Modelling of nutrients' loading into Lake Victoria

The contribution of atmospheric deposition of nutrients towards the total annual nutrient loading into Lake Victoria and the potential of various anthropogenic activities taking place in the lake's catchment area towards increased nutrient loading into the lake were studied. Results from the sampling and analysis of atmospheric deposition of nutrients falling over the lake showed that about 71.5 kt of nitrogen and 2 kt of phosphorus (as particulate) are deposited annually in the lake and that wet atmospheric deposition outweighs the dry deposition by contributing about 74% and 70% of total annual atmospheric nitrogen and phosphorus deposition, respectively. Through validation of other nutrient loads from domestic and land run-off sources, it was concluded that atmospheric deposition accounts for about 71.7% of the total annual nitrogen loading to the lake. IPCC/OECD model results estimated some 20kt of nitrogenous atmospheric emissions and about 0.7kt of particulate phosphorus being emitted from both biomass burning and use of animal manure in the catchment area of the lake and that biomass burning accounted for about 70.4% and 100% of the nitrogen and particulate phosphorus respectively. Simulation of Lake Victoria's water quality parameters using the Bathtub model revealed that the lake's trophic condition is intermediate between eutrophic and hypereutrophic. It is therefore recommended that an immediate move should be to try and cut down, to the lowest minimal level possible, the annual nutrient loading to the lake, both from point sources and non-point sources. It was basically recommended that use of renewable energy is of paramount importance in reducing the biomass burning. These include, the water hyacinth weed) and production of briquettes (from animal dung and other biomass) which will replace the need to encroach the already vanishing forest resources in search of firewood.