In my post in April this year, I outlined the two different Water Footprint guidance standards, and explained the blue, green and grey water footprint components. Based on the Water Footprint Network’s (WFN) guidance standard, we developed a data collection and calculation tool in order to streamline the water footprint assessment process. These were piloted through a study on stone fruit production with Stems Fruit – an interesting learning process for both Blue North and Stems Fruit.
The commodities included in this study included early and late season plums, nectarines and peaches across farms in three different regions: Villiersdorp; Robertson; and Prince Alfred Hamlet. Crop water use was calculated based on data obtained from the Fruitlook platform. Offset against actual irrigation volumes obtained from the farms, the green and blue water footprints were calculated.
The calculated green and blue water footprints clearly reflected the dynamics of farming deciduous fruit trees in the winter rainfall region of the Western Cape. The Western Cape’s winter rainfall coincides with the dormancy period for these trees , when evapotranspiration rates are very low. Irrigation scheduling begins around bud-break in spring, and continues to ramp up until harvest between December and March, depending on the variety. These dynamics resulted in blue water footprints (consumption of surface and ground water) that were far larger than their green water counterparts – i.e. the farming of stone fruit is critically reliant on the effective recharge of surface and groundwater reservoirs during the winter months.
The grey water footprints associated with the application of nitrogen, phosphorous and pesticides (i.e. diffuse sources of pollution) were calculated based on the Tier 1 guidelines developed by Franke et al. (2013). While the grey water footprints associated with N and P application were within a reasonable range, high pesticide grey water footprints attracted our attention (this is in line with a study by Franke & Mathews (2011) on cotton production). Although the concept of a grey water footprint is a simplification, it provided a strong indication of the large negative impacts some pesticides may have on local water bodies.
Water footprinting is valuable as a means of identifying water-related risks and opportunities, and as a means of communicating these risks and opportunities to stakeholders further up the value chain. Blue North is in the process of developing a full agricultural-focused water service offering, of which Water Footprinting will form a component. Watch this space for more info!
Franke, N. a., Boyacioglu, H. & Hoekstra, A.Y., 2013. Grey Water Footprint Accounting: Tier 1 supporting guidelines,
Franke, N. & Mathews, R., 2011. Grey Water Footprint Indicator of Water Pollution in the Production of Organic vs. Conventional Cotton in India,