LAKE VICTORIA BASIN

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: