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. Four future land-use scenarios (A1, A2, B1 and B2) based on the Special Report on Emission Scenarios (SRES) are modelled with the CLUE-S model. Water balance components, groundwater level and baseflow are simulated using the WetSpass model in conjunction with a steady-state MODFLOW groundwater flow model. Results show that the average recharge decreases with 2.9, 1.6, 1.8 and 0.8% for scenario A1, A2, B1 and B2, respectively, over the 20 covered years. The predicted reduction in recharge results in a small decrease of the average groundwater level in the basin, ranging from 2.5 cm for scenario A1 to 0.9 cm for scenario B2, and a reduction of the baseflow with maximum 2.3% and minimum 0.7% for scenario A1 and B2, respectively. Although these averages 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.status: publishe

Effecten van klimaatverandering op het grondwatersysteem in het Grote-Nete bekken, België

Effecten werden gemodelleerd van klimaatsverandering op het grondwatersysteem in het Grote-Nete bekken, België. De gesimuleerde klimaatsscenario's voor het gebied van 525 km2 waren een nat (greenhouse), koud, NATCC (North Atlantic Thermohaline Circulation Change) en droog scenario. Lage, gemiddelde en hoge schattingen van temperatuurveranderingen werden gebruikt voor het natte scenario. Seizoenale en jaarlijkse waterbalanscomponenten inclusief grondwatervoeding werden gesimuleerd gebruikmakend van het WetSpass model, terwijl gemiddelde jaarlijkse grondwaterstanden en afvoeren werden gesimuleerd met een tijdsonafhankelijk MODFLOW grondwaterstromingsmodel. WetSpass resultaten voor de natte scenario's tonen aan dat verwacht wordt dat meer natte winters en droge zomers zullen optreden relatief ten opzichte van de huidige situatie. MODFLOW resultaten voor het natte, hoge temperatuur scenario laten zien dat grondwaterstanden stijgen met maximaal 79 cm, welk een duidelijke invloed zal hebben op plantensoortensamenstelling en -rijkdom. Resultaten verkregen voor het koude scenario laten drogere winters en nattere zomers zien ten opzichte van de huidige condities. Daarentegen voorspellen de droge scenario's droge condities het hele jaar. De grondwatervoeding tijdens de zomer reduceert in dat geval tot nul, wat deels toegeschreven wordt aan de hoge verdamping van bossen en de lage neerslag. De gemiddelde jaarlijkse grondwaterstand reduceert met 0.5 m, met een maximum van 3.1 m aan de oostkant van het Kempisch plateau. Verwacht wordt dat deze veranderingen sterke invloed zullen hebben op aquatische en terrestrische ecosystemen en gewasproductie.status: publishe

Potential impacts of climate change on groundwater supplies to the Doñana wetland, Spain

Climate change impacts on natural recharge and groundwater-wetland dynamics were investigated for the Almonte-Marismas aquifer, Spain, which supports the internationally important Doñana wetland. Simulations were carried out using outputs from 13 global climate models to assess the impacts of climate change. Reductions in flow from the aquifer to streams and springs flooding the wetland, induced by changes in recharge according to different climate projections, were modelled. The results project that the change in climate by the 2080s, under a medium-high greenhouse gas emissions scenario, leads to a reduction in groundwater resources. The reduction in mean recharge ranges from 14%–57%. The simulations show that there is an impact on hydraulic head in terms of the overall water table configuration with decreases in groundwater level ranging from 0–17 m. Most simulations produce lower discharge rates from the aquifer to stream basins, with significant reductions in the larger La Rocina (between −55% and −25%) and Marismas (between −68% and −43%) catchments. Water flows from these two basins are critical to maintain aquatic life in the wetland and riparian ecosystems. Modelled climate-induced reductions in total groundwater discharge to the surface are generally larger than current groundwater abstraction rates. The results highlight that effective strategies for groundwater resources management in response to future climate change are imperative