Reconnaissance investigation of water quality, bottom sediment, and biota associated with irrigation drainage in the San Juan River area, San Juan County, northwestern New Mexico, 1990-91

Selenium concentrations larger than established standards and criteria were present in Gallegos Canyon and Ojo Amarillo Canyon drainages on the Navajo Indian Irrigation Project, a pond on the West Hammond Irrigation Project, and a drain on the Hogback Irrigation Project, New Mexico. Ground-water return flow from irrigated areas contributes substantially to surface water at these sites. Selenium concentrations in 11 surface-water samples from these four areas exceeded the State of New Mexico standard of 5 micrograms per liter for the protection of fisheries. Selenium concentrations in five bottom-sediment samples from three of these areas ranged from 4.5 to 38 micrograms per gram; the geometric mean concentration of selenium in Western United States soils is 0.23 microgram per gram.