Crop Water and Irrigation Requirements Program of FAO (CROPWAT)

CROPWAT (currently in version 8) is a Windows computer program for the calculation of crop water requirements and irrigation requirements based on soil, climate and crop data. In addition, the program allows the development of irrigation schedules for different management conditions and the calculation of scheme water supply for varying crop patterns. CROPWAT 8.0 can also be used to evaluate farmers’ irrigation practices and to estimate crop performance under both rainfed and irrigated conditions. All calculation procedures used in CROPWAT 8.0 are based on the two FAO publications of the Irrigation and Drainage Series, namely, No. 56 "Crop Evapotranspiration - Guidelines for computing crop water requirements” and No. 33 titled "Yield response to water". CROPWAT requires local climatic data, but if these are not available the software can use a representative station from the CLIMWAT database. Similarly, if local soil and crop data are not available, CROPWAT can use standard soil and crop property values. Climate data input can accommodate daily, decadal or monthly values, and converts these into a daily soil-water balance to develop optimal irrigation schedules, using various user-defined options for water supply and irrigation management conditions. Scheme water supply is calculated according to the cropping pattern defined by the user, which can include up to 20 crops. CROPWAT is location-based and has no GIS capabilities.