Uzbekistan is an inland country with very dry summers and cold winters. The main course of the economy is agriculture. There are two basic kinds of agriculture in terms of irrigation: rainfed and artificial irrigation systems. Therefore, in long dry summers it is reasonable to build water reservoirs to keep enough water resources for vegetation period. Because of sedimentation transport water reservoirs sometimes quickly filled with sediment. Estimating the effects of potential sediment accumulation in reservoirs is an important element in the planning of the dam project. Sediment accumulation in a reservoir may reduce the useful storage of water in this reservoir, change the water quality near the dam, increase flooding level upstream of the dam due to sediment aggradation, influence the stability of the stream downstream of the dam, affect stream ecology in the dam region, etc. This article provides a correlation between the reservoir volume reduction from the bottom to a given level, based on the amount of water flowing into the Chimkurgan reservoir and the river basin monitoring data. Based on the results of observations and calculations, the current state of the reservoir was formed on the basis of GIS tools. In the first step we constructed a flow duration curve, which is the cumulative distribution curve of the stream runoff passing the dam.

The article analysis the factors influencing the reduction of reservoir useful volume, including the formation of shores, and proposes and method of their quantitative calculation. The research was provided in the South Surkhandarya reservoir. During the exploitation of the reservoir, were assessed the morphometric index of the basin and changes in a bank due to various influences. The article presented mathematical, statistical calculations of changes in erosion conditions due to displacement of the left banks of the South Surkhandarya Reservoir and changes in pressure in the strata and water saturation of the coastal layers. The proposed method of assessment and calculation will allow development measures to improve the operation of reservoirs based on the determination of morphometric parameters and prevent the formation of shores.