The article analyzes meteorological and hydrological data for the Tobyl River basin. As a result of the study, a clear trend was observed in changes in air temperature values in the Tobyl River basin. And it was found that the fluctuation in precipitation values only during the cold period is statistically significant. An assessment of the summer-autumn and winter minimum flow of the Tobyl River basin showed that in the 80s of the last century, directional changes were observed in the flow characteristics. A connection has also been established between seasonal flow in the Tobyl River basin and synoptic conditions of various forms of atmospheric circulation. The relationship between the epochs of atmospheric circulation and the minimum flow of the river basin. The relationship between the epochs of atmospheric circulation and the minimum flow of the Tobyl River basin shows that the epoch E of the circulation form corresponds to a period of years with an average minimum flow below the norm, form C corresponds to minimum flow values exceeding the normal value, and form E + C, where form E predominates correspond to periods of minimum water flow close to normal in years of average water availability, the same picture is observed in the E+W period.