Based on hydrological data from 1966 to 2019, quantitative estimates of the water balance of the Baksinskoye and Obskoye fens. The decrease in surface evaporation of the swamp and the increase in water runoff occurred in the main distribution of the swamp. This will exacerbate the degree of swamping in the area. The impact of marsh water on groundwater is most likely to occur during the dry season in summer and autumn. During this period: 1) possible overflow of bog waters into underground horizons in areas of 800-900 m; 2) increased permeability. When the water mass is discharged from the fens plain into the river, the impact of the fens water reaches its maximum during the subside of the flood.