SCIENCE BRIEFING BOOKLET
LE SUEUR RIVER WATERSHED
CONTENTS
The Le Sueur River plays an
important role in the Minnesota
River Basin and broader
Mississippi River drainage.
This booklet summarizes some
of the latest scientific research
findings related to the Le Sueur
River Watershed. It includes
excerpts from researchers from
across the state and country who
have engaged in research to better
understand river dynamics, the
complex sediment and nutrient
delivery and transport, the status
of pollution, and broader health of
the watershed. Where possible, the
primary research is listed and can
be found on the website:
www.lesueurriver.org
Produced by
Water Resources Center,
Minnesota State University,
Mankato
Produced for
Le Sueur River Watershed Network
WRC Project Team
Kimberly Musser
Rick Moore
Courtney Thoreson
Nate Henry
Abigail Juelfs
Jessica Nelson
Andrew Stevens
Lina Wang
Overview
Watershed Overview
Watersheds Across Scales
Geologic History
Le Sueur River Paloechannel
Minnesota Valley Creation
Landscape History
Historic Vegetation
Historic and Present Wetlands
Land Use
Land Use
Agriculture
Crop Types
Hydrology
Changes in Hydrology
Drainage
River Flow
Channel Changes
Water Quality
Resource Concerns
Water Quality Standards
Impaired Waters
Recreation
Aquatic Life
Fish Consumption
Sediment
Sediment Sources
Sediment Load
Nitrogen
Phosphorus
Pesticides
Acetochlor
Downstream Impacts
Lake Pepin
Gulf of Mexico
Green Lakes
Lakes
Lakes
References
Special Thanks to
Brooke Hacker
Leo Getsfried
Jon Lore
Patrick Moore
Chad Wittkop
Citizen Advisory Committee
Technical Advisory Committee
Le Sueur River Watershed Booklet (5/30/2013) p. 2
WATERSHED OVERVIEW
What is a Watershed?
A watershed is the land area
that drains water to a particular
stream, river, or lake. It is a land
feature that can be identified by
tracing a line along the highest
elevations between two areas on
a map, often a ridge.
Le Sueur River Watershed
The Le Sueur River watershed
covers a 710,832 acre area in
south central Minnesota within
the Minnesota River Basin. The
watershed drains northwest into
the Blue Earth River which outlets
into the Minnesota River near
Mankato, Minnesota.
Watershed Diagram
The diagram (below) suggests
a typical watershed that starts
with small headwater streams in
higher elevations of the drainage
basin. Water flows down hill from
the drainage divide into larger
streams, eventually joining a
river. As more tributary streams
join the river, the volume of water
increases. This river eventually
flows downstream into an even
larger river at the confluence.
A watershed is like a funnel:
collecting all water within the
drainage area and channeling
it into a stream, river, or lake.
Headwater streams
River
Le Sueur River Watershed Booklet (5/30/2013) Confluence with
larger river
p. 3
Watersheds across scales
Minnesota River Basin
Major Watershed
(Le Sueur River Watershed)
Sub Watershed
(Maple River Sub Watershed)
Minor Watershed
Le Sueur River Watershed Booklet (5/30/2013) p. 4
GEOLOGIC HISTORY
of the Minnesota River is known
A Summary of the Geology of
the Le Sueur River Paleochannel to geologists today as Glacial
As glaciers receded from our
region 15,000 years ago, large
lakes pooled at the margin of the
glacial ice, which blocked drainage
of runoff and meltwater to the
north. One such lake, Glacial
Lake Minnesota, covered much of
the Blue Earth River Watershed.
Initially this lake drained to the
east via the present-day Cannon
River valley. When the front of the
glacier receded to the area around
Mankato, a new, lower drainage
pathway opened via the Minnesota
River valley. Drainage of Glacial
Lake Minnesota via this route
initiated erosion of the presentday Minnesota River valley from
Mankato to its confluence with the
Mississippi.
As ice continued to recede,
meltwater streams fed this new
drainage and began to etch the
course of the Minnesota River
valley above Mankato. When glacial
ice receded into North Dakota and
northern Minnesota, a much larger
glacial lake system developed. Now
known to geologists as Glacial Lake
Agassiz, it grew to twice the size
of all five North American Great
Lakes (Superior, Huron, Michigan,
Erie, and Ontario) combined.
This massive lake drained via the
Minnesota River valley in at least
two distinct phases—from 13,500
to 12,800 years ago, and 11,500 to
10,600 years ago—with peak flow
events capable of filling the entire
width of the present-day valley.
This meltwater-enhanced version
River Warren, named after G.K.
Warren, a 19th century army
general and surveyor who first
noted the unusually small size of
the Minnesota River relative to its
valley.
Following the last of the major
River Warren floods, the
Minnesota River valley in the
Mankato area began to take its
present form—with one major
exception. Today the Blue Earth
River is the major tributary flowing
into the Minnesota River at Land
of Memories Park. Two miles
above its mouth, the Blue Earth
River receives flow from its largest
tributary, the Le Sueur River, just
west of the intersection of highway
66 and county road 90.
The nearly six miles of abandoned
Le Sueur valley created by this
event looks much the same
as it did when river water last
flowed through it 11,000 years
ago. Geologists from Minnesota
State University, Mankato were
recently able to determine the
age of the capture event by
testing sediments deposited by
the ancient Le Sueur River using
a technique called Optically
Stimulated Luminescence (OSL),
which measures the age of the
last exposure of quartz grains
to direct sunlight. Although the
capture event occurred relatively
early on in the Le Sueur’s history,
it gives scientists an opportunity
to study how natural erosion rates
have changed through time in the
watershed, which can inform
our understanding of erosion
and water quality issues today.
The paleochannel (ancient river
valley) is also a unique part of our
regional geologic heritage, as clear,
relatively recent cases of stream
capture of this scale are relatively
rare.
If you were to visit the Mankato
area before about 11,000 years
ago, you would have encountered
a very different configuration of
rivers. Instead of flowing into the
Blue Earth River, the Le Sueur
River flowed independently into
the Minnesota River, near the
intersection of Stoltzman Road
and Riverfront Drive. Stoltzman
Road follows the ancient Le Sueur
valley (or paleochannel) to the
entrance of Rasmussen Woods
Park, where a narrow valley was
carved through resistant bedrock. A
small accumulation of river-rounded
gravels in the soils above the ‘Cliffs’
area of the park is further evidence
that a large river once flowed
through the park.
Le Sueur River Watershed Booklet (5/30/2013) p. 5
Le Sueur Paleochannel
The paleochannel meets the Red
Jacket Trail and highway 66 at the
west edge of Rasmussen Park,
and follows them to Indian Lake
Road, where it continues south.
The paleochannel then briefly
follows highway 90 before turning
to the west at Copper Mountain
Drive, and meeting the present
day Le Sueur. The dramatic
change in course of the Le Sueur
River occurred following a stream
capture event. About 11,000 years
ago, the Blue Earth River captured
the flow of the neighboring river,
offering the Le Sueur a shorter,
steeper path to the Minnesota
River.
Pre-capture configuration
(11,000 years ago)
Modern configuration
The exact cause of this capture
may never be known, but it was
likely triggered by relatively rapid
erosion rates in the lower Blue
Earth River valley, which caused
either a ravine or cutbank to erode
into and capture flow of the Le
Sueur River.
Text and graphics courtesy of Chad Wittkop,
Geology Professor, Minnesota State University,
Mankato.
Belmont, P., Gran, K., Jennings, C.E., Wittkop
C., and Day, S.S., 2011, Holocene landscape
evolution and erosional processes in the Le
Sueur River, central Minnesota, in Miller, J.D.,
Hudak, G.J., Wittkop, C., and McLaughlin, P.I.,
eds., Archean to Anthropocene: Field Guides
to the Geology of the Mid-Continent of North
America: Geological Society of America Field
Guide 24, p. 439-455.
Le Sueur River Watershed Booklet (5/30/2013) p. 6
Minnesota Valley Creation
“The Minnesota River valley was carved during
catastrophic drainage of glacial Lake Agassiz at the
end of the late Pleistocene. The ensuing base-level
drop on tributaries created knickpoints that excavated
deep valleys as they migrated upstream. A sediment
budget compiled in one of these tributaries, the Le
Sueur River, shows that these deep valleys are now
the primary source of sediment to the Minnesota
River.
To compare modern sediment loads with preEuropean settlement erosion rates, we analyzed
incision history using fluvial terrace ages to
constrain a valley incision model. Results indicate
that even though the dominant sediment sources
are derived from natural sources (bluffs, ravines,
and streambanks), erosion rates have increased
substantially, due in part to pervasive changes in
watershed hydrology”
(Gran et al, 2011).
Lake Agassiz
Minnesota River Valley was carved by glacial River
Warren.
Google map of ravines.
Karen B. Gran, Patrick Belmont, Stephanie S. Day, Noah Finnegan, Carrie Jennings,
J. Wesley Lauer, Peter R. Wilcock. Landscape evolution in south-central Minnesota
and the role of geomorphic history on modern erosional processes. GSA Abstract,
April 2011.
LIDAR map of ravine.
Le Sueur River Watershed Booklet (5/30/2013) p. 7
landscape history
Early explorers accounts and
paintings provide glimpses of
what the landscape resembled
before widespread European
settlement. Many explorers
wrote descriptions about
the rich flora and fauna and
Native Americans inhabiting
the Minnesota River valley in
the 1700s and 1800s. They
described a landscape covered
in tall grass, wetlands, shallow
lakes and forested areas with
numerous American Indian
tribes living along the Minnesota
River.
“Early explorers …described
many features we can no longer
see, including huge prairie fires
roaring across the landscape,
abundant prairie chickens
and “prairie dogs”, flocks of
whooping cranes feeding in wet
meadows, and beds of wild rice
in many lakes and Minnesota
River backwaters. Bison and elk
were vanishing by then. Though
the explorers encountered many
difficult circumstances, they
often described the landscape
with awe” (MCBS, 2007).
EXPLORER’S ACCOUNT:
Joseph Nicollet
Field notes from traveling in the
Le Sueur River Watershed in 1838.
Le Sueur River
They camped upon the banks of the Le
Sueur River. The bed of the river was 40
feet wide, full of gravelly banks, current swift
but little water at this season. The river is
called Riviere la Prelle. Its name derives
from the Equisetum uliginosum [E. fluviatile
– common horsetail] which grows very
abundant along its banks (September 22,
1838).
French Explorer Joseph Nicollet
Big Cobb & Maple River
Crossed the [Big Cobb] River, passed a
little wood of overcup oaks [Quercus lyrata],
here we encamped on the [Maple River]…
the borders of the Swamps in the ripe seed
and still sound green foliage (September
24, 1838).
Little Cobb
[After one more mile of woods], we reached
the high prairie; we passed [Perch Lake]
and encamped close by the [Little Cobb]
River at the right bank, where we met a
band of Wehpekuteh Indians [Dakota]
encamped [nearby] (September 23, 1838).
When they met the Little Cobb River on
the way back, they camped there for a
night and they saw smoke from a prairie
fire and it continued into the next day in
which Nicollet and the others got nervous
and uneasy about. Nicollet commented that
“smoke from the burning prairie obscured
the sky.” He observed that this condition
lasted into the following day and “kept us
very uneasy under a strong southwest wind”
(October 9, 1838).
Nicollet’s map of the Hydrographical Basin of
the Upper Mississippi River, 1843.
Seth Eastman’s painting of the Prairie at the
mouth of the Minnesota River, 1830s.
Source: Bray, Edmund C. and Martha Coleman Bray (Eds.). Joseph N. Nicollet on the Plains and Prairies. St. Paul: Minnesota Historical Society Press,
1993.
Le Sueur River Watershed Booklet (5/30/2013) p. 8
historic vegetation
PRAIRIES & BIG WOODS
PREDOMINATE
Adapted from Marschner, F.J. 1974.
The maps below show
Minnesota’s pre-European
settlement vegetation that was
gathered by the Public Land
Surveys from 1853-1870. In
the Le Sueur River Watershed,
prairie, wet prairie, and big
woods were the dominant
vegetation types at that time.
PRESETTLEMENT
VEGETATION LEGEND
Le Sueur River Watershed Booklet (5/30/2013) p. 9
historic wetlands
Historic Extent of Wetlands
Wetlands historically dotted
the Le Sueur River Watershed.
Wetland complexes were
once common on the prairiedominated landscape. Early
explorer’s accounts described
the prairie and wetlands
extending as far as the eye
could see. Settlers moved in and
drained the wetlands to farm the
rich, productive farmland. Today,
almost 90 percent of prairie
wetlands across Minnesota
have been lost.
The map above depicts probable historic wetlands based on MPCA analysis of soils and elevation.
The base layer is the Public Land Survey Plats from 1853-1870.
Le Sueur River Watershed Booklet (5/30/2013) p. 10
wetlands today
Changes in Hydrology
The movement of water across
the broader Minnesota River
Basin before Euro-American
settlement would have been
different from today. The
landscape consisted of a
vast prairie pockmarked with
wetlands. The prairie sod
allowed rapid infiltration of
precipitation. The wetlands
were connected to subsurface
hydrology. The flows of the rivers
were likely sustained by ground water
inputs for most of the year. As prairies
were plowed precipitation followed
surface water runoff paths into lakes
and wetlands which were ditched
and drained in many areas to remove
water rapidly from the landscape thus
enabling large-scale farming (MPCA,
1997).
The map above shows current wetlands and lakes in the Le Sueur River Watershed (National Wetlands Inventory, 1982).
Le Sueur River Watershed Booklet (5/30/2013) p. 11
land use today
Farmland Predominates
Agriculture accounts for the
majority of land use activities
within the watershed. Land use
within the Le Sueur watershed is
primarily agricultural, accounting
for approximately 84 percent of
the available acres. Two-year
corn/soybean rotations comprise
approximately 93 percent
of cropped lands within the
watershed (USDA-NRCS, 2009).
Farm land within the Le Sueur
Watershed is highly drain tiled.
Overall land cover percentages in the
watershed are: Agriculture (83.9%), urban
(6.5%) wetlands (3.5%), forest (1.4%),
grassland (2.4%), and open water (2.1%)
Le Sueur River Watershed Booklet (5/30/2013) p. 12
agriculture
Approximately 96.5 percent
of the watershed is in private
ownership with the state owning
approximately 3.3 percent.
Median Household Income:
$42,629
Livestock
Farms
1,803 farms and 1,700
operators
1,245 full time operators
455 part time operators
Swine and turkey are the most
common livestock in the Le Sueur
River Watershed.
Farms: Full and Part Time Operators
Livestock & Poultry
1,800
700,000
1,600
Farm Size
1,400
455
600,000
1,200
450
500,000
400
1,000
Part Time Operators
350
800
Full Time Operators
300
600
250
400,000
300,000
200,000
400
200
Animal Units
Ownership
100,000
200
150
0
100
0
1
Other
Swine
Turkey
Cattle - Cattle - Chicken
Beef
Dairy
50
0
1-49
acres
50-179
acres
Farmland
180-499
acres
500-999
acres
1,000
acres or
more
Farmland in the watershed is
classified primarily as: prime
farmland, farmland of statewide
significance, and prime
farmland if drained.
Soils
Soils are predominantly glacial till
plains. There are many hydric and
partially hydric soils. Hydric soils
are defined as “soils that formed
under conditions of saturation,
flooding, or ponding long enough
during the grouping season to
develop anerobic conditions in the
upper part.”
Feedlots
There are currently 895 permitted
feedlots and 52 permitted
wastewater dischargers
(MPCA, 2012).
Sources: NRCS Rapid Assessment, 2009.
& NASS Agricultural Statistics
Le Sueur River Watershed Booklet (5/30/2013) p. 13
crop types
Corn and Soybeans - Primary Crops
Corn and Soybeans are the predominant crop in the
Le Sueur River Watershed today.
The map above depicts crop types in the Le Sueur River Watershed based on National Agricultural
Statistic Service Database (NASS, 2010).
Le Sueur River Watershed Booklet (5/30/2013) p. 14
changes in hydrology
1855
The 1855 map illustrates
the likely extent of wetlands
during the public land
survey from 1853-1870.
Beauford Watershed
The maps (right) depict the
changes in hydrology in a small
watershed in the Le Sueur River
Watershed - Beauford (location
map above). Researchers
examined historic aerial photos
over time to assess changes in
the extent of wetlands, open and
subsurface drainage systems.
The study found that Beauford
watershed lost most of its
wetlands from 1855 - 1938 when
the county drainage network
was installed in Blue Earth
County. The study found a direct
correlation between wetland
loss and installation of open
surface drainage systems and
subsurface drainage systems.
The amount of wetland loss
correlates with other scientific
research that estimates that 90
percent of wetlands have been
lost in this part of Minnesota
(Kuehner, 2004).
Maps (right) Source: Nate Henry & Rick
Moore. 2013. Comparison of Spatial and
Temporal Trends of Wetlands to Surface and
Subsurface Hydrology. MSU WRC
1938
By 1938, the county
drainage network (shown
in yellow) was in place and
the majority of wetlands
had been drained.
1991
By 1991, more subsurface
tile (shown in red) was
recorded.
2011
Additional expansion
of subsurface tile was
recorded. Researchers
noted a slight increase in
wetland areas in 20032011 likely due to the
implementation of the
Conservation Reserve
Program (CRP), Reinvest
in Minnesota (RIM), and the
Wetland Reserve Program
(WRP).
Le Sueur River Watershed Booklet (5/30/2013) p. 15
DRAINAGE
Changes in Hydrology
The map below shows percent
potential tile installation across
the Le Sueur River Watershed
based on the criteria below.
Potential tile map based on the following criteria: 2009 USDA Crop data for row crops; 30-meter DEM and slope ranging from
0-3%; and SSURGO soil drainage classes of very poorly drained or poorly drained soils.
Le Sueur River Watershed Booklet (5/30/2013) p. 16
RIVER FLOW
Increasing River Flows
River flows have increased over recent decades.
Many researchers have been trying to understand
what is driving increased flows since the 1940s in area
watersheds.
Many researchers are attributing increased flows to
three primary factors:
(1) An upward trend of precipitation amounts and
intensities.
(2) Reduced spring evapotranspiration and increased
spring runoff due to the gradual shift from perennial
plant cover (prairie, pasture) and winter annuals to row
crops.
(3) Increasing density of tile and ditch drainage to
remove water for row crop production.
Runoff Ratio
Runoff Ratio
Water yield normalized to precipitation
The chart above illustrates the increase in runoff ratio for the
Blue Earth, Le Sueur and Cottonwood River Watersheds
from 1940s to the present (Schottler, 2013)
Water Yield = was calculated for each
watershed by dividing flow by the respective
watershed area.
Runoff Ratio = is water yield divided by
precipitation.
Increased Flow and Water Quality
The increase in streamflow was shown to be
correlated to widening of the river channels
over the past 70 years. Rivers that had
significant increase in annual flow volume
experienced channel widening of 10-40%,
whereas rivers with no flow increase had no
change in channel width.
A recent trend analysis for flow also found
results skewed by season: a large and
significant increase in the spring (May-June)
with much smaller changes in the fall (SeptOct) (Schottler, 2013).
“Changes in streamflow can have important
water-quality consequences such as
increased river erosion, including streamchannel widening, resulting in greater
sediment loading and increased river
turbidity.” Researchers noted that efforts
to mitigate excessive sediment loads and
turbidity must include strategies to manage
watershed hydrology and reverse conditions
contributing to higher river flows (Schottler,
2013).
Le Sueur River Watershed Booklet (5/30/2013) p. 17
CHANNEL CHANGES
Channel Evolution
Premodified
River systems are very complex,
constantly changing and
evolving. The diagram to the
right depicts a channel evolution
model that generalizes how
rivers change over time.
This stage is a stable system at
equilibrium, typically a meandering
or straight channel that is well
vegetated. The system is in frequent
contact with its floodplain.
Disturbed
Something pushes the system out of
equilibrium. Flow increases can push
the system out of equilibrium due to
the increased stream power.
Degradation
As stream flow increases, the river
begins to incise to adjust to the lower
channel base height.
In the Le Sueur Watershed
Degradation & Widening
Currently, much of the Le Sueur
River and major tributaries are
incising and widening due to an
increase in flow. Beyond water
quality impacts, channel widening
can also result in the loss of
productive land or property.
During the down cutting of the
channel, bank stability decreases as
bank height and the steepness of the
bank increases. This leads to bank
destabilization, mass wasting of the
bank, and channel widening.
Aggradation & Widening
Aggradation of the channel is the
dominant feature and channel
widening continues. (Reduction of
stream power and high sediment
loads cause portions of the system
to begin aggrading).
Quasi equilibrium
Degradation = a lowering of
base level over time due to
channel incision processes
(lowering, incising).
Aggradation = a raising
of local base level due to
sediment depostional process
over time (adding material).
Adapted from Simon and Hupp, 1986
If the system remains disturbance free
a new quasi equilibrium will be reached
(Simon and Hupp, 1986). While it is
true that there eventually will be a new
equilibrium, scientists don’t know how
much more channel degradation or
widening will occur before a new level
of stability is reached or how long it will
take to get there.
Le Sueur River Watershed Booklet (5/30/2013) p. 18
CHANNEL CHANGES
Channel Widening Minnesota River
Studies have indicated that the
main channel of the Minnesota
River has widened in places
over the past 70 years by about
50 percent contributing 100,000s
of tons of gross sediment per
year (Lenhart, 2011). On the
Minnesota River mainstem,
researchers have noted a
loss of sinuosity, floodplain
disconnection, and increased
streamflow. Minnesota River
Basin streams are actively
adjusting to changes in flow
leading to higher rates of
channel erosion and less
floodplain deposition
(Lenhart, 2011).
The channel is widening
throughout the system. The
entire cross section of the river
channel is changing. A study
at the Minnesota River (near
Jordan) researchers examined
air photos and noted an annual
rate of increase of 1.41 feet
(0.43 meters) per year from the
1940s to the present
(Gran, 2011).
Channel Widening Le Sueur River
MDNR researchers have been
discovering similar channel
changes in the Le Sueur River. Air
photo analysis from 1939 to 2010
indicates river widening (photos
above). With hydrological changes
(e.g. tiling, loss of water storage,
and intense rainfall events) in the
Le Sueur River Watershed, we are
seeing channel evolution occur in
all areas of the watershed.
Premodified
River Stability
River Stability is the ability of a
stream to transport the sediment
and flows produced by its
watershed, while maintaining a
consistent dimension, pattern,
and profile without aggrading or
degrading (Rosgen, 1996).
Current incision and widening in
the Le Sueur River and tributaries
is a result of the rivers adjusting to
changes in hydrology and climate.
Measured incision and widening
in the Le Sueur River and its
tributaries suggest these rivers
are not stable. This is likely due to
recent changes in hydrology, land
use, and other impacts.
Incising and Widening
Channel Downcutting
Over decades, the river channel
has widened and deepened, putting
more pressure on its banks and
bluffs, which collapse under the
pressure (MPCA, 2012).
Le Sueur River Watershed Booklet (5/30/2013) p. 19
resource concerns
County Soil and Water
Conservation Districts in the
watershed have identified the
following resource concerns as
top priorities for conservation
and cost sharing efforts. This
section is excerpted from the Le
Sueur River: Rapid Watershed
Assessment (NRCS, 2009).
Sediment and Erosion
Control Excessive amounts of
suspended solids from cropland,
urban lands, streambanks
and streambeds is a primary
threat to area waters. Working
hand-in-hand with stormwater
pollution and prevention plans
and nutrient management
plans, counties in the watershed
seek to retain water on the
landscape to reduce flooding
and subsequent soil erosion,
and improve water resources.
Stormwater Management
Local districts recognize that
stormwater runoff volume
from impervious surfaces will
likely increase as development
of the watershed continues.
New developments located
adjacent to existing cities, near
lakeshore or simply placed
in a rural setting need to be
tightly regulated to prevent
the associated nutrient and
sediment runoff impacts to our
water resources.
Drinking Water and Source Water Protection
Parts of the region are particularly susceptible to groundwater
contamination. Ease of infiltration, aging septic systems, abandoned
wells and historical tiling practices threaten public drinking water supplies.
Districts promote public health, economic development and community
infrastructure by insuring a potable drinking water supply for all residents.
Feedlot and Animal Waste Management
Managing farms to minimize excess nutrients, pathogens, and odors
released into the environment is important to the health of surface and
ground water. Agricultural operations need to adequately maintain cropping
systems to reduce nonpoint pollution, while feedlot operations need to
contain their manure storage areas. Erosion and sedimentation from these
operations needs to be closely monitored to reduce the levels of nutrients
entering our surface water resources.
Nutrient Management
Excessive amounts of nutrients, namely phosphorus and nitrogen,
contaminate ground and surface waters and create nuisance algae
presence in area waters. Major contributors are cropland, urban grasses,
municipal wastewater, aging or non-compliant septic systems, and internal
cycling.
Wetland Management
Due to the historical draining of much of the areas wetlands and homgenic
agricultural practices, priority is given to both wetland preservation
and restoration. Wetlands that have been filled and drained retain their
characteristic soil and hydrology, often allowing their natural functions
to be reclaimed. Restoration is a complex process requiring planning,
implementation, monitoring, and management.
Drainage Management
The Area’s agricultural dominance, coupled with vast surface water
resources has resulted in a “tug of war” between the need for cropping
systems and desire for suitable water recreation. To enhance crop
production, tiling systems have been improved and wetlands have been
drained, causing drainage systems to be inundated with increased volumes
of nutrient rich water. These fast flowing systems need to be addressed
now - priority issues include potential storage areas, wetland restoration
and effective management of the current drainage system program.
Source: NRCS Rapid Watershed Assessment, 2009.
Le Sueur River Watershed Booklet (5/30/2013) p. 20
water quality standards
Water quality standards are
the fundamental benchmarks
by which the quality of
surface waters are measured
and used to determine
impairment. Use attainment
status is a term describing
the degree to which
environmental indicators are
either above or below criteria
specified by Minnesota Water
Quality Standards
(Minn. R. 7050, 2008).
Designated Beneficial Uses
These standards can be
numeric or narrative in nature
and define the concentrations
or conditions of surface waters
that allow them to meet their
designated beneficial uses,
such as for fishing (aquatic life),
swimming (aquatic recreation)
or human consumption (aquatic
consumption). All surface waters
in Minnesota, including lakes,
rivers, streams, and wetlands
are protected for aquatic life and
recreation where these uses are
attainable.
Numeric water quality standards
represent concentrations of specific
pollutants in water that protect a
specific designated use. Ideally, if the
standard is not exceeded, the use will
be protected. The MPCA uses a variety
of tools to fully assess designated uses.
Assessment methodologies often differ
by parameter and designated use.
Furthermore, pollutant concentrations
may be expressed in different ways
such as chronic value, maximum value,
final acute value, magnitude, duration
and frequency.
Narrative standards
are statements of conditions in and on
the water, such as biological condition,
that protect their designated uses.
Interpretations of narrative criteria for
aquatic life support in streams are
based on multi-metric biological indices
including the Fish Index of Biological
Integrity (F-IBI), which evaluates the
health of the fish community, and the
Macroinvertebrate Index of Biological
Integrity (M-IBI), which evaluates the
health of the aquatic macroinvertebrate
community.
Protection of aquatic
life means the maintenance
of healthy, diverse and
successfully reproducing
populations of aquatic
organisms, including fish and
invertebrates.
Protection of recreation
means the maintenance
of conditions suitable for
swimming and other forms of
water recreation.
Protection of
consumption means
protecting citizens who eat
fish inhabiting Minnesota
waters or receive their
drinking water from water
bodies protected for this use.
Sources:
Minnesota Pollution Control Website, 2012
https://www.revisor.leg.state.mn.us/
rules/?id=7050
Le Sueur River Watershed Booklet (5/30/2013) p. 21
impaired waters
The map (left) shows the water bodies in the
Le Sueur River Watershed that are meeting
water quality standards and supporting
designated uses.
The map (left) shows the water bodies in
the Le Sueur River Watershed that are
not meeting water quality standards and
supporting designated uses.
Le Sueur River Watershed Booklet (5/30/2013) p. 22
recreation
Protection of recreation means the maintenance of conditions
suitable for swimming and other forms of water recreation.
Is it safe to swim and
recreate in the lakes and
rivers of the Le Sueur
River Watershed?
Bacteria Levels and
Swimming
Disease-causing organisms
(pathogens) in water bodies are
difficult to measure, so indicators
like E. coli bacteria are used to
illustrate the likelihood that a
water body contains pathogens.
Although viruses and protozoa
cause many of the illnesses
associated with swimming
in polluted water, monitoring
for E. coli will tend to indicate
fecal contamination. Untreated
sewage or livestock waste
released into the water can
expose swimmers to bacteria,
viruses, and protozoa.
Children, the elderly, and people
with weakened immune systems
are most likely to develop
illnesses or infections after
swimming in polluted water. The
most common illness associated
with swimming in water polluted
by sewage is gastroenteritis.
The illness can have one or
more of the following symptoms:
nausea, vomiting, stomachache,
diarrhea, headache, and fever.
Other minor illnesses associated
with swimming include ear,
eye, nose, and throat infections
(State of the Minnesota River,
2009).
Le Sueur River Watershed Booklet (5/30/2013) p. 23
aquatic life
Protection of aquatic life means the maintenance of healthy, diverse, and
successfully reproducing populations of aquatic organisms, including fish
and invertebrates.
How are fish and other
aquatic life doing?
Most of the assessed streams
and rivers currently do not
support aquatic life.
What is Aquatic Life Use?
MPCA researchers are charged
with evaluating the water quality
of streams and rivers using the
biological communities that live
there. The group is divided into
two areas of expertise: fisheries,
and benthic macroinvertebrates
or benthos. Researchers
also analyze biological data,
dissolved oxygen, turbidity,
chloride, pH and NH3 to
determine use status.
Le Sueur River Assessment
Report Findings
The map (right) shows what
streams are healthy enough to
support aquatic life (Aquatic Life
Use Supported Map). Only two
stream reaches were found to
be fully supporting of aquatic
life use in the Le Sueur River
Watershed (shown in green).
Most of the streams that were
assessed do not meet state
water quality standards for
aquatic life. (Aquatic biological
impairments are found
throughout the entire watershed
where assessments were made
(shown in red). Twenty-five (25)
new impairments of aquatic
life have been added to the Le
Sueur River watershed during
the 2010 assessment cycle.
FISH ASSESSMENTS
Number of assessed streams
found to be meeting state water
quality standards for aquatic life.
72 - TOTAL SAMPLED
MACROINVERTEBRATE
ASSESSMENTS
Number of assessed streams found
to be meeting state water quality
standards for aquatic life
.
63 - TOTAL SAMPLED
6 - FULLY SUPPORTING
Aquatic Life
4 - FULLY SUPPORTING
Aquatic Life
17 - NOT SUPPORTING
Aquatic Life
16 - NOT SUPPORTING
Aquatic Life
49 - NOT ASSESSABLE
due to channelization and
low flow
43 - NOT ASSESSABLE
due to channelization and low flow
Source: Minnesota Pollution Control
Agency’s Le Sueur River Monitoring and
Assessment Report (2012).
Le Sueur River Watershed Booklet (5/30/2013) p. 24
fish consumption
Le Sueur River Assessment
Report Findings
Fish were tested in the lakes
and rivers listed at right in
order to determine the levels
of Mercury, Perfluorochemicals
(PFCs), and Polychlorinated
biphenyls (PCBs). Assessment
results are summarzed here
and more detail can be found
in MPCA’s Monitoring and
Assessment Report.
Mercury - Northern pike,
walleye, and yellow perch were
collected from Madison Lake,
Reeds Lake, and Bass Lake.
Walleye in Madison Lake and
Northern Pike in Reeds Lake
exceeded the threshold for
impairment.
PFCs - In 2009, Madison
Lake was sampled for PFCs.
Northern pike, walleye and.
panfish species were sampled
and PFOS concentrations in all
samples were at or below the
laboratory reporting level.
PCBs - In 2008, the largest
carp and the two largest channel
catfish collected from the
LeSueur River were analyzed
for PCBs. Both channel catfish
were below the impairment
threshold but the carp was
above. Consequently, the fish
consumption advice for carp in
the LeSueur River is one meal
per month.
Source: Minnesota Pollution Control
Agency’s Le Sueur River Monitoring and
Assessment Report (2012).
Protection of consumption means protecting citizens who
eat fish inhabiting Minnesota waters or receive their drinking
water from water bodies protected for this use.
LAKES
MERCURY
Northern Pike
Walleye
Yellow Perch
PFCs
MADISON LAKE
REEDS LAKE
BASS LAKE
below
above
below
above
not sampled
below
not sampled
below
below
MADISON LAKE
Northern Pike
below
Walleye
below
Panfish
below
RIVERS
PCBs
LE SUEUR RIVER
Channel Catfish
below
Carp
above
Madison Lake
Reeds Lake
Lura Lake
BassLake
Le Sueur River Watershed Booklet (5/30/2013) p. 25
FISH CONSUMPTION
Is it safe to eat fish in the
Le Sueur Watershed?
Mercury and Fish
Consumption
The primary contaminants of
concern in the Le Sueur River
Watershed are mercury and
polychlorinated biphenyls, or
PCBs. In Minnesota, Mercury
contamination of fish is a welldocumented problem. Mercury
is tightly bound to proteins in
all fish tissue, including muscle.
There is no way to reduce the
amount of mercury in a fish
through cooking or cleaning it.
Fish Consumption Advisories
The Minnesota Department of
Health (MDH) advises people
to restrict their fish consumption
due to Mercury accumulation
in sport fish from lakes and
rivers. Large amounts of
Mercury in your body may
harm your nervous system. The
MDH issues fish consumption
advisories for lakes and streams
in Minnesota where fish have
been tested. The advisories
contain recommended rates
of consumption based on
contaminant levels in the fish.
Le Sueur River Consumption
Advisories
Current consumption advice for the Le
Sueur River includes:
- Carp in the Le Sueur River is one
meal per month.
Don’t Eat
Generally, MDH advises avoiding
Minnesota caught walleye longer than
20 inches, northern pike longer than
30 inches, and muskellunge. Nearly
all fish and shellfish contain traces of
methylmercury. However, larger fish
that have lived longer have the highest
levels of methylmercury because
they’ve had more time to accumulate it.
On the other hand, MDH advises that it
is safe to eat Minnesota caught: sunfish,
crappie, yellow perch, bullheads (one
meal per week).
Source: State of the Minnesota River Water Quality
Monitoring Report 2000-2008 (2009)
For More Information
The Department of Health website
is your best resource to learn more
about fish caught in particular rivers,
streams, and lakes.
Minnesota Department of Health’s fish consumption guidelines:
www.health.state.mn.us/divs/eh/fish/index.html
Consumption guidelines are also searchable by lake on the
Department of Natural Resources Lake Finder website.
www.dnr.state.mn.us/lakefind/index.html
Le Sueur River Watershed Booklet (5/30/2013) p. 26
SEDIMENT
What are Total Suspended
Solids (TSS)?
The transport of sediment is
a natural function of rivers.
Modification of the landscape
has accelerated the rate of
erosion of soil into waterways.
Increased runoff has resulted in
stream bank erosion. Elevated
sediment (suspended soil
particles) has many impacts.
It makes rivers look muddy,
affecting aesthetics and
swimming. Sediment carries
nutrients, pesticides, and other
chemicals into the river that may
impact fish and wildlife species.
Sedimentation can restrict the
areas where fish spawn, limit
biological diversity, and keep
river water cloudy, reducing the
potential for growth of beneficial
plant species.
of algae, cyanobacteria, heterotrophic
microbes, and detritus that is attached
to submerged surfaces in most aquatic
ecosystems) and favors undesirable
suspended algae. An overabundance of
algae (phytoplankton) further increases
turbidity, compounding the problem.
Fine-grained sediments that settle on
stream beds cover and degrade the
desirable rock and gravel substrates
that form essential habitats for
invertebrates and fish. During periods of
high turbidity, streams take on a murky
brownish-green cast, greatly reducing
their appeal (State of the Minnesota
River, 2009).
What is Turbidity?
Turbidity refers to how clear the
water is. The greater the amount
of TSS in the water, the murkier
it appears and the higher the
measured turbidity.
Why is Elevated TSS
a concern?
Excessive amounts of sediment
degrade the ecological
health and aesthetics of
the Le Sueur River and its
tributaries. When suspended
sediment, measured by TSS,
is elevated, turbidity increases,
water clarity decreases, and
light penetration is reduced.
Reduced light penetration shifts
stream productivity away from
beneficial periphyton (mixture
The photos above show the dramatic increase in turbidity that often occurs when heavy rains fall on
unprotected soils. Upon impact, raindrops dislodge soil particles while runoff waters easily transport
fine particles of silt and clay across fields or through drainage systems to ditches and tributary
streams throughout the Minnesota River Basin.
Le Sueur River Watershed Booklet (5/30/2013) p. 27
sediment sources
“Using multiple lines
of evidence, we have
demonstrated that under current
conditions, the largest sediment
sources remain near-channel
sources (erosion of bluffs and
channel widening and incision)
within the incised portion of the
“knick zone” of the Le Sueur
watershed” (Gran et al, 2011).
Uplands
Ravines
Near Channel Sources
Bluffs
Banks
Channel Widening
Le Sueur River Watershed Booklet (5/30/2013) p. 28
sediment LOAD
TOTAL SUSPENDED SOLIDS LOAD
The Le Sueur River is one of
the heaviest contributors of
sediment to the Minnesota
River.
As a Percentage
of Mississippi
RiverOf
Total Suspended
Solids Loads
As A Percentage
LockMeasured
and DamAt#3
(2007-2009)
The Load
Lock
And Dam #3
2007-2009
“The nearly complete
transformation of the land
surface, vegetation, and
hydrology over the past two
centuries has increased these
already large sediment loadings
by a factor of four to five. The
average total suspended solids
(TSS) load at the mouth of
the Le Sueur River during the
monitoring seasons from 20002010 was 4 to 5 times higher
than the amount estimated
from pre-settlement valley
excavation. The increased
delivery of water, sediment, and
nutrients to the Minnesota River
from the Le Sueur and nearby
watersheds now represents an
important water quality problem
that the State of Minnesota is
addressing” (Gran et al, 2011).
T
1%
T
6%
T
1%
T
T
5%
6%
T
4%
T
T
T
T LOCK & DAM NO. 3
T
17%
T
7%
5%
92%
T
22%
104%
100%
T T
*20%
92%
T
31%
T
4%
Load
A load is the estimate of
pollutant total amount (mass),
passing a specific location
on a river during a specified
interval of time.
T
30%
T
19%
Watonwan Blue Earth Le Sueur
* 2008 - 2009 Data Only
Watershed Pollutant Load Monitoring Network
4
11/28/2012
Average Total Suspended Solids loads (2007-2009) at different points along the Minnesota, Mississippi
and St. Croix Rivers, expressed as a percentage of the load measured after the convergence of the
three rivers at the Mississippi River lock and dam #3 near Prescott, Wisconsin.
Le Sueur River Watershed Booklet (5/30/2013) p. 29
nitrogen
What are Nitrates?
Nitrogen exists in the environment in
many forms. Nitrate is the oxidized form
of Nitrogen that is commonly found in
the rivers and streams of the Minnesota
River Basin. Because it is highly mobile,
and biologically available, it is of special
concern for aquatic systems.
NITRATE-NITROGEN LOAD
As a Percentage NO2+NO3
of the load
measured
at Mississippi
River
Loads
As A Percentage
Of
The Load
Lock And Dam #3
Lock
andMeasured
Dam #3At(2007-2009)
2007-2009
In recent decades, there has been a
substantial increase in nitrogen fertilizer
use. Elevated Nitrate-nitrogen (nitrate-N)
in the Minnesota River can pollute
aquifers it recharges. Therefore, nitrogen
can affect drinking water. At high enough
concentrations, nitrate-N can cause
infants who drink the water to become
sick and even die (methemoglobinemia).
T
0%
T
1%
Why are elevated
Nitrates a concern?
Nitrate-nitrogen is important because
it is biologically available and is the
most abundant form of nitrogen in
Minnesota River Basin streams. Like
phosphorus, nitrate can stimulate
excessive and undesirable levels of
algal growth in waterbodies. In recent
years, this problem has been particularly
severe in the Gulf of Mexico where
development of a hypoxia zone (low
oxygen) has been linked to excessive
amounts of nitrate carried to the Gulf by
the Mississippi River. Reduced oxygen
levels in the hypoxic zone, brought on by
decomposition of algae, have damaged
the shellfish industry and threaten the
aquatic ecosystem of the Gulf Region.
The Minnesota River has been identified
as a substantial contributor of excess
nitrate to the Mississippi River and the
Gulf Region.
T
<1%
T
T
3%
4%
T
1%
T
T
T
TLOCK & DAM NO. 3
T
19%
T
4%
3%
70%
T
15%
74%
T T
23%*
100%
59%
T
75%
T
6%
T
17%
T
12%
Watonwan Blue Earth Le Sueur
4
* 2008 - 2009 Data Only
11/28/2012
Watershed Pollutant Load Monitoring Network
Average Total Nitrate-Nitrogen loads (2007-2009) at different points along the Minnesota,
Mississippi and St. Croix Rivers, expressed as a percentage of the load measured after
the convergence of the three rivers at the Mississippi River lock and dam #3 near Prescott,
Wisconsin.
MPCA is currently developing a nitrate
standard for rivers based on aquatic life
toxicity.
Le Sueur River Watershed Booklet (5/30/2013) p. 30
phosphorus
What is Phosphorus?
Phosphorus is an important
nutrient for plant growth. Total
phosphorus is the measure
of the total concentration of
phosphorus present in a water
sample. Excess phosphorus in
the river is a concern because
it can stimulate the growth of
algae. Excessive algae growth,
death, and decay can severely
deplete the oxygen supply in
the river, endangering fish and
other forms of aquatic life. Low
dissolved oxygen concentrations
are a concern particularly during
low-flow times or in slow-flowing
areas such as reservoirs and the
lower reaches of the Minnesota
River. Large total phosphorus
loads can have major impacts
both locally and on downstream
receiving waters such as Lake
Pepin.
Phosphorus Sources
consumes in-stream oxygen, as in the
lower Minnesota River downstream
reach. This oxygen demand can lower
dissolved oxygen in the streams and
impair the stream’s ability to support
aquatic life. Some outbreaks of highly
elevated Blue-green algal growth,
termed algal blooms, release toxins
into the water. Instances of this have
occurred within the Minnesota River
Basin and resulted in the death of
animals (including pets) that ingested
these toxins.
Point-source phosphorus
comes mainly from municipal
and industrial discharges to
surface waters. Nonpoint-source
phosphorus comes from runoff
from urban areas, construction
sites, agricultural lands,
manure transported in runoff
from feedlots and agricultural
fields, and human waste from
noncompliant septic systems
(State of the Minnesota River, 2009).
TOTAL PHOSPHORUS LOAD
Total Phosphorous
As A Percentage
Of at
As a Percentage
of Loads
the Load
Measured
The Load Measured At Lock And Dam #3
Mississippi River Lock
and Dam #3 (2007-2009)
2007-2009
Why are elevated Phosphorus
levels a concern?
Phosphorus-enriched streams
are commonplace in the
Minnesota River Basin.
Phosphorus stimulates the
growth of algae and elevated
phosphorus concentrations often
lead to eutrophication which is
characterized by undesirably
high levels of algal growth.
An overabundance of algae
and sediment contributes to
increased turbidity and reduced
light penetration. Water clarity
is greatly reduced under these
conditions, impairing recreational
use and aesthetics of the river
environment. Furthermore,
algal cells eventually die and
their subsequent decomposition
T
1%
T
5%
T
2%
T
T
12%
15%
T
T
T
T
T LOCK & DAM NO. 3
T
8%
31%
T
12%
9%
54%
T
22%
54%
T T
23%*
51%
T
T
T
3%
100%
T
130%
9%
12%
Watonwan Blue Earth Le Sueur
Watershed Pollutant Load Monitoring Network
* 2008 - 2009 Data Only
4
11/28/2012
Average Total Phosphorus loads (2007-2009) at different points along the Minnesota,
Mississippi and St. Croix Rivers, expressed as a percentage of the load measured
after the convergence of the three rivers at the Mississippi River lock and dam #3
near Prescott, Wisconsin.
Le Sueur River Watershed Booklet (5/30/2013) p. 31
downstream impacts - lake pepin
Met Council
Lake Pepin is filling in
Lake Pepin lies downstream of
the confluence of the Minnesota
and Mississippi Rivers. It is a
naturally occurring lake, and
part of the Mississippi River on
the border between Minnesota
and Wisconsin.
Lake Pepin
Elevated Phosphorus Levels
in Lake Pepin, Phosphorus is
accumulating in the sediment
at 15 times the natural rate.
Phosphorus loading to Lake
Pepin appears to have
increased by about seven times
(or more) above natural rates.
Lake water Total Phosphorus
concentrations have increased
from about 50 ppb (parts per
billion) to 200 ppb, making Lake
Pepin highly eutrophic.
Met Council
As the Minnesota River flows
into the Mississippi, it carries
excess sediment and nutrients.
Three rivers contribute sediment
to Lake Pepin: The Minnesota,
St. Croix, and Mississippi
Rivers. Scientists have studied
sources of sediment into the
lake and determined that the
Minnesota River contributes
approximately 85 percent of the
sediment load.
Lake Pepin Algae Bloom
What is Eutrophic?
TOTAL SUSPENDED SEDIMENT YIELD
(Pounds per acre, per year)
Mississippi
River
Basin
28
Minnesota
River Basin
134
A eutrophic body of water,
commonly a lake or pond, that
has high primary productivity
caused by excessive nutrients
and is subject to algal blooms
resulting in poor water quality.
The bottom waters of such
bodies are commonly deficient
in dissolved oxygen which
can be detrimental to aquatic
organisms.
St. Croix
River Basin
13
Sources: Engstrom and Almendinger, 2000
Nater and Kelley, 1998
Le Sueur River Watershed Booklet (5/30/2013) p. 32
downstream impacts - Gulf of MEXICO
The Minnesota River
and the Dead Zone
As the Minnesota River flows
into the Mississippi River,
it carries excess sediment
and nutrients which impact
downstream receiving waters.
The Minnesota River has been
identified as a substantial
contributor of excess nitrates
to the Mississippi River and the
Gulf Region.
What is the Dead Zone?
In recent years, this problem
has been particularly severe
in the Gulf of Mexico where
development of a hypoxic zone
(low oxygen) has been linked to
elevated nitrate levels carried
to the Gulf by the Mississippi
River. Reduced oxygen levels
in the hypoxic zone, brought on
by decomposition of algae, have
damaged the shellfish industry
and continue to threaten the
aquatic ecosystem of the Gulf
Region.
Sources:
Minnesota River Basin Trends Report, 2010.
State of the Minnesota River, 2009.
This image shows the hypoxic zone
(sometimes referred to as the dead
zone) in the Gulf of Mexico. Reds and
oranges indicate areas of low oxygen
concentration. In July 2008, the hypoxic
zone was mapped at 7,988 square
miles—the second largest on record
since measurements began in 1985.
This is larger than the land area of the
state of Massachusetts
Le Sueur River Watershed Booklet (5/30/2013) p. 33
pesticides
The Minnesota Department of
Agriculture (MDA) is the lead
state agency for most aspects of
pesticide and fertilizer regulatory
functions. The MDA Monitoring
Unit collects pesticide samples
from multiple stream locations
in the Minnesota River Basin.
Pesticide monitoring data
indicate the seasonal presence
of several chemicals sometimes
at levels of concern. The most
commonly detected pesticides in
the Minnesota River Basin are
delineated in the table below.
In order to evaluate the
presence of commonly used
pesticides in the rivers and
streams, the MDA conducts
an annual statewide survey of
selected surface water sites.
What are Pesticides?
A pesticide is any substance or
mixture of substances intended
for preventing, destroying,
repelling, or mitigating any pest.
Although often misunderstood
to refer only to insecticides,
the term pesticide also applies
to herbicides, fungicides, and
various other substances used
to control pests. Under United
States law, a pesticide is also
any substance or mixture of
substances intended for use as
a plant regulator.
Most Commonly Detected
Pesticides
In the Minnesota River Basin,
the following three herbicides
are the most commonly detected
pesticides:
* Acetochlor (Surpass, Harness)
* Atrazine (Aatrex)
* s-Metolachlor (Dual, Brawl)
(State of the Minnesota River,
2009).
Le Sueur River Watershed Booklet (5/30/2013) p. 34
ACETOCHLOR IMPAIRMENT
Acetochlor Impairment
Concentrations of acetochlor in
the Le Sueur River and the Little
Beauford Ditch have violated the
MPCA Chronic Water Quality
Standard for Acetochlor, resulting
in their placement in 2008 on the
state’s 303(d) TMDL list of impaired
waters. The Chronic Water Quality
Standard for Acetochlor is 3.6 μg/L
over four days and was established
for the protection of aquatic life.
Since 2005, neither the Le Sueur
River nor the Little Beauford Ditch
have violated the surface water
standard for acetochlor. The highest
acetochlor concentration
measured in Le Sueur River since
2005 is 2.05 ppb; in the Little
Beauford Ditch is 1.46 ppb.
Acetochlor Impairment
Response Plan
The Little Beauford Ditch is a tributary of the Le Sueur River and is located in
Blue Earth County south of the city of Mankato. Two streams, the Le Sueur River
and the Little Beauford Ditch, violated the Minnesota Pollution Control Agency
(MPCA) Chronic Surface Water Quality Standard for Acetochlor and are included
on the Minnesota 2008 Impaired waters list (also known as the 303(d) list). These
streams violated the Acetochlor surface water standard of an average Acetochlor
concentration exceeding 3.6 µg/L over four days (96 hours).
A response to the impairments is
being developed by the Minnesota
Department of Agriculture in
collaboration with an advisory
committee and the Minnesota
Pollution Control Agency. The
MPCA and MDA have worked
together to develop a proposed
“Acetochlor Impairment Response
Plan” for the Le Sueur River and
Little Beauford Ditch. It outlines
specific activities to be completed or
evaluated in response to the water
quality impairments.
For More Information
www.mda.state.mn.us/acetochlor
http://www.pca.state.mn.us/water/
tmdl/tmdl-303dlist.html
Source: Le Sueur River and Little Beauford Ditch
Acetochlor Impairment Response Work Plan
Le Sueur River Watershed Booklet (5/30/2013) p. 35
lake - status
What is the status of
local lakes?
Le Sueur River Watershed
Assessment Report Findings
There are a total of 49 lakes
greater than 10 acres in the
LeSueur River Watershed.
Eleven of those lakes have been
monitored (approximately 22
percent). Nine of the eleven lakes
were able to be assessed during
the 10-year assessment window.
Two of the nine lakes were found
to be supporting of Aquatic
recreation standards (MPCA,
2012).
Overall, the majority of these lakes
possessing assessment level
data have been determined to
be non-supporting of recreational
use. Of the four lakes (Buffalo,
Minnesota, Bass, and Rice) that
have insufficient data to complete
an assessment, only one (Bass
Lake) indicates improving water
conditions. However, two lakes
within the watershed have been
determined to be fully supporting
of recreational use (MPCA, 2012).
49 - LAKES > 10 acres
in the Le Sueur River
Watershed
40 - NOT ASSESSABLE
7 - NOT SUPPORTING
aquatic recreation standards
2 - FULLY SUPPORTING
aquatic recreation standards
9 - ASSESSABLE
Information derived from the Minnesota Pollution Control Agency’s Le Sueur River
Monitoring and Assessment Report, 2012.
Le Sueur River Watershed Booklet (5/30/2013) p. 36
green lakes
Why are local lakes
greening?
Nutrient Loading
A combination of several factors
have degraded lakes in the
Le Sueur River Watershed,
resulting in poor water quality,
abundant algae and lack of
wildlife. These impacts can
be divided into two general
categories:
- External nutrient loading, and
- Internal nutrient loading.
Nutrients flowing into lakes from
their watersheds are referred
to as external loads. The
landscape around these lakes
has been transformed with the
loss of prairie and drainage of
wetlands. The current landscape
is intensively cropped.
Phosphorus fertilizer is being
added to increase/maintain
the productivity of the cropped
acres. These changes have
negatively impacted shallow
lakes.
Internal nutrient loading has also
caused problems for shallow
lakes, and in addition to the
extra water flow, and external
nutrients. Over the last twenty
years, scientists and managers
have begun to understand how
fish affect internal loading, in
particular invasive species like
common carp. They stir up the
bottom as they feed and move
nutrients from the sediments
into the water column (Shallow
Lakes Brochure).
Total Phosphorus
Reducing levels of Total Phosphorus
(TP) will be required in order to
reduce the occurrence of algal blooms
for lakes within the Le Sueur River
watershed. Alternatively, should inlake TP concentrations increase, the
potential for nuisance algal blooms
will also increase. It is important to
limit as much external (watershed)
phosphorus loading to the lakes as
possible to improve or maintain the
current concentrations. Additionally,
the watersheds for each of these lakes
will need to be addressed through
a water quality study to determine
the source and extent of pollution
problems (MPCA Lake Assessment).
The combination of high external
phosphorus loads, shallow lake depth,
high-P sediments, and bottom feeding
fish species makes improving lake
quality very challenging.
Lura Lake - September 2012
Lura Lake - September 2012
Decreasing lake water clarity in
southern Minnesota
A University of Minnesota study
examined lake water clarity using
satellite data from 1985-2005.
Researchers found strong geographic
patterns in Minnesota: lakes in the
south and southwest have low clarity,
and lakes in the north and northeast
tend to have the highest clarity. Over
the 20 year period, researchers found
mean lake water clarity in central
and northern Minnesota stable while
decreasing water clarity trends were
detected in southern Minnesota
(Western Corn Belt Plains and
Northern Glaciated Plains Ecoregions;
Le Sueur River Watershed Booklet (5/30/2013) p. 37
REFERENCES
Adapted from Marschner, F.J. 1974. The original vegetation of Minnesota, compiled from U.S. General Land Office Survey notes [map]. 1:500,000.
Redrafted from the 1930 original by P.J. Burwell and S.J. Haas under the direction of M.L. Heisnselman. St. Paul: North Central Forest Experiment
Station, United States Department of Agriculture. http://files.dnr.state.mn.us/eco/mcbs/prairie_map.pdf
Belmont, P., Gran, K., Jennings, C.E., Wittkop, C., and Day, S.S. 2011. Holocene landscape evolution and erosional processes in the Le Sueur River,
central Minnesota Field Guides. 24, p. 439-455, doi:10.1130/2011.0024(21). http://fieldguides.gsapubs.org/content/24/439.abstract
Bray, E.C, and Coleman, M. 1993. Nicollet on the Plains and Prairies. St.Paul: Minnesota Historical Society Press.
http://books.google.com/books/about/Joseph_N_Nicollet_on_the_Plains_and_Prai.html?id=jJzlmqo0zzgC
Davis, Paul. 2012. Personal interview.
Engstrom, D.R. and Almendinger, J.E. 2000. Historical changes in sediment and phosphorus loading to the Upper Mississippi River: Mass-balance
reconstructions from the sediments of Lake Pepin, St. Paul, MN, Metropolitan Council Environmental Services
http://www.smm.org/scwrs/publications/reports
Gran, K.B., Belmont, .P, Day, S.S., Finnegan, N., Jennings, C., Lauer, J.W., and Wilcock, P.R. 2011. Landscape evolution in south-central Minnesota and
the role of geomorphic history on modern erosional processes. GSA Today, September issue.
Hudak, C.M., and Hajic, E.R. 2005. Landscape evolution of the Minnesota River valley: Geological Society of America, North-Central Section Meeting,
Abstracts with Program, v. 37, no. 5, p. 8.
http://conservancy.umn.edu/bitstream/116090/9/pl3_surficial.pdf
Kuehner, K.J. 2004. An historical perspective of hydrologic changes in Seven Mile Creek watershed. In Proc. ASAE Conference on self-sustaining
solutions for streams, wetlands, and watersheds. St. Paul, MN. ASAE, St. Joseph, MI.
http://streams.osu.edu/streams_pdf/Kuehner.pdf
Lenhart, C., Nieber, J and Ulrich, J. 2011. Minnesota River floodplain deposition and streambank erosion studies. Proceedings of the American Society
of Agricultural and Biosystems Engineers(ASABE) Landscape Evolution and Erosion Conference Proceedings at Anchorage, AK.ASABE: St. Joseph, MI.
http://www.academia.edu/1365253/Assessing_the_Impacts_of_Hydrologic_and_Geomorphic
Minnesota Department of Natural Resources. 2007. Native Plant Communities and Rare Species of the Minnesota River Valley Counties: Minnesota
County Biological Survey, Biological Report 89: St. Paul, Minnesota Department of Natural Resources.
http://mrbdc.mnsu.edu/sites/mrbdc.mnsu.edu/files/public/pdf/MCBS_geology_excerpt.pdf
Minnesota Department of Agriculture, Minnesota Pollution Control Agency, and Minnesota State University, Mankato. 2009. State of the Minnesota River:
Summary of Surface Water Quality Monitoring 2000-2008.
http://mrbdc.mnsu.edu/sites/mrbdc.mnsu.edu/files/public/reports/basin/state_08/2008_fullreport1109.pdf
Minnesota Pollution Control Agency. 2012. Le Sueur River Watershed Monitoring and Assessment Report.
http://www.pca.state.mn.us/index.php/view-document.html?gid=17609
Minnesota Pollution Control Agency: Water Story. 2012. Le Sueur River: Citizens look to heal a suffering river system.
http://www.pca.state.mn.us/index.php/water/water-types-and-programs/surface-water/minnesota-water-stories/water-story-healing-a-river.html
Minnesota Pollution Control Agency. 2012. Watershed Pollutant Load Monitoring Network: 2007-2009 Average Loads.
http://www.pca.state.mn.us/index.php/water/water-types-and-programs/surface-water/streams-and-rivers/watershed-pollutant-load-monitoring-network.
html#data-reporting
Minnesota Rules Chapter 7050. 2008. Standards for the Protection of the Quality and Purity of the Waters of the State. Revisor of Statutes and
Minnesota Pollution Control Agency, St. Paul, Minnesota. http://www.pca.state.mn.us/index.php/view-document.html?gid=17609
Nater, E. A. and Kelley, D. W. 1998. Heavy-mineral chemistry of Lake Pepin sediments. To: St. Croix Watershed Research Station, Science Museum of
Minnesota. http://www.stthomas.edu/geography/faculty/Kelley/dwkelley/kelley_research.html
Novotny, E.V. and Stefan, H.G. 2007. Stream flow in Minnesota: Indicator of climate change. Journal of Hydrology 334: 319-333.
http://www.lccmr.leg.mn/projects/2007/finals/2007_05k_appx_g.pdf
Olmanson, L.G., Bauer, M.E. and Brezonik,P.L. 2008. Development and analysis of a 20-year Landsat water clarity census of Minnesota.s 10,000 lakes .
Remote Sensing of Environment, special issue on Monitoring Freshwater and Estuarine Systems.
http://hico.coas.oregonstate.edu/projects/docs/Olmanson_HICO.pdf
Le Sueur River Watershed Booklet (5/30/2013) p. 38
REFERENCES
USDA-NRCS. 2009. Rapid Watershed Assessment, Resource Profile, LeSueur (MN) HUC: 07020011, http://www.mn.nrcs.usda.gov/technical/rwa/
Assessments/reports/le_sueur.pdf
Rosgen, D.L., and Silvey, H.L. 1996. Applied river morphology. Vol. 1481. Pagosa Springs, Colorado: Wildland Hydrology.
http://www.chelanpud.org/relicense/comm/meet2000/4854_1.pdf
Schottler, S. P., Ulrich, J., Belmont, P., Moore, R., Lauer, J. W., Engstrom, D. R. and Almendinger, J. E. 2013. Twentieth century agricultural drainage
creates more erosive rivers. Hydrological Processes. 10.1002/hyp.9738
http://onlinelibrary.wiley.com/doi/10.1002/hyp.9738/abstract
Schottler, S.P., Engstrom, D. R. and Blumentritt, D. 2010. Fingerprinting Sources of Sediment in Large Agricultural River Systems. Final Report to the
PCA, August, 2010. http://wrc.umn.edu/prod/groups/cfans/@pub/@cfans/@wrc/documents/asset/cfans_asset_290680.pdf
Senjem, N. 1997. Minnesota River Basin Information Document. Minnesota Pollution Control Agency. GPO.
http://mrbdc.mnsu.edu/reports/senjem-norman/minnesota-river-basin-information-document-0
Simon, A., Hupp, C.R. 1986. Channel evolution in modified Tennessee channels. Proceedings, Fourth Federal Interagency Sedimentation
Conference, Las Vegas, March 24–27, 1986, vol. 2, pp. 5–71–5–82.
Tester, J. 1995. Minnesota’s Natural Heritage. University of Minnesota Press, Minneapolis.
United States of America Department of Agriculture. National Agriculture Statistics Service. Agriculture Statistics, 2010. Washington D.C.: United States
Government Printing Office Washington. http://www.nass.usda.gov/Publications/Ag_Statistics/2010/2010.pdf
Le Sueur River Watershed Booklet (5/30/2013) p. 39