Too Many Dams, Too Little Water - Lesotho’s Rivers Could Become "Waste Water Drains"

Transformation Resource Centre
Tuesday, October 31, 2000
Rivers affected by the 5–dam Lesotho Highlands Water Project (LHWP) could deteriorate to "something akin to waste–water drains" if Lesotho delivers as much water to South Africa as the original treaty requires. This is according to the final draft of the Instream Flow Requirements (IFR) study conducted by Metsi Consultants at the request of the Lesotho Highlands Development Authority (LHDA). The report is intended to inform planners’ decisions about the proposed Mashai Dam, which is currently the subject of treaty negotiations between South Africa and Lesotho.

The IFR, heralded experts as being one of the most comprehensive ever undertaken, attempts to predict the long–term impacts of reduced river flows caused by the construction of Katse, Mohale, Matsoku, and Mashai dams. It also recommends measures to compensate for and mitigate against these impacts.

Compensation and mitigation will be a truly formidable task. Adherence to the treaty requirements results in 96 percent reductions in river flow below Katse Dam and 57 percent reductions where the Senqu River flows out of Lesotho. This translates into "critically severe" biophysical and social impacts that will cost between US$2.8–$4.2 million annually to address. Residents living immediately below the completed Katse Dam already report increased numbers of aquatic insect pests, and skin rashes after crossing the low–flowing Malibamatso River.

Dams tamper with a river’s complicated changes between low flow and flood as well as its delicate chemical composition. These changes can trigger a chain reaction of consequences for the ecosystem, which in turn impact communities that depend on these natural systems. For example, a dam may prevent a flood that would have triggered the emergence of insects that would in turn have fed fish that would have provided essential protein to children living along a riverbank. Katse, Mohale, and Mashai dams will only allow floods on the average of once in a 20–year period (rather than the norm of once a year). Katse affects the Malibamatso River, Mohale affects the Senqunyane, and Mashai affects the Senqu. The Malibamatso and the Senqunyane flow into the Senqu.

According to the report, the dams’ impact "will manifest as strongly deteriorating physical and chemical conditions" and major biological changes. They predict dense algal growths throughout the system, which can be toxic to fish; encroachment of exotic plants (at the expense of native plants –– and the species that depend on them); moderate to critically severe increases of blackfly and other pest populations which prey on livestock; reductions in most fish populations, with some species like the Maloti minnow and trout reaching the point of extinction; declines in waterfowl, and an explosion in rodent populations, which could affect crops along the riverbanks.

These changes to the ecosystem will have major social impacts. Many fish and wild vegetable species will be reduced by over 50 percent. Social studies have shown that when species decrease to this extent, communities living near the river no longer make the effort to harvest them (it is often a long, steep hike into and out of the river valley). Therefore, a reduction of 50 percent is effectively a loss of 100 percent of these resources to riparian villages –– a serious situation given the already low nutrition levels in these communities. The low flows will also increase levels of pollutants in the river, causing critically severe increases of diarrhoeal diseases like giardia. Skin and eye diseases are also expected to increase sharply, the authors state. The cost of cash compensation for lost resources and mitigation against public and animal health problems via provision of water supply systems, vaccinations, and VIP latrines will reach nearly $4.28 million annually.

In closing, the report’s authors plead for recognition of Lesotho’s rivers as "living museums, containing species that could help unlock the ancient history of Africa" and as "places of great beauty and spiritual renewal" for the people who live near them. They ask that water resource decision–makers seriously consider these facts before making further developments in the system.

The draft IFR’s dire warnings put Lesotho in a difficult position as it continues to renegotiate the LHWP Treaty with South Africa. If Lesotho decides to stick to the Treaty requirements by building Mashai Dam and delivering 50.8 cubic meters/second to South Africa, the resulting compensation costs may render the venture infeasible to South Africa. If Lesotho decides to allow more water to flow downstream through its dams, less water will be available to sell, again reducing the odds that the project will be cost effective. Either way, South Africa will no doubt choose the least–cost water supply, which may not be more dams in Lesotho.

The consultants present other scenarios that would cause less damage to the ecosystem and the humans living in it. One of these scenarios would allow 38 cubic metres per second of water to flow to South Africa while costing less than $571,000 annually to compensate for resource losses. The question is whether the construction of Mashai Dam will remain cost effective to the South Africans if it means less water for Gauteng along with high pumping and resettlement costs.

Kwame Oduru, General Manager for LHDA’s Environmental and Social Services Group, said, "We are committed to finding an IFR scenario that will balance economic and technical feasibility with environmental acceptability."

The next step in this process is for an LHDA–appointed independent expert panel,

the World Bank, and the European Investment Bank will review the draft document first. The expert panel includes Dr. Jane Doolan, Prof. Tom McMahon (both from Australia), and Dr. Mike Mentis (from South Africa). Oduru said LHDA will release the report to the public in May. At press time, it still had not been released.

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