When it comes to globally-significant bodies of water disappearing before our eyes, the Aral Sea seems to hog the international spotlight. It’s a very glamorous story with lots of intriguing subplots: large-scale irrigation diversion, failed Soviet economic models, environmental contamination, health crises, horrendous dust storms, regional climate change. But by no means is the Aral Sea the only major disappearing lake on the planet.
Until the 1960s, Lake Chad, in the Sahel belt on the southern edge of the Sahara, was the fourth-largest lake in all of Africa. The lake itself is a remnant of an older inland sea dating back 6 to 7 million years that may have been as large as 400 000 km² and was the largest lake on the continent as recently as 22 000 years ago. While Lake Chad has always been an endorheic lake whose size fluctuated with the seasons (the basin was fully covered by water for around half of the year; the other half became a substantial wetland during the dry season), its general size was a substantial 26 000 km² (about the same size as Lake Erie). Yet, by 1998, it had lost 95 percent of its surface area; today, its surface area lies around 1 500 km².
Source: P. Rekacewicz, UNEP-GRID/Arendal, http://maps.grida.no/go/graphic/lake-chad-decrease-in-area-1963-1973-1987-1997-and-2001.
The cause? Partially climate change, but mainly inefficient water over-extraction, primarily from excessive irrigation, downstream damming and overgrazing of livestock. The main introduction of human over-irrigation and large-scale cattle, sheep and goat farming coincided with a series of major droughts in the 1960s, triggering the desertification process. In a negative feedback loop, overgrazing removes vegetation, which reduces the ability to recycle moisture back into the atmosphere. This leads to less precipitation and thus less water and even less vegetation. Around the northern half of the lake, towns that were once right on the water now lie in the middle of desert. Taking large amounts of water from an already shallow, seasonally vulnerable basin (typically 5-to-8 metres deep) has left the average depth of Lake Chad at between 1.5 and 5 metres. This is having severe impacts on local fishing economies as the amount of fish in the lake, and the physical size of the fish, decline drastically. Fishermen fight each other over smaller pieces of a shrinking territory. Those driven off the lake turn to farming the newly exposed lake-basin ground, and compete with other farmers and herders for valuable irrigation water, diverting more and more from the lake in the process. Fishers (anti-diversion) and farmers (pro-) come into conflict over how much water should be taken out of the lake. Many farmers rely on recessional agricultural processes, (i.e. farming floodland using water in the ground rather than irrigation networks) which work in the short term but requires the water to be replenished. Should the lake not come back, the soil will eventually dry out, and the land will become agriculturally useless.
Adding to the complicated issue is that fact that the lake basin lies in four different countries: Chad, Cameroon, Niger, and Nigeria (the larger drainage basin also spreads into a fifth, the Central African Republic). Any reasonable strategy requires international cooperation. The five countries participate in the Lake Chad Basin Commission, which has a rather heady task of trying to preserve a lake whose water is used by 22 million people (a number increasing all the time thanks to the potent birth rate in the area). The commission fully acknowledges the problem and has a well-thought-out strategy; it just has nowhere near enough money or jurisdiction to do anything about it. One of the more ambitious plans is to divert a portion of the Congo River in the Central African Republic 100 km away into the Chari River basin (which provides up to 90% of Lake Chad’s annual water supply) and replenish the lake. It’s prohibitively expensive to do so, however.
Much like the Aral Sea, most mainstream maps, whether paper or electronic, are now hilariously behind the times when it comes to accurately portraying the dimensions of Lake Chad (for example, toggle between layers on Google Maps and contrast the political map of the lake with Google’s own satellite imagery, or take a look at the 2009 map of Chad produced by the United Nations). National Geographic, though, seems to have portrayed it a bit more accurately.
The lake has shown very slight recovery in the past few years around its southern edges; a result of the natural fluctuating level of the lake system (remember, despite human-inflicted damage, 25-to-50 percent of the water fluctuation over the past few decades is still naturally induced). Eventually (but not in this lifetime) the lake will probably return, but not before countless numbers of local flora and fauna are wiped out permanently. It is still a highly sensitive, threatened landscape. Cameroon has acknowledged this by designating its portion of the Lake Chad basin as a wetland of international importance under the Ramsar Convention; it is hoped the entire basin will eventually be managed as a Ramsar site.
Bomford, A. (2006). Slow death of Africa’s Lake Chad. BBC News, 14 April 2006. http://news.bbc.co.uk/2/hi/4906692.stm. Accessed 20 October 2010.
Campbell, R.W. (ed.) (2008). “Lake Chad, West Africa: 1963, 1973, 1987, 1997, 2007.” In U.S. Geological Survey, Earthshots: Satellite Images of Environmental Change. Available at http://earthshots.usgs.gov/LakeChad/LakeChad. Accessed 20 October 2010.
Coe, M.T. and J.A. Foley (2001). Human and natural impacts on the water resources of the Lake Chad basin. Journal of Geophysical Research 106:3349-3356.
Lake Chad Basin Commission (2008). Reversal of Land and Water Degradation Trends in the Lake Chad Basin Ecosystem: Strategic Action Programme for the Lake Chad Basin: Agreed by the LCBC Member States of Cameroon, Central African Republic, Chad, Niger, and Nigeria. 11 June 2008. Available at http://lakechad.iwlearn.org/publications/reports/the-lake-chad-basin-sap-english. Accessed 20 October 2010.
Mayell, H. (2001). Shrinking African Lake Offers Lesson on Finite Resources. National Geographic News, 26 April 2001. Available at http://news.nationalgeographic.com/news/2001/04/0426_lakechadshrinks.html. Accessed 20 October 2010.
Murray, S. (2007). Lake Chad fisherman pack up their nets. BBC News, 15 January 2007. Available at http://news.bbc.co.uk/2/hi/africa/6261447.stm. Accessed 20 October 2010.
United Nations Environmental Program (n.d.). Lake Chad. Atlas of Our Changing Environment. Available at http://na.unep.net/atlas/webatlas.php?id=58. Accessed 20 October 2010.
UNEP/GRID-Arendal Maps and Graphics Library (2002). Lake Chad – decrease in area 1963, 1973, 1987, 1997 and 2001. Available at http://maps.grida.no/go/graphic/lake-chad-decrease-in-area-1963-1973-1987-1997-and-2001. Accessed 20 October 2010.
Vignaud, P. et al. (2002).Geology and palaeontology of the Upper Miocene Toros-Menalla hominid locality, Chad. Nature 418:152-155. Available at http://www.nature.com/nature/journal/v418/n6894/full/nature00880.html. Accessed 19 October 2010.
World Wildlife Fund (2001). Lake Chad flooded savanna (AT0904). Wildworld. Available at http://www.worldwildlife.org/wildworld/profiles/terrestrial/at/at0904_full.html. Accessed 20 October 2010.