Large rivers water quality monitoring: 2009 and 2010 summary report

VanderMeulen, David

The Great Lakes Inventory and Monitoring Network (Network or GLKN hereafter) monitored water quality at a number of sites on the Mississippi River, as well as sites on the St. Croix River and its tributaries. Water quality monitoring at the two national parks associated with these large rivers – Mississippi National River and Recreation Area and St. Croix National Scenic Riverway – is a subset of a larger water quality monitoring effort by Network staff at national parks in the western Great Lakes region. The primary objective of this monitoring program is to monitor water quality in order to describe the current status and trends of common limnological parameters on large rivers and select tributaries. GLKN staff hopes to be able to provide early warnings of change, which may then provide justification for increased monitoring, research, or management action. Monthly water quality sampling was conducted on the St. Croix River and select tributaries in 2009 and on the Mississippi River in 2010 during ice-free months (April through November). Additional samples were collected at select sites on the St. Croix River in April, July, and November 2010. Field measurements included depth profiles of temperature, pH, conductivity, and dissolved oxygen; and water clarity. Water samples were collected for laboratory analyses of nutrients (total phosphorus, total nitrogen, nitrate+nitrite-nitrogen, ammonium-nitrogen, dissolved silica), major ions (calcium, sodium, magnesium, potassium, sulfate, chloride), dissolved organic carbon, alkalinity, and total chlorophyll-a. When applicable, flow measurements at or nearby Network monitoring sites were obtained from active flow gages operated by the United States Geological Survey or the Unites States Army Corps of Engineers. In this report monitoring results from 2009 at SACN and results from 2010 at MISS are compared with federal, regional, and site-specific water quality standards, when applicable. Some of these standards are proposed and under review, while others have been approved by the State of Minnesota and/or Wisconsin. All data collected in 2009 and 2010 are included in appendices. Results indicate that at the Mississippi National River and Recreation Area, relatively poor water quality conditions in the Minnesota River are negatively impacting water quality in the Mississippi River, causing exceedances of water quality standards at downstream sites. At the St. Croix National Scenic Riverway, water quality at sites in the upper river is relatively unimpacted and near EPA reference conditions while Lake St. Croix in the lower river is being impacted by excess nutrients (phosphorus). Tributaries to the St. Croix River including the Snake, Apple, Willow and Kinnickinnic rivers also appear to be impacted by excess nutrients. Park-specific comments and recommendations relating to the sampling season are provided. The Network expects to continue monitoring at St. Croix National Scenic Riverway in 2011 and at Mississippi National River and Recreation Area in 2012. Future monitoring will be used assess current condition as it relates to water quality standards, and to continue to develop a long-term dataset to assess for trends in water quality over time.

Large rivers water quality monitoring: 2009 and 2010 summary report

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