Sapwat is a computer program for the estimation of crop irrigation requirements and for the planning of water requirements by Water User Associations.
SAPWAT was developed to satisfy a need for a user-friendly and credible aid for the estimation of crop irrigation requirements, for the planning of irrigation schemes and for water management by WUAs that can cater for developments in irrigation practice and management.
SAPWAT is not a crop growth model. It is a planning and management aid that is supported by an extensive South African climate and crop database. Some of the major innovations incorporated into SAPWAT are:
- The replacement of the American Class A evaporation pan with reference evaporation from a short grass surface calculated from climatic data by means of the standardised Penman-Monteith procedure now adopted by ISCW/ARC. The short grass surface has the characteristics of a growing crop and this automatically compensates for regional climatic differences.
- The use of the FAO four stage methodology whereby crop factors compatible with the short grass reference evaporation can be developed and modified by applying a simple and understandable procedure.
- The facility to differentiate between soil evaporation and plant transpiration making it possible to cater for field crops, orchards and vegetables in conjunction with a full range of irrigation methods and strategies.