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Impaired Surface Water in Missouri


The quality of Missouri’s water is regulated by  the Water Protection Program of the Missouri Department of Natural Resources and by the Office of Water at the EPA. Every two years, the Water Protection Program issues a Missouri Water Quality Report (Section 305(b) Report), most recently in 2012, and this post reports on its content. They also provides EPA with a Water Quality Assessment and Impaired Waters List, aka a 303(d) List, also most recently in 2012. This document lists all of the water bodies in the state that have been assessed by MODNR to be impaired.

Impaired means that the quality of the water is no longer suitable for one or more of its desired uses. Desired uses vary, but might include any of the following: supporting aquatic life, swimming, drinking water supply, livestock or wildlife watering, fishing or boating, irrigation, and industrial use.

Missouri is home to lots of surface water. There are about 24,431 linear miles of creeks, streams, and rivers, and about 298,867 surface acres of ponds, lakes, and reservoirs. With so much surface water, MODNR has been able to monitor only about 40% of Missouri’s creeks, streams, and rivers, and about 66% of Missouri’s ponds, lakes, and reservoirs. Missouri also has lots of groundwater, and I will focus on it in a later blog.

The quality of surface water is influenced by many factors. Some are natural, having to do with the surrounding geology and topography. For instance, erosion can cause turbidity. Others are caused by people. For instance, runoff from farms pollutes some water bodies with pesticides and herbicides. Sometimes, natural and human factors interact. For instance, erosion is natural, but some land clearing activities can cause increased erosion, leading to siltation and sedimentation of water bodies.

MO Impaired RiversThe report divides Missouri into three regions. Northern and Western Missouri, the Ozark Plateau, and the Mississippi Embayment in the southeastern corner of the state. These three regions have very different soil, bedrock, and topography. In addition, the uses to which the land is put differ. Thus, the impairments that threaten the water are different.

As shown in the first graph at right, MODNR estimates that 8,725 miles (36%) of Missouri streams and rivers are impaired. This represents 5,441 miles of streams and rivers that have been assessed plus 3,304 miles that have not been assessed, but which are suspected to be impaired.

As shown in the second graph at right, MODNR estimates that 70,130 acres (23%) of Missouri lakes and reservoirs are impaired. This represents 69,739 acres that have been assessed, plus 391 acres that have not been assessed, but are suspected to be impaired. Mo Impaired Lakes 2012It is a significant reduction from the previous report: Lake of the Ozarks, which had previously been contaminated by septic systems, is no longer listed as impaired.

The summary provided in the report was last updated in June of 2010. The 303(d) list for 2012 provides more recent data, however detailed information about each impairment and body of water would be required to assemble the data into an overall summary.

In following posts I will present information from the report about the types of activities that have been impaired, about the kinds of sources causing the impairment, and about Missouri’s groundwater.


Missouri Water Quality Report (Section 305(b) Report), 2012. Water Protection Program, Missouri Department of Natural Resources, http://www.dnr.mo.gov/env/wpp/waterquality/305b/index.html.

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