SAPWAT3 is a program for estimating irrigation water
requirements of crops, farms and drainage or administrative
regions for planning purposes.
SAPWAT3 is a further development of the SAPWAT computer
program (Crosby & Crosby, MBB, WRC, 1999) that 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
SAPWAT3 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
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
Pieter van Heerden
Tel: 072 209 9329
Water Research Commission,
Private bag X03,