Non-damaging flow below storage reservoirs is one of the key factors which affect the proper water management, especially the protection valleys against flooding. Following analysis of river flow capacities below reservoirs it should be noted that, over the years, these capacities are subject to significant limitations. It is usually caused by an inappropriate floodplain management. Buildings are often built closer to the river channels, which in consequence causes flooding of the buildings at low flood discharges. Repeated inundations and thus increasing losses oblige the local authorities to maintain low outflows from reservoirs in the first phase of the freshet, which leads to a rapid fulfillment of flood reserves of the reservoirs. Then, the culmination of flood wave often takes place when the reservoirs are filled and consequently high discharges from the reservoirs must be realized. This causes flooding of the areas and buildings below the storage reservoirs. This situation could have been avoided if the riverbeds and floodplains had been adjusted to pass nondamaging flow and adopted it as the basis for the water management of a given reservoir. A significant improvement in reduced reservoir capacities will occur if the values of nondamaging flow below the reservoirs are increased and the losses caused by flood flow are significantly reduced by appropriate spatial development of the areas below the storage reservoirs. The current non-damaging flow below the Mietków Reservoir is a striking example of the issue. Three farms located within the floodplain of the Bystrzyca river have an adverse impact on water management of the reservoir when floods take place.