Modelling Alternative Drinking Water Extraction Strategies for the Sandy Pleistocene Regions of the Netherlands

Abstract

Sufficient provision of high-quality drinking water is vital to a healthy society and the prosperity of local industries, agriculture, and energy sectors. For the sandy Pleistocene regions of the Netherlands, phreatic aquifers are the primary sources of drinking water. However, future socio-economic and climatological stresses increasingly exert pressure on the sustainable utilization of these sources; resulting in an onset of groundwater depletion, drought enhancement, and degradation of groundwater-dependent ecosystems. To ensure adequate water availability whilst maintaining hydro-environmental functioning, the strategic and sustainable management of groundwater is crucial. Changing to alternative manners of exploitation (i.e. strategies) of these regional groundwater sources could help to reduce impacts. However, which alternative strategies are viable, and how they affect the regional hydro-environment remains poorly understood.

This thesis presents an explorative regional study in pursuit of a sustainable drinking water provision system from groundwater for these regions. The approach followed the identification and conceptualization of two innovative alternative extraction strategies: decentralized extractions and seasonal extractions. By a comprehensive quantitative scenario analysis, specified to the northern Achterhoek as case-study, both strategies were evaluated by their impacts on regional groundwater levels, soil moisture content, and evapotranspiration. The hydrological and environmental effects were quantified using the novel developed geohydrological model AMIGO (v3.1) and compared to a reference scenario for the period 01-04-2004 to 31-12-2019.

The results showed that decentralization, and to less extent seasonal extractions, can have a beneficial effect on regional groundwater levels. Decentralized extractions indicated a positive relation to the reduction of local drawdown, increasing under higher quantities of decentralized volumes (0 – 15%). Both the extent and intensity outweighed the adverse effects at decentral locations. Seasonal extractions were found slightly less effective (0 – 5%), except when applied in large volumes (5 – 15%), but showed potential to optimize annual water containment on a regional-scale. The positive effects of both strategies, however, only locally propagated to soil moisture content (0 – 10%) and minimally enhanced regional evapotranspiration (< 1%). The deep groundwater tables prohibited effective interactions ensuing changes in groundwater level, indicating that hydro-environmental functioning could only limitedly be improved under both strategies.

Whilst the results were bilateral, the implications are likely valuable to water managers assessing strategies from a multi-directional perspective. Inevitably, a transdisciplinary approach is required to meet demand and achieve a sustainable drinking water provision. This explorative work thereby contributes by paving the road to more detailed studies and hinting at rough directions of potential future sustainability.