ASSESSMENT AND IMPROVEMENT OF IRRIGATION EFFICIENCY OF MAHAKALI IRRIGATION PROJECT (SECOND STAGE), KANCHANPUR, NEPAL

Abstract

This study assess the irrigation efficiency of the Mahakali Irrigation Project (Second Stage) which is situated in Kanchanpur district, Far Western province of Nepal. The project started in 1987 and completed in 1997 and is under joint management of the Government and Water User Association. The project is 27 years old and has several breaches and failures in canal system. The canal is unable to supply reliable irrigation water especially in dry season causing failure of crop and land being left barren or low enthusiasm of the farmers. The crop coefficient is calculated from the Sentinal 2 data using ARC-GIS software. The crop coefficient along with reference evapotranspiration of the area gives the crop water requirement. Irrigation Efficiency is calculated from the supplied water and crop water requirement. LINGO software is used for scenario analysis of the different management strategy for optimization of benefits with constraints of water availability and maximum cropping area. Benefit Cost ratio and sensitivity analysis is done for the recommended scenario obtained from analysis. The irrigation efficiency is 46% during the wet season and 33% during the dry season in the system with overall 40%. This indicates that the system is more effective at supplying water to the crops during the rainy season when soil moisture levels are higher and there is more water available. Better soil penetration rates and less evaporation losses could be the cause of this increased. On the other hand, the surface irrigation system's effectiveness drops to 33% during the dry season due to a lack of water resources and decreased soil moisture. This can be the result of more runoff, higher evaporation losses, or lower soil penetration rates brought on by dry soil. The system requires to improve its irrigation efficiency.