Lake Naivasha in southern-central Kenya is famed for its flower farms, fisheries and diverse wildlife, including buffalos, hippos and Eurasian migratory birds. The main inflow into the lake is from the Malewa river on the northern shores. At the river mouth, there is a wetland which once spanned 1,350 hectares. Twenty years ago, flooding gouged out the Malewa riverbed so deep that seasonal overflow stopped, and the wetland diminished to 450 hectares.
The original wetland functioned like a natural water treatment plant capturing sediments, organic matter and nutrients before they entered the lake, improving water quality and keeping fish populations healthy. Better water quality also reduced the cost of water treatment for the municipal water supply and commercial farms around the lake.
The wetland itself created macro- and micro-habitats for birds, fish spawning and for larger mammals. Papyrus shading the shallows helped reduce evaporation from the main lake, increasing the water available for wildlife and human livelihoods. But, as the wetlands have diminished, up-stream deforestation is leading to siltation of the main lake.
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