LAKE VICTORIA BASIN

Dominant wind patterns in the Lake Victoria basin

KENYA

Lake Albert

Lake Kyoga Victoria Nile

Kitale

DEMOCRATIC REPUBIC OF THE CONGO

Mbale

Lake Baringo

UGANDA

Eldoret

Jinja

Kampala

Kakamega

Lake Wamala

Lake Bogoria

Kisumu

Nzola

Lake George

Entebbe

Nakuru

Lake Edward

Lake Kachira

Sondu

Mbarara

Lake Kyanebalola

Lake Victoria

Lake Naivasha

Nairobi

Bukoba

Lake Ikimba

Musoma

Ruhengeri

Mara

Lake Kivu

RWANDA

Kigali

Kibungo

Kibuye

Gitarama

Lake Burigi

Mbalageti

Mwanza

Butare

Simiyu

Ngozi

BURUNDI

Gitega

Bujumbura

Dominant winds:

Lake Victoria basin

Capitals Other cities Major settlements

January - February June - September October - December March - May

100 km

TANZANIA

Lake Tangayika

More than 25 000 inhabitants

Copyright©2016GRID-Arendal (LeviWesterveld) ·Cartografare ilpresente/NievesLópez Izquierdo

Figure 1.3: Seasonal wind patterns for the Lake Victoria Basin Source: Lake Victoria Basin Commission 2002

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).

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