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Numeric Nutrient Criteria

Staff Contact: Michael Suplee (406) 444-0831

DEQ has developed 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 reached the point where DEQ developed standards and began implementation of rules. These rules involve not only the numeric nutrient criteria, but also implementation and variance processes. The Environmental Protection Agency issued a letter of approval of standards in February, 2015.

This website contains some of the key technical reports completed as part of the stream and 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 (for example, large rivers such as the Missouri).