Why do rivers on the western slopes of the Urals carry more water than rivers on the eastern slopes?

The rivers on the western slopes of the Ural Mountains carry more water than those on the eastern slopes primarily due to differences in precipitation and evaporation rates.1

The mountains act as a barrier to prevailing westerly winds, which bring moisture from the Atlantic Ocean. Consequently, the western slopes receive significantly more precipitation—reaching up to 40 inches (1,000 mm) in the Northern and Nether-Polar regions—compared to the eastern slopes, which receive only about 12 inches (300 mm).2

In contrast, the eastern slopes experience less moisture and higher rates of evaporation, which further reduces the water volume in those river systems. This disparity is most pronounced in the Northern and Nether-Polar Urals, where the western slopes benefit from the higher accumulation of rain and snow.21