Rock River Watershed

Overall Watershed Tabs

Watershed

Vertical Tabs

Overview

The The Rock River watershed covers 1,075,032 acres in Rock, Nobles, Pipestone, and Murray counties in southwestern Minnesota. It is the largest of the four watersheds in Minnesota that are part of the Missouri River Basin, extending south into Iowa.
Source: MPCA

LINKS
Rock River Watershed - MPCA
Watershed Health Assessment Framework Overview - MDNR
Watershed Health Assessment: Interactive Map - MDNR
Watershed Assessment Tool Mapbook - Rock River - MDNR

ACRONYMS
BWSR - Minnesota Board of Water and Soil Resources
MDA - Minnesota Department of Agriculture
MDH - Minnesota Department of Health
MDNR - Minnesota Department of Natural Resources
MPCA - Minnesota Pollution Control Agency
NRCS - Natural Resources Conservation Service

SYMBOLS
= External link to Website
= Link to PDF

Landscape

Landscape:

Land Use & Crops Map

Source: Watershed Crop Data Layer from the National Agricultural Statistics Service (NASS) (2013).

Nitrogen

Vertical Tabs

Nitrogen Overview

What is Nitrogen?:

Nitrogen (N) is one of the most widely distributed elements in nature and is present virtually everywhere on the earth’s crust in one or more of its many chemical forms. Nitrate (NO3), a mobile form of N, is commonly found in ground and surface waters throughout the country. Nitrate is generally the dominant form of N where total N levels are elevated. Nitrate and other forms of N in water can be from natural sources, but when N concentrations are elevated, the sources are typically associated with human activities (Dubrovski et al., 2010). Concerns about nitrate and total N in Minnesota’s water resources have been increasing due to effects of nitrate on certain aquatic life and drinking water supplies, along with increasing N in the Mississippi River and its impact on Gulf of Mexico oxygen depletion.

Why is Nitrogen a Concern?:

Elevated nitrate levels harm fish and aquatic life.
Because nitrate moves primarily via groundwater and tile drainage waters (not surface runoff), it can pollute drinking water wells.
Nitrate leaving Minnesota via the Mississippi River contributes to the oxygen-depleted dead zone in the Gulf of Mexico.

Where does nitrate come from?

More than 70% of the nitrate is coming from cropland, the rest from sources such as wastewater treatment plants, septic and urban runoff, forest, and the atmosphere.
Municipal wastewater contributes 9% of the statewide nitrate load.
Nitrate leaching into groundwater below cropped fields and moving underground until it reaches streams, contributes an estimated 30% of statewide nitrate to surface waters.

Source: Nitrogen in Minnesota Surface Waters (2013)

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% compared to an average year, however during a wet year, overall loads may increase by 51%.
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% of the nitrate load in the Minnesota, Missouri, and Cedar Rivers, and Lower Mississippi River basins.

Source: Nitrogen in Minnesota Surface Waters (2013)

Tile drainage pathway
In tiled cropland, most of the rainwater that ends up in surface water (ditches, streams) flows through tile drainage. This water can be high in nitrate, but can potentially be treated before reaching ditches.

Groundwater pathway
In cropland without tile drainage, most rainwater flows through the ground to get to surface waters. As it travels through the earth, some of the nitrate is removed, resulting in less nitrate reaching our streams and rivers. However, there are fewer options of controlling this kind of nitrate pollution once it moves below the crop roots.

Where does the nitrate go?

Groundwater nitrate can take from hours to decades to reach surface waters.
The highest nitrate-yielding watersheds are Cedar, Blue Earth and Le Sueur in south-central Minnesota.
The Minnesota River adds twice as much nitrate to the Mississippi River as the combined loads from the Upper Mississippi and St. Croix Rivers.
On average, 158 million pounds of nitrate leaves Minnesota per year in the Mississippi River — 75% comes from Minnesota watersheds.
Nitrate concentrations have steadily increased in the Mississippi River since the mid-1970s.
Nitrate loads leaving Minnesota via the Mississippi River contribute to the oxygen-depleted “dead zone” in the Gulf of Mexico (currently estimated to be the size of Massachusetts). The dead zone cannot support aquatic life, affecting commercial and recreational fishing and the overall health of the Gulf.

How do we reduce the nitrate going into surface waters?

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, riparian zones and other areas)

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% statewide, additional and more costly practices will also be needed to make further reductions and meet downstream needs. Statewide reductions of more than 30% 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.

Nitrogen's Downstream Impacts:

Nitrogen is considered a limiting nutrient in the Gulf of Mexico, the body of water where much of Minnesota’s river and stream waters ultimately discharge. When nutrients in the Mississippi River originating in 31 states reach the Gulf of Mexico, a low oxygen “dead zone” known as hypoxia develops.

Hypoxia, which means low oxygen, occurs when excess nutrients, primarily N and P, stimulate algal growth in the Mississippi River and gulf waters. The algae and associated zooplankton grow well beyond the natural capacity of predators or consumers to maintain the plankton at a more balanced level. As the short-lived plankton die and sink to deeper waters, bacteria decompose the phytoplankton carbon, consuming considerable oxygen in the process. Water oxygen levels plummet, forcing mobile creatures like fish, shrimp, and crab to move out of the area. Less mobile aquatic life become stressed and/or dies.

The freshwater Mississippi River is less dense and warmer compared to the more dense cooler saline waters of the gulf. This results in a stratification of the incoming river waters and the existing gulf waters, preventing the mixing of the oxygen-rich surface water with oxygen-poor water on the bottom. Without mixing, oxygen in the bottom water is limited and the hypoxic zone remains. Hypoxia can persist for several months until there is strong mixing of the ocean waters, which can come from a hurricane or cold fronts in the fall and winter.

Hypoxic waters have dissolved oxygen concentrations of less than about 2-3 mg/l. Fish and shrimp species normally present on the ocean floor are not found when dissolved oxygen levels reduce to less than 2 mg/l. The Gulf of Mexico hypoxic zone is the largest in the United States and the second largest in the world. The maximum areal extent of this hypoxic zone was measured at 8,500 square miles during the summer of 2002. The average size of the hypoxic zone in the northern Gulf of Mexico in recent years (between 2004 and 2008) has been about 6,500 square miles, the size of Lake Ontario.

Hypoxia Task Force
A multi-state Hypoxia Task Force (which includes Minnesota) released their first Action Plan in 2001. This plan was reaffirmed and updated in a 2008 Action Plan. The Hypoxia Task Force established a collaborative interim goal to reduce the 5-year running average areal extent of the Gulf of Mexico hypoxic zone to less than 5,000 square kilometers (1,931 square miles). Further information about Gulf of Mexico hypoxia can be found at: https://gulfhypoxia.net/

A thorough technical discussion of the research associated with Gulf of Mexico hypoxia and possible nutrient reduction options is presented by the US EPA (2007). The report notes that P may be more influential than N in the near-shore gulf water algae growth, particularly in the spring months, when algae and phytoplankton growth are often greatest. In the transition months between spring and summer, the algae and phytoplankton growth are controlled largely by the coupling of P and N. Nitrogen typically becomes the controlling nutrient in the summer and fall months. Based on these more recent findings, emphasis has shifted to developing strategies for dual nutrient removal (P and N). The Science Advisory Board recommends a 45% reduction in riverine TP and TN loads into the Gulf of Mexico (US EPA 2007).

Minnesota’s Contribution to Gulf Hypoxia
Certain areas of Minnesota release large quantities of N and P to Minnesota streams. Much of the nutrients remain in the Mississippi River system, ultimately reaching the Gulf of Mexico. Alexander et al. (2008) used computer modeling (SPARROW) to estimate the proportion of gulf nutrients originating in different geographic areas. The model accounted for the loss of nutrients in the river, river pools, and backwaters prior to reaching the Gulf of Mexico. This modeling indicated that Minnesota contributed 3% of Gulf of Mexico N and 2% of the P. However, with more recent SPARROW modeling, Minnesota’s contribution is estimated to be higher, ranking as the sixth highest state for N contributions behind Iowa, Illinois, Indiana, Ohio, and Missouri. The more recent modeling estimates indicate that Minnesota is responsible for about 6% of the N loading and 4% of the P loading into the Gulf of Mexico (Robertson, 2012 personal communication).

Recognizing that it will take a concerted effort by all states which contribute significant amounts of nutrients to the gulf, the MPCA agreed with other top nutrient contributing states to complete and implement a comprehensive N and P reduction strategy. This plan was completed in 2014 (Mississippi River/Gulf of Mexico Watershed Nutrient Task Force, 2008). The goal of the Action Plan is to reduce nutrients to the Gulf of Mexico while at the same time addressing in-state water protection and restoration.

Minnesota Nitrogen Study
The MPCA conducted a study of nitrogen in surface waters so that we 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.

Source: Nitrogen in Minnesota Surface Waters (2013)

Nitrogen Sources

Nitrogen in Soil:

Excerpts from Nitrogen in Minnesota Surface Waters
Source of Nitrogen in Soil - Results Overview

Nitrogen in Surface Waters:

Excerpts from Nitrogen in Minnesota Surface Waters
Sources of Nitrogen - Results Overview
Sources of Nitrogen - Wastewater Point Source Nitrogen Loads
Sources of Nitrogen - Atmospheric Deposition of Nitrogen in Minnesota Watersheds

Statewide - N Sources to Waters - Average Year

Source: Nitrogen in Minnesota Surface Waters , Sources of Nitrogen - Results Overview (2013)

Cropland sources contribute an estimated 73 percent of the statewide N load during an average precipitation year. Cropland nitrogen is primarily delivered to surface waters through subsurface pathways of tile drainage and groundwater.

Missouri River Basin - N Sources to Surface Waters

Source: Nitrogen in Minnesota Surface Waters , Sources of Nitrogen - Results Overview (2013)

Statewide - N Sources to Surface Waters Chart -Average Year

Source: Nitrogen in Minnesota Surface Waters , Sources of Nitrogen - Results Overview (2013)

Estimated N loads to surface waters from different sources within the Minnesota portions of major basins during an average precipitation year. “Ag” represents cropland sources.

Nitrogen Monitoring

Nitrogen Monitoring Locations:

Watershed Pollutant Load Monitoring Network - MPCA

Water Quality Databases
DNR/MPCA Cooperative Stream Gaging Network – USGS, DNR, MPCA – Stream discharge and links to Division of Waters Resources, climate information, river levels, water quality information, recreation and commonly used hydrologic terms
USGS – USGS discharge Information
EDA Environmental Data Access – Water quality data collected for all MPCA monitoring projects
EQuIS – Environmental Quality Information System – Water quality data from more than 17,000 sampling locations across the state.

Nitrogen Monitoring FWMC:

Source: Watershed Pollutant Load Monitoring Network - MPCA (2014)

Average annual flow-weighted mean concentrations for Total Nitrogen near watershed outlets based on annual averages derived from available information collected in 2007-11.

Nitrogen Monitoring Yields:

Source: Watershed Pollutant Load Monitoring Network - MPCA (2014)

Average annual yield (lbs/acre) for Total Nitrogen near watershed outlets based on annual averages derived from available information collected in 2007-11.

Nitrogen Monitoring Loads:

Source: Watershed Pollutant Load Monitoring Network - MPCA (2014)

Average annual Total Nitrogen Load near watershed outlets based on annual averages derived from available information collected in 2007-11.

Nitrogen Modeling

Nitrogen Modeling FWMC:

Excerpts from Nitrogen in Minnesota Surface Waters - MPCA
Chapter 4: Modeled Nitrogen Loads (SPARROW)

The MPCA’s Nitrogen Study shows elevated nitrate levels, particularly in the southern third of Minnesota.

Source: Nitrogen in Minnesota Surface Waters, Chapter 4: Modeled Nitrogen Loads (SPARROW) (2013)

Data Source: SPARROW flow-weighted mean TN concentration by HUC8 watersheds. The value represents the median FWMC of all subwatershed catchments within the HUC8 watersheds.

SPARROW Modeling for the Cannon River Watershed indicated average flow-weighted mean TN concentration of 8.1 mg/l. This value represents the median FWMC of all subwatershed catchments within the Cannon River Watershed.

Nitrogen Modeling Yields:

Source: Nitrogen in Minnesota Surface Waters, Chapter 4: Modeled Nitrogen Loads (SPARROW) (2013)

SPARROW model annual TN yield results by HUC8 watershed in lbs/acre/year. The basin yields represent the total load delivered to the watershed outlet or state border divided by the sum of the SPARROW (MRB3 2002) catchment area.

SPARROW model annual TN yield results for the Cannon River Watershed was 14.48 lbs/acre/year.

Statewide Comparison of Nitrate+Nitrate-N Yields (lbs/ac)

	Nitrite+Nitrate-N Yield (lbs/ac)
S. Central	11-19
Southeast	8-9
Southwest	4-9
Central	1-2
Northwest	0.1-1
Northeast	0.1-2

Source: Nitrogen in Minnesota Surface Waters (2013)

Nitrogen Modeling Ranking:

Total Nitrogen Contributions to the Mississippi River (percent Load by HUC8 Watershed)

Source: Nitrogen in Minnesota Surface Waters (2013)

Percent contribution of TN delivered to the Mississippi River in Keokuk, Iowa, from each of Minnesota’s HUC8 Watersheds which ultimately drain into the Mississippi River. Each bar represents the percent TN originating from a single watershed, from highest contributor (left) to lowest contributor (right).

Fifteen of the 45 watersheds draining into the Mississippi River from Minnesota each contribute over 3 percent of the modeled load delivered to the Mississippi River in southern Iowa (Keokuk) (Table 4 and Figure 9). Combined, these 15 watersheds contribute 73.7 percent of the total nitrogen load delivered to Keokuk from Minnesota (Figure 10). These higher loading watersheds are mostly located in South-central and southeastern Minnesota. The other thirty watersheds each contribute between 0 and 2.4 percent of the load, and are thus considered relatively minor contributors.

WS #	Watershed Name	% load contribution
33	Lower Minnesota River	7.3
28	Minnesota River - Mankato	6.7
30	Blue Earth River	6.4
32	Le Sueur River	5.7
25	Minnesota River - Yellow Medicine River	5.6
39	Cannon River	5.2
43	Root River	5.2
41	Zumbro River	4.9
19	South Fork Crow River	4.7
48	Cedar River	4.4
29	Cottonwood River	4.3
20	Mississippi River - Twin Cities	3.7
31	Watonwan River	3.4
51	Des Moines River - Headwaters	3.2
26	Chippewa River	3.1
18	North Fork Crow River	2.4
16	Sauk River	1.7
27	Redwood River	1.6
40	Mississippi River - Winona	1.5
15	Mississippi River - Sartell	1.4
38	Mississippi River - Lake Pepin	1.4
17	Mississippi River - St. Cloud	1.4
21	Rum River	1.3
49	Shell Rock River	1.3
10	Mississippi River - Brainerd	1.2
37	Lower St. Croix River	1.1
24	Lac Qui Parle River	1.1
23	Pomme de Terre River	1.0
50	Winnebago River	0.8
36	Snake River	0.8
9	Mississippi River - Grand Rapids	0.7
12	Crow Wing River	0.7
46	Upper Iowa River	0.6
13	Redeye River	0.6
35	Kettle River	0.6
14	Long Prairie River	0.6
53	East Fork Des Moines River	0.5
22	Minnesota River - Headwaters	0.4
44	Mississippi River - Reno	0.4
42	Mississippi River - La Crescent	0.4
34	Upper St. Croix River	0.3
52	Lower Des Moines River	0.2
7	Mississippi River - Headwaters	0.1
11	Pine River	0.1
8	Leech Lake River	0.0
47	Upper Wapsipinicon River	0.0

Source: Nitrogen in Minnesota Surface Waters (2013)

Nitrogen Trends

Nitrogen Trends Summary:

Statewide Nitrate Trends

Excerpts from Nitrogen in Minnesota Surface Waters
Nitrate Trends in Minnesota Rivers
Nitrogen Trend Results from Previous Studies

Nutrient and Suspended-Sediment Trends in the Missouri River Basin, 1993–2003
By Lori A. Sprague, Melanie L. Clark, David L. Rus, Ronald B. Zelt, Jennifer L. Flynn, and Jerri V. Davis

Trends in streamflow and concentration of total nitrogen, nitrite plus nitrate, ammonia, total phosphorus, orthophosphorus, and suspended sediment were determined for the period from 1993 to 2003 at selected stream sites in the Missouri River Basin. Flow-adjusted trends in concentration (the trends that would have occurred in the absence of natural changes in streamflow) and non-flow-adjusted trends in concentration (the overall trends resulting from natural and human factors) were determined. In the analysis of flow-adjusted trends, the removal of streamflow as a variable affecting concentration allowed trends caused by other factors such as implementation of best management practices to be identified. In the analysis of non-flow-adjusted trends, the inclusion of any and all factors affecting concentration allowed trends affecting aquatic ecosystems and the status of streams relative to water-quality standards to be identified. Relations between the flow-adjusted and non-flow-adjusted trends and changes in streamflow, nutrient sources, ground-water inputs, and implementation of management practices also were examined to determine the major factors affecting the trends.

From 1993 to 2003, widespread downward trends in streamflow indicated that drought conditions from about 2000 to 2003 led to decreasing streamflow throughout much of the Missouri River Basin. Flow-adjusted trends in nitrite plus nitrate and ammonia concentrations were split nearly equally between nonsignificant and downward; at about one-half of the sites, management practices likely were contributing to measurable decreases in concentrations of nitrite plus nitrate and ammonia. Management practices had less of an effect on concentrations of total nitrogen; downward flow-adjusted trends in total nitrogen concentrations occurred at only 2 of 19 sites. The pattern of non-flow-adjusted trends in nitrite plus nitrate concentrations was similar to the pattern of flow-adjusted trends; non-flow-adjusted trends were split nearly equally between nonsignificant and downward. A substantial source of nitrite plus nitrate to these streams likely was ground water; because of the time required for ground water to travel to streams, there may have been a lag time between the implementation of some pollution-control strategies and improvement in stream quality, contributing to the nonsignificant trends in nitrite plus nitrate. There were more sites with downward non-flow-adjusted trends than flow-adjusted trends in both ammonia and total nitrogen concentrations, possibly a result of decreased surface runoff from nonpoint sources associated with the downward trends in streamflow. No strong relations between any of the nitrogen trends and changes in nutrient sources or landscape characteristics were identified.

Although there were very few upward trends in nitrogen from 1993 to 2003, there were upward flow-adjusted trends in total phosphorus concentrations at nearly one-half of the sites. At these sites, not only were pollution-control strategies not contributing to measurable decreases in total phosphorus concentrations, there was likely an increase in phosphorus loading on the land surface. There were fewer upward non-flow-adjusted than flow-adjusted trends in total phosphorus concentrations; at the majority of sites, overall total phosphorus concentrations did not change significantly during this period. The preponderance of upward flow-adjusted trends and nonsignificant non-flow-adjusted trends indicates that in some areas of the Missouri River Basin, overall concentrations of total phosphorus would have been higher without the decrease in streamflow and the associated decrease in surface runoff during the study period. During the study period, phosphorus loads from fertilizer generally increased at over one-half of the sites in the basin. Upward flow-adjusted trends were related to increasing fertilizer use in the upstream drainage area, particularly in the 10 percent of the drainage area closest to the monitoring site. This relation was not seen with the non-flow-adjusted trends in total phosphorus concentrations, indicating that decreasing streamflow and associated decreasing surface runoff in the basin during the study period may have offset the effects of increasing fertilizer use.

There were fewer sites with upward trends in suspended sediment than in total phosphorus. Although phosphorus can be transported by sorption to particulate material, the different trend patterns of the two constituents indicate that changes in suspended-sediment concentrations were not contributing to a concomitant change in total phosphorus concentrations in the Missouri River Basin. At some sites, pollution-control strategies or other human activities were contributing to a measurable decrease in suspended-sediment concentrations, but at the majority of sites, there were no measurable effects from pollution-control strategies. Spatial differences in stream density and overbank storage may have contributed to the spatial variability in flow-adjusted trends in suspended-sediment concentrations throughout the basin. Sediment loading probably was less affected by overbank storage at sites with higher stream densities, and consequently, pollution-control strategies may have contributed to measurable decreases in suspended-sediment concentrations at these sites. In contrast, at low stream-density sites where overbank storage was occurring, pollution-control strategies may not have contributed to measurable changes in suspended-sediment concentrations because the sediment loading prior to BMP implementation would have already been attenuated by overbank storage. There were more downward non-flow-adjusted trends than downward flow-adjusted trends in suspended-sediment concentrations, indicating that naturally decreasing streamflow over the study period was as or more influential in decreasing the concentrations of suspended sediment than were pollution-control strategies or other human activities. If streamflow had not decreased during the study period, it is unlikely that overall concentrations of suspended sediment would have decreased at many sites.

The streamflow and flow-adjusted trends in concentration for the period from 1993 to 2003 were placed in a longer context by comparing them to longer term, non-monotonic trends for the period from 1985 to 2003 at a subset of the sites. From 1985 to 2003, streamflow generally decreased from about 1985 to 1991, increased from about 1992 to 1996, and decreased from about 1997 to 2003. During the same period, many flow-adjusted trends in total nitrogen, nitrite plus nitrate, total phosphorus, orthophosphorus, and suspended-sediment concentrations occurred between 1985 and 1991 and between 1997 and 2003; unlike with streamflow, the direction of the flow-adjusted trends varied among sites and among time periods. These longer term, non-monotonic patterns indicated that consistent monotonic changes in streamflow and concentration may not have occurred through the entire period from 1993 to 2003, as indicated by the shorter term trend analysis.

The longer term patterns in streamflow also indicated that the decreasing steamflows observed from 1993 to 2003 in the Missouri River Basin likely will not continue indefinitely. In some parts of the basin, nutrient and suspended-sediment concentrations may have been higher without the decrease in streamflow and the associated decrease in surface runoff that occurred during the study period. Without additional steps to minimize surface runoff or nutrient loading on the land, it is possible that concentrations will increase when streamflow and runoff begin to increase once again. In addition, results from three case studies indicated that a substantial portion of the total flow and nitrate load in streams may consist of ground-water inflow in some parts of the basin. In these areas, nutrient loading to streams may be addressed by management practices focused not only on reducing surface runoff but also on maintaining and (or) improving ground-water quality.

Source: Nutrient and Suspended-Sediment Trends in the Missouri River Basin, 1993–2003

Phosphorus

Vertical Tabs

Phosphorus Overview

What is Phosphorus?:

Phosphorus is the nutrient primarily responsible for the eutrophication (nutrient enrichment of waterbodies) of Minnesota’s surface waters. Phosphorus is an essential nutrient for plants, animals and humans. It is one of the 20 most abundant elements in the solar system, and the 11th most abundant in the earth’s crust. Under natural conditions phosphorus (P) is typically scarce in water. Human activities, however, have resulted in excessive loading of phosphorus into many freshwater systems. This can cause water pollution by promoting excessive algae growth, particularly in lakes. Lakes that appear relatively clear in spring can resemble green soup in late summer due to algae blooms fueled by phosphorus. Water quality can be further impaired when bacteria consume dead algae and use up dissolved oxygen,suffocating fish and other aquatic life.

Why is Phosphorus a Concern?:

An overabundance of phosphorus—specifically usable (bioavailable) phosphorus—results in excessive algal production in Minnesota waters. Phosphorus from point sources may be more bioavailable, impacting surface water quality more than a similar amount of nonpoint source phosphorus that enters the same surface water conditions. Total phosphorus levels of 100 or more ppb categorize lakes as highly eutrophic, with high nutrient and algae levels.

In some water bodies, the concentration of phosphorus is low enough to limit the growth of algae and/or aquatic plants. In this case, scientists say phosphorus is the limiting nutrient. For example, in water bodies having total phosphorus concentrations less than 10 parts per billion (1 ppb – equal to one drop in a railroad tank car), waters will be nutrient-poor and will not support large quantities of algae and aquatic plants.

Phosphorus induced algae bloom
MPCA

Phosphorus Impacts:

Phosphorus contributions to Minnesota surface waters by point and nonpoint sources are known to vary, both geographically and over time, in response to annual variations in weather and climate. Nonpoint sources of phosphorus tend to comprise a larger fraction of the aggregate phosphorus load to Minnesota surface waters during relatively wet periods, while point sources become increasingly important during dry periods.

Minnesota River Basin-Lake Pepin
Three major river basins empty into Lake Pepin in southeastern Minnesota – St. Croix, Upper Mississippi, and the Minnesota. Lake Pepin is listed as an impaired water due to sediment and eutrophication (excessive nutrients and algae). The Minnesota River contributes a majority of the sediment. In a highly turbid water body such as the Minnesota River, much of the phosphorus load is attached to eroded soil particles, especially at higher flows. Much of the particulate phosphorus in the Minnesota River converts to the soluble that can become available to algae. This occurs in several ways: chemical and physical change (diagenesis) of sediment in the river or lake bed, interaction with dissolved chemicals in the water, and decay of organic P releasing dissolved phosphorus from soil particles. Models being used in the Lake Pepin and Minnesota River Total Maximum Daily Load projects keep track of both particulate and dissolved forms of phosphorus.

The Minnesota Pollution Control Agency is currently developing new water quality standards for River Eutrophication and Total Suspended Solids. Visit the MPCA website for more information.

Sources:
Minnesota Nutrient Reduction Strategy - MPCA
Phosphorus: Sources, Forms, Impacts on Water Quality - MPCA
New Water Quality Standards for River Eutrophication and Total Suspended Solids - MPCA

Phosphorus Sources

Phosphorus in Soil:

Phosphorus in Surface Waters:

Excerpts From Minnesota Nutrient Reduction Strategy
Chapter 5 Point and Nonpoint Source Reductions (2013)
Detailed Assessment of Phosphorus Sources to Minnesota Watersheds (2004)
Summary of Phosphorus Loading by Basin (2004)

Statewide Phosphorus Sources, Average Year

Source: Minnesota Nutrient Reduction Strategy, Chapter 5 Point and Nonpoint Source Reductions (2013)

Under normal water flows, roughly two- thirds of the total phosphorus load to lakes and rivers comes from nonpoint sources such as runoff from pasture and croplands, atmospheric deposition and stream bank erosion. Phosphorus loading contributed by runoff from pastures and croplands is largest source of nonpoint phosphorus on a statewide basis. Other nonpoint sources include urban runoff, non-agricultural rural runoff and seepage from individual sewage treatment systems.

Approximately 30 percent of the phosphorus load to Minnesota waters comes from point sources such as municipal and industrial wastewater treatment facilities. The magnitude of various sources of phosphorus varies greatly throughout the state due to the diverse nature of Minnesota’s watersheds.

Mississippi River
Phosphorus Sources to Surface Waters
Current: Average Precipitation Year

Source: Minnesota Nutrient Reduction Strategy (2013)

Phosphorus Monitoring

Phosphorus Monitoring Locations:

Pollutant Load Monitoring Sites in Minnesota

Watershed Pollutant Load Monitoring Network - MPCA

Water Quality Databases
DNR/MPCA Cooperative Stream Gaging Network – USGS, DNR, MPCA – Stream discharge and links to Division of Waters Resources, climate information, river levels, water quality information, recreation and commonly used hydrologic terms
USGS – USGS discharge Information
EDA Environmental Data Access – Water quality data collected for all MPCA monitoring projects
EQuIS – Environmental Quality Information System – Water quality data from more than 17,000 sampling locations across the state.

Phosphorus Monitoring FWMC:

Source: Watershed Pollutant Load Monitoring Network - MPCA (2014)

Average annual flow-weighted mean concentrations (mg/L) for Total Phosphorus near watershed outlets based on yearly averages derived from available information collected in 2007-011.

Phosphorus Monitoring Yields:

Source: Watershed Pollutant Load Monitoring Network - MPCA (2014)

Average annual Total Phosphorus Yield (lbs/acre) near watershed outlets based on yearly averages derived from available information collected in 2007-011.

Phosphorus Monitoring Loads:

Source: Watershed Pollutant Load Monitoring Network - MPCA (2014)

Average annual Total Phosphorus Load (kg) near watershed outlets based on yearly averages derived from available information collected in 2007-011.

Phosphorus Modeling

Phosphorus Modeling Yields:

SPARROW modeling
The SPAtially Referenced Regressions on Watershed attributes (SPARROW) model, developed and maintained by the United States Geological Survey (USGS), was used for the Minnesota Nutrient Reduction Strategy to estimate Total Phosphorus (TP) loads, yields, and flow-weighted mean concentrations (FWMC) in Minnesota 8-digit Hydrologic Unit Code (HUC8) watersheds and major basins.

Modeling Total Phosphorus Yield (lb/ac/yr)

SPARROW model annual TN yield results for the Cannon River Watershed was 0.61 pounds per acre per year (lb/ac/yr).

Source: Minnesota Nutrient Reduction Strategy (2013)

Phosphorus Modeling Ranking:

Source: Minnesota Nutrient Reduction Strategy (2013)

Phosphorus Trends

Phosphorus Trends Summary:

Statewide
Implementation of MPCA’s Phosphorus Strategy and Minnesota Rule Chapter 7053.0255 has resulted in significant wastewater effluent phosphorus load reductions since the year 2000.

Statewide Wastewater Phosphorus Effluent Loading

Source: Minnesota Nutrient Reduction Strategy, Chapter 5: Point and Nonpoint Source Reductions

Municipal and Industrial Wastewater Phosphorus Trends & Projections

Source: Minnesota Nutrient Reduction Strategy, Chapter 4: Management Priorites and Recent Progress

Mississippi River Basin
Summary of Recent Progress in Phosphorus Source Loads by Major Basin
Efforts between 2000 and present have resulted in significant progress in reducing phosphorus loads in the Mississippi River Basin, due to both agricultural BMPs and wastewater treatment plant upgrades.

Source: Minnesota Nutrient Reduction Strategy, Chapter 4: Management Priorites and Recent Progress
Notes: Recent progress is the percent of baseline load remaining after accounting for reductions since 2000.

Source: Minnesota Nutrient Reduction Strategy, Appendix A

Phosphorus Lakes

Phosphorus - Assessed Lakes:

Phosphorus - Nutrient Impaired:

Assessed Lakes (2012) in the Rock River Watershed

Impairment Parameters:
Nutrients = Nutrients
HgF = Mercury in Fish Tissue
HgW = Mercury in Water Column
CL = Chloride
PCBF = PCBs in Fish
PFOS = Perfluorooctane Sulfonate (PFOS) in Fish Tissue

Affected Uses:
AQC = Aquatic Consumption
AQR = Aquatic Recreation
AQL = Aquatic Life

No Lakes Assessed in this watershed

Source: Minnesota Pollution Control Agency Assessed Waters (2012) & Impaired Waters (2012)

Statewide Impaired Lakesheds

Source: Minnesota Nutrient Reduction Strategy, Chapter 2 Setting Goals and Milestones (2013)

For more information about what you can do to protect area lakes, visit MPCA's Lake protection and management website.

Planning and Management

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Contacts

Contacts:

Watershed Contacts - MPCA
Local Government Units and Partner Agencies - BWSR

MPCA Contacts
Mark T. Hanson, Marshall Office
(507)476-4259
mark.hanson@state.mn.us

Kelli Nerem, MPCA project manager
507-476-4251
Kelli.Nerem@state.mn.us

Murray County
Murray County SWCD
Murray County

Nobles County
Nobles County SWCD
Nobles County

Pipestone County
Pipestone County Conservation and Zoning
Pipestone County

Rock County
Rock County SWCD/Land Management
Rock County

Reports

State & Federal Reports:

The Minnesota Nutrient Reduction Strategy - MPCA

Driving forces and building blocks for the Nutrient Reduction Strategy
Hypoxia Action Plan
Clean Water Land & Legacy Amendment
Minnesota Watershed Approach
Groundwater Proection and Nitrogen Fertilizer Management Plan
Minnesota Water Sustainability Framework
Detailed Assessment of Phosphorus Sources to Minnesota Watersheds
Nitrogen in Minnesota Surface Waters
Modeled Nitrogen Loads (SPARROW)
Watershed Pollutant Load Monitoring - MPCA
Long Term Water Quality Monitoring - USGS, Met Council, Manitoba

Regional & Local Reports:

Missouri River Basin
Des Moines and Missouri River Basin Watershed Achievements Report (2009)

Southwest Minnesota
Southwest Regional Development Commission Environmental Planning

Rock River Watershed
Watershed Restoration and Protection (MPCA)
Rock River Major Watershed WRAP Strategy (MPCA)
Rock River near Iowa Border TMDL Project – Ammonia, Fecal Coliform and Turbidity (MPCA)

Murray County
SWCD Reports
SWCD Services
Ag and Solid Waste
Heron Lake Sediment and Phosphorus Reduction Implementation Projects
Accelerated Shallow Lake Restorations and Enhancements (2009-2013)
Riparian Buffer Easement Program - Phase I (2010-2011)
SSTS Imminent Health Threat Abatement Grant Program (2010-2011)
Shallow Lake & Wetland Protection Program - Phase III (2013-2017)

Nobles County
SWCD Plans & Reports
SWCD Grants
SWCD Projects
RIM Wetlands Reserve Program Acquisition and Restoration -  Phase II (2010)
Kanaranzi-Little Rock Watershed District Stimulus Project Completion (2010-2011)
Riparian Buffer Easement Program -  Phase I (2010-2011 )  Phase II (2012-2013)
Feedlot Water Quality Management Grant Program -  2011-2012  2012-2014  2013-2015
Lake Ocheda Shoreline Improvement (2011-2012)
Nobles County Erosion Control Practices (2013-2015)
Shallow Lake & Wetland Protection Program -  Phase III (2013-2017)

Okabena-Ocheda Watershed District
Programs

Pipestone County
SWCD Annual Reports
SWCD Programs & Services
Pipestone County Zoning Ordinance
Southwest Minnesota Survey of Farmers located in Wellhead Study Areas (1998)
SSTS Imminent Health Threat Abatement Grant Program - 2010-2011 2011-2012 2012-2014
Riparian Buffer Easement Program - Phase II (2012-2013)
Feedlot Water Quality Management Program (2012-2014)

Rock County
SWCD Programs
SWCD Reports
Rock County Local Water Management Plan 2017
Discovery Farms Minnesota (2009-2018)
Wellhead Protection Conservation Easement Program – Phase I (2010-2011)
Rock River Turbidity and Fecal Coliform Reduction (2011-2012)
Riparian Buffer Easement Program - Phase II (2012-2013)
SSTS Imminent Health Threat Abatement Grant Program 2012-2014
Feedlot Water Quality Management Grant Program 2013-2015
Rock River Conservation Drainage Water Management Demonstration Sites (2013-2015)

Water Plans

Water Plans:

Rock River Watershed
Percent of County in Watershed

Water Plan Links
Murray County LWMP 2007-2017 amended 2012
Nobles County LWMP 2009-2018
Pipestone County LWMP 2004-2014 amended 2009
Rock County LWMP 2006-2015 amended 2011

Local Water Management Overview
County Comprehensive Local Water Management - BWSR

Strategy - N Reduction

Strategy - N Reduction:

Minnesota Nutrient Strategy Overview
Nitrogen Science
Strategies for Nutrient Reduction - Wastewater

Planning Tools

Minnesota Watershed Nitrogen Reduction Planning Tool - Nitrogen BMP Spreadsheet (Lazarus et al., 2013)

Nitrogen Priority Watersheds & Reduction Milestone

Nitrogen Priority Watersheds	Reduction Milestone

Source: The Minnesota Nutrient Reduction Strategy , Chapter 4: Management Priorities and Recent Projects (2013)

Priority Sources
Priority sources are determined on a basin scale, although it should be noted that different sources may be more or less important at the local scale. Priority sources at the HUC8 scale or smaller will be determined through watershed planning efforts at that scale.

Source: The Minnesota Nutrient Reduction Strategy , Chapter 4: Management Priorities and Recent Projects (2013)

Example BMP Scenario for Nitrogen Reduction
The Minnesota Nutrient Reduction Strategy - MPCA
Excerpts from Chapter 5: Point and Nonpoint Source Reductions

Source: The Minnesota Nutrient Reduction Strategy , Chapter 4: Management Priorities and Recent Projects (2013)

See "Economics" Tab for a Watershed BMP Nitrogen Reduction Scenario.

Strategy - P Reduction

Strategy - P Reduction:

Minnesota Nutrient Strategy Overview
Phosphorus Science
Strategies for Nutrient Reduction - Wastewater

Phosphorus Priority Watersheds & Reduction Milestone
The Minnesota Nutrient Reduction Strategy - MPCA
Excerpts from Chapter 4: Management Priorities and Recent Projects

Phosphorus Priority Watersheds

Source: The Minnesota Nutrient Reduction Strategy (2013)

Priority Sources
Priority sources are determined on a basin scale, although it should be noted that different sources may be more or less important at the local scale. Priority sources at the HUC8 scale or smaller will be determined through watershed planning efforts at that scale.

Source: The Minnesota Nutrient Reduction Strategy , Chapter 4: Management Priorities and Recent Projects (2013)

Agricultural BMPs
Example BMP scenario for Phosphorus Reduction
The Minnesota Nutrient Reduction Strategy - MPCA
Excerpts from Chapter 5: Point and Nonpoint Source Reductions

Source: The Minnesota Nutrient Reduction Strategy, Chapter 5: Point and Nonpoint Source Reductions (2013)

Conservation Practices

Conservation Practices:

Watershed Summary
Rock River Watershed - MPCA

Conservation Practices
Conservation Easements - BWSR
Conservation Implementation - BWSR
Interactive Conservation Easement Map RIM - BWSR
Conservation Practices - MDA

BMP Summary
Excerpts from The Minnesota Nutrient Reduction Strategy - MPCA
Chapter 5 - Point and Nonpoint Source Reductions
Appendix C - Agricultural BMPs

Because agricultural sources contribute the bulk of the statewide nitrogen load and a substantial portion of the phosphorus load, nitrogen and phosphorus reductions from agricultural sources are key to successfully achieving the milestones. Recommended agricultural BMPs and strategy options for promoting adoption of the BMPs to address phosphorus and nitrogen are provided in the links above.

Phosphorus: Based on the SPARROW model and the source attributions developed in the Detailed Assessment of Phosphorus Sources to Minnesota Watersheds (Barr Engineering 2004), agricultural sources contribute an estimated 38 percent of the statewide phosphorus load. A large part of the remaining phosphorus load is due to stream channel erosion, much of which is indirectly affected by agricultural runoff and intensive drainage practices (Schottler et al. 2013).

Nitrogen: Based on the Nitrogen in Minnesota Surface Waters study (MPCA 2013), agriculture contributes 73 percent of the statewide nitrogen load in a typical year.

See "Strategy - N Reduction" and "Strategy - P Reduction" Tabs for example BMP Scenarios for Nitrogen and Phosphorus Reduction.

Models

Models:

Minnesota Watershed Nitrogen Reduction Planning Tool - Nitrogen BMP Spreadsheet (Lazarus et al., 2013)

Minnesota Nutrient Reduction Strategy SPARROW - (MPCA, 2013)

GSSHA Model – Agricultural Water Certification Program – GSSHA Model – (MDNR, In Progress)

Nutrient Tracking Tools

Nutrient Tracking Tools:

USDA-NRCS Nutrient Tracking Tool – Tarleton State (Texas Example)

NTT estimates the nutrient and sediment load leaving a farm field through surface water runoff and leaching below the rooting zone and can be used to quantify the water quality benefits of different agricultural management systems and conservation practices. Designed and developed by the USDA Natural Resources Conservation Service (NRCS), USDA Agricultural Research Service (ARS), and Texas Institute for Applied Environmental Research at Tarleton State University (TiAER), NTT is intended for use by agricultural professionals or others familiar with farm procedures and conservation practices.

Ag BMP Assessment and Tracking Tool – Houston Engineering
Solutions for improving impaired waters often rely on the use of agricultural best management practices (BMPs). The goal of this project is to collect and disseminate thorough and accurate information on the use and effectiveness of agricultural BMPs in the State of Minnesota. Stakeholders can use this information to inform, mock-up and track their BMP implementation strategies.

AG BMP Database - Houston Engineering
The goal of the Ag BMP Database is to provide a comprehensive source of information on the application and effectiveness of agricultural BMPs within the State of Minnesota. The database was developed to hold information on BMPs that are commonly used in the State to address water quality impairments for: sediment, nitrogen, phosphorus, and bacteria.

Ecological Ranking Tools
Watershed Health Assessment Framework - MDNR
The Watershed Health Assessment Framework (WHAF) provides a comprehensive overview of the ecological health of Minnesota's watersheds. By applying a consistent statewide approach, the WHAF expands our understanding of processes and interactions that create healthy and unhealthy responses in Minnesota's watersheds. Health scores are used to provide a baseline for exploring patterns and relationships in emerging health trends.

Ecological Ranking of Parcels for Prioritizing Conservation Activities – NRRI
This site provides a mapping tool by which natural resource managers can visualize and interact with a high resolution map of the spatial data layers. Managers have the ability to specify the relative importance of habitat, soil erosion potential, or other components of the Environmental Benefits Index - a score which represents a summary of the above factors., and view how the ecological ranking of parcels changes under different scenarios.
http://beaver.nrri.umn.edu/EcolRank/

Economics

Economics:

FUNDING GUIDES
Conservation Practices - Funding Guide, MDA
This Minnesota Department of Agriculture website provides an overview of financial and technical assistance for nutrient management.

Conservation Funding Guide: Practice & Payment Information, MDA
On this Minnesota Department of Agriculture website, you can select a conservation practice and compare payments.

COST ANALYSIS PLANNING TOOLS
Minnesota Watershed Nitrogen Nitrogen Reduction Planning Tool
Minnesota Watershed Nitrogen Reduction Planning Tool - Nitrogen BMP Spreadsheet (Lazarus et al., 2013)
The Watershed Nitrogen Reduction Planning Tool (Excel Spreadsheet) was developed as part of the Nitrogen in Minnesota Surface Waters Study by researchers at the University of MInnesota and Minnesota Pollution Control Agency. The project purpose was to develop a framework for a watershed nitrogen planning aid that could be used to compare and optimize selection of "Best Management Practices" (BMPs) for reducing the nitrogen load from the highest contributing sources and pathways in the watershed.

Overview of Nitrogen Reduction Planning Tool
NBMP Tool - Maps
NBMP Spreadsheet (Excel)

Cost Analysis of Minnesota Nutrient Reduction Strategy
An analysis of costs is provided in Chapter 5.5 of the Minnesota Nutrient Reduction Strategy for both wastewater nutrient removal and agricultural BMP implementation.
Excerpts from Chapter 5: Point and Nonpoint Source Reductions
Appendix C: Program Recommendations

Wastewater

Source: Minnesota Nutrient Reduction Strategy, Chapter 5: Point and Nonpoint Source Reductions, 2013

Agricultural BMPs

Source: Minnesota Nutrient Reduction Strategy, Chapter 5: Point and Nonpoint Source Reductions, 2013

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