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Lake Victoria




Identified as the biggest one in África, and second of the world of fresh water, this lake extends along almost 69.000 km2, half of which belongs to Tanzania. Great variety of fishes from the lake are exported to Europe.

Near the lake we find different types of accomodation: camping areas, hotels, bungalows,...

Mwanza is the most important city in the area, it is characterized by its growing industrial peak, although fishing and agriculture continue being the main sources of their populations life. We could visit the city and some fishermen towns.


Another interesting place is Musoma, where besides visiting the city we could also visit some fishermen towns. In the area well-known as Speke Bay we could do different activities as: canoe-trip on Lake Victoria to a fishing village, mountain-bike trip through Masamba Hills, lake cruise, bird walk ...



Lake Victoria receives almost all (80%) of its water from direct precipitation. Average evaporation on the lake is between 2,000–2,200 millimetres (79–87 in) per annum, almost double the precipitation of riparian areas. In the Kenya Sector, the main influent rivers are the Sio, Nzoia, Yala, Nyando, Sondu Miriu, Mogusi and the Migori.




More about Lake Victoria

Lake Victoria has, during its geological history, 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 that 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. The 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.


Lake Victoria and the Great Rift Valley
This geological history probably contributed to the dramatic cichlid speciation that characterises its ecology, as well as that of other African Great Lakes,[6] although there are researchers who dispute this, arguing that while Lake Victoria was at its lowest between 18,000 and 14,000 calendar years ago, and it dried out at least once during that time, there is no evidence of remnant ponds or marshes persisting within the desiccated basin.


If such features existed, then they would have been small, shallow, turbid, and/or saline, and therefore markedly different from the lake to which today's species are adapted.

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





Combined, these rivers contribute far more water to the lake than does the largest single in-flowing river, the Kagera, which enters the lake from the west.The only river flowing out of the lake is the White Nile.The lake exhibits eutrophic conditions. In 1990–1991, oxygen concentrations in the mixed layer were higher than in 1960-1961, with nearly continuous oxygen supersaturation in surface waters.


Oxygen concentrations in hypolimnetic waters (i.e. the layer of water that lies below the thermocline, is noncirculating, and remains perpetually cold) were lower in 1990-1991 for a longer period than in 1960-1961, with values of less than 1 mg per litre (< 0.4 gr/cu ft) occurring in water as shallow as 40 metres (130 ft) compared with a shallowest occurrence of greater than 50 metres (160 ft) in 1961. The changes in oxygenation are considered consistent with measurements of higher algal biomass and productivity.



These changes have arisen for multiple reasons: successive burning within its basin, soot and ash from which has been deposited over the lake's wide area; from increased nutrient inflows via rivers,and from increased pollution associated with settlement along its shores.The lake's eutrophication has also been blamed on the mass extinction of the Haplochromis species 'flock'.


The fertility of tropical waters depends on the rate at which nutrients can be brought into solution. The influent rivers of Lake Victoria provide few nutrients to the lake in relation to its size. Because of this, it is thought that most of Lake Victoria's nutrients are locked up in lake-bottom deposits. By itself, this vegetative matter decays slowly.


Animal flesh decays considerably faster, however, and therefore the fertility of the lake is dependent on the rate at which these nutrients can be taken up by fish and other organisms. There is little doubt that Haplochromis played an important role in returning detritus and plankton back into solution.


With some 80% of Haplochromis species feeding off detritus, and equally capable of feeding off one another, they represented a tight, internal recycling system, moving nutrients and biomass both vertically and horizontally through the water column, and even out of the lake via predation by humans and terrestrial animals and humans. The removal of Haplochromis, however, may have contributed to the increasing frequency of algal blooms,which may in turn be responsible for mass fish kills.