Runoff Dynamics in Catchment Areas with Forest Cover Disturbed by Cutting in the Angara River Basin

In light of large-scale logging in Central Siberia, the problem of restoring the hydrological regime in catchment areas seems very urgent. The Angara River basin is the most indicative in terms of forest disturbance. The purpose of this work is to assess the impact of the area of forest cover that has been disturbed, as well as postlogging reforestation on the hydrological regime of the Angara tributaries using climate databases and remote sensing data. This paper analyzes the runoff dynamics in four Angara tribuaries (the Irkineeva, Chadobets, Mura, and Karabula rivers), whose catchment areas have been subject to large-scale logging. To solve this problem, we use long-term runoff observation data from hydrological station and precipitation data from meteorological stations in the region under study. The analysis of forest cover changes in the studied catchments, taking into account the clearing areas, is carried out using data from the Global Forest Change (GFC) 2000–2020 resource ( https://earthenginepartners.appspot.com/science-2013-global-forest ) and Landsat satellite images. The direction of the reforestation and the forest restoration processes are analyzed based on our own forestry research and forest management materials. It is found that logging decreases the flow of the studied rivers from 1.5 (Mura River) to 4 mm per year (Chadobets River) over the past two decades. Relative equalization of the flow is observed when 16–20 year old clearings are overgrown and when young trees reach the pole wood growth stage. The results and numerical modeling of the dependence of the runoff on the area of forest-cover disturbance show critical values of the share of the fresh cuttings for maintaining the stability of the water content in medium and small tributaries of the Angara. For example, for the smallest of the studied rivers (Karabula), the area of nonrenewed cuttings should not exceed 2% of the catchment area. Cutting on adjacent units is possible only after the formation of closed young growth in the first cutting. The studies show some certainty in studying the conjugation of runoff dynamics and critical transitions of secondary phytocoenoses caused by a gradual change in the vegetation cover in the process of reforestation after the disturbance of the forest cover in the catchment area. As a result of constant changes in the structure of the vegetation cover, future scenarios of hydrological regimes after logging are determined by both further climate changes and the direction of vegetation successions.