'Most endangered' rivers

1 San Joaquin River, California. Threats: water diversions, dams, levees.

2Upper Colorado River, Colorado. Water diversions.

3Middle Mississippi River, Missouri, Illinois, Kentucky. Outdated flood management.

4Gila River, New Mexico. New water diversions.

5San Francisquito Creek, California. Dam.

6South Fork Edisto River, South Carolina. Excessive water withdrawals.

7White River, Colorado. Oil and gas drilling.

8White River, Washington. Outdated dam and fish passage facilities.

9Haw River, North Carolina. Polluted runoff.

10Clearwater/Lochsa rivers, Idaho. Industrialization of a Wild and Scenic river corridor.

Source: American Rivers

The black willow bends of the "backwaters" Edisto River have been named one of the most endangered rivers in the country by American Rivers, a conservation advocacy group.

It all has to do with potatoes.

The south fork of the river was designated one of 10 "whose fate will be decided in the coming year," according to a news release by the group, which called for legislators to amend a state law that allows "excessive agriculture withdrawals" that take up as much as 35 percent of the river's flow during drier summer months.

It remains to be seen whether the designation will help budge legislators, who passed that law only a few years ago.

"What excessive withdrawals are they talking about," asked Reggie Hall, of the S.C. Farm Bureau Federation, adding that the law gives farmers 7 percent of "safe yield" and that the "actual use is much more minimal than that."

The designation was spurred by a recent controversy over an 800 million gallon-per-month withdrawal sought by the Walther potato farm in Windsor, south of Columbia. That has been settled, for now, with both sides compromising. But the legal wrangling showed that the law to decide withdrawals wasn't going to decide anything.

Water, sewer, industrial and even residential use are increasing on the once "country" Edisto, along with agriculture. The river runs almost the length of the state from near North Augusta to the Lowcountry ocean. Pollution is becoming an issue.

Considered one of the longest free-flowing blackwater rivers in the world, the Edisto has had a big influence on preserving the "green" of Charleston environs. It feeds two-thirds of the water flowing into the vast Ashepoo, Combahee Edisto (ACE) Basin delta south of Charleston. An unprecedented, private-public conservation begun by landowners in that delta has blossomed into a "greenbelt" of three-quarters of a million acres around the metro area, helping preserve the riverine landscape that is the Lowcountry.

The basin needs that water flow.

"We know the answer is not to just ignore (the withdrawal) problem. The Walther experience taught us that if nothing else," said Tim Rogers, president of the grass-roots advocate Friends of the Edisto group. "The bigger problem is still there and still needs to be resolved. It's just not sustainable."

The "endangered" designations, announced early Wednesday, are an annual listing by American River used to call public attention to local river issues. The Catawba-Wateree and Santee rivers have been designations in South Carolina in the past 10 years.

"I think it's really important that agriculture develop a contingency plan (for Edisto water withdrawal restrictions) that other users have during low flow and drought. That's the biggest concern we have," said Gerritt Jobsis, the group's Southeast regional director. "We do not intend this as a way of 'slamming' anyone. It's a wake-up call. This is a shared resource and it's important that all users manage in a sound way."

Reach Bo Petersen at 937-5744, @bopete on Twitter or Bo Petersen Reporting on Facebook.