2017 Lake Victoria

Lake Victoria

 

Lake Victoria (Image credit: Wiki)

Lake Victoria
(Image credit: Wiki)

Named after Queen Victoria by the explorer John Hanning Speke, who was the first European to discover it, and which he did alone in 1858 while on an expedition with Richard Francis Burton to locate the source of the Nile River.

It is the world’s 2nd largest freshwater lake by surface area; only Lake Superior in North America is larger. In terms of its volume, Lake Victoria is the world’s ninth largest continental lake.

 

Lake Victoria occupies a shallow depression in Africa and receives its water primarily from direct precipitation (80%) and thousands of small streams. The largest stream flowing into this lake is the Kagera River, the mouth of which lies on the lake’s western shore. It is drained solely by the Nile River near Jinja, Uganda, on the lake’s northern shore.

Average evaporation on the lake is between 2.0 and 2.2 metres per year, almost double the precipitation of riparian areas

 

During its geological history it has gone through changes ranging from its present shallow depression, through to what may have been a series of much smaller lakes.

Geological cores taken from its bottom show Lake Victoria has dried up completely at least three times since it formed. These drying cycles are probably related to past ice ages, which were times when precipitation declined globally. Lake Victoria last dried out 17,300 years ago, and it refilled beginning about 14,700 years ago. Geologically, Lake Victoria is relatively young – about 400,000 years old – and it formed when westward-flowing rivers were dammed by an upthrown crustal block.

 

The lake’s shallowness, its limited river inflow, and its large surface area compared to its volume make it vulnerable to the effects of climate changes.

 

Primary inflows Kagera River
Primary outflows White Nile (river) (known as the “Victoria Nile” as it flows out of the lake)
Catchment area 184,000 km2
238,900 km2  basin
Basin countries Tanzania
Uganda
Kenya
Max. length 337 km
Max. width 250 km
Surface area 68,800 km2
Average depth 40 m
Max. depth 83 m
Water volume 2,750 km3
Shore length 3,440 km
Surface elevation 1,133 m
Islands 84 (Ssese Islands, Uganda)
Settlements Bukoba, Tanzania
Mwanza, Tanzania
Musoma, Tanzania
Kisumu, Kenya
Kendu Bay, Kenya
Homa Bay, Kenya
Kampala, Uganda
Entebbe, Uganda
Jinja, Uganda

 

Since the 1900s, Lake Victoria ferries have been an important means of transport between Uganda, Tanzania and Kenya. The main ports on the lake are Kisumu, Mwanza, Bukoba, Entebbe, Port Bell and Jinja. Until Kenyan independence in 1963, the fastest and most modern ferry, MV Victoria, was designated a Royal Mail Ship. In 1966, train ferry services between Kenya and Tanzania were established with the introduction of MV Uhuru and MV Umoja. The ferry MV Bukoba sank in the lake on May 21, 1996 with a loss of between 800 and 1,000 lives, making it one of Africa’s worst maritime disasters.

The Lake Victoria basin is one of the most densely populated rural areas in the world. Its shores are dotted with cities and towns, including Kisumu, Kisii, and Homa Bay in Kenya; Kampala, Jinja, and Entebbe in Uganda; and Bukoba, Mwanza and Msoma in Tanzania.

These cities and towns also are home to many factories that discharge their waste directly into the lake and its influent rivers. These urban areas also discharge raw sewage into the river, increasing its eutrophication that in turn is helping to sustain the invasive water hyacinth.

 

The Water hyacinth has become a major invasive plant species in Lake Victoria. The release of large amounts of untreated wastewater (sewage), agricultural and industrial runoff directly into Lake Victoria over the past 30 years, has greatly increased the nutrient levels of nitrogen and phosphorus in the lake triggering massive growth of exotic Water hyacinth, which colonised the lake in the late 1990’s”.

 

This invasive weed creates anoxic (total depletion of oxygen levels) conditions in the lake inhibiting decomposing plant material, raising toxicity and disease levels to both fish and people. At the same time the plant’s mat or “web” creates a barrier for boats and ferries to maneuver, impedes access to the shoreline, interferes with hydroelectric power generation, and blocks the intake of water for industries. On the flip side, Water hyacinth mats can potentially have a positive effect on fish life in that they create a barrier to overfishing and allow for fish growth, there has even been the reappearance of some fish species thought to have been extinct in recent years.

Growth of the Water hyacinth in Lake Victoria has been tracked since 1993, reaching its maxima biomass in 1997 and then declining again by the end of 2001.

 

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