During the summer-autumn period, field research on evaporation measurement from a surface of the small reservoir located near the city of Novocherkassk were conducted. The main characteristics of studied water object, and also the plan of its arrangement are provided in the article. The technique of definition of evaporation from a reservoir surface is described. At the end of field research, schedules of change of water temperatures in the reservoir, and also changes of depths during the summer-autumn period were constructed. As a result of data processing, the correction factor was calculated on the reservoir depth, and also the schedule of its change for all the summer-autumn period depending on depth is constructed. In the article some settlement ways of evaporation definitions are given. Analyzing them, we come to a conclusion that the most acceptable formula for evaporation definition from small reservoirs is B. D. Zaykov's formula. The comparative analysis of calculations of evaporation on B. D. Zaykov's formula is provided. The first calculation is made with application of correction factor on a depth, offered by B. D. Zaykov, which is defined proceeding from zone of a reservoir and its depth. However, it is noticed that with a depth of reservoir up to 2 m this factor is equal to 1 for all zones, despite various climatic conditions. The second calculation is made with application of correction factor on depth, calculated on the results of the field research. As a result, we come to a conclusion that according to the field research the layer of evaporation is 70 cm and the second result of calculation was the closest to it. Therefore the correction factor on depth, ??, depends on a zone, a season, and ambient environment temperature. In a steppe zone, f or the 2 m depth reservoir the correction factor is assumed from 0.82 to 0.96.
