Evapotranspiration estimates from remote sensing for irrigation water management

Abstract

Climate change impacts and increasing demands on Morocco's water resources present serious challenges to irrigation districts and water managers. Modernization of irrigation practices and delivery systems can help conserve water by improving efficiencies and water productivity. Satellite imagery from Landsat and MODIS and the METRIC surface energy balance method were used to derive objective estimates of crop evapotranspiration (ET) in three Moroccan irrigation sectors. The METRIC analysis requires satellite imagery with thermal (surface temperature) information, as well as high-quality weather data. The spatially distributed ET estimate maps were combined with surface water supply records and weather data and used as inputs to a water balance analysis to estimate the quantity of supplemental groundwater used for irrigation. The results are useful as a pre-project, baseline condition for investments in irrigation methods and system improvements. The remote sensing data analysis provides useful results for large irrigated areas that have little information on crop consumptive use and irrigation efficiency and almost no information on groundwater abstraction. A similar approach can be used to monitor and assess the system during and after the irrigation improvement project is completed.