWE simulations.

Description: 〈b〉Process-Based Flood Frequency Analysis in an Agricultural Watershed Exhibiting Nonstationary Flood Seasonality〈/b〉〈br〉 Guo Yu, Daniel B. Wright, Zhihua Zhu, Cassia Smith, and Kathleen D. Holman〈br〉 Hydrol. Earth Syst. Sci. Discuss., https//doi.org/10.5194/hess-2018-513,2018〈br〉 〈b〉Manuscript under review for HESS〈/b〉 (discussion: open, 1 comment)〈br〉 The relationship between flood severity and probability is a key component of flood risk management, and depends on factors including rainfall, soil wetness, and watershed properties. In this study, we combine radar rainfall data and flood simulations to better understand how these factors 〈q〉shape〈/q〉 flood frequency. We apply our method to an agricultural watershed in the Midwestern U.S where the flood properties is changing. Conventional methods will fail to account for these changes.

Description: 〈b〉Joint editorial: Invigorating hydrological research through journal publications〈/b〉〈br〉 Nevil Quinn, Günter Blöschl, András Bárdossy, Attilio Castellarin, Martyn Clark, Christophe Cudennec, Demetris Koutsoyiannis, Upmanu Lall, Lubomir Lichner, Juraj Parajka, Christa D. Peters-Lidard, Graham Sander, Hubert Savenije, Keith Smettem, Harry Vereecken, Alberto Viglione, Patrick Willems, Andy Wood, Ross Woods, Chong-Yu Xu, and Erwin Zehe〈br〉 Hydrol. Earth Syst. Sci., 22, 5735-5739, https://doi.org/10.5194/hess-22-5735-2018, 2018〈br〉 〈p〉Editors of several journals in the field of hydrology met during the General Assembly of the European Geosciences Union (EGU) in Vienna in April 2017. This event was a follow-up of similar meetings held in 2013 and 2015. These meetings enable the group of editors to review the current status of the journals and the publication process, and to share thoughts on future strategies. Journals were represented at the 2017 meeting by their editors, as shown in the list of authors. The main points on invigorating hydrological research through journal publications are communicated in this joint editorial published in the above journals.〈/p〉

Description: 〈b〉Hybridizing Bayesian and variational data assimilation for high-resolution hydrologic forecasting〈/b〉〈br〉 Felipe Hernández and Xu Liang〈br〉 Hydrol. Earth Syst. Sci., 22, 5759-5779, https://doi.org/10.5194/hess-22-5759-2018, 2018〈br〉 Predicting floods requires first knowing the amount of water in the valleys, which is complicated because we cannot know for sure how much water there is in the soil. We created a unique system that combines the best methods to estimate these conditions accurately based on the observed water flow in the rivers and on detailed simulations of the valleys. Comparisons with popular methods show that our system can produce realistic predictions efficiently, even for very detailed river networks.

Description: 〈b〉Estimating changes of temperatures and precipitation extremes in India using the Generalized Extreme Value (GEV) distribution〈/b〉〈br〉 Kishore Pangaluru, Isabella Velicogna, Tyler C. Sutterley, Yara Mohajerani, Enrico Ciraci, Jyothi Sompalli, and Vijaya Bhaskara Rao Saranga〈br〉 Hydrol. Earth Syst. Sci. Discuss., https//doi.org/10.5194/hess-2018-522,2018〈br〉 〈b〉Manuscript under review for HESS〈/b〉 (discussion: open, 0 comments)〈br〉 The regional extreme mean temperature values increase moderately compared to the historical values at about 1.82 and 2.92 °C in the 50-year period under RCP6.0 and 8.5 scenarios. Comparing the 10- to 50-year return periods, the warm extremes increase at about ~ 3 °C especially over the eastern and western regions of India. The effect of increasing radiative forcing under higher concentration pathways is larger on cold temperatures compared to warm extreme temperatures.

Description: 〈b〉Dealing with non-stationarity in sub-daily stochastic rainfall models〈/b〉〈br〉 Lionel Benoit, Mathieu Vrac, and Gregoire Mariethoz〈br〉 Hydrol. Earth Syst. Sci., 22, 5919-5933, https://doi.org/10.5194/hess-22-5919-2018, 2018〈br〉 We propose a method for unsupervised classification of the space–time–intensity structure of weather radar images. The resulting classes are interpreted as rain types, i.e. pools of rain fields with homogeneous statistical properties. Rain types can in turn be used to define stationary periods for further stochastic rainfall modelling. The application of rain typing to real data indicates that non-stationarity can be significant within meteorological seasons, and even within a single storm.

Description: 〈b〉Replication of ecologically relevant hydrological indicators following a covariance approach to hydrological model parameterisation〈/b〉〈br〉 Annie Visser, Lindsay Beevers, and Sandhya Patidar〈br〉 Hydrol. Earth Syst. Sci. Discuss., https//doi.org/10.5194/hess-2018-536,2018〈br〉 〈b〉Manuscript under review for HESS〈/b〉 (discussion: open, 1 comment)〈br〉 The ecological impact of change to river flow may be explored through the simulation of ecologically relevant flow indicators. Traditional approaches to model parameterisation are not well-suited for this. To this end, this paper considers the ability of a 〈q〉modified covariance approach〈/q〉. Improvements in performance and consistency are observed relative to: (1) the limitations of traditional approaches; and (2) four comparative studies.

Description: 〈b〉Seasonal behaviour of tidal damping and residual water level slope in the Yangtze River estuary: identifying the critical position and river discharge for maximum tidal damping〈/b〉〈br〉 Huayang Cai, Hubert H. G. Savenije, Erwan Garel, Xianyi Zhang, Leicheng Guo, Min Zhang, Feng Liu, and Qingshu Yang〈br〉 Hydrol. Earth Syst. Sci. Discuss., https//doi.org/10.5194/hess-2018-524,2018〈br〉 〈b〉Manuscript under review for HESS〈/b〉 (discussion: open, 0 comments)〈br〉 Tide-river dynamics play an essential role in large-scale river deltas because they exert a tremendous impact on delta morphodynamics, salt intrusion, and deltaic ecosystems. For the first time, we illustrate that there is a critical river discharge, beyond which tidal damping is reduced with increasing river discharge and the underlying mechanism was explored by using an analytical model. The results are useful for guiding sustainable water managements and sediment transport in tidal rivers.

Description: 〈b〉Mapping soil hydraulic properties using random forest based pedotransfer functions and geostatistics〈/b〉〈br〉 Brigitta Tóth, Gábor Szatmári, Katalin Takács, Annamária Laborczi, András Makó, Kálmán Rajkai, and László Pásztor〈br〉 Hydrol. Earth Syst. Sci. Discuss., https//doi.org/10.5194/hess-2018-552,2018〈br〉 〈b〉Manuscript under review for HESS〈/b〉 (discussion: open, 0 comments)〈br〉 This paper analyses differences in performance and spatial patterns between soil hydraulic maps derived with indirect and direct mapping methods. Maps of saturated water content, field capacity and wilting point are interpreted for a 5775 km〈sup〉2〈/sup〉 catchment at 100 m resolution. Advantages and disadvantages of the two methods are discussed. Absolute difference in soil water retention values are less than 0.025 cm〈sup〉3〈/sup〉 cm〈sup〉−3〈/sup〉 between maps derived with indirect and direct methods for 65–86 % of the catchment.

Description: 〈b〉Turbulent mixing and heat fluxes under lake ice: the role of seiche oscillations〈/b〉〈br〉 Georgiy Kirillin, Ilya Aslamov, Matti Leppäranta, and Elisa Lindgren〈br〉 Hydrol. Earth Syst. Sci., 22, 6493-6504, https://doi.org/10.5194/hess-22-6493-2018, 2018〈br〉 We have discovered transient appearances of strong turbulent mixing beneath the ice of an Arctic lake. Such mixing events increase heating of the ice base up to an order of magnitude and can significantly accelerate ice melting. The source of mixing was identified as oscillations of the entire lake water body triggered by strong winds over the lake surface. This previously unknown mechanism of ice melt may help understand the link between the climate conditions and the seasonal ice formation.

Description: 〈b〉Using paleoclimate reconstructions to analyse hydrological epochs associated with Pacific decadal variability〈/b〉〈br〉 Lanying Zhang, George Kuczera, Anthony S. Kiem, and Garry Willgoose〈br〉 Hydrol. Earth Syst. Sci., 22, 6399-6414, https://doi.org/10.5194/hess-22-6399-2018, 2018〈br〉 Analyses of run lengths of Pacific decadal variability (PDV) suggest that there is no significant difference between run lengths in positive and negative phases of PDV and that it is more likely than not that the PDV run length has been non-stationary in the past millennium. This raises concerns about whether variability seen in the instrumental record (the last ~100 years), or even in the shorter 300–400 year paleoclimate reconstructions, is representative of the full range of variability.

Description: 〈b〉Estimating the effect of rainfall on the surface temperature of a tropical lake〈/b〉〈br〉 Gabriel Gerard Rooney, Nicole van Lipzig, and Wim Thiery〈br〉 Hydrol. Earth Syst. Sci., 22, 6357-6369, https://doi.org/10.5194/hess-22-6357-2018, 2018〈br〉 This paper uses a unique observational dataset of a tropical African lake (L. Kivu) to assess the effect of rain on lake surface temperature. Data from 4 years were categorised by daily rain amount and total net radiation to show that heavy rain may reduce the end-of-day lake temperature by about 0.3 K. This is important since lake surface temperature may influence local weather on short timescales, but the effect of rain on lake temperature has been little studied or parametrised previously.

Description: 〈b〉Open-source Arduino-derived data loggers designed for field research〈/b〉〈br〉 Andrew D. Wickert, Chad T. Sandell, Bobby Schulz, and G.-H. Crystal Ng〈br〉 Hydrol. Earth Syst. Sci. Discuss., https//doi.org/10.5194/hess-2018-591,2018〈br〉 〈b〉Manuscript under review for HESS〈/b〉 (discussion: open, 0 comments)〈br〉 Measuring Earth's changing environment is a critical part of natural science, but to date, most of the equipment to do so is expensive, proprietary, and difficult to customize. We addressed this challenge by developing and deploying the ALog, a low-power, lightweight, Arduino-compatible data logger. We present our hardware schematics and layouts, as well as our customizable code library that operates the ALog and helps users to link it to off-the-shelf sensors.

Description: 〈b〉Technical note: Decomposing a time series into independent trend, seasonal and random components〈/b〉〈br〉 Dongqin Yin, Hannah Slatford, and Michael L. Roderick〈br〉 Hydrol. Earth Syst. Sci. Discuss., https//doi.org/10.5194/hess-2018-601,2018〈br〉 〈b〉Manuscript under review for HESS〈/b〉 (discussion: open, 0 comments)〈br〉 We focused on seeking for a decomposition approach which can produce independent decomposed components as a basis for understanding variability in hydro-climatic time series. We find that the rarely adopted two-way ANOVA model in hydro-climatic variability (rather than the traditional methods using linear trend or moving average) will produce independent components. This method is further applied to explore the variability in global precipitation and is expected to be useful for other variables.

Description: 〈b〉Empirical and analytical methods to characterize the efficiency of floods to move sediment in a small semi-arid basin〈/b〉〈br〉 Abdesselam Megnounif and Sylvain Ouillon〈br〉 Hydrol. Earth Syst. Sci., 22, 6335-6355, https://doi.org/10.5194/hess-22-6335-2018, 2018〈br〉 From a classification of river discharge, the effective or dominant discharge is the one whose class corresponds to the maximum sediment supply. The efficiency of the Wadi Sebdou (NW Algeria) was examined over 1973–2004. Two subdivisions allowed a correct distribution of frequencies and supplies of water and sediments. Their effective discharge, close to the 〈q〉half-load discharge〈/q〉, was compared to analytical values based on statistics and rating curves. Return periods were also explained.

Description: 〈b〉Derivation of the mean annual water-energy balance equation based on an Ohms-type approach〈/b〉〈br〉 Xu Shan, Xindong Li, and Hanbo Yang〈br〉 Hydrol. Earth Syst. Sci. Discuss., https//doi.org/10.5194/hess-2018-598,2018〈br〉 〈b〉Manuscript under review for HESS〈/b〉 (discussion: open, 0 comments)〈br〉 The Budyko hypothesis has been generally used to quantify how much precipitation transforms into evaporation in one catchment. To approach this hypothesis, previous studies proposed analytical formulas derived based on mathematic reasoning. Differently, this study drew a new derivation for this hypothesis based on fundamental physical principles. It clearly reveals the underlying assumptions in the previous mathematic reasoning and promotes hydrologic understanding on this hypothesis.

Description: 〈b〉Principal components of thermal regimes in mountain river networks〈/b〉〈br〉 Daniel J. Isaak, Charles H. Luce, Gwynne L. Chandler, Dona L. Horan, and Sherry P. Wollrab〈br〉 Hydrol. Earth Syst. Sci., 22, 6225-6240, https://doi.org/10.5194/hess-22-6225-2018, 2018〈br〉 Description of thermal regimes in flowing waters is key to understanding physical processes and improving bioassessments, but has been limited by sparse data sets. Using a large annual temperature data set from a mountainous area of the western U.S., we explored thermal regimes using principle component analysis. A small number of summary metrics adequately represented most of the variation in this data set given strong temporal coherence among sites.

Description: 〈b〉Isotopic reconnaissance of urban water supply system dynamics〈/b〉〈br〉 Yusuf Jameel, Simon Brewer, Richard P. Fiorella, Brett J. Tipple, Shazelle Terry, and Gabriel J. Bowen〈br〉 Hydrol. Earth Syst. Sci., 22, 6109-6125, https://doi.org/10.5194/hess-22-6109-2018, 2018〈br〉 Public water supply systems (PWSSs) are important infrastructure susceptible to contamination and physical disruption. In general, PWSSs are analyzed using hydrodynamic models, which requires detailed supply infrastructure information. In this paper, we have shown that stable isotope mixing models can also provide useful information on PWSSs. The method developed here can be useful in studying decentralized PWSSs, validating hydrodynamic models and solving water right issues.

Description: 〈b〉Understanding the water cycle over the upper Tarim Basin: retrospecting the estimated discharge bias to atmospheric variables and model structure〈/b〉〈br〉 Xudong Zhou, Jan Polcher, Tao Yang, Yukiko Hirabayashi, and Trung Nguyen-Quang〈br〉 Hydrol. Earth Syst. Sci., 22, 6087-6108, https://doi.org/10.5194/hess-22-6087-2018, 2018〈br〉 Model bias is commonly seen in discharge simulation by hydrological or land surface models. This study tested an approach with the Budyko hypothesis to retrospect the estimated discharge bias to different bias sources including the atmospheric variables and model structure. Results indicate that the bias is most likely caused by the forcing variables, and the forcing bias should firstly be assessed and reduced in order to perform pertinent analysis of the regional water cycle.

Description: 〈b〉A review of the (Revised) Universal Soil Loss Equation ((R)USLE): with a view to increasing its global applicability and improving soil loss estimates〈/b〉〈br〉 Rubianca Benavidez, Bethanna Jackson, Deborah Maxwell, and Kevin Norton〈br〉 Hydrol. Earth Syst. Sci., 22, 6059-6086, https://doi.org/10.5194/hess-22-6059-2018, 2018〈br〉 Soil erosion is a global problem and models identify vulnerable areas for management. One such model is the Revised Universal Soil Loss Equation. We review its different sub-factors and compile studies and equations that modified it for local conditions. The limitations of RUSLE include its data requirements and exclusion of gullying and landslides. Future directions include accounting for these erosion types. This paper serves as a reference for others working with RUSLE and related approaches.

Description: 〈b〉Studying catchment storm response using event- and pre-event-water volumes as fractions of precipitation rather than discharge〈/b〉〈br〉 Jana von Freyberg, Bjørn Studer, Michael Rinderer, and James W. Kirchner〈br〉 Hydrol. Earth Syst. Sci., 22, 5847-5865, https://doi.org/10.5194/hess-22-5847-2018, 2018〈br〉 We show event- and pre-event-water volumes as fractions of precipitation, rather than discharge, to provide an alternative and more insightful approach to study catchment hydrological processes. For this, we analyze 24 storm events using high-frequency measurements of stable water isotopes in stream water and precipitation at a pre-Alpine catchment. Antecedent wetness and storm characteristics are dominant controls on event-water discharge and pre-event-water mobilization from storage.

Description: 〈b〉The CAMELS-CL dataset: catchment attributes and meteorology for large sample studies – Chile dataset〈/b〉〈br〉 Camila Alvarez-Garreton, Pablo A. Mendoza, Juan Pablo Boisier, Nans Addor, Mauricio Galleguillos, Mauricio Zambrano-Bigiarini, Antonio Lara, Cristóbal Puelma, Gonzalo Cortes, Rene Garreaud, James McPhee, and Alvaro Ayala〈br〉 Hydrol. Earth Syst. Sci., 22, 5817-5846, https://doi.org/10.5194/hess-22-5817-2018, 2018〈br〉 CAMELS-CL provides a catchment dataset in Chile, including 516 catchment boundaries, hydro-meteorological time series, and 70 catchment attributes quantifying catchments' climatic, hydrological, topographic, geological, land cover and anthropic intervention features. By using CAMELS-CL, we characterise hydro-climatic regional variations, assess precipitation and potential evapotranspiration uncertainties, and analyse human intervention impacts on catchment response.

Description: 〈b〉The PERSIANN family of global satellite precipitation data: a review and evaluation of products〈/b〉〈br〉 Phu Nguyen, Mohammed Ombadi, Soroosh Sorooshian, Kuolin Hsu, Amir AghaKouchak, Dan Braithwaite, Hamed Ashouri, and Andrea Rose Thorstensen〈br〉 Hydrol. Earth Syst. Sci., 22, 5801-5816, https://doi.org/10.5194/hess-22-5801-2018, 2018〈br〉 The goal of this article is to first provide an overview of the available PERSIANN precipitation retrieval algorithms and their differences. We evaluate the products over CONUS at different spatial and temporal scales using CPC data. Daily scale is the finest temporal scale used for the evaluation over CONUS. We provide a comparison of the available products at a quasi-global scale. We highlight the strengths and limitations of the PERSIANN products.