Water use efficiency of table and wine grapes in Western Cape
The economically important grape sector fo the Western Cape, South Africa, puts a high pressure on the scarce water resources of this province. The challenge is to keep the grape industry economically viable while simultaneously saving water resources.
The objective of the study was to understand the spatial and temporal variation of water use efficiency in table and wine grape vineyards in the Cape winelands area using remote sensing technology.
Water consumption, biomass production, yield and water use efficiency were estimated for the grape growing seasons (September-April) of 2004-5, 2005-6 and 2006-7. The summer of 2004-5 was relatively wet, but many areas had a shortage of irrigation water due to the dry preceding winter. The summer of 2005-6 was relatively dry, but water supply in the irrigated areas was sufficient. 2006-7 was an average year concerning rainfall and irrigation water availability.
The project focussed on six grape growing areas: the Hex River Valley, Worcester, Paarl, Franschhoek, Stellenbosch and Somerset West. Most table grape vineyards are found in Hex River Valley, Worcester and Paarl. Wine grape vineyards in Stellenbosch and Somerset West are rainfed or only receive a small amount of supplementary irrigation. Wine grape vineyards in Worcester and all table grape vineyards require a more frequent (intensive) irrigation.
The Department of Agriculture will use the new technology to inform growers on how productively they are managing their water resources. The spatial variations in water consumption (actual evapotranspiration), grape yield, water use efficiency and crop water deficit will provide strategic insight in who is doing well and who is unnecessarily over-consuming water resources.
Water use efficiency of wine grapes can also be expressed in liters of wine needed per liter of wine produced. Approximately 1,000 kg of wine grapes is needed to produce 775 liters of wine. Knowing the actual evapotranspiration and the yield of wine grapes, it is possible to calculate the amount of water needed to produce a liter of wine, i.e. the Wine Water Productivity (l/l). The evapotranspiration values in these calculations did not include the water used by the vineyards during the winter months and the water needed for the wine production process itself.
- Wine Water Productivity (liters water needed to produce one liter of wine) in Paarl
- Wine Water Productivity (liters water needed to produce one liter of wine) in Worcester
Results
The final report provides a complete overview of study methodology and results, but a summary is available as well. The final results were also presented at the Department of Agriculture on July 18, 2008. Furthermore a poster with results of 2004-5 and 2005-6 is available.
A number of publications resulted from the grape study. The quarterly magazine of the Western Cape Department of Agriculture, AgriPROBE, had WaterWatch in the picture in its issue of September 2007 (Vol. 4, no. 3). The article thoroughly describes the application of satellite images in the monitoring of water use efficiency of vineyards in South Africa.
Caren Jarmain presented the paper Remote sensing tools for water use efficiency of grapes in the Winelands Region, Western Cape at the 13th SANCIAHS symposium, 6 & 7 september 2007 in Cape Town.
The magazine Water Wheel published the article Satellites to Assist SA in Determining Evaporation in January/February 2009. And the article Using satellite imagery to determine the water use efficiency of grapes in the Western Cape could be found in SA Irrigation 30 (2).
Results in Google Maps
New results for the season 2010-11 are currently being validated, but will be made available soon! Please send an email to Annemarie Klaasse (a.klaasse(at)waterwatch.nl) if you like to be updated on new datasets!
Sept. '04 - Apr. '05 | Sept. '05 - Apr. '06 | Sept. '06-Apr. '07 | |
Water consumption |
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Table grape yield |
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Wine grape yield |
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Table grape water use efficiency |
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Wine grape water use efficiency |
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Biomass production |
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Biomass water use efficiency |
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