SAPWAT 3 is a software program for estimating irrigation water requirements of crops, farms and drainage or administrative regions for planning purposes.


SAPWAT – Overview screenshot SAPWAT 3 is a further development of the SAPWAT computer program (Crosby & Crosby, MBB, WRC, overview_small1999). It is used for estimating irrigation water requirements of crops, farms and bigger areas for the planning and management of crop and area irrigation water requirements. Data is stored for easy reference.

It is based on the FAO 1998 Irrigation and Drainage paper 56 “Crop Evapotranspiration” by Allen, Pereira, Raes and Smith. It uses the internationally accepted Penman-Monteith approach to calculating reference evapotranspiration, as described by these authors.

SAPWAT 3 contains 50 years’ daily weather data for each quaternary drainage region of South Africa, as well as the full set (3262 weather stations) of monthly CLIMWAT weather data (FAO Irrigation and Drainage paper 49).

It is designed as a calculating shell, giving the user full control of data used in irrigation water estimation. Existing data can be added to, edited or reviewed by the user.

Multi-year weather data is used to statistically analyse estimated irrigation requirements for different levels of risk.

The facility to do enterprise budget analyses is included, as is the facility to do small-scale water harvesting analysis and design.

Crop irrigation requirement estimates are used for irrigation system design, as peak requirement and cycle length, two crucial elements in design, can be deduced from the results.

Development funding was provided by the Water Research Commission (http://www.wrc.org.za).

Crop irrigation

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