Let’s Connect the Dots

Last month I rode with a NamWater official to one of their drinking water reservoirs - the Swakoppoort Dam. It’s about 90 miles northwest of the City of Windhoek. This dam is critically important to supplying drinking water to the residents of Windhoek. It collects water from the ephemeral Swakop River during the rainy season, and during the dry periods no water flows in to the dam. The dam is suffering from algal bloom and slowly turning green which is a big cause of concern to the NamWater management team. I wanted to see how much damage the algal bloom has caused to Swakoppoort water quality and what is causing the algal bloom in the dam in the first place. The water quality was below the levels a water quality professional would like to see (Picture 1). Fortunately, the algae growth has yet to reach the point of no return, so there is still hope that the dam water can be salvaged.

Now let me bring another dam into the picture: Goreangab dam. This dam is located just outside the western border of Windhoek. Many years ago, this dam was a big part of the water supply chain. Now, it has turned into a green-slimy lake. The algae are so thick in the water that even swimming in Goreangab dam is prohibited. E. coli and other microbe levels register off the scale. This huge water reservoir is just sitting there as a reminder of good water gone bad. Water is scarce in Namibia, and especially in Windhoek, so losing such a big reservoir is a very unfortunate blow.

So, what went wrong with the Goreangab dam? The answer is found at the Gammams Wastewater Treatment plant (Picture 2 below), which feeds this dam. The effluent coming out of Gammams treatment plant can follow two possible routes: Route one, it can go into a series of maturation ponds where the effluent will be allowed to further purify under natural conditions before it is utilized by the Reclamation Plant for ultra-purification and mixed with drinking water supplies. (Check my December 18, 2012, blog posting on the treatment plant). In route two, the effluent can follow towards the Goreangab reservoir, which feeds the Goreangab Dam. The determining factor whether the effluent would go into the maturation ponds or into Goreangab reservoir is the levels of nutrients; i.e., nitrates and phosphate levels. Effluent with low nutrient level is diverted to the maturation ponds because it will be ultimately used for human consumption while the effluent with high nutrient levels is sent to Goreangab reservoir. Algae love these nutrients, especially the phosphates. With lots of sunlight, warm temperatures, and abundant supplies of phosphates, algae grow unabated. That’s what precisely happened to Goreangab reservoir and Goreangab dam. Over time a nice and clean water reservoir became unusable.

Let’s Connect Dots: Now let’s move back to Swakoppoort Dam. Although the Gammams treatment plant is about 90 miles away from the Swakoppoort dam, the effluent from Gammams treatment plant can still reach this dam. The connecting link is the previously discussed Goreangab dam. Unfortunately, the spillover from the Goreangab dam goes into local seasonal creeks and rivers. During the dry season, most of the spillover effluent dries out before it reaches the Skapoppoort dam. But in the rainy season, all the residue which had been accumulating in the dry river bed flows into the Swakop River, which fills the Swakoppoort Dam. So the high nutrient effluent from Gammams treatment plant ends up in the Swakopoort dam. This is what is causing algal blooms in the Swakoppoort dam. Although NamWater is aware of the problem but very little has been done so far to change the situation.

Suddenly, the Watershed monitoring and Integrated Water Resource Management (IWRM) studies that the MSDGC has been conducting to protect our water resources made a lot of sense to me. Using a holistic approach is the only way to manage our water resources and protect them from pollution or they might go the Swakoppoort Dam way.





Swakoppoort Dam water turning green








Geographic locations and proximities of Gammams Wastewater Treatment
Plant, Goreangab Dam, Swakoppoort Dam and Von Bach Dam.

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Close up of the City of Windhoek area. Goreangab Dam is located on the north-west side of the City of Windhoek. The white buildings just south of Goreangab Dam is Gammams WWT plant.