Abstract

Within the framework of the preparation of the Dutch National Policy Plan for Drinking and Industrial Water Supply, the RIVM Groundwater Model for the Netherlands (LGM) is developed. The main goal of the study was to elaborate upon the effects of groundwater abstraction on terrestrial ecosystems (not considered in this report). LGM is used to assess the effect of changes in groundwater abstractions upon the geohydrological system. The effect is expressed in terms of hydrological variables, namely the changes in phreatic waterlevel, groundwater head in deeper aquifers, flux between the upper boundary of the geohydrological system and the top aquifer, and fluxes across the aquitards. Several types of groundwater abstractions were distinguished, namely abstractions from phreatic aquifers, semi-confined aquifers, and riverbank infiltration. In eight scenario's, the yearly amount of groundwater was increased or decreased, with respect to the reference groundwater abstractions occurred in 1988. LGM is a coupled system of so-called AQ-computer program packages (e.g.AQ-FEM) and a Geographic Information System (GIS). The main task of the GIS-environment is the storage, processing and visualisation of spatially data, including the moddelling results. The AQ-computer programs are based on the numerical technique of finite elements. The saturated multi-aquifer geohydrological system consists of a series of aquifers separated by aquitards. The flow in the system is assumed to be quasi three-dimensional.