Sensitivity of the Himalayan hydrology to land-use and climatic changes

Land-use and climatic changes are of major concerns in the Himalayan region because of their potential impacts on a predominantly agriculture-based economy and a regional hydrology dominated by the monsoons. Such concerns are not limited to any particular basin but exist throughout the region including the downstream plains. As a representative basin of the Himalayas, the Kosi Basin (54,000 km²) located in the mountainous area of the central Himalayan region was selected as a study area. We used water balance and distributed deterministic modeling approaches to analyze the hydrologic sensitivity of the basin to projected land-use, and potential climate change scenarios. Runoff increase was higher than precipitation increase in all the potential precipitation change scenarios applying contemporary temperature. The scenario of contemporary precipitation and a rise in temperature of 4 deg C caused a decrease in runoff by two to eight percent depending upon the areas considered and models used. In the absence of climatic change, the results from a distributed water balance model applied in the humid south of the basin indicated a reduction in runoff by 1.3% in the scenario of maximum increase in forest areas below 4,000 m.