Remove pollution to control hyacinth
The water hyacinth cannot clog the Nahoon river, it is a misconception that it can. The plants will be washed down stream into the Estuary where the saline water will kill the plants, according to Kim Weaver, Community Engagement Officer for the Centre for Biological Control at Rhodes University’s Zoology and Entomology Department.
“Contrary to popular belief, water hyacinth is not able to remove nutrients fast enough to clean the water. However, once the removal of the weeds opens up space in the water, the likelihood of other problem plants to proliferate increases, highlighting the importance of managing pollution in the water,” added Weaver.
This comes after fears by locals that the widespread water hyacinth in the Nahoon river will eventually kill all the species. The hyacinth washed up on the Nahoon River after a heavy storm in February, 2020. The plant is one of the fastest growing plants known and if it is not controlled, it grows rapidly and forms a mat like layer.
“We have been monitoring the Nahoon River's invasive plant species, as the water hyacinth is not the only culprit here, for a while and it is alarming at how water hyacinth has taken over the system. We have released biological control insects on the Nahoon system over the years, unfortunately the system appears to be heavily polluted so this just exacerbates the infestation,” said Weaver.
Water hyacinth is one of the most invasive aquatic plants in the world originating from the Amazon Basin in South America. Water hyacinth was first recorded in South Africa in the early 1900s and has spread rapidly throughout the country’s waterways and dams.
The Centre for Biological Control is largely funded by the Department of Environment, Forest and Fisheries and their mandate is to research and implement biological control of invasive species. Weaver stressed the need for Municipalities to fix the water treatment works to address nutrient inflows. Invasive alien species, in terms of the law must be removed.
Spokesperson for the Metro, Samkelo Ngwenya the national Department of Water and Sanitation is mandated by legislation to coordinate efforts to control Water Hyacinth, as the custodian of water in South Africa.
“Of course, as a municipality our role is to ensure that we avoid sewage spillage and other similar contamination of streams and rivers, as this tends to result in more proliferation of hyacinths. As a municipality we would be part of any efforts led by the national Department of Water and Sanitation to implement control measures,” said Ngwenya.
Christo Theart, Chairperson of the Nahoon Estuary management believes that the old sewerage infrastructure causes polluted storm water to end up in the river and the beach, leading to the growth of hyacinth. He claims that polluted water makes it easier for the plant to grow as it takes nutrients out of the water.
The plant cannot survive in salt water, and if possible, to remove, it will only be for a short or medium term until the municipality fixes the sewerage infrastructure. It is hard to completely remove the plant as the water hyacinth grows fast and is able to double its size every 8 to 12 days. Its seeds can lay dormant in the sediment for 15 years.
SAM. We are in discussions with the Water and Sanitation Department of the BCMM. At a recent meeting they indicated that the Cambridge pump station will soon get a backup power supply. This will diminish sewerage spills into the Nahoon River below Cambridge Location.
The Forum is expecting the implementation of the Nahoon Estuary Management Plan by the Metro, which includes the audit and maintenance of the sewerage infrastructure and provision of a backup supply to all pump stations that affect the estuary.
East London Museum scientist Kevin Cole said, ‘The species of Eichhornia (water hyacinth) is normally either controlled mechanically, using bio-control agents or registered herbicides. An active programme of physically removing the hyacinth before it gets out of control is probably the best method,” he said.
Today masses of water hyacinth has been dislodged from the middle reaches of the Nahoon River and is being deposited along the coast at the mouth.
“Biocontrol can be highly effective and is also environmentally friendly. However, because it is a natural process it may take a longer time to get control of the problem. The most effective way to control water hyacinth is to remove pollution from the waterways,” concluded Weaver.