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Harare and its satellite towns sit upstream of their supply dams, but almost entirely in the catchments of these same dams, providing many opportunities but also creating serious dangers.
The opportunities are obvious. The high run-off from rainfall falling on all those roofs, roads and parking lots in urban areas flows into the dams, boosting raw water supplies with fairly clean water.
And if the engineering plans of the 1980s were properly implemented and maintained six huge sewage treatment plants would be processing adequately the waste water and sewage of the metropolitan area and returning almost pure water to the rivers that feed the dams; if done properly more than half of what is pumped out of the dams would be returned to the dams and returned as clean low-nutrient water that would not pollute.
This would allow Harare and surrounding towns to continue growing without having to worry too much about finding the huge sums required to build new dams on other river system and pump water long distances to the city. The water problems of Bulawayo and Harare highlight the different challenges facing these cities. Bulawayo is short of raw water to purify since all its supply dams are fed purely by rain water falling in rural areas; Harare has adequate supplies of raw water, but a shortage of purification capacity.
The engineers of the 1980s making the plans knew that the proper technology existed, the activated sludge plants, that could process sewage and split it into water that was basically of drinking quality and solid waste that could be used for land fill.
These technologies would replace older technologies that did not process sewage properly, the water being rich in nutrients that had to be used for irrigating grass fields that were used to raise beef cattle. Cities and towns were banned from dumping this nutrient-rich effluent into rivers.
By the early 1990s the giant Firle sewage plant on the Mukuvisi as it leaves Harare and the Crowborough plant on the Marimba as it left the city were operational. The engineers who designed them won international prizes and the quality of the water in the two rivers downstream of the plants was of significantly higher quality than the water upstream. They were that good. Similar plants were designed for the Ruwa, Nyatsime, Gwebi catchments and for Norton.
Except for Ruwa, where some work has been done, little was done to expand the first prize-winning plants, build or upgrade the rest or even maintain what was there. The result has been a continual deterioration of what is dumped in the rivers, the turning of Lake Chivero especially into a midden and high costs at the main purification plant, Morton Jaffray, which instead of processing almost totally clean water has to do much of the work that the sewage plants are supposed to do at lower cost.
The four councils involved simply have to find the will to give priority to making sure they do not make a mess. The technology in a warm and sunny country like Zimbabwe is cheaper than that needed in cold and cloudy Europe, where sewage is properly processed.
Namibia goes the furthest in Southern Africa by having sewage treatment plants so good that the resulting effluent is very close to pure water and can be processed by purifications plants directly without having to go through a river or dam.
Hand-wringing is not nearly as effective as some sensible investment. In the end, proper treatment of the waste water in Harare metropolitan area, plus sitting hard on industries that dump unwanted waste and oils into drains, will save a lot of money. It is an investment that pushes ever backwards expensive projects to add more dams and long pipelines.
Online Reporter