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Development of Nutrient Criteria for Water Quality

In 2001, the U.S. Environmental Protection Agency published water quality criteria for nutrients (nitrogen and phosphorus) as called for in section 304(a) of the Clean Water Act. These criteria were developed as a starting point for states, authorized tribes, interstate commissions, et al., to develop criteria that would be appropriate for their own jurisdictions. This approach was due to the recognition that the determination of suitable limits for nutrients for water bodies is a highly complicated issue. It is governed by wide variation in local ecological conditions, as well as the uses placed upon the waters. Too much nutrient loading to a water body can cause rapid growth of algal blooms, organic enrichment and depletion of dissolved oxygen. Too little may result in insufficient enrichment of the aquatic food chain, which would be detrimental to a healthy aquatic biological community.

Developing the nutrient criteria that will protect the waters of the state requires significant analysis of water quality data. It also requires input from citizens concerned with the impact of implementation of nutrient criteria. With this in mind, a plan for developing nutrient criteria in Missouri was developed in 2005 and is presented here.  There is also an update of the proposed schedule for development.


Nutrient criteria for lakes and reservoirs were adopted as part of the water quality standards rule in October 2009.  The part of the rule applicable to nutrients is at 10CSR 20-7.031(4)(N), on page 16.  The department has drafted a policy for implementation of the rule. In August, 2011, EPA denied approval of a substantial part of this rule, expressing some technical issues with the criteria that were introduced.  The department is in the process of addressing these concerns, with the goal of including them as part of ongoing revisions to the water quality standards. The department is currently amending 10 CSR 20-7.031 to include numeric nutrient criteria for lakes and reservoirs. Documents associated with this rulemaking can be found on the Water Protection Program's Rules in Development webpage.

Nutrient Criteria Analysis

Rivers and Streams

Stakeholders began meeting in 2009 for briefings on how criteria development for streams will proceed.  These meetings were suspended so a technical workgroup could take the time necessary to make recommendations for criteria that will be scientifically defendable and sufficiently protective of the state's streams and rivers.  Criteria will be based on a compilation of several lines of evidence, including a statistical review of available data, a USGS study of algae response to nutrients in the Ozarks, and analyses of macro-invertebrates and chlorophyll-a as response variables.  When all analyses are complete, stakeholder meetings will be reconvened for consideration of the recommendations.

Upcoming Meetings

Past Meetings

Nutrient Criteria Technical Subcommittee
July 30, 2014
Attendance Sheet
Draft Reply to EPA Regarding Missouri's Numeric Nutrient Criteria

Nutrient Criteria Technical Subcommittee
Sept. 20, 2012
Meeting Notes
Detailed Nutrient Regressions

Nutrient Criteria Stakeholders Group
Aug. 13, 2012
Meeting Notes

Nutrient Criteria Technical Subcommittee
July 23, 2012
Meeting Notes
Revised Lake Nutrient Rule
Presentation: Lake Rule Rationale
UMC-MDC Chl-a and Secchi Depth Recommendations
Influence of Environmental Variables in Small Lake Impoundments (Michaletz et al, 2012)
Missouri Reservoirs: An Analysis of regional limnology (Jones et al, 2008)
Fish Catch and Water Quality in Agriculturally Eutrophic Lakes (Egertson and Downing, 2004)
Production of Fish Populations in Lakes (Downing and Plante, 1993)
Sportfish Harvest Predicted by Summer Chlorophyll-a (Jones and Hoyer, 1982)
Water Clarity and Quality Black Bass and Crappie Fisheries in Alabalma (Maceina et al, 1996)
Responses of Channel Catfish to Stocking Rate (Michaletz, 2009)
Oligotrophication and its Discontents: Effects of Reduced Nutrient Loading (Ney, 1996)

April 5, 2012
Meeting Notes
Presentation: Primary Lake Fish Kills and Alternative Lines of Evidence
The Florida Situation

Feb. 9, 2012
Lines of Evidence
Meeting Notes
Presentation: Lines of Evidence
Presentation: Chlorophyll Maxima

Sept. 21, 2011
EPA letter on nutrient criteria
EPA presentation

July 19, 2011
Meeting Summary
Nutrient Criteria Implementation Procedure
Nutrient NPDES Flow Chart
Tables A1-A6
Tables B1-B11

Nov. 16, 2010
Meeting Summary

Examination of Algal Community Data for Establishment of Nitrogen and Phosphorus Criteria
Nutrient Criteria Database Quality Assurance and Statistical Analysis
Draft Rule: Nutrients in Streams
Biological Response to Nutrients in Central Plains Regional Streams of Missouri
Ecological Indicators
Table 5: Matrix of Summary Statistics
Nutrient Lines of Evidence

Feb. 11, 2009
Meeting Summary

Presentations and handouts Nutrient Plan, Nutrient Benchmarks 1MB

March 10, 2009
Meeting Summary

Presentations and handouts Criteria by other States