Human practices threaten the security of fresh water systems that supply nearly 80 percent of the world's population, according to a study by Rivers in Crisis. The researchers claim the study is the first to quantify the impact of human-induced stresses on a global basis.

The study, published in the Sept. 30, 2010, issue of Nature, assessed threats to human water security, which involves water purity, availability, and biodiversity. It created a database of 23 environmental stressors ranging from pesticide, nitrogen, phosphorus, mercury pollution, and soil salination to agriculture, aquaculture, and invasive species. It ranked the threats and modeled how they affect fresh water systems.

Although 80 percent of the world's population faces high-level threats to water security, nations deal with these problems differently. Developed nations invest in water technology, including dams, reservoirs, aqueducts, and purification systems, to supply their populations. While this offsets pollution, over-use, and other stressors, it fails to address the underlying problems.

In the developing world, many of the most threatened rivers are being degraded by the same stressors attacking rivers in similar condition in wealthier nations. Most developing countries, however, do not have the money to invest in engineered solutions to treat those symptoms. (One developing nation, China, is using its newfound wealth to build a $60 billion water system to reroute water to Beijing and its growing coastal cities.)

Rivers in Crisis also classified 65 percent of the habitats associated with continental discharge as moderately to highly threatened.

The working group describes the study as "a tool for prioritizing policy and management responses" to the crisis. It recommends limiting threats at their source rather than through more costly remediation. It suggests preserving river ecosystems in remote locations, reengineering water systems to protect biodiversity in developed nations, and integrating water security and biodiversity in developing nations building new water systems.

The multidisciplinary working group includes researchers from the City University of New York and University of Wisconsin, Swiss Federal Institute of Technology Zurich, University of Hong Kong, University of New Hampshire, Australian Rivers Institute, University of Washington, and University of Western Australia.

Improving the security of water supplies is the aim of a standard issued earlier this year jointly by the ASME Innovative Technologies Institute and the American Water Works Association. The standard, ASME-ITI/AWWA J100 RAMCAP Standard for Risk and Resilience Management of Water and Wastewater Systems, uses the Risk Analysis and Management for Critical Asset Protection process developed by ASME. The standard is designed to guide operators of water supply systems in identifying potential man-made and natural threats to their facilities and in preparing for them.