Geography.
Lake Victoria is the most important natural resource in the Sub-Saharan region of Africa. It is the
second biggest fresh water lake in the world, and has a surface area of approximately 69.500 km2 (26.800 square
miles) with an adjoining catchments area measuring 184.000 km2. The
Kenyan share of the Lake is 6% while Uganda has 45% and Tanzania 49%. The surrounding lake communities in the riparian states
(Tanzania, Uganda and Kenya) is approximately 30 million, with a large proportion being totally dependent on the lake for
water, food and economic empowerment.
The Source of the Nile.
Despite it’s vast size, Lake Victoria, remained one of the last physical
features in Africa to be discovered by the 19th century explorers from Europe. The early charts of Ptolemy delineate
a vague patch of water lying to and east of the “Mountains of the Moon”, but it was not until August 1858 that
Mr. Speke and Mr. Burton stumbled to its southern shore near Mwanza. Mr. Speke later wrote that he felt no doubt that the
lake he had stumbled upon gave birth to that interesting river, the source of which had been the subject of so much speculation,
and the object of so many explorers. He further wrote; the lake at my feet is the most elusive of all explorers’ dreams,
the source of the legendary Nile.
Depth, Water Temperature and
Water Fluctuation.
Lake Victoria is relatively shallow and has a gentle slope on the shores hence
any slight change in Lake Level “affects a considerably large land area”.
The lake has a mean depth of about 40 meters, with the deepest part at 82 meters. The range in water temperature in
the Lake lies within the range in air temperature during a significant portion of the year. it is important to note that the
water balance in Lake Victoria is dominated by evaporation and rainfall in the lake; with minor contributions from river inflow
and outflow. The outflow of water, into the River Nile through the Owen Falls Dam, account for only 20 per cent of water loss
from the lake. The remaining 80 per cent is taken by evaporation. Similarly, the inflow through the many rivers from the catchments
area only contributes 15 - 20% while rainfall on the lake accounts for 80 - 85%. Of the inlets, the River Kagera, which flows
from Rwanda, contributes about 46%, Kenya’s River Nzoia and Sondu/Miriu River about 15% (Top of Page)
Fish Population.
The wide variety of fish in Lake Victoria is
an interesting evolutionary phenomenon – more than 200 species of haplochrominas has evolved in the lake. Scientifically,
it is puzzling that so many diverse species unique to these waters could evolve in so uniform an environment. Evolutionary
biologists speculate that, hundreds of thousands of years ago, the lake may have dried into a series of smaller lakes causing
these brilliantly coloured cichlids to evolve differently. These fish are greatly sought after for aquariums. One unique characteristic
for which cichlids (tilapia being the best known) are noted for is the female’s habit of nursing its fertilized eggs
and young in its mouth. To the people of Lake Victoria, the cichlids have been their livelihood – the catch, preparation
(sun-drying) and sale of these fish fit well within the resources available to them.
"The Ecological Disaster".
Lake Victoria appears to be a classic case of wrecking an ecological
community by introducing a predator – the Nile perch. The perch was introduced into the lake some 20 years ago, probably
for sport, and has come to dominate the lake. Although people argue how the voracious Nile perch came to be there, most believe
that it has been an ecological disaster eating most of the smaller native fish. However, some scientists and biologists now
have evidence that the perch is not wholly responsible for the rapid decline of the number of the smaller fish. A survey has
shown that in most places the biologists found few cichlids and many Nile perch. But in some places they caught hundreds of
specimens of many species, not only cichlids but also other species believed to be in decline. Nile perch were present in
the same catches, often in large numbers. The areas that were rich in cichlids were all reserves, where fishing is banned.
Close by, where fishing is allowed, the cichlids were rare. This evidence suggests that over-fishing with fine-meshed nets
is partly to blame for the “ecological disaster” in Lake Victoria.
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