ALBERT

Description: In many catchments the geographical demarcation does not coincide with the limits of the aquifers, so groundwater may be exchanged beyond their topographic boundaries. By studying groundwater exchanges, the natural resources of a catchment can be better assessed, and the divergences between hydrological models and measurements can be explained. The aim of this work is to reveal the importance of including groundwater exchanges in the hydrological modelling of some catchments, using a water balance model. For this purpose, a simple example is conducted. The so-called model Parent Model Scheme is modified to only allow groundwater exchanges, and it is applied to the headwater of the Segura River Basin District, located in the southeast of Spain. This area is selected because groundwater plays an important role in surface hydrology. The results reveal that groundwater exchanges cannot be neglected in some catchments when assessing water resources, since their integration in the hydrological model corrects errors in the water balance. Moreover, this paper proves that water balance models are a useful tool for estimating groundwater exchanges between catchments, which can be contrasted with more complex distributed models or isotopic tracers if there is enough information available. This article is protected by copyright. All rights reserved.

Description: Las Tablas de Daimiel National Park is a series of wetlands which naturally originated from groundwater discharges from the Mancha Occidental aquifer, Spain. Despite the relatively large size of this aquifer, 30 years of intensive groundwater pumping have significantly depleted the water table. As a result, wetlands only remain functional due to artificial inflows. Infiltration loss is therefore a key parameter to evaluate how much water is needed to maintain ecosystem functionality. Although yearly infiltration estimates existed prior to this work, these did not take into account key parameters such as the temporal evolution of the flooded area. This paper presents a more concrete estimate of the average infiltration losses. Infiltration is calculated as the closure term of daily water balances during a period of time where all other elements were known to an acceptable accuracy. A validation mechanism is provided to check the potential utility of the calculated infiltration in wetland management practices. Copyright © 2008 John Wiley & Sons, Ltd.

Description: In many catchments, the geographical demarcation does not coincide with the limits of the aquifers, so groundwater may be exchanged beyond their topographic boundaries. By studying groundwater exchanges, the natural resources of a catchment can be better assessed, and the divergences between hydrological models and measurements can be explained. The aim of this work is to reveal the importance of including groundwater exchanges in the hydrological modelling of some catchments, using a water balance model. For this purpose, a simple example is conducted. The so-called parent model scheme is modified to only allow groundwater exchanges, and it is applied to the headwater of the Segura River Basin District, located in the southeast of Spain. This area is selected because groundwater plays an important role in surface hydrology. The results reveal that groundwater exchanges cannot be neglected in some catchments when assessing water resources because their integration in the hydrological model corrects errors in the water balance. Moreover, this paper proves that water balance models are a useful tool for estimating groundwater exchanges between catchments, which can be contrasted with more complex distributed models or isotopic tracers if there is enough information available. © 2015 John Wiley & Sons, Ltd.

Description: Uruguay has stimulated the development of its forest sector since the promulgation of Forest Law N° 15 939 in December of 1987. Nevertheless, the substitution of natural grasslands with forest plantations for industrial use has raised concerns regarding hydrological processes of groundwater recharge and water consumption involving evapotranspiration. The purpose of this study is to assess the effects of this substitution approach on water resources. Input data were collected from two small experimental watersheds of roughly 100-200 hectares located in western Uruguay. The watersheds are characterized by Eucalyptus Globulus ssp. Maidenni and natural grasslands for cattle use. Total rainfall, stream discharge, rainfall redistribution, soil water content and groundwater level data were collected. Groundwater recharge was estimated from water table fluctuations and from groundwater contributions to base flows. Seasonal and annual water budgets were computed from October of 2006 to September of 2014 to evaluate changes in the hydrological processes. The data show a decrease in annual specific discharge of roughly 17% for mean hydrological years and no conclusive effects on annual groundwater recharge in the forested watershed relative to the reference pasture watershed. Reduced annual specific discharge is equivalent to the mean annual interception. The computed actual annual evapotranspiration is consistent with international catchment measurements. Reduction rates vary seasonally and according to accumulated rainfall and its temporary distribution. The degree of specific discharge decline is particularly high for drier autumns and winters (32 to 28%) when the corresponding rainfall varies from 275 to 400 mm. These results are of relevance for water resources management efforts, as water uses downstream can be affected. These findings, based on a study period dominated by anomalous wet springs and summers and by dry autumns and winters, oppose earlier results based on 34 years of rainfall and discharge data drawn from Uruguayan large basins. Copyright © 2016 John Wiley & Sons, Ltd.

Description: Depression storage (DS) is the maximum storage of precipitation and runoff in the soil surface at a given slope. The DS is determined by soil roughness which in agricultural soils is largely affected by tillage. The direct measurement of DS is not straightforward because of the natural permeability of the soil. Therefore, DS has generally been estimated from 2D/3D empirical relationships and numerical algorithms based on roughness indexes and height measurements of the soil surface, respectively. The objective of this work was to evaluate the performance of some 2D models for DS, using direct and reliable measurements of DS in an agricultural soil as reference values. The study was carried out in experimental microplots where DS was measured in 6 situations resulting from the combination of 3 types of tillage carried out parallel and perpendicular to the main slope. Those data were used as reference to evaluate 4 empirical models and a numerical method. Longitudinal altitudinal profiles of the relief were obtained by a laser profilometer. Infiltration measurements were carried out before and after tillage. The DS were largely affected by tillage and its direction. Highest values of DS are found on rougher surfaces mainly when macroforms cut off the dominant slope. The empirical models had a limited performance while the numerical method was the most effective, even so, with an important variability. I In addition, a correct hydrological managements should take into account that each type of soil tillage affects infiltration rate differently. This article is protected by copyright. All rights reserved.

Description: Current climate change models for the south east UK predict changing rainfall patterns, with increased incidence of extreme events. The Chalk aquifer in the UK and northern France is susceptible to groundwater induced flooding under such conditions. In this methodological study we apply a frequency domain analysis approach to the Chalk aquifer to derive a transfer function between effective rainfall and groundwater level from 7 years of monitoring data from the North Heath Barn site, near Brighton. The derived transfer function was calibrated and validated against monitoring data, and then used to predict groundwater level for rainfall models for high, medium and low emissions scenarios from the UKCP09 database. The derived transfer function is most closely comparable to the linear aquifer model, despite evidence for both matrix and fracture or karst water flow in the Chalk, with transmissivity and unconfined storativity at the catchment scale of 1548 m 2 day −1 and 1.6x10 −2 . The application of the transfer function to UKCP09 rainfall data suggests that groundwater induced flooding may be about four times more frequent by 2040-2069 compared to 1961-1990 and seven times more frequent by 2070-2099. The model data also suggest an increase in the duration of groundwater minima relative to the reference period. Compared to deterministic modelling which requires detailed knowledge of aquifer heterogeneity and processes, the transfer function approach, although with limitations, is simpler, incorporating these factors into the analysis through frequency and phase coefficients, and thus may have the potential for groundwater risk assessment in other areas. This article is protected by copyright. All rights reserved.

Description: Temporal stability of soil water content is an often-observed phenomenon, which characterization finds multiple applications. Climate and variability in soil properties are usually mentioned as factors of temporal stability of soil water content, but their effects are far from clear. The objective of this work was to use soil water content modeling to evaluate the effects of climate and soil hydraulic properties on the temporal stability of soil water at different measurement schedules. We selected four representative climates found in USA and simulated the multiyear soil water content dynamics for sandy loam, loam, and silty clay loam soils, all having the lognormal spatial distribution of the saturated hydraulic conductivity. The CLIMGEN and the HYDRUS6 codes were used to generate weather patterns and to simulate soil water content respectively. Four different methods were applied to select the representative location. The low probability of having the same variability of mean relative differences of soil water under different climates was found in most of the cases. The probability that the variance of mean relative differences depended on sampling frequency was generally higher than 91% for the three soils. The inter-annual difference in mean relative differences variation from short and intensive summer campaigns was highly probable for all climates and soils. The representative locations changed as climate and measurement scheduling changed, and they were less pronounced for coarse textured soils. The Representative location selection methods based solely on bias provided more consistency as compared with other methods. The temporal stability appears to be the result of the interplay between climate, soil properties, and survey protocols. One implication of this factor interaction effect on temporal stability soil water content is that a simulation study can be useful to decide on the feasibility of including a search for temporal stability-based representative locations for a specific site. Copyright © 2013 John Wiley & Sons, Ltd.

Description: Environmental tracers, such as tritium, have generally been used to estimate aquifer recharge under natural conditions. A tritium tracer test is presented for estimating recharge under semi-arid and irrigated conditions. The test was performed along 429 days (June 2007-August 2008) on an experimental plot located in SE Spain with drip irrigation and annual row crops (rotation of lettuce and melon), in which common agricultural practices were followed in open air. Tritiated water was sprinkled (simulated rainfall) over the plot, soil cores were taken at different depths and a liquid scintillation analyzer was used to measure tritium concentration in soil water samples. Tritium transport, as liquid as vapor phase, was simulated with the 1D numerical code SOLVEG. Simulations show that the crop water use was below potential levels, despite regular irrigation. Continuous high water content in soil promoted a great impact of rainfall events on the aquifer recharge. The results obtained from tritium tracer test have been compared with other independent recharge assessment, soil water balance method, in order to evaluate the reliability of the first one. Total recharge from tracer test was 476 mm for the October 2007-September 2008 period, versus 561 mm from soil water balance method for the same period, which represents 37.1 and 43.7% of the applied water (1284 mm, irrigation + precipitation), respectively. Copyright © 2012 John Wiley & Sons, Ltd.

Description: Abstract The main objective of this research was to analyse the effect of soil management on soil sealing and on soil water content under contrasting tillage practices and its influence on corn yield. The experimental research was carried out in a field cultivated with irrigated corn differentiated into three zones representing a gradient of soil texture (Z1, Z2, and Z3, i.e., increasingly coarser). Two plots under different soil management practices (conventional intensive tillage, CT, and no‐tillage, NT) were selected in each zone. The susceptibility to sealing of each soil and the steady infiltration rates were evaluated in the laboratory subjecting the soils to rainfall simulation applied at an intensity of 25 mm h−1. In addition, soil porosity under each treatment was quantified. Soil water content (0–90 cm depth) was determined gravimetrically at the beginning and the end of the growing cycle and at the surface (0–5 cm) during three growing seasons and continuously at two depths (5–15 and 50–60 cm) during the last growing cycle. Soil water content was simulated using the SIMPEL model, which was calibrated for the experimental conditions. Corn yield and above‐ground biomass were also analysed. Significant differences in soil sealing among zones, with decreasing soil sealing for coarser textures, and treatments were observed with infiltration rates that were near twice in NT than in CT, being the effect of soil cover significant in the reduction of soil detachment and soil losses. NT showed higher soil water content than CT, especially in the surface layers. Above‐ground biomass production was smaller in CT than in NT, and in the areas with higher sealing susceptibility was 30% to 45% smaller than in other zones, reaching the smallest values in Z1. A similar reduction in corn yield was observed between treatments being smaller in CT than in NT. No‐tillage has been confirmed as an effective technique that benefits soil physical properties as well as crop yields in relation to CT, being its impact greater in soils susceptible to sealing.