A man-made canal is draining the Amite River dry, and to save it, officials will have to redirect the flow.

In the 1950s, the U.S. Army Corps of Engineers dug a diversion canal linking the flood-prone Amite River to Blind River. Crucially, to regulate the flow between river and canal, they built a weir — an underwater rock wall that directs most of the stream into the Amite but allows drainage into the canal during periods of high water.

But the old weir has worn down, and now most of the Amite flows straight into the canal, with little water following the bend in the river.

Under normal circumstances, 70 percent of the water should continue into the lower Amite. Now it’s down to 20 percent, said Tom Killeen, administrator of the Inspection Division of the Louisiana Department of Environmental Quality.

In addition to lowering water levels, there are less obvious repercussions. Left unchecked, the river will continue to lose oxygen, will become saltier and will experience a buildup of sediment — bad news for boaters, freshwater fish and plant life.

Officials have begun designing repairs to the weir, though no one has found money for the project, and any completion date is still probably years in the future.

The river is not yet in crisis, said Amite River Basin Commission Executive Director Dietmar Rietschier.

“This is something that eventually, sooner or later, has to be rectified,” he said.

But concerns already are surfacing.

“I know the lower end of the Amite is seeing some problems,” said Head Commissioner John Templet, of the Ascension Waterways Commission.

People complain to him that the river is stagnant during dry periods. Once, the Amite was between 6 and 10 feet deep where it meets Lake Maurepas, but now it can get down to 4 feet, Templet said.

“You’ve got significantly shallower water, just from silting,” he said.

When a river runs swiftly, it carries sediment with it. But when the water slows down, it deposits soil and sand, which can further choke the way.

A 2007 Amite River Basin Commission study found that when the upper Amite was at “medium flow,” the water sped along at 3,680 cubic feet per second. Upon hitting the weir, the water continued into the canal at a brisk 3,490 cfs. However, the flow down the lower river plummeted to just 657 cfs. During low water, the river crawled at 12 cfs.

Worse, it sloughed backward, returning the water toward the canal.

Besides dropping silt, slogging water fails to aerate the river. The 2011 DEQ study found the lower Amite is no longer meeting the requirements to be considered a site for fish and wildlife propagation, and the department pointed to low levels of dissolved oxygen as a primary cause.

Killeen said the department hasn’t specifically studied the river’s fish but said anglers already have noticed that they aren’t catching what they used to.

Beyond the bank, the nearby cypress and tupelo swamps depend on a healthy river as well, Killeen said. They need fresh water and nutrients from the Amite, and even now, if a big storm flushes Lake Maurepas brine into the marshes, the trees could suffer.

The good news is that when the weir is fixed, the downstream systems should start improving quickly, he said.

However, the work that has begun is still in the early stages. The Ponchartrain Levee District has paid $130,000 for engineers to begin designing repairs, seeking permits and looking for funds. The work began in June and is expected to take until early next year, said Ponchartrain Levee District Executive Director Monica Salins. At that point, the district will turn the project back over to the basin commission and local government.

It remains unclear how much the repairs to the weir might cost and how long the project will take.

Rietschier hopes to finish within two or three years, though it will depend on permitting and financial backing.

He has wanted to work on the project since the commission’s 2007 study but said issues with the Comite River Diversion Canal demanded the organization’s attention.

The weir, which sits a few feet inside Ascension Parish, has generated discussion in the parish.

Local government is waiting for the levee district to finish its work and will talk with the basin commission but has not yet become involved in the repairs, said public information officer Lester Kenyon.

He said it is unclear what involvement Ascension might have with the project in the future.

While the weir is within Ascension, most of the lower Amite runs through Livingston Parish.

“We understand the water’s not doing what it’s supposed to do because of that weir,” said Parish President Layton Ricks, adding that Livingston would help look for money to pay for the repairs.

“We’re there in a supportive role more than anything,” he said. “The grant dollars just don’t flow like they used to.”

State Rep. Clay Schexnayder, R-Gonzales, pledged his support.

“The weir has been a problem for a while now, and nothing has been done. … The lower part of the Amite River is starting to silt in,” he said. “If we don’t get water flow down the Amite River … we’re gonna lose a lot of trees, a lot of fish, a lot of water — natural water, fresh water.”

Officials said that once the weir is repaired, they can begin looking at solutions to the settled sediments. Fixing the weir may push enough water downriver to push silt out, though dredging may be necessary.

First, though, the underlying problem needs to be fixed.

“Nobody has really been maintaining the weir,” Rietschier said. “The weir has settled over the years. It needs to be brought back to the standard.”

Follow Steve Hardy on Twitter, @SteveRHardy.