16
The hydrological processes of the Basin are influenced
by seasonal winds, as depicted in Figure 1.3. During
January and February and from June to September, the
wind is predominantly from the east, blowing parallel
to the equator. These relatively dry winds pick up
moisture while crossing the Lake and deposit it in the
western catchments, particularly the Bukora Catchment
in Uganda. Between March and May and from October
to December, the wind pattern changes towards
the northern parts of the Lake (Lake Victoria Basin
Commission 2002).
Geology and Soils
The LVB is geologically relatively young, formed
through tectonic forces over 400,000 years ago (Yisong
et al. 2004; Johnson et al. 2000). Most of the Lake Basin
is made up of Precambrian bedrock, with the exception
of the Kavirondo Gulf in the north-eastern corner.
Tertiary and recent alkali volcanic and sedimentary
units dominate the terrain. The nature of the land
drained upstream affects the physical chemistry of the
water: the majority of the rocks (mentioned above) are
rich in silicates, aluminium and iron (Yisong et al. 2004;
Johnson et al. 2000).
The Basin is characterized by different types of soils
suitable for a variety of crops, including maize, beans,
cassava and sugarcane. Ferrosols – characterized by
high acidity and low base saturation – are dominant
within the lower parts of the Basin. Vertisols, which are
also common, are dark-coloured clays that expand and
contract markedly with changes in moisture content
and develop deep drying cracks. The vertisols soils are
extensively cultivated.
Drainage
The LVB consists of rivers, streams and wetlands. The
Kagera River provides the largest inflow into the Lake,
contributing up to 33 per cent of surface water inflow.
It originates in Rwanda and Burundi (as the River
Akagera), as well as in parts of south-western Uganda,
before passing through Tanzania. The other major
rivers flowing into Lake Victoria are the Bukora and
Katonga, which originate in Uganda; the Nzoia, Sio,
Mara, Yala, Awach, Gucha, Migori and Sondu, which
originate in Kenya; and the Mori, Simiyu, Grumeti,
Mbalageti and Magogo-Moame, which originate in
Tanzania (Lake Victoria Basin Commission 2007a)
(Figure 1.4 and Table 1.2).
Figure 1.3: Seasonal wind patterns for the Lake Victoria Basin
Source: Lake Victoria Basin Commission 2002
Kigali
Bujumbura
Kampala
Nairobi
Kisumu
Nakuru
Eldoret
Kitale
Kakamega
Jinja
Entebbe
Bukoba
Musoma
Mwanza
Mbale
Mbarara
Ruhengeri
Kibuye
Butare
Gitarama
Kibungo
Ngozi
Gitega
KENYA
UGANDA
DEMOCRATIC
REPUBIC OF THE
CONGO
RWANDA
BURUNDI
TANZANIA
Lake
Albert
Lake
Kyoga
Lake
Baringo
Lake
Bogoria
Lake
Naivasha
Lake
Kivu
Lake
Tangayika
Lake
George
Lake
Kyanebalola
Lake
Ikimba
Lake
Burigi
Simiyu
Mbalageti
Mara
Nzola
Sondu
Victoria Nile
Lake
Kachira
Lake
Wamala
Lake
Edward
Lake Victoria
100 km
Dominant wind patterns in the Lake Victoria basin
Lake Victoria basin
Capitals
Other cities
Major settlements
More than 25 000 inhabitants
January - February
June - September
October - December
March - May
Dominant winds:
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