Water table level dynamics in the drained part of the great Vasyugan mire

Abstract

Relevance. The need to assess mire-river interaction in Western Siberia under the influence of drainage and the pyrogenic factor. Aim. To study water table level dynamics in the Great Vasyugan Mire and the patterns of its change under the influence of drainage and the pyrogenic factor. Objects. Nоrtheastern part оf the Great Vasyugan Mire clоse tо Pоlynyanka village, Bakchar district, Tоmsk regiоn. Methods. Hydrological monitoring of drained and pristine part of the Great Vasyugan Mire is organized within the small model catchments of the Gavrilovka River and Klyuch River in the Vasyugan station of the Siberian Research Institute of Agriculture and the Peat branch of the Siberian Research Institute оf Agriculture and Peat RAS. Water table level monitoring was carried out in 2022 using Solinst Levelloger (Canada) with a frequency of 1 hour. River discharge measurements were made in different water periods using an acoustic current meter OTT Hydromet. The research methodology included an assessment of the spatial and temporal variation in water levels over the drained territory of the Great Vasyugan Mire in the Gavrilovka River basin in comparison with pristine part and depending on the main meteorological factors, correlation curves construction of mire water level and river discharges, the specific yield calculation. Statistical analysis of the data was carried out using the nonparametric Wilcoxon test, correlation and cluster analysis. Results. The studies shown that the drained area of the Great Vasyugan Mire within the Gavrilovka River basin is characterized by a significant transformation of the hydrological regime; there is a significant decrease in the water levels and an increase in the amplitude of their fluctuations. The influence of the pyrogenic factor is expressed in a certain increase in water levels as a result of the surface burnout and the leveling of microtopography. An analysis of the spatial variation of the water levels showed that it depends on the vegetation type of key sites, the slope of the surface, and the degree of surface burnout. It also depends on the location of the site relative to the lagg area, zones of backwater flow formed near overgrown drainage ditches, dirt roads and main ditch drainage zones. As a result of the forest reclamation and fire event in the study area of the Great Vasyugan Mire, active decomposition of plant residues was noted. This led to a decrease in the storage capacity (specific yield) of the upper peat layer. A decrease of the specific yield will increase the runoff from the mire area, which means the increase of possibility of extreme hydrological events in the conditions of growth in the amount of precipitation.