BEKWAAM, a model fit for reservoir design and management

In the Province of Limburg in the Netherlands a new reservoir will be used for the drinking water production of 20 million m3 per annum from the rear 2002. With the use of this reservoir the WML is shifting towards the use of surface water (River Meuse) as primary source instead of ground water. This in view of the general Dutch policy pertaining to desiccation abatement and ground water pollution control. Because the River Meuse is known to be polluted with various numbers of constituents, predominantly nutrients, and on occasion with heavy metals and pesticides, the reservoir water quality model BEKWAAM has been constructed to be able to predict the water quality of this reservoir. The model simulates processes like heating, decay, sedimentation and eutrophication. The model was calibrated using data of two existing reservoirs in the Netherlands. The first simulation results of BEKWAAM indicate that significant high temperature differences are expected between river water and reservoir water, a point to be dealt with in the design of the inlet construction, to prevent stratification. Furthermore is was concluded that, providing thorough mixing takes place, the average depth of 20 m of this new reservoir induces sufficient light limitation. Finally the expected ammonium-nitrogen concentrations will not exceed a value of 0.05 mg NH4-N/l, despite the fact that average River Meuse concentration ranges from 0.1–1.7 mg NH4-N/l. This is caused by processes like nitrification and uptake by algae.