灌溉排水系统工程

Impact of Climate Change on Crop Water Requirement in Kamala River Basin of Nepal

Abstract

Manoj Lamichhane*, Yogendra Mishra and Abin Raj Chapagain

The future climate, which has a crucial role in any hydrological events that occur within the basin, will have more uncertainty. Due to changing climatic variables, the basin's water balance will become more unpredictable. Not only will climatic parameter changes, but it will also adversely affect the water management within the basin. In this study, an effort has been carried out to compare the future River flow of the Kamala basin and the future water demand of the Kamala irrigation command area. The CROPWAT and AQUACROP model, based on climatic, soil, and crop data, was used to estimate the future Crop Water Requirement (CWR), Irrigation Water Requirement (IWR), and Biomass yield. Since the Hydrological station is absent within the basin, the simulation of the future river flow of the Kamala basin using any hydrological model was unworkable. Therefore, the WECS method is used to forecast the future monthly flow of the Kamala River. The two emission scenarios, ssp245 and ssp585, were conducted based on cropping intensity of 170% and 300%, and IWD for each sub-scenario over 12 months was estimated. For the first sixth months, IWR is increased in the future period as maximum and minimum temperature increases, and the IWR for monsoon season is less required due to increases in precipitation, and again for the post-monsoon season, IWR is increased compared to historical IWR. The highest irrigation water requirement occurred in March under ssp245 and ssp585 and CI 300%. In contrast, October and August have the lowest irrigation water demand under ssp245 and ssp585 scenarios. Based on the finding, the production of the crop with an irrigation system is higher than in a rain-fed system. For paddy, the rain-fed system produced a dry yield of 6.58 tons/ha, whereas the dry yield of the irrigated field has 7.05 tons/ha. The future river flow is insufficient to meet the irrigation water demand in the first five months in the near future under both ssp245 and ssp585 scenarios. The magnitude of deficiency in ssp585 is comparatively higher than in ssp245. Therefore, all of these findings suggest that the crop water requirement of KIP is insufficient in the future to provide a year-round irrigation system.