Despite the various categories of defining the life of water reservoirs, the notion life of reservoir most often relates the period of the operation to such silting degree that makes impossible the realization of the tasks of the reservoir. In this work it was show the change of the value of the silting degree and sediment trap efficiency of chosen reservoirs and was estimates the time after which small water reservoirs will be silted in 50%. This is the period, which by Pitt and Thomson [1984] is defined as HLT, i.e. half-life time. The following reservoirs were chosen to studies: Krempna on the Wisłoka river, Zesławice on the Dłubnia river and Cierpisz on the Tuszymka river. The elaborated silting forecast of the change of the silting degree, make by the Gončarov's method [Wiśniewski, Kutrowski 1973], made possible the qualifi-cation the HLT silting time of small water reservoirs. It was stated that the life of studied reservoirs carried out from 17 to 40 years. The differentiation of the HLT value results from the hydraulic conditions of the inflow and flow through the re-servoir of the water and sediment which one can characterize in the very general method using the sediment trap ...
The sedimentation index was introduced and defined by Churchill. This index is the ratio of the water retention time in the reservoir and the average flow velocity of water through the reservoir. Churchill developed sediment trap efficiency (STE) of reservoir in the function of sedimentation index. The ability to use the sedimentation index to characterize the silting process of small reservoirs, as well as the possibility of using the Churchill's method was made on the basis of the results of four small reservoirs. For testing two reservoirs in cascade and two reservoirs parallel configuration were chosen. It has been found that it is possible to use the sedimentation index to determine the initial sediment trap efficiency of small reservoirs, regardless of their relative position on the watercourse. It is not possible to determine reduce the STE of the individual years of operation using the Churchill's formula. It has been shown that in the reservoirs in parallel configuration the sediment trap efficiency is reduced with the same intensity, but in the reservoirs in cascade in the upper reservoir sediment trap efficiency is faster reduced than in the lower reservoir of the cascade. Also elaborated silting intensity dependence of the sedimentation ...
The results of the calculations of the sediment trap efficiency of small reservoirs were introduced in the work. The sediment trap efficiency was appointed the symbol . Nine small reservoirs located in the Upper Vistula river basin were chosen to analyses. This efficiency became determined on the basis of the sediment balance and compared with the results of applied Brune's method and its modification, worked out by Gill, Heinemann and Jothiprakash and Garg. It was stated that the possibility of the use of these methods to delimitation of the initial sediment trap efficiency of small reservoirs existed. The initial concerns to the beginning of operation. These methods can have the use in the case of the small reservoirs the whose capacity-inflow ratio is larger from 1%. Also it was stated, that the results of the calculations of the sediment trap efficiency in the successive years of the operation of small reservoirs executed using Brune's method and Gill's, Heinemann's and Jothiprakash's and Garg's formulae they do not represent real value of , determined on the basis of the sediment balance. Estimated methods can not the be used to the qualification of the sediment trap efficiency of small reservoirs in ...
