Water Discharge of Imja Khola in Khumbu Himal

Abstract

Observations of water discharge from a drainage area of 142.5 km2 including glacier zones were made at Dingboche (4330 m) in east Nepal. The annual discharge of this drainage was estimated as 1.7 × 108m3. The annual variation of the discharge showed a tendency to increase in summer and decrease in winter. It is assumed that precipitation during the monsoon season strongly contributes to high discharge in summer. On the basis of the data of ablation of glaciers and precipitation in this region, preliminary estimates of water balance in the drainage during a year were made. Since the variation of daily mean air temperature at Lhajung near Dingboche had a good correlation with the vatiation of daily discharge in summer but not in winter, the contribution of melt water from glaciers to the variation of the discharge was also discussed on the basis of the air temperature over glaciers estimated from the monthly mean temperature at Lhajung. Diurnal variations of the discharge in different months showed periodic tendencies which might be due to the diurnal variations of discharge of melt water from glaciers. The seasonal change of this tendency can be explained by the change of air temperature. Monthly discharge in depth of runoff from this drainage was compared with that at a point 460 m in altitude, in the lower part of this drainage. The latter was nearly twice as much as the former during the monsoon season, since precipitation in the upper drainage during the monsson season is less than below.