Water hyacinth, the weed which once choked Africa’s greatest lake waters, threatening the lives of other organisms and cutting fish production is back again.
Speaking here yesterday, Martin Katua the Noxious Weeds Control specialist with Lake Victoria Environment Management Project (LVEMP) II said a survey conducted in October 2010 by the department of water hyacinth in the Ministry of Agriculture, Food Security and Cooperatives revealed that the weed now covered 518 hectares.
In 1997 the water weed covered about 2000 hectares of the lake before it was reduced by 80 percent nine years later, through spirited control measures.
Since then, Katua said the weed has been spreading due to continuous inflow of water hyacinth through Kagera River and availability of nutrients which favour proliferation of the weed in the lake.
“Right now we are planning to release weed insects into the lake to check the renewed spread of the water hyacinth,” he added.
He urged industrialists and people living around the lake to refrain from discharging pollutants and sediments because they carry a lot of nutrients which favour the growth of the weed.
At least six community development driven projects funded by the World Bank have been put in place by LVEMP II to check the spread of the weed in the lake, he said. The cost of the projects is 170m/-, he added.
He mentioned the areas of operations in which the projects have been put in place as Nyarusurya in Musoma Municipality and Suguti village in Musoma Rural District in Mara Region.
Others are Nyahiti area in Mwajombo village in Misungwi District, Chato and Mlila in Chato District and Nyamkazi in Kagera Region.
Studies suggest that water hyacinth was introduced in Africa in 1879, only to find its way to the continent’s largest lake 110 years latter.
The plant spread started first along the shorelines, forming thick mats that covered an estimated area of 20,000 hectares (about 77 square miles) of the lake by 1998.
By 1995, around 90 per cent of the Ugandan coastline was covered by the plant.
It covered substantial areas of the shore, particularly in Uganda, blocking waterways, disrupting hydropower, and decreasing the profitability of fishing.
Hyacinth also provided refuge for some fish species from the introduced Nile Perch. It largely disappeared from the Lake in the late 90s, perhaps, but not clearly, due to the introduction of a weevil used for biological control.
But in December 2006, according to different satellite images taken, the water hyacinth had returned. The die-off of native plants affects fish and other aquatic animals, according to studies.
Water hyacinth clogs irrigation canals and pipes used to draw water from the lake for cities and villages on its shoreline.
Besides, the plants impede water flow, creating abundant habitat for disease-carrying insects like mosquitoes.
The weed can also sap oxygen from the water until it creates a ‘dead zone’ where plants and animals can no longer survive.
Typically, only aggressive measures can control the fast-growing plant, LVEMP mangement notes.