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Evaluation of
the Salton River Desalination Solution
as proposed by US Filter

 

Stuart H. Hurlbert, Colin J. Brauner, Lucy Caskey, Marie F. Coe, Barry A. Costa-Pierce,
Joan S. Dainer, Paul M. Detwiler, Deborah M. Dexter, Victoria Matey, Kristen M. Reifel,
Ralf Riedel, Brandon K. Swan, Mary Ann Tiffany, and James W. Watts
Salton Sea Ecosystem Research Group
Center for Inland Waters
San Diego State University

December 27, 2002

Nature and scope of this document

This evaluation represents the unsolicited opinion of a group of scientists who belong to or have recently worked in the Salton Sea Ecosystem Research Group at San Diego State University.   All have considerable experience and knowledge of ecological and environmental issues at the Salton Sea.  This document represents a slight revision of a draft that was distributed on December 10, 2002; conclusions remain unchanged from that earlier version. We address primarily ecological issues, and offer no comment on cost and engineering issues.

More official, agency-sponsored evaluations of the US Filter proposal may be carried out at a later date, and they would be welcome to make use of the information presented here.  We feel, however, that given the attention this proposal has received and our understanding that some decision-makers feel that it has strong merit, it is desirable for its significant problems to be made clear now.

The proposal has most of the same weaknesses found in a proposal put forward last year by the Pacific Institute, and some greater ones.  That proposal received scrutiny by almost 70 experts brought together in several workshops and a symposium by the U.S. Department of the Interior Salton Sea Science Office (SSSO). A report on the conclusions of those experts was made available to the public last summer.  Its existence simplifies evaluation of the US Filter proposal for those willing to consult the evaluation of the earlier proposal.

The new proposal by US Filter may be found on its website at:

http://www.usfilter.com/water/water.asp?wid=593

The proposal by the Pacific Institute is on its website at:

http://www.pacinst.org/salton_sea_proposal.pdf

The SSSO evaluation of the Pacific Institute proposal is found on a website of the U.S. Bureau of Reclamation at:

http://www.lc.usbr.gov/saltnsea/pdf_files/sciofc_rvw.pdf

Brief description of project proposed by US Filter

A dike would be built along the 10 ft isobath all around the edge of the Sea, and this would retain and channel the inflows of all the rivers, streams and drainage ditches into what the proposal calls the Salton River.  Water with a salinity 3 g/L would flow from south to north along both sides of the Sea and be taken out at the northern end.  There it would be treated in a desalination plant and used as a new source of freshwater for Southern California. 

Brine wastes from this plant would be discharged into the Sea proper, which would over time drop in level.  When it had dropped in level sufficiently, an internal irrigation ditch would be constructed parallel to and just below it, on the exposed lake bottom.  This would be used to receive excess waters from the Salton River and to distribute them for purposes of irrigating portions of the increasingly exposed bed of the Salton Sea.  This irrigation would increase plant cover and perhaps reduce dust problems to some extent.

The Salton River impoundment would have a total water surface area of about 40,000 acres and a maximum depth of 10 feet.  The proposal indicates that the residual Salton Sea would eventually shrink to 38,000 acres (~50 sq miles), but does not specify what assumptions that number is based on.

By comparison, the impoundments proposed by the Pacific Institute would have had, under their most expansive plan, a surface area of about 28,000 ac and a maximum depth of 15 feet.  The residual Sea under this plan would have shrunk only to about 147,000 acres.

The present Salton Sea has a surface area of about 239,100 acres (assuming lake level at -228 ft) and a maximum depth of about 50 feet.

Benefits of the project proposed by US Filter

As far as the Salton Sea values for wildlife and human recreation and environmental quality in the surrounding region are concerned, the overwhelming majority of effects of this project would be negative.  However, there would be greatly increased freshwater supplies for accommodating and stimulating further population growth in those areas of Southern California able to tap those supplies.

And the internal irrigation ditch proposed would allow virtually any portion of the exposed lakebed to be irrigated with gravity flows.  This could create many strips or patches of vegetation that would reduce entrainment by wind of salts and dust into the atmosphere. This would be a benefit only relative to the Pacific Institute proposal or to simply letting the Sea shrink.  It would not be an improvement over present conditions.  The possibly extensive areas of salt grass (Distichlis) and salt cedar (Tamarix) habitat that would be produced would have low value as wildlife habitat. 

Negative features of the project proposed by US Filter

From an ecological or environmental point of view, the essence of the US Filter project is that it would replace the present Salton Sea with three new types of ecosystems: a large freshwater impoundment, a highly saline residual Salton Sea, and an exposed lake bottom partially covered with salt grass and other vegetation.

We have mentioned above how the partially vegetated exposed lake bottom might prevent further worsening of air quality but would otherwise have little value for wildlife and none for people.

The same applies to the highly saline residual Sea that would remain in the lowest portions of the lake's northern and southern basins.  As the Sea shrank in size and increased in salinity there would be a period of years when increased abundances of aquatic invertebrates (mostly crustaceans and insects) would create a rich food supply for birds that utilize these as food.  However, the residual Sea anticipated in the US Filter proposal would be smaller and increase in salinity more rapidly than would the residual Sea described in the Pacific Institute proposal.  In part this accelerated salinity increase would result from the discharging of waste brines from US Filter's proposed desalination plant into the residual Sea.  The residual Sea would be nothing more than a brine waste pit.  No plants would grow in its vicinity.  Low topographic relief would allow slight fluctuations (e.g. a few feet) in its level to result in large fluctuations in its areal extent.  At low levels, large expanses of salt flat would be susceptible to wind erosion and contribute to air pollution.  Its salinity would quickly rise to levels lethal to all organisms except a few species of bacteria and algae; invertebrates would be absent.  This brine pit would have no positive values for wildlife or people.

The freshwater impoundment referred to as the Salton River would initially be nothing more than a sluggish extension of the New and Alamo rivers with all the negatives that would entail. A more accurate name for it would be the New Alamo River, as it would have nothing in common with the present Salton Sea. It would differ from the impoundments proposed by the Pacific Institute in two key ways.  It would deliver these contaminated river waters to the shoreline of every residential development, marina, and park on the Sea's current shoreline.  And much larger portions of it would be colonized by vegetation than would be the case with the deeper main impoundment proposed by the Pacific Institute. 

The SSSO evaluation of the Pacific Institute proposal noted the following key negative features of their freshwater impoundment that would also characterize the impoundment proposed by US Filter: present unique fishery would be replaced by one dominated, probably, by carp, catfish, and tilapia; parasite loads on fish would be increased relative to those in present Salton Sea fish; selenium levels in fish would likely be several-fold higher than in present Salton Sea fish thus precluding a sport fishery in the impoundment;

levels of other contaminants and pathogens would be higher than in the present Salton Sea, putting the Salton River off limits for swimming and water contact sports in general; increased selenium levels in fish and invertebrates would pose greater threat to birds feeding on those organisms; tremendous increase in aquatic, semi-aquatic and terrestrial vegetation along the shoreline of the Salton River, combined with the lowered salinity, would increase the abundance of biting insects along the Sea's shoreline, including a mosquito species (Culex tarsalis) that is a known vector of various types of encephalitis.

The new belt of vegetation along the shoreline would be roughly 100 miles long for the Salton River, as opposed to about 50 miles long for the Pacific Institute's proposed impoundments.  The narrow nature of the Salton River and consequent reduced wave action in it would also likely result in this vegetation belt being wider than would be the one likely under the Pacific Institute proposal. That is, submergent and emergent aquatic vegetation could colonize deeper water, e.g. possibly out to depths of 6 ft.  This, combined with accumulation of sediments delivered by the rivers, would tend to rapidly infill the Salton River in the absence of large scale and continuous dredging and vegetation control operations.  The high productivity of this vegetation would also result in the sediments of the Salton River becoming a highly organic muck, in making most portions of the shoreline inaccessible, and in greatly limiting views (e.g. for birders) from the shoreline.

Conclusions

For the Salton Sea, its wildlife, the people who live in the region, and the people who come there for recreation from other regions, the US Filter proposal has no redeeming features.  It is a document that appears to have been written in ignorance of basic ecological knowledge and principles and in ignorance of the earlier evaluation of a similar proposal by the Pacific Institute.

As such, scientists and decision-makers cannot regard it as a serious proposal meriting much further attention at this time.  In principle, it could be modified to deal with the problems outlined above.  In fact, it is very difficult to envisage how its fundamental flaws could be remedied, as restoration of the Salton Sea to a healthier state is not an objective of the project outlined in the US Filter proposal

For further information, contact: Stuart H. Hurlbert, Director, Center for Inland Waters and Professor of Biology, San Diego State University, San Diego, California 92182-4614, tel. 619-594-5409, email: shurlbert@sunstroke.sdsu.edu

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