Effects of physical mixing on the environment of satellite lakes and dams of lake Victoria, Kenya
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In the Lake Victoria (Kenya) catchment are found several small lakes and dams. The satellite lakes and dams are important aquifers and buffer zones for the lake. Besides the water bodies are important water sources both for livestock and domestic use. A study conducted in the water bodies between January 2003 and December 2004 showed that effects of eutrophication are wide spread in the lakes and dams. An investigation of primary productivity and effects of physical mixing and material transport was done. In Lake Sare, Lake Victoria waters are transported to the satellite lake during both day and night through Goye causeway that connects the two. The water bodies have higher rates of primary productivity than Lake Victoria. Spatial extent of oxygen depletion due to respiration of organic matter in the water column is lower than the rates of primary productivity. Variability of oxygen depletion is dependent on local thermal and hydrodynamic processes that appear to be controlled by seasonal and short-term wind regimes. Advective transport and convective mixing augmented by wind effects control distribution of nutrients. An analysis of sediment grab samples showed that nutrient fluxes and loading is primarily external rather than from sediments. From the chemical parameters that were measured, soluble reactive phosphorus concentrations ranged from 4.44 to 35.28, Nitrate/nitrite ranged from 4.69 to 335.88 mg/l, ammonia from 29.18 mg/l to 473.14 mg/l and silica from 5.01mg/l to 50.06 mg/l. Fish catches particularly indigenous fish species like Schilbe intermedius, Labeo Victorianus, Protopterus aethipicus and Clarius gariepinus depicted stunted growth possibly due to heightened eutrophication and reduced dissolved oxygen levels due to reduced mixing on the water/air interface as a result of macrophyte cover.
- Conference Papers