| Abstract: | An analysis of hydrologic and geodetic data from numerous reservoirs lying in different climatic zones, has allowed the two main phases in filling the reservoir during its life to be distinguished, firstly silting of an originally deep reservoir, and secondly silting of a reservoir which has become shallow or initially was not deep. During the first phase, the reservoir plays a role as an accumulator of sediment, so that its trap efficiency for total mineral material is much reduced, and its trap efficiency for suspended load decreases to zero. This phase ends when the mean depth reaches a critical value which is specific for each reservoir. During the second phase, shallowing of the reservoir is much slower, and over short time periods it can play a role as a net exporter of sediment. A general model of reservoir sedimentation is proposed and is tested by data on the long-term and seasonal courses of siltation in selected reservoirs in the Vistula drainage basin, Poland. The rate of sedimentation is analysed for both phases of siltation, and the useful lifetime of a reservoir, which corresponds to the first phase of siltation, has been computed according to a methodology proposed. |
