By Jeffrey R. Deacon and Norman E. Spahr

Available from the U.S. Geological Survey, Branch of Information Services, Box 25286, Denver Federal Center, Denver, CO 80225, USGS Water-Resources Investigations Report 98–4236, 8 p., 10 figs.

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INTRODUCTION

The Eagle River flows from the Continental Divide through the towns of Minturn, Avon, Edwards, Wolcott, Eagle, and Gypsum and joins the Colorado River near Dotsero, Colorado (fig. 1). Drainage area of the watershed is approximately 950 square miles. Land use in the basin is predominantly forest and rangeland with agriculture and increasing urban/recreational land uses along the river corridor. The agriculture primarily is hay fields, which require no fertilization. The population of Eagle County, which encompasses the entire Eagle River drainage, has increased by approximately 200 percent between 1970 and 1990 (U.S. Bureau of the Census, 1970 and 1990). Influxes of skiers to the county during the winter cause temporary population increases. State and local agencies are concerned about the effects of increasing urban development and the influx of people during winter on water quality and stream biota in the Eagle River. One approach to determine land-use effects on streams is by monitoring water quality over time. A water-quality assessment needs to include the evaluation of chemistry, habitat, and biological conditions of a stream. The U.S. Geological Survey (USGS) in cooperation with the Colorado Department of Public Health and Environment (CDPHE) established five sites in 1997 on the Eagle River to characterize baseline water quality and stream biota. This baseline information will be useful for future trend assessments of water quality and stream biota at these sites.

Five sites were selected on the Eagle River to collect water-quality and stream-biota data during two low-flow periods (fig. 1). Site 1 represents minimal effects from urban/recreational land use. Sites 2, 3, and 4 are within areas of increasing urban/recreational land use. Site 5 is near the mouth of the Eagle River and represents the outlet from the study area and the cumulative effects of all land uses. Low-flow periods can be important from water-quality and stream-ecology perspectives because less water is available to dilute any contaminants entering the streams.

This study was based on a limited data set from only two sampling periods. The objectives of this study were to (1) characterize the current water quality and biological community at selected sites in the Eagle River; (2) assess relations among nutrient concentrations and stream biota at selected sites; (3) describe changes in the algal community over time at one site; and (4) assess differences in summer low-flow conditions and peak winter recreational-use low-flow conditions. This report presents results of field measurements and chemical (major ions and nutrients) and biological (benthic algae and macroinvertebrates) sampling during summer (1997) and winter (1998) low-flow conditions.

Table of Contents

Introduction

Data Collection

Water Quality

Hydrology and Major-Ion Water Chemistry

Nutrients

Habitat

Algae

Macroinvertebrates

Summary

References