Agriculture accounts for 93 percent of fresh water use, producing runoff that degrades water quality with silt and chemicals, the report says. Dams, diversions or canals fragment 60 percent of the world's largest rivers, trapping runoff and sediments. While dam construction has slowed in the United States, the report says many more are being built in the basins of the Yangtze River in China, the Tigris and Euphrates rivers in the Middle East, and the Danube River in Eastern Europe. Also being depleted is the world's groundwater, the sole source of drinking water for 1.5 billion people, the report says. Half the world's wetlands were lost in the 20th Century as land was converted to agricultural and urban use or contaminated with diseases such as malaria, according to the report.
Invasive species pose another problem, competing with native species for food and habitat.
Twenty percent of the world's 10,000 fresh water fish species have become extinct, threatened or endangered in recent decades. The findings are bad news for the environment and the economy, said Carmen Revenga, who helped write the institute's report.