River Minimum Flow Changes under Dammed Reservoir Conditions

The main aim of this study was to assess what range of downstream low flow changes is caused by dam construction directly. An investigation was based on the assumption that the difference in change ratio of flow between gauging cross-sections located downstream and upstream position of dammed reservoir identifies the scope of changes determined by dam construction. Three dammed reservoirs located on Polish rivers were selected for analysis. They were different in size, hydrological regime and water management purposes. For each reservoir pair of water, gauges were selected. The input data were daily discharge series collected by the Polish Institute of Meteorology and Water Management. For each time series 20-year period before and after dam construction was established. Comparison of annual minimum flow ratios for these peri-ods as well as analysis of low flow dynamics and inertia allowed to identify range and direction of changes caused by investigated reservoirs.