The San Joaquin River topped the list released Wednesday by American Rivers. The group said that the river, which flows 366 miles from the Sierra Nevada Mountains to San Francisco Bay, is threatened by outdated water management.
"The river and its tributaries support some of the most productive and profitable agriculture in the world, irrigating more than two million acres of arid land," the group said. "However, the river is so heavily exploited that it runs dry in certain stretches. The current drought is placing additional stress on the river and revealing the inadequacies of status quo water management for both people and the environment."
The Upper Colorado was in second place, with increasing demands for its water and new diversions putting it at risk. It was followed by the Middle Mississippi with American Rivers saying a planned levee will cut it off from its floodplains, threatening downstream communities with flooding.
The Gila River, a 649-mile tributary of the Colorado in New Mexico and Arizona, is in danger because of a pipeline and water diversion, American Rivers said. In fifth place is San Francisquito Creek, flowing only 13 miles into San Francisco Bay, with the Searsville Dam threatening to prevent steelhead trout from reaching spawning grounds.
On the other side of the country, the South Fork of the Edisto River in South Carolina is threatened by the increasing diversion of its water for agriculture. Colorado's White River could be at risk because of 15,000 proposed oil and gas wells.
In Washington State, salmon, steelhead and bull trout often die trying to pass the outdated Buckley Dam on another White River, American Rivers said. In North Carolina, polluted runoff into the Haw River threatens the water supply for a million people.
Rounding out the list is the Clearwater in Idaho with its tributary, the Lochsa River. The group said that development of Canadian tar sands to the north could bring "megaloads" of supplies to narrow roads running through the rivers' valleys.