Fair and sustainable irrigation water management in the Babai basin, Nepal

This paper attempts to find a strategy to provide year-round irrigation for cultivating three crops per year in the southern plains of the country taking a case study of the Babai basin. Despite having enough flows during the summer for growing rice in total 27,000 ha area, the dry season flows of the Babai river can irrigate only 6,300 ha in winter and 4,000 ha in spring limiting the cropping intensity to 138.50%. It is proposed to irrigate the 7,500 ha southern dry area at the right bank bringing water from a large snow-fed river: the Karnali. Water balance study of the three irrigation regions to be irrigated from the Babai source preserving their existing water rights showed that the year-round irrigation at the west with the proposed arrangement will fall short of only 13.9 million m(3) water volume. At the east side, the head reach area and the tail portion will fall short of 19.4 and 66.4 million m(3) of water to insure a cropping intensity of 250%. The deficits can be fulfilled by means of capturing the excess river water of rainy season in local reservoirs and by making conjunctive use of groundwater. The proposed solution is financially, environmentally and socially viable being a cost effective, user friendly and should be the linchpin towards attaining a sustainable year-round irrigation in the region.