Submitted to: Transactions of the ASAE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/20/2004
Publication Date: 1/20/2005
Citation: Santhi, C., Muttiah, R.S., Arnold, J.G., Srinivasan, R. 2005. A GIS-based regional planning tool for irrigation demand assessment and savings using SWAT. Transactions of the American Society of Agricultural Engineers (ASAE). 48(1):137-147. Interpretive Summary: Several years of drought in the Rio Grande river basin have caused water shortages and conflict between the U.S. and Mexico. Farmers in the lower Rio Grande valley have experienced loss of crops and income due to water shortages. In this study, the SWAT watershed model was modified to simulate irrigation canals and irrigation water management for use as a regional irrigation planning tool. The new model was validated for crop evapotranspiration and canal conveyance efficiency. It was then applied to analyze regional irrigation demands and potential water savings of alternative conservation measures. The results of this study show potential water savings in the lower Rio Grande valley from improved irrigation methods and different cropping systems. Also, the model developed in this study provides a tool for regional planners and irrigation district managers.
Technical Abstract: Regional planning for irrigated agriculture needs thorough understanding of the hydrological processes and spatial and temporal variations associated with hydrological factors such as rainfall, soils and crops grown among different units of the region. The objective of this study was to improve the capabilities of a basin-scale hydrologic simulation model for regional 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 for estimating irrigation demand. The tool is capable of simulating hydrological processes associated with soil-plant-water interactions and capable of capturing the spatial and temporal variability of the major inputs/factors, which are important in regional planning. The tool was applied to the irrigation districts in the Lower Rio Grande Valley in Texas, USA. It was validated for crop evapotranspiration and canal conveyance efficiency and applied for analyzing the demand and potential water savings of alternative water conservation measures. Estimated potential water savings were 234.2, 65.9 and 194.0 Mm3 for conservation measures related on-farm management improvements, replacing sugarcane with corn and improving canal conveyance efficiency, respectively. Results indicated that on-farm management measures might be as beneficial as improving canal conveyance systems. The planning tool (with hydrological modeling and GIS capabilities) and estimations made would be useful for regional planners and irrigation district managers. The tool could be used for other irrigation systems as well.