Reducing potential damages by freshet abatement in hydropower lakes. An argument for financing hydropower projects

Dam reservoirs with significant water volumes (storage coefficients exceeding 8-10%) cause diminishing of the maximum flow downstream, especially due to the aleatory variation of the initial water level in the reservoir. Depending on the flow reduction in the dam, a methodology for determining the flow for the whole water course downstream is proposed, taking into account various potential combinations for flood generation in the catchment area. Differences between potential damages caused by floods in case of natural conditions versus those occurring in case of engineered zones result in important public financial benefits, amounting up to around 30% of the investments required for dam construction. For instance, in the case of hydropower lake Dragan on the Crisul Repede River the damages diminished down to about 50% for downstream watercourse. (authors)