This WRC study was conducted to better understand the usefulness of water footprint (WF) information for carrots (Daucus carota), beetroot (Beta vulgaris), cabbage and broccoli (Brassica oleracea), lettuce (Lactuca sativa), maize (Zea mays) and wheat (Triticum aestivum) produced on the water-stressed Steenkoppies Aquifer, Gauteng, South Africa.

Despite the relative simplicity of the Water Footprint Network (WFN) methodology, some complexities were encountered in its application on vegetable crops, including the variation in outcomes depending on weather conditions, crop simulation model outputs, and water contents of the produce.

Water footprints according to the WFN were used to develop the catchment WF framework, in which total ET of agriculture was estimated by linking WFs of crops with total yields produced on the aquifer.  Total ET of agriculture, together with other water flows, was used to calculate a catchment water balance.  According to the catchment water balance, total water flowing into the aquifer exceeds total water losses on an annual basis.  This can either be explained by errors in the assumptions made for this study, or by the possibility that other losses may occur from the aquifer boundaries that we are currently not aware of.  There was, however, a good correlation between estimated and measured outflows, and water outflows are very similar to precipitation inflows during years with low rainfall and/or high agricultural water use.