Assessing the Blue and Green Water Footprint of Lucerne for Milk Production in South Africa

The Global Water Footprint Standard approach was used to calculate the volumetric blue and green water footprint indicator for lucerne production as important feed for dairy cows in a major lucerne production region in South Africa. The degree of sustainability of water use then was assessed by comparing water use to water availability for the region. The results show a volumetric water footprint indicator of 378 m3/tonne of lucerne. Of the total blue and green water footprint, 55% is green water footprint and 45% is blue water footprint. Thus, albeit in a major irrigation area of South Africa, the largest component of the total water requirement is met by effective rainfall. The assessment of sustainability of water use showed that the period when lucerne requires irrigation water furthermore corresponds to the period where the water scarcity index is smaller than 100%. The water footprint thus is considered sustainable from an environmental perspective. This research proves the benefit of using context specific data to assess the water footprint of a crop, and the importance of a sustainability assessment in a water footprint assessment to generate information useful for informing water users and managers towards sustainable freshwater use.