The Environmental Defense Fund says it will file suit to force the Environmental Protection Agency to take steps to halt increasing salinity in the Colorado River.

An attorney for the group, George Pring, said the suit could affect future development in the seven-state river basin. He said a plan developed by the seven states and approved by EPA doesn't meet congressional requirements, and he charged the federal agency with "total failure over a 10-year period to live up to the congressional mandate to control salinity in the Colorado River."

The 1,450-mile river rises in Colorado and flows through the Southwest United States and part of Mexico before emptying into the Gulf of California. The states in the basin are Wyoming, Colorado, Utah, New Mexico Arizona, Nevada and California.

The amount of dissolved salt can be increased not only by natural forces, as rain and melted snow wash over soil before emptying into the river, but by human activity such as irrigation that sends the water over fields where it can pick up more salt.

Pring said stations should be established near each state's borders to monitor limits on salt in the river at those points.