REMOTE SENSING AND GEOGRAPHIC INFORMATION SYSTEM BASED IRRIGATION MANAGEMENT – A CASE STUDY OF NEPAL

Abstract

Irrigation water management involves multilevel activities including assessment of crop water requirement, water availability at intake source, delivery of water as per irrigation scheduling with physical irrigation infrastructure facilities for conveying water up to the farm level. The present study was conducted to estimate crop water requirement, irrigation scheduling, water balance study and performance evaluation of Kankai Irrigation System (7000 ha), Jhapa, Nepal. Also, Land use land cover and crop classification maps of command area were generated from satellite image pertaining to 15th October, 2016, using Remote Sensing (RS) and Geographic Information System (GIS). The reference evapotranspiration (ETo) has been computed from selected climatological methods; Hargreaves, Blanney-Criddle, Priestly – Tailor and Penman-Monteith methods. The reference evapotranspiration (ETo) was calculated using 15 years (2001-2015) of meteorological data. The Penman – Monteith method has been used for calculation of crop water requirement. Further, crop water requirement in conjunction with water balance study was carried out for the analysis of surface water whether it is surplus or deficit at the intake source. The existing cropping intensity, estimated from survey, was 184 % with the total crop coverage of 12880 ha. The fortnightly calculated crop water requirement was found to be 61.33 MCM, 64.67 MCM and 12.86 MCM for monsoon (6440 ha), spring (3710 ha) and winter (2730 ha) season respectively of the Kankai Irrigation System (KIS). The fortnightly calculated surface water balance analysis of KIS for 7000 hectares showed that irrigation supply was found to be shortfall for March (=0.8 MCM) and April (=8.22 MCM). The deficit surface water supply can be augmented by the conjunctive use of surface and groundwater. The irrigation schedule from CROPWAT model for spring rice, winter wheat and winter maize showed that wheat and maize require 6 irrigation applications with an average interval of 20 and 25 days, respectively. The rice required frequent irrigation with 5-day interval during initial, development and mid-season stages and continued till 10 days before the end of the growing season. The gross irrigation requirement for rice, wheat and maize were 2255.80, 242.50 and 251.50 mm respectively. The performance evaluation of system was also carried out by identifying various system performance indicators. The physical infrastructures performance of the headworks, main canal system observed from walk through survey was found in good condition and satisfactory. The application efficiency was calculated by determining the ratio of water used by crops in evapotranspiration and water delivered at field head and was found to be 62 % of Kankai Irrigation System (KIS), which is average and needs to be improved. The agricultural productivity per hectare per total irrigated area was estimated from local market price of year 2015/16 obtained from survey conducted in KIS, study area, and was found to be US$ 893 per hectare which is satisfactory. The WUA collect irrigation service fee (ISF) from farmers and used for operation, maintenance and management of the system. The irrigation service fee (ISF) performance is only 64 % out of targeted which has to be improved. It has been concluded from the evaluated performance indicators results, the performance of the system was found average and satisfactory.