Kariba weed threatens again
Pauline Lourens
The rapid spread of the invasive Kariba weed in the Kat river, the Garden Route Dam and other inlets has alarmed residents and environmentalists.
The idea for tackling the arduous task of clearing the weed from the Kat river was mooted at an impromptu meeting held on the Kat river banks in the suburb of Eden on Monday night, 7 May.
However, the George Municipality's Parks Department and the National Department of Environmental Affairs (DEA) are the bodies responsible for preventing the weed (Salvinia molesta) from completely taking over our waterways and dam.
Urgency
The DEA's biodiversity officer of production, Reley Bell, who was involved in combating the Kariba problem on the Garden Route dam in 2013, 2014 and
2016, stated on Friday 11 May, "The most important aspect to remember regarding Kariba weed is that it flourishes in dirty water and sewage wastewater that enters the dam from various points.
On the system this is our biggest challenge, which needs to be addressed firstly and most urgently. An integrated control approach is the way forward; George Municipality indicated they will spray the big infestation and from the DEA side we will search for suitable Kariba weed sites to populate with weevil insects."
The two-thronged approach will use "biological control with the (approved aquatic herbicide) chemical spray control method on the water system."
In short, she says, "The authorities in the George area of the Garden Route Dam need to put things in place to stop the sewerage entry points on the system, because the insects will only be effective if the water pollution is under control."
Residents raise the alarm
Canoeists and hikers raised the alarm about the latest infestation, saying the weed has trebled in volume since it was spotted in November last year.
A thick carpet is now visible at all inlets into the dam, including the Kat river.
Currently, the weed lines the shores of the Garden Route Dam and was seen floating near the dam wall.
The green flower-like weed which floats on top of the water thrives in nutrient-rich water. Concerned ratepayers speculate as to whether the intermittent sewage spills into local rivers are stimulating the growth of the plant. For more than two years, there have been sewage spills from the ageing and porous sewerage lines in Fernridge and Denneoord, polluting the Kat / Mitchell river, which flows into the Garden Route Dam (see article elsewhere on this page).
Forum
At the 7 May meeting, concerned residents spoke to aquatic researcher/scientist and NMU lecturer Dr Jackie Dabrowski, who shared their conviction that the issue should be tackled urgently.
She agreed that the formation of a catchment management forum comprising local decision makers and interested and affected parties is needed to find practical and implementable solutions for both the pollution and Kariba weed.