The Santee River has landed on a list of the nation’s 10 most imperiled waterways as a fight escalates over the river’s future.

American Rivers, in a report being released this morning, says the once-mighty Santee will remain little more than a lazy stream if a state-owned utility doesn’t change the way it operates two dams above the river.

The environmental group’s annual report says the Santee is the sixth most endangered river in the country, not because of pollution, but because so little water is found there today. Dams that formed lakes Marion and Moultrie in the 1940s diverted 97 percent of the water from parts of the river, most notably in its upper reaches.

American Rivers wants some water restored to the Santee to help replenish depleted fish populations and to enhance wildlife-rich flood plains. The national nonprofit group focuses on protecting and restoring rivers. It receives funding from charitable foundations and its approximately 40,000 members.

“This river is not at all what it used to be,” said Andrew Fahlund, a vice president of American Rivers. “But it is a river that could be more than what it is today. The Santee has the potential to be an incredible treasure for the state of South Carolina.”

Santee Cooper, the power company that runs the dams, is considering the idea of adding water to the Santee as part of an application for a new 30-year dam operating license from the federal government. Federal and state agencies could require Santee Cooper to increase flows, depending on how environmental studies turn out.

The Santee Cooper license renewal is one of numerous requests being made by power companies through the Carolinas as licenses to run dams expire, but has been more contentious.

Before dams were built to supply power in the coastal plain, the Santee was the largest river in South Carolina and had one of the largest drainage basins on the East Coast. Rivers that feed the Santee begin in the North Carolina mountains before forming the waterway near Columbia.

The river, which includes the vast Sparkleberry Swamp above Lake Marion, empties into the Atlantic Ocean south of Georgetown.

Some species of fish, such as American shad and the federally endangered shortnose sturgeon, would recover if Santee Cooper put more water back into the river, the group says. The dams kept some fish from getting upstream near Columbia to spawn, which caused some species to shrink in numbers during the 1900s, according to the National Marine Fisheries Service in Charleston.

American Rivers, which has issued an endangered rivers report for two decades, doesn’t expect a full restoration of water into the Santee, but its report says “even a modest increase in flows would reinvigorate” parched flood plains while helping fish and wildlife.

The report urges the S.C. Department of Health and Environmental Control to act. DHEC must issue a water quality approval for new operation of the dams.

Santee Cooper spokeswoman Laura Varn said it is too early to tell if that can be done.

She said a key issue is how putting water into the Santee River would affect lake levels in Moultrie and Marion, both popular with recreational boaters and anglers.

“It’s all a question of balance,” Varn said. “The heart of the issue is the right lake level to meet everyone’s needs, to help us maintain the environmental integrity of the system.”

St. Stephen tackle shop worker Maria Pinckney said she would like to see more water in the Santee. Pinckney and her father sometimes fish in the river below the dam, but he is at times frustrated with the flow.

“The larger the amount of water, the more people would like it,” she said. “Right now, my father calls it a puddle.”

The river has suffered most from a lack of water in its upper reaches near Pinckney’s home, where boating has also been limited. The lower river, which includes the scenic Santee River delta, has had some water restored over the years, but it still is substantially less than before the dams were built.

Environmental groups and some government natural resource agencies have complained Santee Cooper is being difficult to work with. They claim the company has not consulted them enough on environmental studies it is conducting. The studies are being done for the Federal Energy Regulatory Commission as part of Santee Cooper’s request for a new license.

The American Rivers report calls Santee Cooper “uncooperative,’’ but Varn said her company had tried to include various interest groups as it studies increasing flows.

Reach Fretwell at (803) 771-8537 or sfretwell@thestate.com.