SAPWAT CHANGE OF CUSTODIANSHIP AND CLIMATE DATABASE UPGRADE

South Africa faces increasing climate variability, rapid population growth, and rising competition for limited water resources. Irrigated agriculture, the country’s largest water user, is under pressure to improve efficiency, making accurate estimates of crop water requirements essential. For more than two decades, the SAPWAT software has been the national standard for irrigation planning, widely used by farmers, advisors, researchers, and the government. However, the continued use of SAPWAT now faces critical challenges. The custodian can no longer sustain its maintenance and provide decision support. Consequently, the continued use of SAPWAT in new computer operating environments is infeasible without proper maintenance. SAPWAT uses a dated quaternary catchment dataset that does not cover the last 25 years of climate change, casting doubt on the validity of crop water-use estimates under current climate conditions. The implementation of the FAO 56 dual crop coefficient methodology to estimate crop water requirements in SAPWAT is not well documented, and it is unclear to what extent SAPWAT incorporates the recent methodological improvements in crop water estimation. Without the transfer of custodianship and technical evaluation, the relevance, reliability, and future use of SAPWAT are at risk, directly impacting water allocation and irrigation water management in South Africa.