Earth observation mapping of irrigated areas and water use in South Africa

This dataset was produced to quantify the spatial extent of irrigated agriculture and the consumptive water use of irrigated crops across South Africa for the period 1 August 2014 to 31 July 2015. Earth observation and geographic information system techniques were applied to generate national-scale, monthly evapotranspiration datasets at a spatial resolution of 250 m using the ETLook energy balance model. These datasets described vegetation water use, biomass production, evaporation, transpiration and interception losses under varying climatic and land-use conditions.

A comprehensive agricultural field boundary database was compiled by integrating multiple national and provincial datasets. Machine learning and rule-based classification methods were applied to distinguish irrigated from rainfed fields using time-series evapotranspiration, precipitation and vegetation indices derived from MODIS and Landsat 8 imagery. The resulting irrigated area map was iteratively refined through expert review, stakeholder engagement and manual validation.

The final dataset indicated that approximately 1.33 million hectares of land were actively irrigated during the study period, representing about 1.1% of South Africa’s land surface. The total consumptive water use from irrigated agriculture was estimated at 10 221 million cubic metres per year. The dataset also supported crop-specific water use analyses and was used to demonstrate water accounting assessments in selected secondary catchments.

The dataset provided a consistent, repeatable national benchmark for assessing irrigated agriculture, water consumption and water availability. It supported improved water resource planning, irrigation efficiency assessments and decision-making related to agricultural water management under conditions of increasing water scarcity.