Mighty Zambezi under threat…Low water levels pave way for world’s worst water weed

Leonard Ncube
THE world’s worst water weed — the water hyacinth — has invaded the mighty Zambezi River upstream near Victoria Falls waterfalls, a development that might negatively impact on economic activity downstream. With the presence of the weed, power generating projects are under threat, at a time the country is battling with a crippling power deficit.

New power project, the Batoka Hydro-electric Power station, spearheaded by the Zambezi River Authority (ZRA), is threatened by the weed. If the Kariba Dam is invaded by the weed power generation could be affected the same way Africa’s largest lake, Lake Victoria shared by Kenya and Tanzania was affected.

The government, through Environment, Water and Climate Minister, Oppah Muchinguri-Kashiri, has ordered an investigation into the source of the water weed in the Zambezi River.

Minister Muchinguri-Kashiri, who recently toured the Victoria Falls Rainforest said the growth of the weed was a cause for concern.
She said the weed was associated with raw sewer discharge into water bodies.

“I want a report on this plant because we need to manage raw sewer leakage into the river. Usually it grows under conditions where there is raw sewer finding its way into the river. It should be a cause for concern because if raw sewer is flowing into water bodies that can be dangerous to dams and rivers downstream,” said the Minister.

Water hyacinth is a free-floating perennial tropical American plant that was introduced as ornamental in the Amazon and came as a pot plant from South America decades ago as it produces very beautiful flowers.

In some warmer regions it has become a problematic invasive weed of waterways with its dark green leaf blades that are attached to a spongy, inflated thick and heavily branched, dark fibrous root system underneath. The weed blocks sunlight into water and research has shown that it affects the level of oxygen which fish and other water life live on.

In Zimbabwe it came in 1937 and has been a menace in Lake Chivero, Lake Mutirikwi, Mukuvisi and other rivers.
On the Zambezi River, the water hyacinth has been spotted about 100 metres from the Devil’s Cataract waterfall in the Rainforest.
Minister Muchinguri said allowing the weed to spread in the Zambezi River would negatively impact on tourism.

Ecologists say the aggressive invading plant whose thick mats can cover the entire surface of a water body causes oxygen depletions that kill fish, animals and plants that live underneath the water.

They say the water weed should be controlled at all costs.
Minister Muchinguri-Kashiri said she would engage her Zambian counterparts to help deal with the weed.

“We wish to work with Zambia to make sure we put in place a system to clean the river. We will be having a meeting for Sadc Ministers of Environment and I’ll raise the issue. This weed is a sign of a hazard coming,” said Minister Muchinguri-Kashiri.

With the weed invading approximately all rivers, lakes and dams in Zimbabwe, it is high time the government mandated research institutions to come up with solutions to deal with raw sewage, especially renewable energy projects such as biogas.

The Ministry of Energy and Power Development should intensify research to promote making of biogas from the weed.
Minister Muchinguri-Kashiri said: “We need to control it from upstream and I’m glad Chinhoyi University are taking raw sewage as an opportunity to produce organic fertiliser.” The Environment Minister was on a mission to investigate the situation on water levels at the Victoria Falls following recent media reports that Zambezi River was dry.
A Zimbabwe Parks and Wildlife Management Authority ranger, Fanuel Nleya, briefing Minister Muchinguri-Kashiri said after noticing the presence of the weed, efforts are being made to engage their Zambian counterparts since they share the river.
“We share a boundary with Zambia and we need to talk to them because this weed is a menace. We’ve a joint programme to eradicate lantana camara from the Rainforest and similar engagements should be used to clear this as well,” said Nleya.
Environmentalists are concerned the water weed, if not controlled, could rapidly spread, covering entire surfaces of the river and impacting on water flow. They say the weed can end up blocking sunlight.
This could have dire economic and social impacts to fishing activities in Binga and Kariba as well as affecting water supply to the resort town of Victoria Falls which draws water from the river.
Victoria Falls draws its water from a point about 100m from where the weed is.
The town’s mayor, Councillor Sifiso Mpofu, said the local authority was ready to partner any organisation with the initiative to weed out the plant.
“As a council we can’t sit when our water sources are being threatened. We’re ready to join hands with anyone to remove the weed because the issue of water is critical,” he said.
If not controlled the invasive weed could threaten both aquatic and human life since people and animals downstream rely on Zambezi River for water.
Activities such as boat cruise upstream from the main waterfalls and even white water rafting downstream will be difficult to perform if the weed is left to thrive. The low water levels are conducive for the weed to start growing.
Water hyacinth can also cause various diseases, according to research.
The hyacinth can also affect the Matabeleland-Zambezi Water Project as the plant seeds may be carried up the Gwayi-Shangani River due to backwash.
“If the weed is really water hyacinth, authorities should take urgent action to prevent it from spreading because in less than two years the river would be submerged by the weed thereby killing tourism activity,” said an environmentalist in the resort town.
However, ZRA chief executive officer, Munyaradzi Munodawafa, feels the weed poses no immediate threat as it can easily be controlled.
He said the weed can be controlled through an artificial parasite.
“We aren’t worried about the damage it can cause downstream, we’ll control it. There is a weevil which eats the plant. We had the same plant near Maramba Lodge and it was controlled,” said Munodawafa.
ZRA says Zambezi River water levels have improved although still far below expected levels.
Only about 500 cubic litres fall through the Mosi-oa-Tunya falls per minute against an expected more than 1, 000 cubic litres during this time of the year.
In December only about 100 cubic litres were falling down the waterfalls per minute as water was restricted to the Devil’s Cataract on the Zimbabwean side while the Zambian side was dry.
On a normal rainy season, more than 2,000 cubic litres of water roar down the waterfall per minute according to ZRA.
The presence of the water weed could jolt into action the Aquatic Weed Management Committee to start executing its mandate of identifying water impoundments.
Formed in July 2000, the Aquatic Weed Management Committee also has a duty to manage the aquatic weed and train national parks personnel in control strategies.

Pin It