Earlier this year, the MPCA released results of its study, “Nitrogen in Surface Waters,” which shows elevated nitrate levels, particularly in southern parts of the state. At the Dec. 18 BALMM meeting, David Wall (photo at right), the MPCA hydrologist who coordinated the study, will present the findings.

Concern about nitrate has grown in recent years because studies show that nitrate in surface water is toxic to fish and the aquatic life food chain, and nitrate in drinking water is potentially harmful to humans. Nitrates are a particular concern in southeastern Minnesota where karst makes water resources vulnerable to contamination.

The MPCA conducted the study of nitrogen in surface waters so Minnesotans can better understand the nitrogen conditions in Minnesota’s surface waters, along with the sources, pathways, trends and potential ways to reduce nitrogen in waters.

The study was a collaborative effort led by MPCA, with assistance from the University of Minnesota and the U.S. Geological Survey. The report team used more than 50,000 water samples collected at 700 stream sites and used 35 years of monitoring data and findings from 300 published studies.

In addition to the potential harm to aquatic life and drinking water sources here, nitrate leaving Minnesota via the Mississippi River contributes to the oxygen-depleted dead zone in the Gulf of Mexico and to the degradation of Lake Winnipeg in Canada.

The study found that in Minnesota, more than 70 percent of the nitrate is coming from cropland, the rest from regulated sources such as wastewater treatment plants, septic and urban runoff, forest, and the atmosphere.

How does nitrate move from cropland into our water?

• The amount of nitrate reaching surface waters from cropland varies tremendously, depending on the type of crops, tile drainage practices, cropland management, soils, climate, geology and other factors. Tile drainage is the highest estimated cropland source pathway.
• Precipitation amounts have a pronounced effect on nitrate loads. During a dry year, loads may drop by 49 percent compared to an average year, however during a wet year, overall loads may increase by 51 percent.
• Nitrate concentrations and loads are high throughout much of southern Minnesota, resulting largely from leaching through large parts of intensively cropped soils and into underlying tile drains and groundwater.
• Cropland sources account for an estimated 89 to 95 percent of the nitrate load in the Minnesota, Missouri, and Cedar Rivers, and Lower Mississippi River basins.

Tactics for reducing cropland nitrate going into surface waters fall into three categories:

• Manage in-field nutrients (i.e., optimize fertilizer rates, apply fertilizer closer to timing of crop use)
• Manage and treat tile drainage water (i.e., plan tile spacing and depth; control drainage; construct and restore wetlands for treatment purposes; and bioreactors)
• Diversify vegetation/landscape (i.e., plant cover crops; plant more perennials on marginal cropland) 

Nitrate fertilizer efficiency has improved during the past two decades. While further refinements in fertilizer rates and application timing can be expected to reduce nitrate loads by roughly 13 percent statewide, additional and more costly practices will also be needed to make further reductions and meet downstream needs. Statewide reductions of more than 30 percent are not realistic with current practices.  

To see progress, nitrate leaching reductions are needed across large parts of southern Minnesota, particularly on tile-drained fields and row crops over thin or sandy soils. Only collective incremental changes by many over broad acreages will result in significant nitrogen reductions to downstream waters.

Several state agencies have developed a state-level nutrient reduction strategy to address Minnesota’s contribution to the Gulf of Mexico’s hypoxia issue. Minnesota contributes the sixth highest nitrogen load to the Gulf. The strategy will identify how further progress can be made to reduce nitrate and phosphorus entering both in-state and downstream waters.  

The MPCA is also working with the U.S. Environmental Protection Agency and other states to evaluate the effect nitrate has on aquatic life in order to develop and adopt toxicity standards.

For more information, visit the nitrogen study webpage.

The MPCA recently announced the draft 2014 Impaired Waters list, which will be open for public comment in January 2014.

Ten lakes and 20 stream reaches across the state have been removed from this year’s list, an accomplishment which represents monumental work on the part of watershed organizations around the state.

“In recent years, thanks in part to the Clean Water, Land, and Legacy Amendment, MPCA has greatly accelerated its schedule for assessing surface waters. Because of that, we are finding many more water bodies with impairments,” said Assistant Commissioner Rebecca Flood. “At the same time, our local partners are making impressive progress on improving water quality problems, so in every biennial cycle, we are able to remove a few more lakes and streams from the list.”

Highlights of this year’s list include:

• Thirty-two miles of the Mississippi River have been impaired since 2008 because of the presence of certain perfluorochemicals (PFCs) in fish tissue. Over the past several years PFC concentrations have decreased markedly in the impaired sections of the Mississippi, and three out of four sections of the river can now be removed from the Impaired Waters list for this particular problem.
• Two sections of the Red River of the North near Fargo-Moorhead, which had been impaired since 1994 because of fecal coliform bacteria, have been removed from the draft list. Working cooperatively, the two cities enhanced their flood mitigation efforts and improved stormwater and wastewater infrastructure to reduce bacteria levels in the river to a safer level. The river now meets state water quality standards for fecal coliform bacteria.  
• Nine metro-area lakes have been removed from the list as a result of work to correct their impairments. Howard Lake in Anoka County was restored by removing rough fish such as carp that disturbed the lake bed, and installing barriers to keep them out. These actions improved water quality and allowed rooted vegetation to be re-established in the lake.

Most of the changes to the list are a result of intensive monitoring conducted in 18 watersheds around the state in 2012 and 2013, as well as statewide assessments for bacteria in large rivers, for pesticides, and for nitrates in drinking water. The MPCA conducts intensive monitoring in 8-9 of the state’s 81 major watersheds each year, a process which will enable every watershed in the state to be monitored by 2018.

Work is still underway to assess waters used for growing wild rice to identify those that exceed acceptable levels of sulfates. The MPCA plans to make the results of the wild rice sulfate standard assessments available as an addendum to this version of the Impaired Waters list when the wild rice and sulfate assessments are complete.

A series of public meetings will take place throughout the state in December to present the content of the Impaired Waters List. Individuals who are unable to attend in person can participate in a broadcast of the meetings in real time. (Email miranda.nichols@state.mn.us prior to the meeting for more information.)

• Thursday, Dec. 10, 9-10 a.m., MPCA Office, 520 Lafayette Road N., St. Paul
• Wednesday, Dec. 11, 1-2 p.m., MPCA Office, 714 Lake Ave., Detroit Lakes
• Wednesday, Dec.18, 11 - 11:30 a.m., MPCA Office, 18 Wood Lake Dr. SE, Rochester (in conjunction with BALMM meeting)

Formal written comments on the list will be accepted from Jan. 2 - 31, 2014. For more information, visit the Impaired Waters List webpage or contact Miranda Nichols (651-757-2614, miranda.nichols@state.mn.us).