Nutrient Criteria Development
in Missouri - An Update

Over the past 14 months, the Lakes of Missouri Volunteer Program staff has been participating in stakeholder meetings in an attempt to develop nutrient criteria for the state of Missouri. This article summarizes a few of the approaches the group has been evaluating for generating criteria for the lakes of the plains region of Missouri.

The EPA is trying to return waterbodies to their natural state by mitigating some of the negative impacts humans have made on their environment. This is a laudable goal, and there is no doubt that human activities on the land have had a profound impact on water quality. Nutrients cause nuisance algae blooms and rank among the most common pollutants in America’s waterways.

Water quality standards are set to reduce the risk that pollutants will impair a waterbody’s designated use. Unlike other pollutants, however, nutrients aren’t toxic at some specific concentration, but rather cause a gradual decline in ambient conditions that ultimately leads to stinky, green, hypereutrophic lakes. Because the loss of water quality is gradual, identifying the phosphorus concentration where impairment begins is extremely difficult.

Since we can’t specifically define where nutrient impairment begins, we are using historical levels of nutrients as a starting point and then declaring, somewhat arbitrarily, that a certain number of our lakes have too many nutrients. This article is an examination of the methods currently available for determining nutrient impairment in Plains region lakes.

The data set is made up of 82 reservoirs from the Plains regions of the state, which encompasses the northern and western parts of Missouri. Each reservoir has been sampled by the University of Missouri during at least 4 years. Long-term phosphorus values for the reservoirs range from a low of 14 to a high of 182 micrograms per liter (ug/L), with a median value of 50 ug/L.

Phosphorus concentration graph

Mean phosphorus data from the Plains regions
(2005 LMVP data)

Vertical line at 20 ug/L represents the regional value proposed by EPA for the plains ecoregion and the 35 ug/L line represents the Regional Techical Advisory Group’s proposed value. Actual impairment would likely be determined by looking at long-term averages for a lake.

Back to the Fall 2006 Water Line

Brought to you by the Lakes of Missouri Volunteer Program