A GIS-BASED REGIONAL PLANNING TOOL FOR IRRIGATION DEMAND ASSESSMENT AND SAVINGS USING SWAT

Abstract

Regional planning for irrigated agriculture requires a thorough understanding of the hydrological processes andspatial and temporal variations associated with hydrological factors such as rainfall, soils, and crops grown in different unitsof the region. The objective of this study was to improve the capabilities of a basin-scale hydrologic simulation model forregional planning of irrigated agriculture. In this study, a Geographical Information System (GIS) based hydrological model,Soil and Water Assessment Tool (SWAT), was configured as a regional planning tool with a canal irrigation capability forestimating irrigation demand. The tool was capable of simulating hydrological processes associated with soil-plant-waterinteractions and capable of capturing the spatial and temporal variability of the major factors, which are important inregional planning. The tool was applied to the irrigation districts in the Lower Rio Grande Valley in Texas. It was validatedfor crop evapotranspiration and canal conveyance efficiency and applied to analyzing the demand and potential watersavings of alternative water conservation measures. Estimated potential water savings were 234.2, 65.9, and 194.0 Mm3 forconservation measures related to on-farm management improvements, replacing sugarcane with corn, and improving canalconveyance efficiency, respectively. Results indicated that on-farm management measures might be as beneficial asimproving canal conveyance systems. The planning tool (with hydrological modeling and GIS capabilities) and estimationsmade would be useful for regional planners and irrigation district managers. The tool could be used for other irrigationsystems as well.