The Water System Explorer: understanding interactions between the natural and anthropogenic water system on a regional scale

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In the Netherlands the natural water system has been altered significantly to address human needs. Historically, the main water issues were related to water excess. However, recent dry years (2018-2020, 2022) have made it clear that drought affects many sectors as well. To deal with both extremes, a transition of the water system is needed with integral solutions. Exploring the effects of measures needed to improve the water system is challenging and needs to be done in an integrated way that considers the natural water system as well as the anthropogenic influence on that system. Often these effects are investigated using complex, spatially-distributed models that usually don’t include all interactions between water users and the water system, have long calculation times and require a certain computer capacity. To attain a first crude estimate of the effects, it is also possible to use a different approach like system dynamics models. System dynamics models provide less details and include less spatial variation, but can include more interactions between the different subsystems and have short calculation times. We have developed a system dynamics model, the Water System Explorer, that can be used to simulate the effect of human interventions on the water system. The Water System Explorer provides insight into the water system at a regional scale and can be used as a tool to support conversations between different stakeholders in a region. It is a strong simplification of reality, so it serves to give a first indication of potential measures and their effects, including trade-offs, in a specific region. The Water System Explorer includes the natural and anthropogenic system. For the natural system, four different landuse types are defined: agriculture, urban area, groundwater-dependent nature and groundwater-independent nature. The phreatic groundwater level is determined for each land use type, which interacts with the surface water and deep groundwater. The anthropogenic system includes the water demand of industry and households, drinking water supply and a wastewater treatment plant. Several interventions are included, for example, a ban on water abstractions for agriculture, introducing separated sewers, increasing surface water levels, applying managed aquifer recharge and re-use of effluent in agriculture, industry, or drinking water supply. The Water System Explorer has been applied for a region in the Netherlands. The tool reproduced general characteristics of the water system and illustrated the side-effects of water system interventions as a result of feedback mechanisms. The tool shows much potential for gaining insight into a regional water system to discuss measures with all stakeholders and for education purposes.