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guideline for food items consumed by fish and wildlife. The maximum selenium concentration in an aquatic-invertebrate sample was 19.2 micro- grams per gram dry weight in a sample from Woods Canyon, in the newly irrigated area. Sele- nium concentrations in whole-body suckers (all species) were larger in samples from the Mancos River than in sucker samples from the Montezuma Valley or San Juan River. Selenium concentra- tions in whole-body suckers were significantly higher in samples collected from the San Juan River downstream from the Dolores Project than in samples collected upstream from the project. An assessment of the effects of irrigation drainage from the Dolores Project on endangered fish, such as the Colorado squawfish (Ptychocheilus Lucius) in the San Juan River, could not be made for the reconnaissance investigation. Whole-body samples of fathead minnows from Woods Canyon, in the newly irrigated area, and from the Mancos River had selenium concen- trations associated with adverse effects on fathead minnows. As in water samples and other biota samples, the largest selenium concentrations in speckled-dace samples from the Montezuma Valley were collected from Navajo Wash. Selenium concentrations in bird eggs were within the range of uncertainty regarding biologi- cal significance. The largest selenium concentra- tion in a biota sample collected in 1990 was 37.5 micrograms per gram dry weight in a mallard liver from Woods Canyon, in the newly irrigated area. Selenium concentrations ranged from 10 to 69 micrograms per gram dry weight in six bird- tissue samples collected in July 1989 within the irrigated area of the Mancos Project, upstream from the Dolores Project. Mercury concentrations in warm-water game fish in reservoirs in the Dolores Project area may be of concern for human consumption of fish. Weekly dietary limits are most restrictive for con- sumption of walleye, northern pike. and bass from McPhee, Narraguinnep, Totten, Summit, and Puett Reservoirs. Chromium concentrations in biota samples were indicative of chromium contamina- tion, although chromium concentrations in water and bottom-sediment samples were not elevated. The maximum chromium concentration in a biota sample was 440 micrograms per gram dry weight in a crayfish from the Mancos River. Some con- centrations of aluminum, boron, cadmium, copper, lead, and zinc in biota exceeded background con- centrations reported in the literature, but generally the concentrations were not toxicologically signif- icant or the toxicological significance was not known. Previously mined areas in the upper Dolores River basin could have been a source of trace metals and may have been transported into the Dolores Project in the irrigation water supply. Concentrations of organochlorine pesticides and PCB's in fish and birds in the Dolores Project area were indicative of background concentra- tions. Polycyclic aromatic hydrocarbons were analyzed in fish-bile samples from 10 sites, but the biological significance of the data is not known. 18 J ( J p , INTRODUCTION During the last several years, there has been increasing concern about the quality of irrigation drain- age and its potential harmful effects on human health. fish. and wildlife. Concentrations of selenium greater than water-quality criteria for the protection of aquatic life (U.S. Environmental Protection Agency, 1987) have been detected in subsurface drainage from irri- gated land in the western part of the San Joaquin Valley in Califomia. In 1983. incidences of mortality. birth defects, and reproductive failures in waterfowl were discovered by the U.S. Fish and Wildlife Service at the Kesterson National Wildlife Refuge in the western San Joaquin Valley where irrigation drainage was impounded. In addition. potentially toxic trace ele- ments and pesticide residues have been detected in . other areas in Western States that receive irrigation drainage. Because of concerns expressed by the U.S. Congress, the U.S. Department of the Interior (DOl) started a program in October 1985 to identify the nature and extent of irrigation-induced water-quality prob- lems that might exist in the Western United States. The 001 developed a management strategy and fonned an interbureau group known as the ''Task Group on Irriga- tion Drainage", which prepared a comprehensive plan for reviewing irrigation-drainage concerns for which the 001 may have responsibility. Initially, the Task Group identified 20 areas in 13 States that warranted reconnaissance-level investi- ' gations related to three specific activities: (1) Irrigation or drainage facilities constructed or managed by the DOl. (2) national wildlife refuges managed by the DOl, and (3) other migratory-bird or endangered-species management areas that receive water from DOl-funded projects. l ... fo1 III Or Pr> tio c c c C Id N o S< w ac 2 Reconnaissance Inve8llgetlon 01 Water Quality, Bottom Sediment, and Biota AsIOCIated with Irrigation Drainage In the Dolores Project Area. Southwestern Colorado ond Southeastern Utah, 199CHl1