More than half the world's lakes face ecological disaster, but Switzerland's success in cleaning Lakes Geneva and Constance shows that disaster can be avoided.

Scientists warn that pollution and overuse of lakes puts the health of one billion people at risk, globally. The conservation of lakes is the topic of an international conference in Shiga, Japan, which lasts until Friday.

Decision-makers around the world have largely ignored lakes while focusing on rivers and oceans, even though lakes hold nearly 90 percent of all surface fresh water, according to the World Water Council.

The Council notes that Switzerland is among countries that have done the best job in restoring the water quality of lakes.

Liquid evidence

"Lakes are clearly visible signs of what humans are doing to the environment as people relate to lakes in their daily life," Bill Cosgrove, vice-president of the World Water Council, told swissinfo.

Because of their location near big cities, lakes host a myriad of activities: transportation, trade, industry, energy production, fishing, irrigation, water supply, tourism, sports and recreation. Lakes are also on the receiving end of waste waters and agricultural runoffs. The resulting pollution and overuse are a threat, not only for the lakes, but also for health, according to the Council.

"Lakes are affected by situations in which Nature is no longer able to cope as waste from population is just too much to accommodate", says Cosgrove.

The most endangered lakes in the West are the Great Lakes shared by the United States and Canada, lake Balaton in Hungary, lake Arre in Denmark, lake Biwa in Japan and lake Baikal in Russia. Water levels of the Aral Sea, located between Uzbekistan and Kazakhstan, have dropped so much that the lake, formerly the fourth largest in the world, is now just the eighth largest.

In the developing world, the lakes most threatened include Lake Bhopal in India, Lake Taihu in China and Lake Victoria, the biggest lake on the African continent, which is shared by Uganda, Kenya and Tanzania.

Notable Swiss effort

"Switzerland is high on the list of countries that are doing an excellent job, as well as Japan", says Cosgrove, noting the recovery of Lake Geneva and the Lake of Constance. He stressed that the success of the Swiss approach is based on "awareness of the people and responsiveness of the decision-makers".

"Lake Geneva is surviving well because people living in the area are aware of the problems of the lake and realize its importance", he adds. Indeed, water quality in both Lake Geneva and the Lake of Constance has significantly improved since the 1980s, even though they are subject to great pressure from urban and agricultural activities. In these cases, lake restoration involved stringent control measures, including advanced wastewater treatment systems.

In the case of a much smaller lake, such as Lake Trummen, which is only one square kilometer in size, dredging operations cleaned up the lake from top to bottom, sediment included.

The World Water Council notes that such restoration is expensive, which presents an obstacle for developing countries. The kind of investment made in Switzerland and elsewhere in Europe is more difficult in other parts of the world, Cosgrove explains.

The dredging process of Lake Trummen was replicated in Lake Tunis. The Tunisian government bought the land surrounding the lake, dredged the lake and removed the chemicals out of the waters. As a result, water quality improved dramatically, so much so that the value of the land increased by a hundred times, allowing the government to recover all its costs.

However, even in such a successful case in the developing world, cost constraints prevented authorities from dredging the sediment at the bottom of the lake Tunis.

by Marie-Christine Bonzom

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