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Numeric Nutrient Criteria

Staff Contact: Michael Suplee (406) 444-0831

DEQ is developing numeric water quality criteria intended to control excessive nutrient (nitrogen and phosphorus) pollution in Montana's streams, rivers, and lakes. The intent of numeric nutrient criteria is to assure a level of water quality that will protect the beneficial uses of these waterbodies. DEQ has strived to base the numeric nutrient criteria on the best available science and data.

Montana River

Our understanding of how and when nitrogen and phosphorus impact streams and small rivers has reached the point where we are now moving into the beginning of the rule-making phase for these waterbodies. Rule making will involve not only the numeric nutrient criteria themselves, but also how they will be implemented. The public will be afforded opportunities to provide comment to DEQ and the Board of Environmental Review both before and during rule making.


This website contains some of the key technical reports completed as part of the stream and small river criteria-development process. The website will be updated periodically with additional reports and other information as the development of numeric nutrient criteria for other surface waters proceeds.