Development of planning tools for the ecologically sound operation of reservoirs

Within the state of Northrhine Westphalia, Germany, 72 reservoirs store and provide water for manifold uses; many of them are combined in multipurpose systems. Often their management and operation still follow rules originally developed during their planning phase or shortly thereafter. After decades of operation it has become evident that the rule curves used have caused noticeable ecological changes in the downstream reaches of the reservoirs. The stage agency for environment has initiated the development of planning instruments to enable reservoir operators to improve release rules by using dynamic short-term and long-term control policies. The concept is based on deterministic real-time modeling using daily or hourly time-steps according to stream flow intensities. For the daily operation heuristic rules are being developed based on long-term historic records, while flood control is based on actually measured and forecast inflows. Flood waves might be propagated through the reservoirs to cause high frequency, but low intensity floods to reactivate downstream flood plains as part of the aquatic/amphibious environment