MONTREAL, June 2 (UPI) -- Researchers in Canada say a geographically explicit, high-resolution global database of large dams and reservoirs will aid sustainable river-flow management.

Researchers at McGill University say the map, the result of a four-year effort, will allow close assessment of critical environmental and social trade-offs associated with dams and reservoirs within the global river network, impossible until now because data describing their location, size and purpose have been incomplete and inadequate, a university release reported Thursday.


The multiyear project is the result of collaboration by a team of scientists from around the globe, coordinated by the Global Water System Project and led by McGill University's Bernhard Lehner.

"Thorough continental assessments and ongoing sustainable dam management and planning haven't been possible due to a lack of data. We've only been able to look at dams on a case-by-case basis," Lehner said.

"The Three Gorges Dam [in China], for example, has been heavily investigated, but no one ever included the 100-plus large dams upstream from it in a single impact assessment.

"Now we can look at all of them at the same time to figure out what the combined effect is," Lehner said. "This gives us a holistic view of a whole river basin."

The map contains information on 6,862 dams and their associated reservoirs.

The team found that nearly 50 percent of large rivers -- those with an average flow of more than 35,000 cubic feet per second -- are affected by large dams and reservoirs worldwide.