Precipitation, melt and runoff in the northern Tien Shan

Precipitation and snow distribution, melt of glaciers and snow, and runoff formation in two basins in the northern Tien Shan are calculated and described. Major climatic features are a spring-summer precipitation maximum occurring simultaneously with ice and snow melt. Precipitation increases with altitude except in winter when an air temperature inversion occurs. Air temperature is a good predictor of glacial melt. Typical hydrographs have two hoods: one is formed from melt of seasonal snow cover, and the other is formed from melt of glacial ice. The second flood is usually larger than the first. In mountain basins of the northern Tien Shan direct runoff from rainfall averages about 7-12% of annual volume. The glacial runoff is 18-28% of average annual runoff in basins with area of glaciation not less than 30-40%, but during summer it can increase to 40-70% of average annual runoff. Surface runoff from seasonal snow melt during spring and summer is 18% of average annual runoff; the groundwater component is 34-38% of average annual runoff.