Handbook for Irrigation of Wine Grapes in South Africa

Chapter 7

7.4 THE WATER FOOTPRINT OF WINE In Section 7.3 the focus was only on effective water use with respect to irrigation. The water footprint is a more comprehensive way to express the water use efficiency of production processes (http://waterfootprint.org/en/water-footprint/what-is-water- footprint/). In the case of wine production, the water footprint is expressed as unit of water used per unit of wine produced, e.g. per liter or bottle. In addition to the water used on farms (blue), the water footprint also includes rainwater (green), as well as water required to remediate pollution generated by wine production (grey) as explained in Table 7.20. TABLE 7.20. The different components of the wine production water footprint. It is the volume of vineyard irrigation water abstracted from natural resources, e.g. boreholes, rivers or dams. This includes water used for irrigation, as well as disease, pest and weed control. It is the volume of rainwater that is lost via evaporation and transpiration, or in- corporated into the grapevine structure after it had been stored in the root zone. It is the volume of water required to dilute pollutants, e.g. winery wastewater, so that it conforms to water quality standards as set by water governing authorities. The magnitude of the water footprint of wine is determined by numerous factors. For example, the blue water footprint of high yielding cultivars, e.g. Colombar or Mourvédre, is most likely to be lower than that of less fertile cultivars under the same cultivation conditions. Furthermore, evaporation losses under micro-sprinkler irrigation are appreciably higher, compared to drip irrigation as explained in Chapter 2. Consequently, micro-sprinkler irrigated vineyards will have a higher blue water footprint than drip irrigated vineyards. On the other hand, the contribution of evaporation to the green water footprint will be comparable for micro-sprinklers and drip, since rainwater evaporates over the total surface. In semi-arid regions such as the Lower Olifants River and Lower Orange River regions, the green water footprint of wine production will be less, compared to regions where the annual rainfall is higher. The types and amounts of chemicals used for winemaking, as well as volumes of wastewater produced varies substantially between wineries (Howell & Myburgh, 2018 and references therein). Consequently, the grey water footprint of wineries will vary concomitantly. Based on the foregoing, it is clear that there cannot be a single, optimum water footprint per unit wine produced. In fact, it was shown that the water footprint varied from 100 to 985 liters of water per liter of wine produced in Italy (Lamastra et al. , 2014). In South Africa, however, the knowledge on the water footprint of wine is rather limited. Similar to most other industries, the water footprint of wine production has an impact on the environment. Therefore, grape growers and wineries should make a concerted effort to reduce the water footprint as far as possible, but still maintain sustainable wine production under a given set of conditions. Green Grey Component Description Blue

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