The Ob River Water and Sediment Runoff Under Changing Climate Conditions

Changes in the Ob River sediment runoff caused by current climatic and socio-economic changes in Russian Federation have a multidirectional character in the middle and lower courses of the watercourse. According to meteorological observations, the air temperature in the studied region increased by 2 °C, and annual precipitation layers by more than 80 mm/yr, while the area of agricultural land in the middle reaches of the river decreased by 40% compared to the period before 1990. A decrease in acreage in the catchment area of the middle stream caused a three-fold decrease in sediment runoff during the high water period, while the activation of thermal erosion processes in the lower reaches led to a two-fold increase in sediment runoff during the same period. As a result of water and sediment runoff modeling according to climate forecasts, it was found that by the end of the 21st century, the average annual water runoff of the Ob River for the RCP 2.6 scenario increases by 20% relative to the period 1991–2020, while sediment runoff almost does not change. At the same time, the RCP 8.5 scenario provides a decrease in water and sediment runoff.