Runoff of the Lena Basin Rivers in the Trans-Baikal Territory and its Relationship with Atmospheric Precipitation

The objective of the article is assessment of many-year changes of the Lena River basin rivers’ runoff on the territory of Trans-Baikal Kray and its correlation with atmospheric precipitation as a leading factor of the water flow formation. Studying of the rivers’ water regime and determination of their water content cycles is especially relevant in view of extreme climate changes over the past decades and the necessity to elaborate a strategy of sustainable social/economic development of regions in contemporary conditions. However, the Lena River basin hydrological characteristics within the boundaries of Trans-Baikal Kray have been studied insufficiently. Methods. The analysis was carried out according to the data on the average monthly water consumption over the period from 1976 to 2018. To analyze the current climatic conditions we have used air temperature and atmospheric precipitation observation data from six meteorological stations. When used Pearson correlation analysis we have revealed correlation between the runoff at the posts under study and its within-year dynamics, as well as have calculated the connection with atmospheric precipitation. We have revealed many-year tendencies of the water flow by calculation and analysis of linear trends computed by the least-squares method and by plotting differential integral curves. Results. More than 80 % of river runoff is formed during the spring-summer period, at that the total winter (December-March) runoff on the average is less than 2 % of the annual runoff. In the studied sections of large rivers (Chara, Olekma), the average annual water discharge varies from 3.20 to 54.5 m3/s, small (Karenga, Bugarikhta, Kuanda) – from 10.2 m3/s up to 47.3 m3/s. The greatest consistency of water discharges is noted for the spring (April-June) and summer (July-September) hydrological seasons, since it is due to the distribution of atmospheric precipitation during the year, with which their significant correlation was revealed. During the study period, the full cycle in the sections of the studied rivers was not traced, which most likely indicates its longer duration relative to other rivers of the Trans-Baikal Kray. At present, we observe the high-water phase of the hydrological cycle.