WSP07583

• File Number: 8270.200
• Description: Selenium
• State: CO
• Basin: Gunnison
• Water Division: 4
• Date: 1/1/1996
• Author: USGS
• Title: Detailed Study of Selenium and Other Constituents in Water-Bottom Sediment-Soil-Alfalfa and Biota Associated with Irrigation Drainage - Uncompahgre Project Area and in the Grand Valley - 1991-93
• Water Supply Pro - Doc Type: Report/Study

OOl:H2

': ",'

were discovered by the U.S. Fish and Wildlife Service
(FWS) at the Kesterson National Wildlife Refuge in
the western San Joaquin Valley, California. where
irrigation-drainage water was impounded. Because of
the concern that problems related to selenium or other
trace inorganic or organic constituents in irrigation
drainage might not be limited to the Kesterson
Reservoir area, the U.S. Department of the Interior
(001) began a program in 1985 to determine whether
irrigation-related problems existed at other 001
constructed or managed irrigation projects, national
wildlife refuges. or other wetland areas for which the
001 has responsibility. About 600 irrigation projects
and major wildlife resource areas have been
constructed or are managed in 17 Western States by
001 bureaus. The program evolved into five phases
(Deason, 1986): (1) Site identification, (2) reconnais-
sance investigations, (3) detailed studies, (4) planning,
and (5) remediation. Activities in the first three phases
are conducted by study teams consisting of scientists
from the U.S. Geological Survey (USGS), the FWS,
the Bureau of Reclamation (BOR), and the Bureau of
Indian Affairs. A USGS scientist heads each study
team. Phase 4 and phase 5 of the program are headed
by the BOR.
The reconnaissance investigations are designed
to determine whether irrigation drainage (I) has
caused or has the potential to cause harmful effects on
human health or on fish and wildlife or (2) might limit I
the suitability of water for beneficial uses. The
duration of the reconnaissance invesligalions was
about 2 years. Detailed studies were initiated if the
reconnaissance investigations indicated that
potentially serious water-quality problems were
related to irrigation drainage. The purpose of detailed.
studies is to gather sufficient information to provide
the scientific understanding needed for development
of reasonable alternatives to mitigate or resolve
identified problems. The purpose of planning is to
develop coordinated action with appropriate Federal,
Stale, and local agencies and water users for remedia-
tion of problem areas. The final phase involves
implementalion of remedial actions developed during
planning.
A reconnaissance investigation of the Gunnison
and Uncompahgre River Basins and of Sweitzer
Lake (fig. 1) documented elevated concentrations of
selenium in some water, bottom-sediment, and biota
samples collected in 1987-88 (Butler and others,
]99]). The reconnaissance report indicated that

irrigation drainage from the Uncompahgre Project, a
BOR irrigation project, might be a primary source of
selenium, dissolved solids, and other constituents to
the Gunnison and Uncompahgre Rivers and to
Sweitzer Lake. The eXlenl of the irrigated area served
by the Uncompahgre Project is shown in figure I. The
Uncompahgre Project area is defined as the irrigated
area served by the Uncompahgre Project plus adjacent
areas in the lower Gunnison River Basin, such as the
Smith Fork, North Fork, and Tongue Creek Basins
(fig. I). Because of the limited scope of the reconnais-
sance studies, source areas and distribution of
selenium in the Uncompahgre Project area were not
determined, nor were effects to biota documented.
Also, trace-element data for water and biota were
not collected in other irrigated areas in the lower
Gunnison River Basin. Because of these factors, a
delailed study of the Uncompahgre Project area Was
initiated in 1991.
The Grand Valley was included with the
Uncompahgre Project area in the detailed study. There
are similarities of climate, physiography, agricultural
crops, and geology between the Grand Valley and the
Uncompahgre Project area. Also, the BOR identified
irrigation drainage in the Grand Valley (fig. I) as a
large source of dissolved solids (salinity) to the upper
Colorado River (Bureau of Reclamation, 1978). A
marine shale, the Mancos Shale, was identified as the
primary source of the salinity, and selenium problems
have been documented in other Western States where
marine shales are irrigated (See and others, ] 992;
Stephens and others, ]992). Historical selenium
data for the Colorado and Gunnison Rivers also
indicated that the Grand Valley might be a source
area of selenium.

Purpose and Scope

This report describes results of the detailed
study of the Uncompahgre Project area and of
the Grand Valley during 1991-93. The general
objectives of the detailed study are (I) to determine
the sources, distribution, movement, and fate of
contaminants in the hydrologic and biologic syslems;
and (2) to measure contaminant concentrations,
determine exposure pathways, and document effects
on biota.

INTRODUCTION 3