The article describes the influence of the exploitation condition of the reservoirs on the hydraulic parameters of the Big Fergana main channel in Fergana valley. Fractional and variable chemical composition of the sediments flowing with the water into the reservoir as well as their changes during the growing season is considered to be the main factor of this process. As a result of field experiments, it was found that the main share of sediments flowing into the reservoir consists of sand particles with a size of 0.01-0.1 millimeters. Analysis of the working effectiveness of the reservoir showed that 45-50% of these particles are kept within the reservoir, while the other pass further to the channel. Surveillance and experimental studies on the reservoir are mainly based on sedimentary particles of 0.10-0.05 and 0.05-0.01 mm and their water content is around 71-85.4%, with a larger size of 0.1 mm. and sediments with a diameter greater than the average for most of the aquifer. The obtained results indicate the influence of the sedimentary water reservoir on the hydraulic parameters and functioning capacity of the Big Fergana channel.