Lake Naivasha chokes under the water hyacinth

Lake Naivasha chokes under the water hyacinth

Story By Wanyua Mary

Lake Naivasha is facing a serious threat, thanks to the water hyacinth, a deadly weed that has wreaked havoc to tourist hotels, flower farms, marine transport and fishing activities in the basin.

While there are other threats to the lake such as overfishing and pollution of the lake waters, the hyacinth has so far been the strangest phenomenon. The weed is continually blocking fish landing sites and communal water points along the lakeshore.

The weed, scientifically known as Eichoirnia Crassippes, is found in lakes, swamps, dams and riverine wetland throughout the main drainage systems of Africa. The noxious weed is continually shocking life out of Kenya’s most economically potential lakes:-Lake Naivasha and Lake Victoria. Scientists, however, believe that the water hyacinth originated from the Amazon basin and brought to East Africa as a pot plant that later found its way into the lake waters. Its rapid proliferation has been blamed on the emission of untreated industrial effluents and agrochemicals into the lake.

The proliferation of the hyacinth is straightforwardly credited to the enrichment of the water environment by the effluent from the expanding agricultural activities around the lake and in the upper catchment, says Dr John Githaiga a conservation biologist at University of Nairobi. Dr Githaiga adds that the continued infestation of the weed could result in food insecurity as it blocked access to fishing ground and could also have great effect on Tourism in the Basin.

The hyacinth has been spreading very fast over the lake and interfering with light penetration, dissolved oxygen, fish breeding sites, landing beaches and ecology especially due to increasing water levels in the lake. The influx of fertilizer and sediments facilitates the rapid growth of the weeds.

The hyacinth forms a mat of vegetation so thick that fishermen cannot launch their boats or bring fish to market on the shore. Sunlight does not filter through the plants, so native plants in the lake don’t get the light they need. The die-off of native plants affects fish and other aquatic life. Water hyacinth can also sap oxygen from the water until it creates a “dead zone” where plants and animals can no longer survive. Typically, only aggressive measures can control the fast-growing plant.

Conservationists argue that the weed can be controlled by mechanical means manpower and machines, but this has mostly been unsuccessful since the weed grows faster than mechanical clearance can cope with it. Though various herbicides are also effective, they could have significant risks for other wetland biodiversity. Some have continue to say that the destruction of the weed will lead to loss of billion of shillings since the weeds can be used in production of organic fertilizers and biogas

Urgent measures need to be put in place to control the rapid growth of the deadly water hyacinth before more devastating effects are experienced. The farmers in the upper catchment in the basin are encouraged to sustainably use their land to reduce the effluent of fertilizers and sediments in the lake which catalyses the growth of the weed.