Salome Alweny
1 July 2007
Kampala — Lake Victoria water levels may have increased in quantity due to the recent rains but the quality still remains a question to ponder. The quality of Lake Victoria recently came to the limelight when, on April 3, the Daily Monitor broke the story of a strange matter growing on Lake Victoria shores particularly at Kitubulu Bay in Entebbe.
Experts from different government departments were immediately dispatched to the scene to assess the situation. Their findings showed that the lake is eutrophied - meaning excess nutrients like phosphorous and nitrogen have made the lake fertile to enable the growth of green matter that experts call algal blooms.
Excess nutrients in a lake can stimulate growth of toxic green algae which can also make the water unfit for swimming (especially at the beaches) or exposure to domestic animals and pets, as well as changing the taste and smell of water.
This scenario has already enabled the growth of waterweeds like water hyacinth in various parts of the lake. It has also led to depletion of oxygen in water, which has already caused massive fish deaths especially at Kitinda landing site in Entebbe.
Greenish water
On April 12, the experts reported that the situation was coming back to normal as the thick blooms that had piled up in Kitubulu Bay and the eastern shores of the lake had cleared.
This, however, cannot be considered good news as the water in the lake has transformed from clear fresh water to weed choked, greenish water.
This transformation is not limited to the shores alone. Experts have noted that this is a lake-wide problem.
"The inner shores are already seriously affected...the lake is critically sick" were the words of Dr Nicholas Azza, a senior water analyst who is also assistant commissioner for water quality in Water Resources Department of the Ministry of Water and Environment.
Results from the water quality and ecosystems management components of Lake Victoria Environment Management Programme (LVEMP) shows that annually, 49,500 tons of Nitrogen and 5,700 tons of phosphorous are loaded into the lake through various non point sources including changes in catchment of the lake such as deforestation, poor agricultural practices and utilisation of agrochemicals like fertilizers within the shores of Lake Victoria catchment.
Destruction of wetlands has also been cited as a major contributor of phosphorous and nitrogen loads into the lake. Point sources cited include industries (discharge of untreated industrial wastes), municipal discharges and poor sanitation at landing sites/fishing villages around the lake Victoria catchment areas.
Tom Kabanda, a liminogist at Makerere Univerity, explains that the changes that have been seen in the lake so far and those that are yet to be seen are mere signs that the lake is undergoing an ecological change.
Dr Azza too gives credence to Kabanda's explanation that it has taken decades for the lake to get eutrophied and for the signs we see today to show up. "It is my belief that eutrophication (excess nutrient enrichment of the lake) has not initiated a new shift in lake conditions, but amplified and accelerated a trend that was already underway due to more natural causes."
Azza explains that the change started way back after the completion of Uganda railroad.
"The Uganda railway led to explosion of human and livestock population in the Lake Victoria catchment around 1930. The high human population stimulalated plantation agriculture, cash crop exports and opened up Lake Victoria region to settlement through immigration hence large-scale deforestation and agricultural conversion," he says.
According to Azza, the commissioning of the hydropower station at Owen Falls Dam in 1954 further catalysed economic growth within the Lake Victoria catchment area, leading to the emergence of new activities like rapid expansion of towns and cities, increasing road construction, discharge of untreated municipal and industrial effluents and encroachment in wetlands, all of which have a potential to further increase nutrient export into the lake.
"The export of the nutrients from the catchment may have only been aggravated by the sudden rise in the lake levels in the early 1960s that followed unusually heavy rains, causing extensive flooding of the shoreline, drowning of the shoreline swamps and possible release of plant nutrients from flooded soils and drowned decomposing plants," Azza further explains.
He says progressive human disturbance of Lake Victoria's catchment has increased nutrient inflows to the lake and spurred the emergence and area covered by blue green algae.
Climate factors
Although scientists say the problem has been accelerated by the excess nutrient loads into the lake, other studies show that the warming trend in the climate of East Africa accompanied by a decrease in the duration of strong winds also contributed to the pollution as it has altered the lake's water column structure and mixing pattern, triggered changes in the plankton community structure hence pollution of the lake.
Dr Azza says though it will take time for the lake to recover, there is still room to save it.
"If we do not act now, the blue green algae will establish its dominance and once a lake has an established water bloom it is difficult to reverse the trend because algal cell populations are carried over from year to year"Azza says.
He adds: "If we do not, the water in the near shores will permanently turn green leaving it unpalatable for consumption, swimming especially in the beaches and fish will continue dying as the water body permanently turns smelly".
The responsible government agencies that have been monitoring the condition have made recommendations, some of which are already under implementation.
Dr Henry Aryamanya, the National Environment Management Authority boss, wants to see proper catchment managemnt like adopting proper agricultural practices that reduce nutrient bound soil into the lake.
What should be done
He also wants to see people manage agrochemicals such as fertilizers properly, protecting wetlands and planting more trees to minimise discharge into water courses.
A technical report on algal blooms at Kitubulu, Entebbe shows that to reduce nutrient loads into the lake, people must practise contour ploughing especially on hilly areas, mulching and use slow release fertilizer pellets.
The technical report further recommends that people should use animal waste as organic manure. The programme officer for Lake Victoria Regional Local Authority's Cooperation, George Wesonga, says industries and municipal towns should establish wastewater treatment plants to reduce pollutant loads into Lake Victoria.
He says there is need to increase sewerage coverage in urban areas and improve general sanitation coverage especially at the landing sites. For now, Azza says the interventions needed to save Lake Victoria are so big that no single funding agency can manage alone.
LVEMP phase two, which is in the offing with support from the Swedish International Development Agency, is set to enable industries within the Lake Victoria catchment area to adopt cleaner production and improve their environmental performance, Dr Azza says.
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