Stream Standards for Toxics and Irrigated Agriculture Using New Mexico as a Case Study

by John W. Hernandez, New Mexico State Univ, United States,

Document Type: Proceeding Paper

Part of: Irrigation and Drainage


New Mexico follows a policy of 'antidegradation' with respect to the existing quality of a stream, but its standards specifically exclude return flows from irrigated agriculture from being regulated 'point sources' of discharge. Risk assessment has become a powerful tool in the development of regulations for hazardous substances in the work place, in drinking water, and in ambient air. In setting the initial water quality standards for toxic substances for aquatic life, New Mexico used a risk assessment approach. It appears that EPA is willing to allow the states time to add new toxic standards if they will do three things: identify those toxics that are known to be present in state-streams at potentially harmful levels; provide a time-table for this process and for the subsequent setting of standards; and demonstrate that certain criteria are not needed. If other western states are like New Mexico, the process of establishing new, numerical stream standards for toxics is still in its early stages. State agencies and water quality commissions and boards will have little other choice than to use the criteria that EPA has developed for toxics.

Subject Headings: Water quality | Water pollution | Toxicity | Standards and codes | Rivers and streams | Case studies | Quality control | New Mexico | United States

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