Rainfall analysis and design of water harvesting structure in water scarce Himalayan hilly regions

Irregular rainfall pattern and high surface runoff are the main reasons of water scarcity and subsequent drought conditions in Himalayan hilly regions. Hence in this study, an attempt was made to assess the water scarcity in these regions through rainfall and runoff analysis. The Henval watershed, covering an area of 6608 ha (66.08 km²) and lies between 78° 15’ to 78° 25’ E longitude and 30° 20’ to 30° 30’ N latitude at an elevation that varies from 1200 to 2760 m above (MSL) was taken up for this study. The rainfall in the study area starts during May and lasts upto November. It was noticed that the uniformity of rainfall was pronounced from 23^rd to 37^th week (4^th June to 10^th September), whereas during the other weeks rainfall distribution was poor and erratic. Analysis of surface runoff by SCS CN model indicated that a considerable portion of precipitation flows off the watershed as runoff resulting in water scarcity and the main reason of agricultural drought in the watershed. Hence, there is a great need of storage of the water from runoff for future needs to avoid drought. Farm ponds can be used for storing water during rainy season as in hilly watersheds, they are found to be economical. As the study area is rainfed, a number of farm ponds can be constructed in higher order drainage networks of the area for water storage.