Environmental hazard of selenium in the Animals La Plata water development project.

A hazard assessment of selenium was conducted for the Animas La Plata Project, a multiple-use water development proposed for Colorado and New Mexico by the United States Bureau of Reclamation. A published protocol for aquatic hazard assessment of selenium was applied to environmental monitoring data to assess current threats to biota in the water supply rivers (Animas, La Plata, and Mancos Rivers). Hazard evaluation were also made for two proposed reservoirs (Ridges Basin and Southern Ute Reservoirs) based on estimated concentrations of selenium. The assessment protocol indicated moderate hazard in the Animas and La Plata Rivers, and high hazard in the Mancos River and both of the proposed reservoirs. These ratings indicate that the risk of selenium poisoning in fish and aquatic birds is substantial. Moreover, the geology and climate of this site make it prone to irrigation-induced selenium contamination of water and biota. The water supplies already contain dangerously high concentrations of selenium that may increase further due to agricultural irrigation drainage. The stage is set for significant environmental problems unless a development scenario can be devised that will effectively reduce ecological risks.