Press Release

FOR IMMEDIATE RELEASE
Contact Tom Kirk (760) 564-4888

July 20, 2001

Control of phosphates may be the key to eventually reducing the Salton Sea’s eutrophic conditions, according to a recently published scientific paper.

The paper suggests testing a chemical that has been used for the past 50 years to control algal blooms in other lakes and reservoirs to neutralize the phosphates that flow into the Sea from municipal and agricultural runoff. Eutrophication is a natural process where a body of water becomes rich in
dissolved nutrients. For the Salton Sea, it means high fish populations, massive fish die offs as well as the noxious odors that at times permeate the lake.

While nitrogen and phosphorus are nearly always the chemical elements that act as primary nutrients to create eutrophic conditions in lakes, the scientists found that phosphorus is the main controlling factor in producing those
conditions in the Salton Sea.

“Think of it as building houses,” said the paper’s editor, Jim Setmire, a U.S. Geological Survey hydrologist who is working with the U.S. Bureau of Reclamation.

“Even if you have an infinite amount of wood, but only enough nails for two houses, how many homes can you build? In this case, nitrates are the ‘wood’ and phosphates, the ‘nails.’ We are attempting to limit the number of eutrophic “houses” by taking away the ‘nails,’” he said.

According to the scientific paper, the addition of aluminum
sulfate--also known as alum--to the New and Alamo rivers may help to deal with the phosphates.

While the sheer size of Salton Sea prohibits direct treatment in the lake, the scientists state the alum treatment “may be able to be added to the tributaries to tie up the phosphorus before the water enters the Salton Sea.”

The paper is entitled “Eutrophic Conditions at the Salton Sea.” It stems from a workshop held last September at the University of California, Riverside.

In addition to Setmire, eight other scientists contributed to the work: Chris Holdren from the Bureau of Reclamation; U.S. Geological Survey scientists Dale Robertson, John Elder, Roy Schroeder; Chris Amrhein, a professor at the University of California, Riverside; Geoff Schladow, an associate professor at the University of California, Davis; Hank McKellar, an
associate professor at the University of South Carolina and Rick Gersberg, a professor at San Diego State University.

“These highly-qualified scientists have given us important insights into the eutrophication processes at the Salton Sea,” according Tom Kirk, executive director of the Salton Sea Authority.

“The question of eutrophication at the sea is a complex one, but as we have tried to do throughout the restoration effort, we have responded to concerns raised and taken a science-based approach to addressing these issues,” Kirk
added.

The Salton Sea Authority recently received a $570,000 grant from the State Water Resources Control Board to determine the most efficient and cost effective means to reduce phosphorus loading from external sources. This project will investigate alum treatment as well as the control of phosphorus containing sediments.

The scientists state that introduction of the alum to the rivers “at or near their outlets to the Salton Sea could remove significant loads of phosphorus and decrease the eutrophication of the Sea.”

They caution, however, that will take up to five years for an
effect on eutrophication to be seen.

The paper also recommends that experiments be initiated to
investigate the ratio of alum to phosphorus and the possible addition of polymers that would be needed to remove at least 80 percent of the incoming phosphorus.

The paper points out that alum “has been added to lakes and
reservoirs since the 1950’sto control algal blooms by reducing internal phosphorus loading.” It states that when added to water, it forms aluminum hydroxide that works to absorb the phosphorus thereby forming a chemical barrier on the sediments.

The scientists also determined that while nutrients have flowed into the sea at increased rates over the last 30 years, because of some unknown process that takes place in the water the eutrophic state of the sea is virtually unchanged since the 1960’s.

Phosphorus comes mostly from external sources such as agricultural and municipal runoff that flows into the Sea via the New and Alamo rivers. Scientists estimate that a reduction of from 50 to 80 percent from external sources will be needed to reduce eutrophication at the sea.

(Note to Editors: A complete copy of the paper has been posted on the Bureau of Reclamation website.
To go directly to the document, which is a pdf file, the address is:
http://www.lc.usbr.gov/~saltnsea/pdf_files/scidocs/eutrofin.pdf)

 

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