Question

Collect the information of one lake and prepare a table of organisms adapted at different zones

Answer 1

Lake TURKANA

Lake Turkana is the biggest permanent desert lake in the world, a UNESCO World Heritage Site with a shoreline longer than the whole of Kenya’s sea coast. Yet 10,000 years ago its surface was 150m higher than today.

 It spread south as far as the now desolate Suguta Valley and fed the headwaters of the Nile. Today it has been reduced to a mere sliver of its former expanse. A gigantic natural sump, with rivers flowing in but no outlets, it loses a staggering 3m of water through evaporation from its surface each year (nearly a centimetre every day). As a result, the lake water is quite alkaline – although you can just about drink it, and it’s not hostile to all aquatic life.

Turkana’s water level is subject to wild fluctuations. From the mid-1980s to 1997, the level receded steadily, leaving parts of the former shoreline more than 8km from the lake. But heavy El Niño rains in 1998 led to a 6m rise in the lake level in less than a year. Fish stocks recovered and former fishing communities rediscovered their vocation. Since then, however, the level has fallen again, the lakeshore receding by as much as 1km in some places. The massive Gilgel Gibe III dam under construction on Ethiopia’s Omo River – Lake Turkana’s biggest source – poses a huge threat to the lake and may lower the water surface by up to 10m with a rise in salinity that would threaten fish stocks and wildlife and the livelihoods of thousands of people. The Friends of Lake Turkana, who are active in opposing the dam, have a highly recommended website (wfriendsoflaketurkana.org).

The prehistoric connection with the Nile accounts for the presence of enormous Nile perch (some weighing more than 100kg) and Africa’s biggest population of Nile crocodiles – some 10,000 to 22,000 of them. Turkana is one of the few places where you can still see great stacks of crocs basking on sand banks. There is a profusion of birdlife, too, including European migrants seen most spectacularly on their way home between March and May.Hippos, widely hunted and starved out of many of their former lakeshore haunts through lack of grazing, manage to hang on in fairly large numbers, though you won’t see many unless you go out of your way.