Levels of nitrate and phosphate in some satellite lakes within the Lake Victoria basin, Tanzania

Abstract

Levels of nitrates (NO₃-N) and phosphates (PO₄-P) in some satellite lakes within the Lake Victoria basin were determined in Kagera (Lake Burigi), in Mara (River Mara) and in Mwanza region (Lake Malimbe) during August/September 2002 (dry season) and January/February 2003 (wet season). Water samples were collected using a van Dorn water sampler at chosen points from both deep and shallow areas of the water bodies. Results of the two surveys revealed that deep and shallow areas of the lakes had varying nutrient levels. In deep waters, PO4-P values ranged between 0.171-0.225mg/l, 0.067-0.364mg/l, and 0.043-0.096 mg/l in Lake Malimbe, Burigi and Mara River, respectively. NO₃-N values ranged between 0.034-0.762mg/l, 0.019-1.367 and 0.034-1.54mg/l in Lake Malimbe, Lake Burigi and Mara River, respectively. In shallow areas, PO₄-P values ranged between 0.144-0.343 mg/l, 0.072-0.203mg/l and 0.025 –0.096 mg/l in Lakes Malimbe, Burigi and Mara River, respectively. NO₃-N values ranged between 0.035- 0.932 mg/l, 0.017-0.622 mg/l and 0.028-0.912 mg/l in Lakes Malimbe, Burigi and Mara River, respectively. Generally, levels were higher during the dry than during the wet season. Appropriate pollution control measures should be taken though levels encountered are still within those recommended in the Tanzania Water Utilization (Control and Regulation) Amendment Act of 1981 for receiving waters.


Tanzania Journal of Science Vol.30(1) 2004: 1-10