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The water hyacinth is back

By Vision Reporter

Added 31st December 2006 03:00 AM

BARELY five years after it was exterminated from the River Nile and Lake Victoria, the water hyacinth is back. Like the Nile, large masses of the water weed can be seen floating downstream in Jinja district. The hyacinth is concentrated at Nalubaale (former Owen) Falls and Kiira dams.

BARELY five years after it was exterminated from the River Nile and Lake Victoria, the water hyacinth is back. Like the Nile, large masses of the water weed can be seen floating downstream in Jinja district. The hyacinth is concentrated at Nalubaale (former Owen) Falls and Kiira dams.

By George Bita

BARELY five years after it was exterminated from the River Nile and Lake Victoria, the water hyacinth is back. Like the Nile, large masses of the water weed can be seen floating downstream in Jinja district. The hyacinth is concentrated at Nalubaale (former Owen) Falls and Kiira dams.

The weed that reproduces both sexually by way of seeds and vegetatively through budding is rated among the most reproductive plants. Its seeds can germinate in a few days or remain dormant for 15-20 years.

The water hyacinth, known by the scientific name Eichhornia crassipes, is a native of South America and considered the world’s worst aquatic plant.

Though quite unclear how the weed reached Africa and particular Uganda, its ornamental properties could have lured somebody into bringing it here. Many Americans grow it in ponds for decorative purposes and with the increasing popularity of water gardening, some grow it for economic gains.
Dickson Lufafa, a National Environment Management Authority (NEMA) official, says the hyacinth forms dense mats that interfere with navigation, recreation and power generation. “The weed competitively excludes native vegetation.

"It also creates low oxygen conditions beneath the water, which disrupts aquatic life,” Lufafa explains.
Joseph Kapere, a fisherman on Lake Victoria, says the hyacinth has greatly hindered boat movements between islands.

“Sometimes we find the landing sites covered with the weed. Management at most sites levies sh5,000 per boat landing to pay for removing the water weed,” Kapere says.

He adds that one of the most affected landing sites is Kisima I on Napoleon Gulf in Jinja district. Workers extracting the weed from Nalubaale dam reservoir clear away about 20 boatloads daily.

“The Kiira Dam has floating metallic barricades to keep the hyacinth from getting to the turbines. However, there are times when the barricades break and the weed floats towards the dam,” Kapere adds.

He says that the weed affects water flow, which creates good breeding conditions for mosquitoes that transmit malaria.

“The population of mosquitoes drastically rises every time the hyacinth appears. Many fishermen have already suffered severe malaria attacks as a result,” he adds.

However, Lufafa says the water weed has some advantages like treating unsafe water.

“The hyacinth obtains nutrients directly from the water body and this helps in extracting pollutants, which is vital in waste-water treatment,” he says.
Kapere explains that in the past, the hyacinth was removed from the River Nile and Lake Victoria through mechanical harvesting and the biological control method.

According to Kapere, chemicals like aquatic herbicides, 2, 4-D, diquat, complexed copper and endothall dipotassium salt could be used although experts have come up to dispute their application.

The Washington State department of ecology website shows that only endothall dipotassium salt is permitted to be applied in Washington waters.

The website also shows that mechanical harvesting, although used for nearly 100 years in the American state of Florida, is ineffective for large-scale control. It is categorised as very expensive and unable to keep pace with the rapid plant growth in large water bodies.

Lufafa says biological control of the offensive weed has registered good results internationally by use of weevils belonging to Neochetina species and a moth, Sameodes albiguttalis.

“We have been able to suppress this menace before and I think with persistent weeding, it will be weeded out again,” says Lufafa.

However, given the hyacinth’s infamous history, total eradication may after all be a case of just sending it into a temporary state of dormancy.

The water hyacinth is back

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