New Sense in Nuisance - JaniPad

Controlling the
Hyacinths on Lake
Victoria
The water hyacinths on Lake Victoria are a regional
problem affecting the coastlines of Kenya, Tanzania
and Uganda. It reached its peak on Lake Victoria
in 1998, covering a water surface area of 17 231
hectares. By year 2000, the amount had decreased
to approximately 500 acres but a few years later, the
water hyacinth experienced a resurgence (Petersen,
2007). The lake-wide decrease has mainly been a result
of biological control, but the weather phenomenon,
El Niño, of 1997 and 1998 most likely played an
important part in accelerating the decline of hyacinth
growth (Williams et al, 2005).
In controlling the water hyacinths, mechanical as
well as chemical methods were designated for a rapid
short-term control of the plant in restricted areas. For
a long-term control, a biological control programme
was established in which two weevil species,
neochetina bruchi hystache and neochetina eichoniae
warner, were introduced to the lake (The World Bank,
1996). These interventions have been implemented
by the Lake Victoria Environmental Management
Project, a programme aimed at rehabilitating the lake’s
ecosystem for the benefit of the people in the area as
well as the national economies of which they are part.
The programme is funded by The World Bank and the
Governments of Kenya, Uganda and Tanzania (The
World Bank, 2001). The first phase of the LVEMP
was implemented during 1997-2005 (The World
Bank, 2006) and it is intended to be followed up with
a second phase in the near future.
The damage that the weevils cause the water hyacinths
eventually lead to that they sink to the bottom of the
lake (Wilson, 2005). As mentioned, the rotting plant
material reduces the oxygen content of the lake water,
and as the effect of the weevils result in the decay of
enormous amounts of water hyacinths, the ecological
balance of the lake is affected. Moreover, the plant’s
ability to absorb nutrients and pollutants would not
be taken advantage of as they would be re-released into
the lake. Thus, an alternative way of controlling the
water hyacinth is necessary in which the entire plant
should be removed. This method entails an additional
benefit by weakening the reproduction ability of the
hyacinth as removing it, especially before flowering,
would ensure that the plant does not seed the water
(Jembe et al, 2008).
The overall cost of the water hyacinth control was
approximately USD 8.31 million, which constituted
11% of the total LVEMP cost. Within Kenya, the
costs were approximately USD 2 792, which was
10% of the Kenyan project cost. The removal has been
necessary in enabling among other things commercial
waterborne transport and the avoided costs have been
estimated to be approximately USD 25-40 million in
the period 2000-2005 for the whole lake. For Kenya,
the cost was estimated to be USD 8-13 million (World
Bank, 2006).
Floating water hyacinths on Lake Victoria
Reality Studio 09 - New Sense in Nuisance
page 13 of 97