It was studied seasonal dynamics of inoculation of microorganisms from water samples of some reservoirs of Uzbekistan in a comparative perspective. It was found that in samples of water of Kattakurgan reservoir TC in 1 dm3 in summer in the water samples from the middle of the reservoir is 2.2 times higher than normal, above the dam - 10.4 times, from the recreational area - 18.8 times. In the spring, TC was 2-3 times smaller than in the summer, but TBC, on the contrary, more. Exceeding in this parameter 4.5 - 26.0 times is mentioned in the water of Tuyamuyun reservoir. In the spring, quality of the water by TC not differ, by TBC is significantly better than in the summer. These parameters of water of Charvak reservoir are at the upper limit of normal. The quality of the water of Charvak reservoir repeatedly exceeded microbiological parameters of Kattakurgan reservoir and Tuyamuyun reservoir.