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Lake Victoria is at risk of dying off from pollution!

Seeming pristine from a distance, Lake Victoria is at risk of dying off from pollution!

At 26,560 square miles (69,000 square kilometers), Lake Victoria is the world's largest freshwater lake, second only to Lake Superior in North America. The lake is shared by East African states of Kenya (6%), Uganda (45%) and Tanzania (49%). The lake with a 3450 km-long shoreline lies at altitude of 1135 meters above sea level, has a mean depth of 40 meters and maximum depth of 80 meters.

Lake Victoria basin is used by communities and industries as a source of food, energy, water and transport. The lake is also a sink for human, agricultural and industrial waste. The Lake provides employment for up to 30 million people. The Lake’s catchment area of 258,700 square kilometers has a GDP of US$ 300-400 million and supports nearly one–third of the total population of East Africa. The Lake is the source of River Nile, which is renown for whitewater rafting and flows to Egypt through Sudan.

The causes of rising pollution levels in the Lake are as many as they are diverse and each of the three East African nations is culpable. The Lake has for along time been a sink to excessive nutrients and untreated effluent that have led to fish die-offs, algal blooms and the spread of hyacinth, a ferocious waterweed. Although mostly eradicated now, the remnants of hyacinth on Lake Victoria deplete dissolved oxygen, sunlight and are an obstacle to water transport. Along the shoreline, hyacinth provides habitat for malaria mosquitoes and snails which habour bilharzia parasites.

Nakivubo Channel Industry DischargeIn Uganda, point sources and non-point sources such as deficient sewage and industrial wastewater plants, small-scale workshops, waste oil from parking lots and car repair garages are major sources of pollution load for the lake. The sewer system in Kampala city serves only a small fraction of the city population and only 10% of all sewage generated in Kampala gets treated. Guesthouses, slum dwellings and industries discharging untreated wastewater in Nakivubo channel, which flows into Murchison Bay contribute lachrymal pollution load and depleted oxygen levels in Lake Victoria. An engineer from AWE has recorded dissolved oxygen (DO) levels of less than 2 mg/liter in Murchison Bay yet most fish species die off at DO of 4 mg/liter. Riding a motorboat at the point where Nakivubo channel discharges into Murchison Bay churns up a trail of black sewage sludge. Nakivubo Channel carries approximately 75% of the nitrogen and 85% of phosphorus nutrient load discharged daily into Murchison Bay. The high nitrogen and phosphorous levels are responsible for excessive eutrophication and algal blooms seen in the Bay.

Often, Murchison Bay is covered in a green floating blanket of algae that is as viscous as wall paint. Algal blooms clog water treatment plants, deoxygenate lake water causing fish die-offs and cause a skin condition known as swimmers itch. Murchison Bay is home to water treatment plants that supply Kampala city and neighbouring towns. Uganda’s National Water & Sewerage Corporation (NWSC) is experiencing rising treatment costs because lake water is dirtier and increasingly expensive to treat to potable quality. Ironically, the single largest polluter of Lake Victoria is NWSC’s Sewage Treatment Plant at Bugolobi, which discharges 15,000 m3/day of inadequately treated sewage into Murchison Bay.

Nakivubo Channel CultivationNakivubo wetland and other major catchment wetlands, which when still lush and thick played the vital role of tertiary purification of effluent and stormwater discharging into the lake, have long been encroached and degraded by settlement and cultivation. Widespread lakeshore cultivation and soil erosion also contribute excessive sediment and nutrients into the lake. Stormwater flowing in Nakivubo Channel now carries along tones of soil straight into the lake.

Nakivubo Channel

Kenya’s side is not a rosy picture either. Towns of Kakamega and Kisumu discharge inadequately treated sewage in rivers draining into Lake Victoria because of deficient treatment plants. Kisumu’s sewage plant at Kisat with a design capacity of 9000 cubic meters now receives 15000 cubic meters of effluent, much of which flows into Lake Victoria without treatment. In Kakamega, sewage lagoons at Nabongo have been neglected for more than 3 years and are grossly inefficient.

Not to be left out, Tanzania’s town of Mwanza located near Lake Victoria discharges large quantities of untreated waste into the lake. Waste from fish processing factories, oil processing plants, textile facilities and tanneries is discharged into the lake without pretreatment. A study by Tanzania’s University of Dar es Salaam on lakeshore sediments to investigate their heavy metal content revealed high concentrations of Zinc, Copper and Lead metals. Another study by Makerere University in Uganda identified alarming levels of lead in yams cultivated in Nakivubo wetland through which Kampala city’s effluent flows before discharging into Lake Victoria. In both studies, the metals were attributed to industrial sources.

Clearly, more than anything else, it is discharge of untreated effluent and the lack of enforcement of discharge standards that are killing Lake Victoria.


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