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Study region The area of study is the northern part of Belgium (Flanders). The seven evaluated Aquifer Thermal Energy Storage (ATES) systems are positioned in key aquifers, which contain major groundwater resources for the region. Study focus The increasing number of ATES systems leads to concerns by drinking water companies and environmental regulators about the long term impacts of ATES systems on the groundwater quality. This study assesses the influence of ATES on groundwater chemistry by means of a literature review, and a comparison of groundwater quality monitoring data at seven ATES systems with ambient groundwater quality values from 69 monitoring wells. New hydrological insights for the region The results of the analysis of the hydrochemical data confirm that the small temperature differences (Δ T ≤ 10) at which the ATES systems are operating do not influence the concentrations of the main chemical constituents. Mixing of shallow with deeper groundwater during ATES operation, on the other hand, can alter groundwater quality. The results of this study, however, suggest that the groundwater quality changes are rather small, so that there is no immediate risk for the drinking water supply. However, the installation of ATES systems in the vicinity of public drinking water supply well fields should be handled with care, especially in phreatic aquifers.

Land-cover impacts volume, intensity and contamination of runoff generated by rainfall events in catchments. This study demonstrates how the method used for estimation of land-cover proportions impacts the runoff from a distributed, physically based hydrological model - WetSpa. The study area is the urbanized catchment of Biala River, situated in the northeastern part of Poland. Three scenarios of land-cover proportion estimation were tested: a semi-distributed approach where the average proportion of impervious surface cover per land-use type is estimated based on hard classification of a high-resolution IKONOS scene and two distributed approaches with land-cover class proportions estimated at the level of individual cells based on hard classification of a high-resolution IKONOS scene and sub-pixel classification of a medium-resolution Landsat 5 TM scene respectively. Validation of the three scenarios based on a comparison of modeled versus observed discharge shows that best results are obtained for the two distributed scenarios with a Nash-Sutcliffe efficiency (NS) of 0.62 for the hard classification approach and NS = 0.63 for the sub-pixel approach. The hard classification approach performed best in the estimation of peak discharges. The semi-distributed modeling scenario resulted in the lowest simulation efficiency (NS = 0.40) and did not perform well in estimating observed peak discharges. It is concluded that scenarios in which land-cover proportions are distributed improved considerably the simulation results of hydrological processes in physically based models.

The runoff amount and intensity on catchment scale is strongly related to the spatial distribution of impervious area cover, which is the predominant cover type in urbanized area. This can only be taken effectively into account when a fully- distributed hydrological model is used. In this paper we investigate the assessment of imperviousness by a multi- resolution remote sensing technique. The remote sensing approach uses a classified high resolution (HR) Ikonos image that covers part of the research area to train a neural network based sub-pixel classification model that estimates impervious surface cover proportions within the pixels of a medium-resolution (MR) Landsat ETM+ image that covers the entire area. The GIS based distributed WetSpa model was used for studying the influence of different imperviousness scenarios on runoff generation with an hourly time step. It shows that estimates of imperviousness derived from satellite data may strongly improve those made by experts, as well as the necessity of application of fully-distributed grid-based hydrological models for urban runoff simulation.

The amount and intensity of runoff on catchment scale are strongly determined by the presence of impervious land-cover types, which are the predominant cover types in urbanized areas. This paper examines the impact of different methods for estimating impervious surface cover on the prediction of peak discharges, as determined by a fully distributed rainfall-runoff model (WetSpa), for the upper part of the Woluwe River catchment in the southeastern part of Brussels. The study shows that detailed information on the spatial distribution of impervious surfaces, as obtained from remotely sensed data, produces substantially different estimates of peak discharges than traditional approaches based on expert judgment of average imperviousness for different types of urban land use. The study also demonstrates that sub-pixel estimation of imperviousness may be a useful alternative for more expensive high-resolution mapping for rainfall-runoff modelling at catchment scale. ispartof: Sensors vol:8 issue:2 pages:910-932 ispartof: location:Switzerland status: published

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As recognized in the European Water Framework Directive, groundwater-dependent wetlands and their diverse ecosystems have important functions which need to be protected. The vegetation in such habitats is often dependent on quality, quantity and patterns of river discharge and groundwater-surface water interaction on a local or reach scale. Since groundwater-surface water exchange studies on natural rivers and wetlands with organic soils are scarce, more functional analysis is needed. To this end we combined different field methods including piezometer nests, temperature as tracer and seepage meter measurements. Some of these measurements were used as inputs and/or as validation for the numerical 1-D heat transport model STRIVE. In transient mode the model was used to calculate spatially distributed vertical exchange fluxes from temperature profiles measured at the upper Biebrza River in Poland over a period of nine months. Time series of estimated fluxes and hydraulic head gradients in the hyporheic zone were used to estimate the temporal variability of groundwater-surface water exchange. This paper presents a hierarchical approach for quantifying and interpreting groundwater-surface water interaction in space and time. The results for the upper Biebrza show predominantly upward water fluxes, sections of recharge, however, exist along the reach. The fluxes depend more on hydraulic gradients than on riverbed conductivity. This indicates that the fluvio-plain scale is required for interpreting the exchange fluxes, which are estimated on a local scale. The paper shows that a conceptual framework is necessary for understanding the groundwater-surface water interaction processes, where the exchange fluxes are influenced by local factors like the composition of the riverbed and the position of the measurement on a local scale, and by regional factors like the hydrogeology and topography on a fluvio-plain scale. The hierarchical methodology increases the confidence in the estimated exchange fluxes and improves the process understanding. The accuracy of the measurements and related uncertainties, however, remain challenges for wetland environments. Gaining quantitative information on groundwatersurface water interaction can improve modeling confidence and as a consequence helps to develop effective procedures for management and conservation of valuable groundwater dependent wetlands. ispartof: Hydrology and Earth System Sciences vol:16 issue:7 pages:2329-2346 status: published

Centimetre-scale saturated hydraulic conductivities (K) are derived from air permeability measurements on a selection of outcrops of the Neogene aquifer in the Campine area, Belgium. Outcrop sediments are of Miocene to Quaternary age and have a marine to continental origin. Grain size analyses for the same outcrops and corresponding K predictions using previously developed models are also presented. We discuss outcrop hydrogeological properties and quantify the heterogeneity within the outcrops in detail using geostatistical variography. Moreover, outcrop-scale K values, their anisotropy and dispersivities are numerically calculated as a means to upscale such small-scale measurements to a larger scale commensurate with the scale of flow and transport modelling. By studying the small-scale variability as observed in outcrops, we gain crucial understanding of the larger-scale behaviour of the corresponding hydrogeological units within the Neogene aquifer, the most important groundwater reservoir of Flanders. The results of this study will equally improve conceptual hydrogeological model building and parameterization.

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In this paper, a multi-resolution approach is presented for mapping surface imperviousness in urbanised areas. The approach involved two steps. First, a detailed land-cover map was produced from a high resolution (HR) Ikonos image that covers part of the Brussels metropolitan area. The output of the classification was improved with post-classification techniques. This enhanced HR classification of a relatively small area was then used to train a neural network based sub-pixel classification model that estimates impervious surface cover proportions within the pixels of a medium-resolution (MR) Landsat ETM+ image that covers the entire agglomeration of Brussels. Both the HR and the MR map were used as input to a rainfall-runoff simulation on the upper catchment of the Woluwe River. Three alternative land-cover scenarios were tested: one for which a single impervious surface coefficient was defined for all urban classes, a second in which separate coefficients were derived for different types of urban morphology and finally, a spatially fully distributed scenario was applied where each cell in the simulation model was assigned its own coefficient based on the HR and MR maps of imperviousness. The study points to some interesting conclusions: it shows that estimates derived from satellite data may strongly differ from those made by experts for some urban classes, that the use of spatially distributed land-cover information obtained from satellite derived maps produces higher peak discharges, and little difference was observed between results obtained with detailed impervious surface maps derived from HR data and sub-pixel estimates derived from MR data. This proves that multi-resolution methods, which provide information on surface imperviousness for areas of large extent at relatively low cost, may be an interesting alternative for expensive HR mapping for rainfall-runoff modelling at catchment level.

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Human activities have led to the loss of a large proportion of biodiversity in riverine wetlands in western Europe (Van Urk 1984; Cirujano et al. 1996). In the second half of the twentieth century, many floodplains, fens, and riparian woodlands were cultivated for agricultural purposes. In addition, the remain- ing riverine wetlands lost species due to the impact of human activities (Rich and Woodruff 1996; McCollin et al. 2000). Recently, policy has become more focused on conservation of the remaining wetlands and on rehabilitation of disturbed rivers and floodplains (Jongman 1998). The management and reha- bilitation of wetlands is difficult without adequate knowledge of the hydrolog- ical and ecological processes responsible for the functioning and biodiversity of undisturbed wetlands.

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