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Flaws, underutilization hurt diversion efforts
By John McQueen
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The Davis Pond water project has seemingly been in the planning and construction phase forever. At a cost of $119.6 million, the world's largest freshwater diversion project started in November 1996, and is now in the final phase before being able to work at full capacity.

“We're addressing some of the issues of the ponding area and on the west side of the guide levee,” said Chuck Villarubia, coastal resource science supervisor for the Department of Natural Resources. “We're hoping that this work can be completed by the end of the year.”

Many thought the project would be well on its way to doing what it was intended to do after the ribbon-cutting ceremony held in March of last year.

“When you're speaking of a project the size of Davis Pond, it's sometimes hard to predict some of the things that have occurred,” Villarubia said. “The biggest difference in Davis Pond and Caernarvon is the two major bodies of water in (Lake) Cataouatche and Salvador.”

The Davis Pond diversion has been beset with design flaws, which are supposed to be corrected by year’s end.
The Davis Pond diversion has been beset with design flaws, which are supposed to be corrected by year’s end.

The ponding area is the 9,300-acre space south of the two-mile long outflow channel that is bordered by a rock weir near Lake Cataouatche. Vegetation had grown so much around the structure — certainly a good sign considering the project's purpose — that the water would not be able to flow properly. The settling of the guide levee occurred much sooner than expected, and overflow could have occurred. Vinyl sheet pile is being placed in the affected areas.

Along with these technical difficulties, Villarubia says that it was and will continue to be important to be sensitive to shrimpers in the area expecting a good year, especially considering the poor seasons of the past few years.

Helping preserve what is left of the Barataria Basin relative to healthy marsh is the reason for the project, which is being funded by the federal (75 percent) and state (25 percent) governments. While the project is expected to preserve only 33,000 acres of marsh with its introduction of nutrient-laden Mississippi River water, it is expected to benefit 777,000 acres, roughly the land area of the state of Rhode Island.

Consisting of four 14-foot square gated culverts, inflow and outflow channels, east and west guide levees, and the rock weir separating the ponding area and Lake Cataouatche, Davis Pond is designed to pump upwards of 10,650 cubic feet per second (cfs) of river water into the basin, ideally mimicking the floods that refurbished the marsh prior to the Mississippi River being leveed off.

The actual amount of diversion taking place is dependent on the time of year and the salinity levels in the estuary. These standards were set by the Davis Pond Advisory Committee, the group in charge of governing how Davis Pond will be utilized.

By enriching the area in question, the state is protecting an economic benefit of $15 million per year for fish and wildlife, plus $300,000 for recreation, making it unquestionably one of the areas most in need of attention. The intense tropical season of 2002 accelerated the loss of land in the basin; many users of the region fear what might happen if steps aren't taken to stem the powers of nature.

The Caernarvon diversion, designed to funnel 8,000 cubic feet of river water per second into dying marshes, has operated at 16 percent of capacity in its first decade.
The Caernarvon diversion, designed to funnel 8,000 cubic feet of river water per second into dying marshes, has operated at 16 percent of capacity in its first decade.

“The past few years, we've really seen the loss of land increase,” says Eric Muhoberac, owner of Louisiana Paradise Fishing Charters and Guided Tours.

The similar diversion project in Caernarvon continues to do well, according to Villarubia, even though it has averaged around 1,300 cfs for the 10 years it has been open. Constantly met with opposition from commercial and recreational fishermen for its outflow during certain times of the year, Villarubia says that the project is pretty much going according to plan.

“Of course, we'd like to see what the effect would be on a consistently higher flow, but we've also learned to be cognizant of the people who depend on the marsh right now,” he said.

 

Studies have shown very positive marsh enhancement numbers, and Villarubia said updated studies should be available soon. Soil studies — what Villarubia calls biomass studies — from LSU and the University of Louisiana at Lafayette have been as positive as could have been hoped relative to the soil gained from the river being able to support plant life.

But LSU researcher Rex Caffey said most of the alluviation in the Caernarvon area occurred early on in the project’s history, when it was operated at higher flow levels.

Smaller diversion projects near Myrtle Grove and West Pointe a la Hache, operating since 1993 and which at full capacity divert around 2,000 cfs, have been received with mostly positive analysis thus far. These also are designed to help the fragile Barataria basin.

Future projects, such as the one being planned near Head of Passes that will divert river water into the West Bay area, are in the feasibility study stages.

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