By MATTHIAS MUGISHA
About 6,300 tonnes of the water hyacinth (Eichhornia crassipes) has been invading Lake Victoria per day, for about three years now. The weed is threatening to choke the lake like it did in the 1990s.
This comes at a time when the lake is facing other threats such as overfishing, environmental degradation and pollution that have reduced fish stocks, jobs and revenue.
During its peak invasion of the lake, the water hyacinth, with its characteristic thick-floating mats, reduced the supply of clean water, caused difficulties in water extraction, increased transportation costs and reduced fish catches.
It also decreased the number of landing sites and disrupted power generation at Jinja due to build-up of the weed on the dam.
How it entered Uganda The water weed, which is native to South America, entered Lake Victoria from Rwanda via River Kagera near Kasensero in Rakai district.
Experts suspect that it was probably introduced as an ornamental plant for garden ponds due to its beautiful flowers. Since the water hyacinth lacks natural enemies, an abundance of space, favorable temperature conditions and abundant nutrients makes it spread like a bush fire.
Lake Victoria is under threat and the very people this water source is supposed to serve are the ones threatening its existence. Until World Environment Day, June 5, in a campaign, Save Lake Victoria, Vision Group media platforms will run investigative articles, programmes and commentaries highlighting the irresponsible human activities threatening the world’s largest fresh water lake.
The water hyacinth grows so fast, doubling in biomass every six to 18 days, the exact time being dependent on location and time of year (Lindsey and Hirt, 1999). It increased rapidly between 1992 and 1998, was greatly reduced by 2001 and has since resurfaced.
Late last year, media reports indicated that the weed had covered almost five acres of water in Kisumu, Kenya. The reports added that it had invaded Lwangini Beach in Kisumu and halted fishing and other activities there.
The water hyacinth fl ourishes in all continents, except Europe (Lindsey and Hirt, 1999). In Europe, it cannot flourish as a
result of climatic conditions, but it exists there.
Importance of Lake Victoria Lake Victoria is at the centre of a large number of communities. Bordered by Kenya, Tanzania and Uganda, it is the second largest lake in the world, with a surface area of almost 96,000km2.
Lake Victoria is a source of food, drinking and irrigation water, as well as energy and a means of transport. It is also a convenient disposal site for human, agricultural and industrial waste, which is destroying it.
The damage done to water hyacinth by the weevils
Efforts to fight water hyacinth In Uganda, the weed has been fought using mechanical and biological means. Chemical control was least favoured, owing to the potential damage that herbicides could do to the lake and agriculture.
Emmanuel Bbanda, 75, left his work as a policeman to battle the water hyacinth. He says they started fighting the weed in 1996 under a company called Aquatic Unlimited from the US.
“We used to fasten barriers to poles and trees on the banks of River Kagera to trap the water hyacinth and then harvest it,’’ Bbanda, recalls. However, the following year, their equipment was washed away by floods when the river burst its banks.
In 1998, the Government, under the Ministry of Agriculture and the Egyptian government, launched a $20m project, the Uganda-Egypt Aquatic Weed Control, to prevent the water weed from spreading on Lake Victoria.
In 1991, weevils were introduced and Bbanda was among the people who got training on how to multiply them in tanks. In 2003, they abandoned the biological weed control and started removing the weed using heavy-duty machinery, under a contract with the Uganda Government and that of Egypt.
The project was called Uganda-Egypt Aquatics, under the Ministry of Agriculture and Fisheries then. According to Bbanda, apart from the mouth of River Kagera, water hyacinth harvesting machines were installed in Kalangala, Port Bell Wanseko and Kikoge on Lake Kyoga in Nakasongola.
At River Kagera, five labourers were hired to load the weed onto five trucks. “We used to harvest 6,300 tonnes a day,’’ Bbanda remembers. The project ended in 2010 and the water hyacinth has since been invading Lake Victoria from Rwanda without any hindrances.
A breeding project for the weevils, which was started by the Government 10 years ago, stopped. The project was partially successful on lakes Victoria, Kyoga and Edward.
Using the weevil succeeded in fighting the water hyacinth on lakes, but failed on rivers. This was because of the high water current on rivers that interrupts the breeding cycle of the weevils, which, in turn, affects their multiplication rate.