Aeration device churns New River

June 14, 2001|By RUDY YNIGUEZ, Staff Writer

CALEXICO — A couple miles north and west of here is the latest effort to reduce the excessive amount of organic matter in the New River.

The Citizens Congressional Task Force on the New River has installed an aeration device expected to increase the amount of dissolved oxygen used by bacteria to break down organic matter and expected to increase bugs and the amount of algae for fish to eat.

"There's no dissolved oxygen in this water hardly at all," Lesicka said.

Such devices lend themselves to possibly be used as a diversion point for gravity-fed wetlands as used along the river in the Brawley and Imperial areas, where sedimentation and vegetation ponds are used to remove suspended solids in the river as well as filter out pollutants such as sewage, nitrogen, phosphates and heavy metals.

"It doesn't look like much but I think it will probably get the job done," Lesicka said.


After passing over the structure, the water almost takes on a whitewater look.

Lesicka said the task force chose this location because of its proximity to the border, the high concentrations of bacteria and because the Imperial Irrigation District had a ready amount of concrete debris in the area.

"If this works we'll install others," Lesicka said.

Jim Setmire, a U.S. Geological Survey hydrologist on loan to the U.S. Bureau of Reclamation, said the dissolved oxygen content of the New River was sampled during the 1970s and found to be low. During summer months when bacteria metabolisms work harder, the oxygen content is even lower, he said.

"The chemical reaction rates are faster," Setmire said, adding there is a lot of organic matter in the New River coming up from Mexico.

Bacteria use oxygen as a source of energy to break down organic matter, but that uses up the oxygen. So in summer there would be no dissolved oxygen for 20-30 miles, Setmire said. Without dissolved oxygen there are no fish, no bugs, no living things in the water.

Another aeration device — the institutional memory about which is lacking — is referred to as the rock weir near Seeley, has a much more pronounced effect on the river's water.

"It really aerates the water," Setmire said, adding that measurements show increased levels of oxygen downstream of the weir as well as increased amounts of bugs that live in the river's water and sediment.

Because the New River tends to clean itself, Setmire said there is not much difference in the river's biodiversity once it reaches the Salton Sea as found in the Alamo River.

"The (New River) functions as a wastewater treatment plant," he said. "The river kind of cleans itself but it needs oxygen."

He said little oxygen is added through contact between a river with a smooth surface and the air as compared to the amount added through increased surface contact caused by the turbulence of an aeration structure or a drop.

Setmire said it is unknown how much oxygen will be added to the river from the aeration structure but measurements will be taken, as well as for the number of bugs.

Steve Muth, natural resource specialist with Reclamation, said the $55,000 cost of the Calexico-area structure — which includes permits, design and construction — came from one of several federal appropriations bills for restoring the Salton Sea.

"That's a cheap structure we put in," Muth said, adding that the task force is considering the installation of poured concrete structures in the $500,000 to $750,000 range that will allow more control and aeration of the water. "That's what we're looking at if we think it's worth it."

The task force's next meeting is at 1 p.m. at the Brawley Irrigated Desert Research Station.

Staff Writer Rudy Yniguez can be reached at 337-3440.

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