SRM: SATELLITE IMAGERY TO DETERMINE WATER EFFICIENCY
By: Andre Roux, Director: Sustainable Resource Management
Water is a critical resource in the Western Cape and there is strong competition between the urban, industrial and agriculture sectors within the catchment area that provide water to the Cape Metropole. Irrrigated agriculture is responsible for 43% of the water usage from surface water resources and thus need to ensure the efficient use of irrigation water.
The effective and efficient use of irrigation water is one of the top priorities of the Department of Agriculture and a water conservation project was launched in 1999 to determine the water use efficiency of crops in certain areas. Over a period of four years, this project resulted in an increase in water use efficiency (kg of fruit produced per cubic meter of water) of between 15 and 20%. This in-field monitoring however requires extensive personnel and financial resources and a more cost efficient method to reach the same objectives had to be found.
The use of satellite imagery provides an opportunity to obtain this new objective and a pilot project was embarked upon with the appointment of the CSIR in Stellenbosch and Waterwatch in the Netherlands. The study aims at spatially estimating water use efficiency in table and wine grapes in Western Cape with remote sensing technology.
Water Use Efficiency of table grapes in Hex Valley. Highly productive areas are consistent between the two seasons of study. (click for larger image)
Conclusions
Many conclusions can be made from the project results but due to limited space, only a few will be highlighted.- Water use efficiency of grapes in Western Cape is in general quite good, although it varied considerably between fields, regions and between years.
- The considerable spatial variation in WUE in the grape producing areas, suggest that WUE can be improved.
- Spatial estimates of WUE can be used to evaluate differences in management practices and suggest improvements.
- Water use efficiency is influenced by many factors. The availability of water per farm (access to ground water and storage capacity) and management of water in times of scarcity play an important role.
- The production objectives influence the water use efficiency. High quality red wine grapes require less water that high yielding vineyards producing grapes for the brandy industry.
- Variations in water use efficiencies in Hex Valley are very large. This can partly be contributed to the large number of cultivars grown.
- The varieties Dauphine, Thompson, Barlinka and Crimson have highest water use efficiencies, while the varieties Victoria and Flame have relatively low water use efficiencies.
- It seems that farmers with their own water resources at the outskirts of the area are able to manage their water resources better, resulting in higher water use efficiencies.
The recommendation is that the study should be extended.
Read the entire article here.
Google Earth Project Overlays are available on the Waterwatch site, or from here (right-click, save file as to download):
What is Google Earth?
Google Earth is software on which you can view the globe in astonishing detail.
It can also be used to show spatial information in a user-friendly way.
WaterWatch has created several Google Earth overlays with project results.
Google Earth will enable us to present our products in a novel way to our customers.
In order to view these project results you need to have Google Earth installed on your computer. You can download Google Earth by following this link.
