Nuisance or resource? Water hyacinth clogs Africa's power

A stranded fisherman trapped in water hyacinth in L Victoria after strong winds pushed him off course near Rakwaro Beach on July 30, 2021. [Denish Ochieng, Standard] 

Water hyacinth is a fast-growing aquatic plant known for its striking purple flowers and substantial ecological impact. Despite its aesthetic appeal, it is considered one of the most invasive species affecting dams and rivers globally.

This plant can obstruct turbines, reduce water flow, and significantly increase maintenance costs at hydroelectric power stations. One such example is the Rusumo Falls Hydroelectric Project, a joint initiative between Burundi, Rwanda, and Tanzania, which generates 80 megawatts of electricity shared among the three nations.

According to Patrick Lwesya, Project Manager at Rusumo Power Company, water hyacinth poses a major threat to the plant’s operations. “We remove between 10 and 15 tonnes of water hyacinth daily. It clogs the intake section of the hydroelectric power station, resulting in a 5-megawatt drop in electricity supply. We often have to remove it manually,” he explains.

Several large hydropower schemes across Africa are struggling with similar challenges. The Owen Falls hydropower scheme at Jinja on Lake Victoria has also been severely affected. The rapid reproduction rate of water hyacinth has forced authorities to dedicate increasing amounts of time and resources to prevent the weed from entering turbines, where it can cause mechanical damage and power interruptions.

The weed’s ability to reproduce quickly and spread widely has also hindered fishing and water transport in many water bodies. For example, Lake Naivasha in Kenya suffers from severe infestations. The plant disrupts ecosystems by depleting oxygen, blocking waterways, and creating breeding grounds for mosquitoes, thereby affecting local livelihoods, particularly fishing, and weakening natural flood protection.

The impact of water hyacinth is not confined to East Africa. It is also a growing concern in some of the world’s largest dams, such as the Kariba Dam on the Zambia-Zimbabwe border, which feeds into the Zambezi River and supplies power to Harare. The dam has been facing pronounced infestations in recent years.

Experts identify three primary strategies to control or eradicate water hyacinth: biological, chemical, and physical methods, each with its own merits and limitations.

“Chemical control is the least preferred option due to the unknown long-term environmental and health effects,” says environmental expert Dr John Kakonge.

Research by Practical Action has shown that while herbicides such as 2,4-D, Diquat, and Glyphosate have proven effective against small infestations, they are less successful in larger areas and pose risks where communities rely on water sources for drinking and washing.

Physical control involves manual or mechanical removal using dredgers, aquatic weed harvesters, or cranes. While widely used, it is costly and largely ineffective in controlling large-scale infestations. “Manual control is becoming increasingly difficult due to the growing volume of hyacinth on the river Kagera,” says Lwesya.

He adds that Rusumo Power Company is planning to install floating booms to prevent the plant from reaching the intake. “We’ve made procurement plans for the booms from a company in Asia. The current situation is unsustainable,” he said. 

Among all methods, biological control is considered the most sustainable and environmentally friendly. It involves introducing natural enemies that specifically target the water hyacinth, such as certain weevils, moths, and fungi. “Biological agents are self-regulating and environmentally harmless, making them a preferred long-term solution,” Dr Kakonge adds.

Nonetheless, for immediate relief, physical removal remains the most viable approach. However, the logistics involved are extensive, often requiring a fleet of water and land-based vehicles to transport the weed. Densely packed mats of water hyacinth can weigh up to 200 tonnes per acre.

Despite its harmful effects, the weed has been repurposed in some communities for practical use. Though composed of over 95 per cent water, the plant’s fibrous structure is rich in energy and protein. It has been utilised in animal feed, biogas production, fertiliser, and as raw material for crafts and textiles, among other uses. Additionally, it shows promise in wastewater treatment and composting.