MISSISSIPPI RIVER WATER QUALITY AND THE CLEAN WATER ACT: Progress, Challenges, and Opportunities by National Research Council of the National Academies

Author:National Research Council of the National Academies
Language: eng
Format: epub
Tags: Environment and Environmental Studies : Water Quality
Publisher: NATIONAL ACADEMY PRESS
Published: 2008-02-15T00:00:00+00:00

NUTRIENT CRITERIA AND TMDLS FOR THE MISSISSIPPI RIVER

None of the 10 Mississippi River mainstem states currently have numeric criteria for nitrogen or phosphorus applicable to the river (listings in Tables 4-4, 4-5, and 4-6 relating to excessive nutrients are based on narrative, not numeric, criteria; UMRBA, 2006). Without such standards, whether they are adopted by individual states or by the EPA, there is little prospect of significantly reducing or eliminating hypoxia in the northern Gulf of Mexico.

Eschewing a “one-size-fits-all” approach in view of the fact that the appropriate concentrations of nutrients (which are necessary for aquatic life) vary with waterbody size, climate, and geology, the EPA has issued guidance for the states to use in developing numeric nutrient criteria (e.g., EPA, 2002). At the same time, the EPA has noted that its recommendations were based on data from smaller waterbodies and that large rivers might require a distinctively different approach (Parker, 2005). As matters stand today, most states are focusing primarily on phosphorus and chlorophyll, and most do not plan to address criteria for large mainstem river systems in the near future (Amy Parker, U.S. EPA, personal communication, 2006).

Even if the Mississippi River mainstem states ultimately develop numeric nutrient criteria for the stretches of the Mississippi River within or on their respective borders, achievement of those criteria would not necessarily resolve the problem of hypoxia in the Gulf of Mexico. To be effective, such criteria would have to be designed specifically with a view to dealing with that large-scale problem. An adequate approach to remediating northern Gulf of Mexico hypoxia would entail establishing numeric nutrient standards for the mouth of the Mississippi and Gulf of Mexico waters that permit no more nutrient flow into the Gulf than could be accommodated by natural processes without significant oxygen depletion. Louisiana, Mississippi, and other Gulf states have the authority to establish such standards to protect their own waters. If they exercise that authority, upstream states will have to create nutrient standards and TMDLs sufficient to achieve the downstream state standards because states must consider the impact of their own water quality standards on waterbodies in adjoining and downstream states. However, the task for upstream states in setting standards with that aggregate downstream effect would require more interstate cooperation and coordination than historically has occurred on the Mississippi River.

In lieu of adequate state action in this situation, the EPA has the legal authority to intervene and create in effect a watershed-wide regime necessary to achieve the same result. At least under certain circumstances, the EPA’s authority under Section 303(c) extends beyond merely harmonizing inconsistent state water quality standards. Under Section 303(c)(4)(B), the EPA can establish a water quality standard “in any case where the Administrator determines that a revised or new standard is necessary to meet the requirements” of the Clean Water Act. Accordingly, the EPA can establish a more demanding standard than any of the states included within a significant national watershed as long as, in the EPA’s judgment, that standard is necessary

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