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.
