Changing of the riverine sediment load supply into Lake Baikal: The natural and anthropogenic causes (Russia)

摘要

The influences of natural and anthropogenic factors on temporal changes in sediment load of the main Baikal rivers (Upper Angara River and Barguzin River) were analyzed through the relationship between hydro-climatic parameters (air temperature, precipitation, water discharge and sediment load) and their variation tendencies for the periods of 1945-2014, 1945-1975 and 1976-2014. Mann-Kendall test, abrupt change test were employed to analyze the hydro-climatic data. The results indicated that the air temperature increased on 1.0-1.1 degrees C in the watersheds over the warming period (1976-2014), and the precipitation had an insignificant decreasing trend in this period, and the reduction was - 2.6% and - 4.9%. The statistically insignificant increasing in water discharge was 4.2% and 1.3% in the Upper Angara and Barguzin over the period 1976-2014, respectively. Meanwhile, there was a strong decrease in sediment load of - 66% and - 70%. The abrupt decrease the sediment load in the Upper Angara since the mid-1970s was caused by the combination of human activities in river basin and changes of natural processes. In the Barguzin basin, the significant anthropogenic impact against the background the changes of natural processes in the mid-1980s was began. In the Upper Angara, the period of rapid decline of sediment load from 1976 to 1984 continued, in the Barguzin - from 1976 to 1991, after that, the other regime of sediment load had established. In recent decades, the actual sediment load supply from the Upper Angara and Barguzin into Lake Baikal are 92 x 10(3) t ty(-1) and 27 x 10(3) t ty(-1) or 22% and 18% of the 1945-1975, respectively.