If you thought looking at dam level height was a good indication of the water situation in the Western Cape then I may have some bad news for you. The size and capacity of dams are comparatively insignificant when compared to natural underground water supplies like aquifers.
For instance the Table Mountain Group (TMG) Aquifer streaches though most parts of the Western Cape, while the Cape Flats Aquifer runs from coast to coast (Muzenberg to Milnerton). These are two completely different types of aquifers. The Cape Flats Aquifer in comparatively shallow, only a few meter below ground, while the TMG Aquifer is far deeper. Both these aquifers do get recharges by rain but unlike the Cape Flats Aquifer that recharges seasonally, the TMG Aquifer recharges slowly over hundreds of years. A slow, gentle rain lasting several hours allows rainwater to seep into the ground, recharging seasonal aquifers, while heavy rains tend to run off into rivers and dams.
It is these shallow seasonal aquifers that most trees and plants dig their roots into in search of water, and the same water source that wellpoints (not boreholes) tap into to extract ground water.
This means that depending on the quality of rainfall either ground water (aquifers) or dam recharge is favoured. Even as our dams might be close to full, our underground water supplies might not be. Keep this in mind when you next look at dam levels to see if water restriction will be imposed.
Dam levels of the Western Cape as verified by DWAF on 17 January 2011.
- Wolwedans Dam level currently at 68.5% vs 36.3% the same time last year.
- Although there has been some heavy rainfall across South Africa, Western Cape dam levels are down 7.4% vs the same week last year.
- Unfortunately there is not a single river in the Western Cape that could be dammed. Due to population growth, we are using more water yet still have the same amount of storage capacity?!
- If the trend continues, the Western Cape will have serious water shortages in the next two years.
FSC = Full Storage Capacity in million cubic meters.
Figures are indicated as a percentage 86%, 86.3% etc of full storage capacity.
|Dam||FSC||This Week||Last Week||Last Year|
|Berg River dam||127.1||86||86.3||98.9|
|Ernest Robertson Dam||0.5||101.1||100.5||85.8|
|Garden Route Dam||10||100||100||29.4|
|Roode Els Berg Dam||7.8||47.1||51.6||79.7|