Developing Numeric Nutrient Criteria For Mississippi

Author(s): Young, A.; Caviness, K.

Nutrient loads, including nitrogen and phosphorus, have been a major cause of impairments in water bodies nationwide. In 2001 the USEPA developed an Action Plan requiring that all states develop numeric nutrient criteria in order to protect uses from nutrient pollution. Since then, the Mississippi Department of Environmental Quality (MDEQ) has been active in pursing this goal, including creating a Nutrient Criteria Development Plan and collecting data to derive scientifically defensible nutrient criteria. A technical advisory group (TAG) consisting of members of state, federal, and research scientists has been formed to aid MDEQ in deriving these criteria with their technical knowledge and regional experience. The methods used to determine criteria are data compilation, classification of waters, and data analysis. In an effort to be more scientifically defensible, MDEQ is applying the multiple lives of evidence approach for nutrient criteria development. The multiple lines of evidence approach involves looking at several lines of analysis, such as distributional analysis, stressor-response, scientific literature, and water quality models to create a final endpoint. In addition to developing criteria, MDEQ recognizes that moving forward the implementation of these criteria is also a priority of the state. An implementation work group has been formed to address issues such as permits, assessment, total maximum daily loads (TMDLs), waste load allocations (WLAs), and watershed planning. The MDEQ, along with the support of the TAG and the involvement of stakeholders, are making great strides in developing criteria for the Mississippi’s rivers, streams, lakes, coastal and Delta waters.

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