Home – Home – Jornals – Geography and Natural Resources 2020 number 2

Presented are the results from studying the underground runoff of the Oka river basin, including 23 single catchments. Most of the basin of the Oka (a large left tributary of the Angara river) is located within the mountain-folding region and scarcely covered by data of routine observations of the river runoff. The underground runoff for the rivers within the Oka basin was determined by an integrated hydrological-hydrogeological method of genetic separation of river hydrographs having regard to the withdrawal of a part of the runoff for aufeis formation, considering different drainage schemes of water-bearing material by riv ers. Most river basins of the Eastern Sayan are characterized by the absence of bank stream flow control, because even in small river basins the depth of erosional incision exceeds considerably the thickness of the drainage zone which is determined by the occurrence depth of effective crevassing. Under these conditions, almost complete drainage of the massifs by rivers occurs. For the unexplored rivers, the underground runoff was determined by the method of transition coefficients from single water dis charges obtained during the hydrometric survey of the winter low-level water. Within the mountain-folding region, the specific groundwater runoff varies over a wide range from 0.5 to 9.2 L/s/km ² and depends on the landscape-climatic conditions, primar ily on the atmospheric precipitation amount as well as on hydrogeological conditions of particular catchments associated with the occurrence of permafrost and with differences in tectonic activity in different parts of the study area.