Estimation of Water Budget in Kathmandu Valley, Nepal

Abstract

Water is essential to every human community and is essential resources for economic development, agricultural productivity; industrial growth etc. Of all the resources of water the primary source of water is the rain. The rainwater will recharge the ground water and the remaining water will transformed as surface flow.

Many studies related to hydrology and meteorology were carried out in the Katmandu Valley. Most of those studies are discharge calculation and rainfall variability. However there is still lack in the studies of variability of water surplus and water deficit within the valley. Therefore the main purpose of my study is to estimate the water balance components. Thornthwaite method is applied for this purpose. In this study of water budget, seven stations are taken and water balance components are found to be different for each station.

Kathmandu Valley receives 1819 mm of annual rainfall. During monsoon season it receives about 1461 mm amounting about 80% of annual value while in premonsoon season, post-monsoon season and winter season

it receives about 237 mm (13%), 68 mm (4%) and 53 mm (3%) respectively. The average yearly temperature is 17.6 ˚C. July is the hottest month with Mean Monthly temperature of 22.9 ˚C while January is the coldest month with Mean Monthly temperature of 9.6 ˚C. From the climatological balance of Katmandu Valley, it is found that there is high amount of water surplus (788 mm) compared to water deficit (23 mm). Therefore soil water demand for dry period could be easily fulfilled by utilizing about 3% of water surplus. The measured specific discharge of Katmandu valley is compared with estimated water surplus and the results showed only 4.48% difference in value. This study will provide the information of climatological balance and specific discharge of the given area. This information will be useful for sustainable management of water resources in local and small watershed environment.