Estimating groundwater resources in hardrock areas - a water balance approach

Abstract

Among decisionmakers in counties and municipalities, there is a great need for simple but hydrogeologically correct estimations of the groundwater resources.Today's methods are often based on extensive field investigations and complicated mathematical flow modelling or too simplified annually based water balances. In this paper, a groundwater balance method is presented that is especially adapted to small and complex aquifers, such as in hardrock, in which the storage capacity of the aquifers gives the extraction limits. The balance is focused on the development over time of the storage, to which groundwater recharge and withdrawal from well users are added and drawn. A computerised system has been developed as an expert system for users, who are not professional hydrogeologists. The balance can be used for calculating the maximum acceptable number of consumers in an area or for the set of a maximum acceptable sanitary standard, based on available groundwater resources. The balance method has so far been used as a planning tool within several areas around Stockholm, Sweden. The results are reasonable, compared to experiences of the real groundwater situations in the areas, although a true validation has not yet been carried out.