Saturday, March 25, 2006

Lakes Under Siege: Lake Chad and the Aral Sea.

Once the fourth largest lake in Africa and the sixth largest body of water in the world, Lake Chad is disappearing fast. In 1963 the surface area of the lake was 25,000 square kilometers (km*2), but today it barely accounts for 1,350 km*2. The lake is shared by Camaroon, Chad, Niger and Nigeria; countries which along with Central African Republic (CASR) constitute the Lake Chad Basin Commission (LCBC), which in French is called Commission du Basin du Lac Tchad (CBLT). The basin extends to almost one million km*2 (about four times the area of mainland U.K.), and is home to around 20 million people. The lake is very shallow, of the order of only 5 - 8 meters deep, and its waters provide a living for crop farmers, herders, fishermen and entire local communities. Now, in the wake of the receding waters, many find their livelihoods under threat.The lake is fed by the Chari and Longone rivers, and is land-locked with no outlet to the oceans. Since it is on the edge of the Sahara desert, high temperatures ensure that the evaporation rate of water from the lake is also high, at around 2,000 mm per year. This may be compared with an annual rainfall of 1,500 mm in the south but just 100 mm in the north.
The level of the lake has varied over time, according to the prevailing global temperature and regional rainfall. At one point in its history Lake Chad was sufficiently vast that modern historians refer to it as "Mega-Chad", while at other times it has all but disappeared. These changes over millennia can all be ascribed to natural phenomena, with human influence playing at most a bit part. This is no longer the case, and in recent decades, human activities in the lake's watershed mean that ever increasing volumes of water must be withdrawn in order to build dams, for irrigation and other purposes. The pressure of population is compounded by climate change, with the apparently inexorable advance of the Sahara.
The recent drying-up of lake Chad appears to have started in the 1960's, and then continued unabated for two decades. Its principal cause was a dramatic lack of rainfall for more than 10 years combined with record high temperatures. During the disasterous Sahelian drought of 1968 - 1973, the lake decreased in surface area by 20%. By the 1980's and 1990's, water flow from the rivers had been deliberately diverted from the lake, increasingly for use in irrigation schemes. It is estimated that only about two-thirds of streamflow from the river Chari now reaches Lake Chad. The extent of streamflow diversion remained at a comparatively low volume until the late 1970's, when the Chad basin countries started to rapidly increase the density of their cash crop (e.g. food and fibre) production. According to UNEP GRID, "...between 1953 and 1979, irrigation had only a modest impact on the Lake Chad ecosystem. Between 1983 and 1994, however, irrigation water use increased four-fold. About 50% of the decrease in the lake's size since the 1960's is attributed to human water use, with the remainder attributed to shifting climate patterns."
Clearly, the lake's fishermen have been greatly and adversely affected by its shrinkage, while some farmers have benefited from the exposure of the seabed, which provides a moist and fertile soil for growing crops and grazing animals on. The sustainable future of Lake Chad is not assured, as population pressures for water, land and food increase. There are serious environmental problems associated with Lake Chad, which include soil salinisation, invasion of unwanted plant varieties, increasing demands for irrigation, loss of fisheries, all of which are accompanied by an increase in the poverty of the Chad basin nations. Governments dependent on Lake Chad water have appealed for international support to help replenish the lake. The Science-in-Africa web site reported that the project "(Lake Chad Replenishment Project"), would entail damming the Oubangui River at Palambo in the Central African Republic (CAR) and channeling some of its water through a navigable canal to Lake Chad. It is a large-scale project which requires heavy resources." Thus spake Niger's Minister of environmental and Hydraulic Affairs, Adamou Namata. It is reassuring to note that there is a will among some of the relevant governments of the region to save the lake.
Though apparently unrelated, being thousands of miles distant, it is the Aral Sea whose history points to a potential and disarming future for Lake Chad. Forty years ago, the Aral was the fourth largest inland body of water in the world. Due to an unbridled exploitation of water resources, today the sea - really a land-locked lake - faces extinction. The Aral Sea is shared by Uzbekistan and Kazakhstan. There are two main rivers in Central Asia, the Amudarya and Syrdarya, which provide the main arteries for water flow into the Aral. Both Uzbekistan and Kazakhstan lie downstream of both rivers, while upstream are a number of countries, including Tajikistan, Kyrgystan and Afghanistan. Turkmenistan uses a major canal to withdraw a disproportionate quantity of the Amudarya's water before it reaches Uzbekistan's irrigation canals and farmlands.
Human activities in the region have increased markedly since the 1960's, and accordingly the pressure on streamflow diversions has intensified, to the extent that since the late 1970's, in many years, the flow of either one or both of the rivers has not made it as far as the Aral Sea. In consequence, the water level in the Aral has fallen steadily, and has dropped to a total of about 20 meters on average since 1960. Indeed, much of the "sea" is now dry land, with the hulls of beached ships resting on it. Since the Aral Sea was also heavily polluted from industrial processes, e.g. cotton production, a mainstay of Uzbekistan's economy, the loss of its water has uncovered a multitude of environmental sins, where dust from the contaminated seabed now is blown around indiscriminately by the Central Asian winds. Kazakhstan's leaders made a decision to save the northern part of the Aral, called the "Little Aral". The larger Aral to the south has since been divided into eastern and western provinces, on the edge of complete dessication and dust. The lucrative fishing industry that once supported 60,000 people has disappeared, mainly due to the loss of fish caused by the fall in both the quantity and quality of the Aral waters.
There is probably nothing that can be done to save the Aral Sea - its conditions are past the point of no-return. In contrast, Lake Chad might yet be saved, but only if there is sufficient political will to do so.

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