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The Klamath Basin is a key area on the Pacific flyway and a major resting place for migratory waterfowl as well as a residence for a large variety of wildlife. The basin also is an important agricultural area with extensive areas irrigated by U.S. Bureau of Reclamation water projects. Contamination of wildlife areas with toxic substances associated with irrigation water has been a problem in some areas of the Western United States. The size and significance of the Klamath Basin as a resource to both humans and wildlife, along with past and present use of pesticides, was the reason for this reconnaissance investigation of existing or potential contamination associated with federally operated irrigation projects. Previous studies as well as observations made during this project indicated that existing and potential environmental concerns included eutrophication of the basin waterways, past and present pesticide usage, and waterfowl diseases. The first two of these concerns are directly related to irrigated agriculture. Waterfowl diseases may be directly or indirectly associated with irrigation. Samples of water were analyzed for major chemical constituents and trace elements. Bottom sediment and various biological tissues representing several trophic levels were analyzed for trace elements and organochlorine compounds. A small number of waterfowl samples were analyzed for organophosphate pesticides. Samples were collected at various locations around the basin that represented areas upstream and downstream and within irrigated areas. Analytical data show that water is enriched with sodium and sulfate ions as it travels through the streams, irrigated fields, and canals in the basin. The probable source of these salts is evaporation of irrigation water that has leached them from soils. Concentrations of trace elements in water generally were low throughout the basin, with the exception of arsenic, which was 62 micrograms per liter in one flooded pond in the Lower Klamath refuge. Arsenic enrichment of water, bottom sediment, and certain biological tissues in comparison with other sampling locations was associated with the Lower Klamath Lake area and may be due to naturally occurring volcanic deposits or springs in that area. Arsenic was bioconcentrated by aquatic plants, and concentrations were highly correlated with arsenic in water. Mercury concentrations also were higher in all media sampled in the Lower Klamath Lake area than in other areas of the basin. The one exception was 0.22 microgram per gram of mercury in bottom sediment at Link River below Link River Dam. Concentrations of selenium were near or less than reporting levels and much less than levels of lexicological significance in all samples with the exception of western grebe livers. Selenium in these tissues may have accumulated from sources outside of the Klamath Basin. Organochlorine compounds were detected in most samples and in all media sampled. Concentrations of DDE were the highest and most widespread. DDD was unusually high in eggs of western grebes from Tule Lake. Concentrations of PCBs and the sum of DDT and its metabolites approached the lower confidence limit of the interim U.S. Environmental Protection Agency guidelines for nonpolar organic compounds in sediment. Concentrations of organochlorine compounds in waterfowl tissues and bottom sediment were highest in the Tule Lake area.

Reconnaissance investigation of water quality, bottom sediment, and biota associated with irrigation drainage in the Klamath Basin, California and Oregon, 1988-89