Ecological Systems and Devices Annotation << Back HYDROLOGICAL REGIME OF RIVERS IN THE DRAINAGE BASIN OF LAKE TUNAYCHA (SAKHALIN ISLAND) D.A. Bobrova Lake Tunaicha is located in the southern part of Sakhalin Island and is the second largest lake on the island. In addition, oz. Tunaycha belongs to the protected areas of regional significance. Currently, the hydrological regime of the watercourses flowing into the lake has not been studied. This paper describes the rivers of the drainage basin of Lake Tunaicha (Sakhalin Island), studies their hydrological regime, calculates the average annual water consumption, annual volume and intraannual distribution of runoff. In total, at least 38 watercourses flow into the Tunaycha. In addition, water exchange is carried out through the channels with 7 lakes located directly on the territory of the lake’s catchment basin. According to calculations, the total annual flow of all rivers flowing into the lake. Tunaycha, is 307.6 million m3. Keywords: Lake Tunaycha, average annual runoff, volume of runoff, intra-annual distribution of runoff. DOI: 10.25791/esip.6.2023.1382 Pp. 84-97.