Predicting land-use change and its impact on the groundwater system of the Kleine Nete catchment, Belgium

Land-use changes are frequently indicated to be one of the main human-induced factors influencing the groundwater system. For land-use change, groundwater research has mainly focused on the change in water quality thereby neglecting changes in quantity. The objective of this paper is to assess the impact of land-use changes, from 2000 until 2020, on the hydrological balance and in particular on groundwater quantity, as results from a case study in the Kleine Nete basin, Belgium. New is that this study tests a methodology, which couples a land-use change model with a water balance and a steady-state groundwater model. Although the averages found appear to indicate small changes in the groundwater system, spatial analysis shows that much larger changes are located near the major cities in the study area. Hence, spatial planning should take better account of effects of land-use change on the groundwater system and define mitigating actions for reducing the negative impacts of land-use change

Evaluating the impact of river restoration on the local groundwater and ecological system: a case study in NE Flanders

River restoration changes the interaction between groundwater and surface water. Therefore, it is expected to have an impact on ecosystems at the interface between groundwater and surface water. Quantifying and generalizing the level of change of this interaction for different hydrogeological environments is scientifically and practically challenging. In this paper we investigated the impact of different restoration measures and the effect on the interaction of the temporal resolution of the groundwater modeling methodology. The interaction is analysed in the water bodies and wetlands in the valley of the Zwarte Beek, one of the most valuable nature reserves of Flanders. In the past, several changes have been made to the river and drainage system. These adaptations are now considered to be bottlenecks in maintaining a good ecological and hydrological status of its water dependent biotopes. Hence, in the context of the EU Water Framework Directive, it is necessary to (at least partly) restore the initial natural situation. The measures proposed include the reinstatement of old meanders and the removal of a weir. By removing the weir, fish migration is again possible. Reconnecting old meanders increases the habitat diversity. We used transient groundwater modeling to evaluate the impact on the groundwater system of the wetlands. Results indicate that a peat layer, present in most of the wetland, minimizes the effects of the restoration on the groundwater table. The largest changes are confined to the areas near the old meanders and the weir. Steady-state situations do not allow a calculation of average lowest and highest groundwater levels, which are essential for simulating ecological site conditions. Hence, transient simulations with 14 days time steps are required to detect a considerably greater range of groundwater fluctuation than indicated by the seasonal simulation. It is shown that the river restoration project thus resulted in an improvement of the structure of the watercourse rather than the rewetting of the valley. We concluded also that high resolution transient groundwater modeling is an essential step towards river restoration and ecohydrological predictions

Delineating groundwater-surface water exchange flux using temperature-time series analysis methods

Groundwater-surface water interactions can play a crucial role in river-, riparian and wetland management. Their delineation and quantification at various spatial and temporal scales has become an important aspect in the study of contaminant transport and attenuation processes at the groundwater-surface water interface. One of the main parameters of interest is the groundwater-surface water exchange flux, which provides indications regarding stream-aquifer connectivity, the local flow regime as well as hydrogeological properties of the streambed. One of the methods to assess vertical exchange flux is through the analysis of temperature time-series. In this paper we delineate vertical exchange flux from temperature-time series collected at a Belgian River by comparing established numerical and analytical techniques with a novel approach. Results indicate a spatial variability of vertical fluxes over two orders of magnitude at the site

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Spatial and temporal variability of groundwater recharge in Geba basin, Northern Ethiopia

This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/ This author accepted manuscript is made available following 24 month embargo from date of publication (July 2017) in accordance with the publisher’s archiving policyWetSpa, a physically based, spatially distributed watershed model, has been used to study the spatial and temporal variation of recharge in the Geba basin, Northern Ethiopia. The model covers an area of about 4, 249 km2 and integrates elevation, soil and land-use data, hydrometeorological and river discharge data. The Geba basin has a highly variable topography ranging from 1000 to 3280 m with an average slope of 12.9%. The area is characterized by a distinct wet and long dry season with a mean annual precipitation of 681 mm and temperatures ranging between 6.5 °C and 32 °C. The model was simulated on daily basis for nearly four years (January 1, 2000 to December 18, 2003). It resulted in a good agreement between measured and simulated streamflow hydrographs with Nash-Sutcliffe efficiency of almost 70% and 85% for, respectively, the calibration and validation. The water balance terms show very strong spatial and temporal variability, about 3.8% of the total precipitation is intercepted by the plant canopy; 87.5% infiltrates into the soil (of which 13% percolates, 2.7% flows laterally off and 84.2% evapotranspired from the root zone), and 7.2% is surface runoff. The mean annual recharge varies from about 45 mm (2003) to 208 mm (2001), with average of 98.6 mm/yr. On monthly basis, August has the maximum (73 mm) and December the lowest (0.1 mm) recharge. The mean annual groundwater recharge spatially varies from 0 to 371 mm; mainly controlled by the distribution of rainfall amount, followed by soil and land-use, and to a certain extent, slope. About 21% of Geba has a recharge larger than 120 mm and 1% less than 5 mm

Assessment of Conceptual Model Uncertainty for the Regional Aquifer Pampa del Tamarugal - North Chile

In this work we assess the uncertainty in modelling the groundwater flow for the Pampa del Tamarugal Aquifer (PTA) ¿ North Chile using a novel and fully integrated multimodel approach aimed at explicitly accounting for uncertainties arising from the definition of alternative conceptual models. The approach integrates the Generalized Likelihood Uncertainty Estimation (GLUE) and Bayesian Model Averaging (BMA) methods. For each member of an ensemble M of potential conceptualizations, model weights used in BMA for multi-model aggregation are obtained from GLUE-based likelihood values. These model weights are based on model performance, thus, reflecting how well a conceptualization reproduces an observed dataset D. GLUE-based cumulative predictive distributions for each member of M are then aggregated obtaining predictive distributions accounting for conceptual model uncertainties. For the PTA we propose an ensemble of eight alternative conceptualizations covering all major features of groundwater flow models independently developed in past studies and including two recharge mechanisms which have been source of debate for several years. Results showed that accounting for heterogeneities in the hydraulic conductivity field (a) reduced the uncertainty in the estimations of parameters and state variables, and (b) increased the corresponding model weights used for multi-model aggregation. This was more noticeable when the hydraulic conductivity field was conditioned on available hydraulic conductivity measurements. Contribution of conceptual model uncertainty to the predictive uncertainty varied between 6% and 64% for ground water head estimations and between 16% and 79% for ground water flow estimations. These results clearly illustrate the relevance of conceptual model uncertainty.JRC.H.7-Land management and natural hazard