Control model Spree/Schwarze Elster — a tool to optimise rehabilitation of water resources in the Lusatian mining district

The river basins of the Spree and Schwarze Elster have been disrupted by the long-lasting intensive lignite mining process in the Lusatian district, resulting in a large cone-shaped groundwater depression of 4000 km2. Its volume is about 10 billion m3, or about 15 times the annual groundwater recharge of that region. Special problems relate to the flooding and future use of remaining pits. With regard to water quality (acidification) it is necessary to accelerate the natural filling process by supplying surface water. This depends on its availability, as well as on the regional water balance. For the Lusatian river basins, long-term water resource planning models exist. These models combine on a monthly basis a stochastic simulation model of runoff with a deterministic analysis of water demand and availability of water resources. Based on these models, the overall and long-term water management strategies are developed. To control the daily water balance and to supply water for flooding the remaining pits, a short-term control model is now under development. It is based on the long-term strategy, but takes into account the actual runoff of the region, discharge in the rivers and water consumption. In this paper both the models and their applications are discussed.