Water balance of Lake Baikal for the operation period of the Irkutsk HPP
V.M. NIKITIN1, N.V. ABASOV1, E.N. OSIPCHUK1, T.V. BEREZHNYKH1, V.Yu. GEORGIEVSKY2, A.V. IZMAILOVA2, T.G. MOLCHANOVA2, T.V. FUKSOVA2
1Melentiev Energy Systems Institute, Siberian Branch, Russian Academy of Sciences, Irkutsk, Russia
2State Hydrological Institute, St. Petersburg, Russia
Keywords: water balance, surface inflow, useful inflows, precipitation, evaporation, discharge through the HPP, climatic changes
Abstract
Presented are the results from investigating changes in the water balance components of Lake Baikal for the operation period of the Irkutsk HPP (1960-2020) on the basis of analyzing the long-term dynamics, including the surface inflow, discharge through the Irkutsk HPP, precipitation on the lake surface, and evaporation from the lake surface in monthly, quarterly and yearly resolutions. The surface inflow constitutes the main component of the inflow portion of the water balance and is determined from observational data obtained at 32 posts on the rivers flowing into the lake and from calculated values of the inflow from the part of the catchment which is not covered by hydrometric observations. It is pointed out that the share of the large rivers (Selenga, Upper Angara, and Barguzin) accounts for about two-thirds of the total surface (river) inflow. Over the last several decades, the proportion of the inflow via the Selenga river has decreased by 20 % against the preceding period. An analysis of the long-term changes in the river and useful inflows showed the existence of two periods with low water: 1976-1981 and 1996-2017 as well as two periods with abundance of water: 1960-1975 and 1982-1995, and an increase in the inflow since 2018. A comparison is made of the water balance components for two periods of equal duration: 1971-1995 and 1996-2020. A disturbance of the uniformity is observed for the discharges through the Irkutsk HPP. The study revealed an increase in mean annual temperature by 1-2 °C and a decrease in atmospheric precipitation almost throughout the lake drainage basin. The annual values of precipitation after 1996, compared with the preceding period, decreased throughout the territory of the lake drainage basin by 30-60 mm. Using two extreme periods of low water (2014-2017 and 1976-1981) we consider the role of the Irkutsk HPP in the regulation of the level regime of the lake.
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