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Kenya: Report Offers Insights Into What Caused Rise of Rift Valley Lakes

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5 years ago

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Climate change, human activities and movement of tectonic plates are the reasons for the rise of Rift Valley lakes, a new report says.

According to the report titled “Rising water levels in Kenya’s rift valley lakes, Turkwel Gorge Dam and Lake Victoria”, different explanations have been advanced to explain these rising water levels, key among them being the transfer of water and energy between the land surface and the lower atmosphere (hydro-meteorology). Due to climate change, this has led to increased moisture availability, causing a rise in rainfall and discharge of the rivers feeding the lakes.

There is also more soil in runoff, occasioned by land-use changes that have increasingly added to the siltation of the lakes.

Dr Thecla Mutia, an environmental scientist at the Geothermal Development Company explained that climate change has led to increased moisture availability as seen in the discharge of rivers feeding the lakes and run-off occasioned by land-use changes, leading to high sediment load in the rivers, shoreline flooding, erosion, and geological changes.

“We have also seen severe degradation of land due to human activity that has resulted in higher rainfall run-off from land and less percolation in groundwater systems, leading to a larger volume of water flowing directly and rapidly from the land surface into the lakes,” said Dr Mutia at a virtual conference on rising levels of the Rift Valley lakes in Eastern Africa. The multi-agency team behind the report were of a similar opinion, noting that changes in land-use practices had led to increased runoff.

Fault terrain

At the same time, all the Rift Valley lakes are situated in fault terrain in the geologically active Eastern Africa Rift Valley and are therefore controlled by the geological structures.

The increasing water levels are changing the composition of lake water thus affecting biodiversity. This is manifested in the reduced number of flamingoes as the growth of the algae they feed on has been affected by the change in the alkalinity of lake waters.

“The increased inflow of freshwater into some of these lakes has created instability in the already fragile ecology of the lakes, negatively affecting the resilience and distribution of certain water species. In some catchment areas, severe landslides occurred regularly,” point out the researchers.

The team cited Lake Naivasha on this front, with the affected areas including Kihoto Settlement and Kamere beach, where over 1,500 households were displaced, and a number of hotel facilities, properties, and power transformers submerged, posing a hazard to the community.