WSP10325

• File Number: 8272.100.60
• Description: Colorado River Basin Salinity Control Forum
• Basin: Colorado Mainstem
• Water Division: 5
• Date: 10/1/1999
• Author: CRBSCF
• Title: Supplemental Report on the 1999 Review - Water Quality Standards for Salinity - Colorado River System
• Water Supply Pro - Doc Type: Report/Study

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California Regional Water Quality Control Board
Colorado River Basin Region

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Winston H. Hickox
Secretary for
Environmental
Protection

Internet Address: http;/lwww.swrcb.ca.gov/-rwqcb7
73-720 Fred Waring Drive, Suite 100, Palm Desert, California 92260
Phone [phone]' FAX [phone]

Gray Davis
Governor

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TO: Colorado River Basin Salinity Control Forum
106 West 500 South, Suite 101
Bountiful, UT 84010

SUBJECT: Selenium in the Colorado River

DATE: AUG 23 1999

We applaud the efforts of the Colorado River Basin Salinity Control Forum and all of its members in
working to control salt in the Colorado River. In our region, located in the southeastern corner of
California, one component of the salinity in the Colorado River that is of particular concern is selenium.

Selenium occurs in natural waters most commonly as selenious acid and selenic acid, which correspond,
respectively, to the salts selenite and selenate. Selenium is present in many rock and soil formations in
the Colorado River Basin, and its concentration in the Colorado River is increased by activities such as
agriculture and mining, which increase erosion in these seleniforous formations. Selenium is a constituent
of concern when it is present at elevated levels, due to its ability to bioaccumulate in animal tissue, and its
harmful effects at elevated concentrations. Selenium toxicity can lead to reproductive failure, deformities,
and death among aquatic organisms and water birds and can also adversely affect people.

The Salton Sea, located in Southeastern California, is fed almost entirely by Colorado River water that is
imported for agricultural purposes via the All-American Canal. The Salton Sea provides vital habitat for
more than 380 species of birds, including threatened and endangered birds such as the Brown Pelican
and the Yuma Clapper Rail, and is an important link on the Pacific Flyway. The Salton Sea also supports
several fish species, including the endangered desert pupfish, and a productive sport fishery.

Due to the high rates of evaporation in the Salton Sea watershed, salts that are present in Colorado River
water are further concentrated in the watershed. This evaporation causes the concentration of selenium
in the New and Alamo Rivers, the main tributaries to the Salton Sea, to be approximately three times the
concentration of selenium in the lower Colorado River; the concentration of selenium in the New and
Alamo Rivers is approximately 6 ppb, while the concentration of selenium in the lower Colorado River is
approximately 2 ppb (1). Nearly all of the selenium present in the Salton Sea Watershed is imported via
Colorado River Water (2). In addition, efforts to conserve water in the Imperial Valley by reducing
agricultural surface runoff threaten to further increase the concentrations of selenium in the waterbodies
feeding the Salton Sea, due to the high concentrations of selenium present in subsurface agricultural drain
water (approximately 25 ppb). This potential increase in selenium concentrations due to water
conservation may have the effect of impeding water conservation efforts in the Imperial Valley.

Biological effects of the concentrations of selenium present in the tissues of fish and birds in the Salton
Sea watershed include reproductive depression in migratory birds and hazards to the reproduction of the
desert pupfish (3). In addition, the concentrations of selenium present in fish in the Salton Sea watershed
make these fish hazardous food items for birds and potentially humans. In response to concerns about
health effects of selenium accumulation, California's Heath Advisory Board has issued a warning stating
that people should not consume more than four ounces of fish caught in the Salton Sea in any two week
period.

In addition to the effects of concentrated levels of selenium in the Salton Sea watershed. preliminary data
from both Arizona (4) and California (5) have shown elevated levels of selenium in the tissues of some
fish samples taken from backwaters of the lower Colorado River itself. The levels of selenium present in
these fish tissue samples were above the 2 ppm (wet weight) Health Advisory Threshold for fish
consumption (6). Also, selenium concentrations found in the tissues of asiatic clams taken from the lower

California Envit

'rotection Agency

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