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In 1988, reports for seven of the reconnaissance investigations-were published. Reports for the remaining two areas were published in 1990. Based on results of the first nine reconnaissance investigations, four detailed studies were initiated in 1988: Salton Sea area, Stillwater Wildlife Management area, middle Green River basin area, and Kendrick Reclamation Project area. Eleven more reconnaissance investigations were initiated in 1988: California: Sacramento Refuge Complex California-Oregon: Klamath Basin Refuge Complex Colorado: Gun~ison and Uncompdhgre River basins and Sweitzer Lake Pine' River Project Colorado-Kansas: Middle Arkansas River basin Idaho: American Falls Reservoir New Mexico: Middle Rio Grande Project and Bosque del Apache National Wildlife Refuge Oregon: Malheur National Wildlife Refuge South Dakota: Angostura Reclamation Unit Belle Fourche Reclamation Project Wyoming: Riverton Reclamation Project All studies were conducted by interbureau field teams composed of a scientist from the U.S. Geological Survey as team leader, with additional U.S. Geological Survey, U.S. Fish and Wildlife Service, and U.S. Bureau of Reclamation scientists representing several different disciplines. The reconnaissance investigations were directed toward determining whether irrigation drainage: (1) has caused or has the potential to cause significant harmful effects on human health, fish, and wildlife, or (2) may adversely affect the suitability of water for other beneficial uses. The middle Arkansas River basin was selected for study primarily because historical records indicated the occurrence of high concentrations of selenium in surface water in the basin. Selenium is a primary element of concern in drainage from irrigated land. The median selenium concentration from 1975 through 1987 in the Arkansas River near Coolidge, Kans., was 19 ~g/L, the highest of any site in the U.S. Geological Survey National Stream Quality Accounting Network (NASQAN). Concentrations of selenium greater than the State drinking water standard (10 ~g/L) have been detected at several other sites on the Arkansas River and its tributaries in the study area. The Fryingpan-Arkansas project, constructed and operated by the U.S. Bureau of Reclamation, provides a supplemental water supply to irrigators in the study area. Although there are no U.S. Fish and Wildlife Service refuges in the study area, it is used intensively by migratory waterbirds, and several State- operated wildlife areas are located in the study area. 4