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 rate by stating that in the case of reservoirs with a lower sedimentation rate values the silting intensity is greater, as well as higher is the silting degree.