Lower
Mississippi River Basin Planning
Scoping
Document
June 2001
balmm
About BALMM
A locally led alliance of
land and water resource agencies has formed in order to coordinate efforts to
protect and improve water quality in the Lower Mississippi River Basin. The
Basin Alliance for the Lower Mississippi in Minnesota (BALMM) covers both the Lower Mississippi and
Cedar River Basins, and includes a wide range of local, state and federal
resource agencies. Members of the Alliance include Soil and Water Conservation
District managers, county water planners, and regional staff of the Board of
Soil and Water Resources, Pollution Control Agency, Natural Resources
Conservation Service, U.S. Fish and Wildlife Service, University of Minnesota
Extension, Department of Natural Resources, Minnesota-Wisconsin Boundary Area
Commission, the Southeastern Minnesota Water Resources Board, the Cannon River
Watershed Partnership, and others. BALMM meetings are open to all interested
individuals and organizations. Existing staff from county and state agencies
provide administrative, logistical and planning support. These include: Kevin Scheidecker,
Fillmore SWCD, Chair; Norman Senjem, MPCA-Rochester, Basin Coordinator;
Clarence Anderson, Rice SWCD, Area 7 MASWCD Liaison; Bea Hoffmann, SE Minnesota
Water Resources Board Liaison.
This Basin Plan Scoping Document is the fruit of a year-long
effort by participants in BALMM. Environmental Goals, Geographic Management
Strategies and Land-Use Strategies were developed by either individual BALMM
members or strategy teams. An effort was made to involve those who will
implement the strategies in developing them. Each strategy was presented at
least once at a monthly BALMM meeting, and subsequently revised based on
comments received, before being included in this draft document. Other parts of
the document were prepared by the Basin Coordinator, who drew on a multitude of
published sources to describe the basin’s geology, water quality, and
land-water relationships.
CONTENTS
Page
I. Introduction..................................................................................................... 5
II.
Basin Description....................................................................................... 10
A. Overview..................................................................................................... 10
B. History......................................................................................................... 11
C. Geology....................................................................................................... 15
D. Land Use, Landscape Features and Water
Quality............................... 16
III.
Water Quality................................................................................................. 19
A. Basinwide Surface Water Conditions and
Trends................................. 19
B. Mississippi River Water Quality............................................................... 25
1. Lake Pepin and Upstream.................................................................... 25
2. Downstream of Lake Pepin.................................................................. 28
C. Water Quality of Major Tributaries........................................................... 29
D. Lake Water Quality.................................................................................... 35
E. Ground Water Quality................................................................................ 45
IV. Land-Water
Relationships......................................................................... 49
A. Sediment..................................................................................................... 50
B. Nutrients (Nitrogen and Phosphorus)....................................................... 54
C. Fecal Coliform Bacteria............................................................................ 57
D. Pesticides................................................................................................... 61
E. Hydrologic Modification............................................................................. 61
V. Environmental
Goals.................................................................................. 65
A. Water Quality Goals................................................................................... 65
B. Water Quantity Goals................................................................................. 65
C. Aquatic Ecosystem Goals........................................................................ 65
VI. Geographic
Management Strategies...................................................... 66
A. Watershed
Management........................................................................... 66
B. Aquifer Protection...................................................................................... 72
C. Floodplain Management........................................................................... 77
VII. Land-Use Strategies................................................................................... 85
A.
Perennial Vegetation: Maintain/Increase Acreage............................... 85
B.
Wetland Protection and Restoration....................................................... 92
C.
Soil Conservation on Row-Crop Land.................................................... 96
D.
Urban and Rural Residential Land Management................................ 102
E.
Nutrient and Pesticide Management.................................................... 107
F.
Animal Feedlot Management................................................................ 113
G.
Mining Activities Management.............................................................. 117
VIII. Monitoring and Evaluation.................................................................... 119
IX.
Future Directions..................................................................................... 125
TABLES
Page
303(d) List of Impaired Waters 1998.............................................................. 20
Long-Term Water Quality Trends.................................................................. 32
Lower Mississippi River Basin Lake Assessment.................................... 36
Lake Zumbro Water Quality............................................................................. 38
2000 Crop Residue Survey Results.............................................................. 50
Effect of Crop Residue on Soil Loss............................................................ 51
Agencies and Groups Involved in Water
Quality Monitoring............... 121
FIGURES
Map: Lower Mississippi River Basin............................................................... 9
1998 Impaired Waters List............................................................................... 20
Lake Zumbro Summer Mean Total Phosphorus........................................ 39
Lake Zumbro Summer Mean Chlorophyll-a................................................ 39
Lake Zumbro Summer Mean Secchi Transparency................................. 40
Estimated Summer TP Loading Rate to Lake
Pepin................................ 42
Lake Pepin Summer Mean Total Phosphorus........................................... 43
Lake Pepin Summer Mean Chlorophyll-a.................................................... 44
Lake Pepin Summer Mean Secchi Transparency..................................... 44
Agro-Ecoregion Map of the Lower Mississippi
River Basin................. 110
I: Introduction
In the summer of 1999 an ad-hoc group of county, state and
federal agency representatives started meeting to discuss the possibility of
creating a basin plan for the Lower Mississippi River and Cedar River Basins in
southeastern Minnesota. Shortly
thereafter, Governor Jesse Ventura launched the Water Unification Initiative,
as a result of which seven Basin Teams composed of state and federal agency
representatives were appointed to assist in the development of the next state
water plan, called “Water Plan 2000” (the title was later changed to
“Watermarks”). Thus two basin planning
groups became established at roughly the same time in the Lower Mississippi and
Cedar River Basins, with similar purposes and overlapping membership.
The Basin Team
produced a report that was provided to the State Planning Agency in February 2000
for inclusion in Watermarks. It focused on water quality goals, objectives and
indicators for the basin. Watermarks was published in September 2000. Over the
next two years, the seven Basin Teams will be responsible for developing
strategies whereby the environmental goals and objectives outlined in
Watermarks can be achieved. These will be included in a statewide plan
scheduled to be published in September 2002.
The ad-hoc basin planning group that started meeting in
August 1999 contributed to the development of water quality and land use
objectives in Watermarks and, since February 2000, has been developing
strategies by which these goals and objectives can be accomplished over the
next decade. The planning group calls
itself the Basin Alliance for the Lower Mississippi in Minnesota (BALMM). It
meets monthly and is staffed informally by Kevin Scheidecker, Fillmore Soil
& Water Conservation District Manager, who serves as chair; and Norman
Senjem, MPCA-Rochester, who serves as basin coordinator. A secretarial position staffed by
BWSR-Rochester currently is vacant. Membership includes most of those who
belong to the Basin Team, in addition to representatives of many local, state,
regional and federal agencies.
In addition to the BALMM
activities, two public forums were conducted by the MPCA to seek advice and
comment on water quality goals and strategies. The first was held Feb 7, 2000,
and the second on Nov. 8, 2000, in Rochester. Citizens who had participated in
the May 1999 “The Governor’s Forums: Citizens
Speak Out on the Environment” in Rochester were invited to attend a similar
event to provide input into Watermarks on Feb. 7, 2000. County commissioners
and water planners also were invited, as were members of the public through a
widely distributed news release. Thirty-six people participated in the first
forum, which made use of keypad technology to provide instant feedback on how
the group voted on specific questions. Demographically, the group was evenly
split among urban, rural-farm and rural-non-farm. Forty-six percent were
citizens, 34 percent government staff, and 20 percent elected officials. Using
the document Water Plan 2000 Objectives:
Lower Mississippi/Cedar River Basins, the group evaluated the adequacy of
the Water Quality and Ecosystem objectives as a whole, and then evaluated each
of the land-use objectives from the standpoint of both effectiveness in accomplishing environmental objectives, and the feasibility of implementing them. In
addition, the group suggested several additional objectives to add to the
report, two of which were subsequently added to the Basin Plan Scoping Document
Geographic Management Strategies: Groundwater Recharge Areas; and Floodplain
Management). Comments also were used to modify existing objectives and indicators.
The second public forum was held on Nov. 8, 2000, to provide
the public an opportunity to comment on the Draft Basin Plan Scoping Document.
An informal Open House was combined with a keypad voting session similar to
that used at the first forum. Once again, the discussion and voting focussed on
both the effectiveness and feasibility of each strategy. Forty-two individuals
participated, including citizens (61%); government staff (27%) and elected
officials (12%). Results of the Citizens Forum were reviewed at the next BALMM
meeting, and were used to revise the Basin Plan Scoping Document.
The final strategies for land-use, geographic management and
monitoring included in this Basin Plan Scoping Document will be provided to the
Basin Team for inclusion in the “Strategies” portion of Watermarks. In
addition, they will be further refined and developed by BALMM sub-teams and
through interaction with basin citizens and stakeholders to develop a final
Basin Plan.
Purpose of Basin Planning
To an ever-increasing extent, water quality protection and
improvement efforts in Minnesota are being organized by major drainage basin.
Public and private funding sources are showing a growing preference for working
through basin initiatives rather than funding a host of separate, uncoordinated
efforts within the same basin. The purpose of BALMM is to create an organized,
unified effort in the Lower Mississippi/Cedar River basins that will:
1.
Make the case to the public, elected officials and funding
sources for giving priority attention to water quality restoration and
protection in southeastern Minnesota;
2.
Establish ongoing coordination of local, state, tribal and
federal agencies to plan and implement water quality protection and restoration
activities that are economically and environmentally sustainable and reflect
local and downstream issues and priorities.
The Basin Plan Scoping Document is a guide toward the
pursuit of these broad goals that the BALMM has developed in its first year. As
such, it will be used by Alliance members to guide and coordinate
implementation activities in the basin, even as it continues to be refined and
elaborated into a more complete Basin Plan. This approach suits the
implementation orientation of Alliance members while conforming to the state’s
schedule for the development of basin plans in the context of Watermarks.
Making Connections
The core of the Scoping Document is found in the strategies
that have been developed by Alliance members to manage the land in the context
of watershed management, aquifer protection and floodplain management to
achieve environmental goals and objectives. Goals for Water Quality and
Quantity and Ecosystem Health are described in Part IV, while strategies for
attaining these goals are described in Parts V and VI. Strategies have been
developed at the basin scale, for use throughout the Lower Mississippi River
Basin, but with a view to making connections with land-use planning activities
at both smaller and larger geographic scales. Accordingly, goals and objectives from comprehensive local water
plans from counties within the basin were collected, organized, and distributed
to Alliance members to help guide the development of strategies. This should
help to ensure that activities undertaken at the basin scale are compatible
with and supportive of land-use activities undertaken by counties.
Similarly, an attempt has been made to relate strategies
developed for southeastern Minnesota to those being developed for the larger,
189,000 square mile Upper Mississippi River Basin, defined as the drainage area
upstream of Cairo, Illinois, where the Ohio River joins the Mississippi River.
Toward this end the Alliance has reviewed the recently published strategy by
the Upper Mississippi River Conservation Committee, entitled “A River that
Works and A Working River: A Strategy for the Natural Resources of the Upper
Mississippi River System.” This
strategy lists nine objectives for the river system as a whole, which includes
the drainage basin as well as the main channel and its floodplain. In particular, improving water quality for
all uses (Objective 1), Reduction in erosion and sediment impacts (Objective
2), and Manage channel maintenance and disposal to support ecosystem objectives
(Objective 7) are explicitly supported by the BALMM strategies. Other
objectives, which deal with particular aspects of managing the Mississippi
River and its floodplain, appear to be less directly related to the land-use
management activities of local and state government participating in the
Alliance.
In addition, the Alliance is keeping abreast of developments
concerning hypoxia in the Gulf of Mexico, its
relationship to nutrient inputs to the Mississippi River
originating in Minnesota, and the “Draft Action Plan for Reducing, Mitigating
and Controlling Hypoxia in the Northern Gulf of Mexico” that was developed by
the Mississippi River/Gulf of Mexico Nutrient Task Force. Concern about nitrate-nitrogen contamination
of ground water is high in southeastern Minnesota’s karst region of fractured,
porous bedrock. Because of the close
interaction between surface water and ground water in karst geology, this
concern extends to the trend of steadily increasing concentrations of
nitrate-nitrogen in the region’s rivers. Reversing this trend is a
key water quality goal for the basin that is seen as
supporting efforts to reduce nutrient loads to the Gulf of Mexico.
Pool Planning
An attempt will be made also to relate the management of
tributary watersheds to goals established for the main channel and backwaters
of specific navigation pools, through pool planning. Pool plans are being
developed for Pools 1-10 by the Fish and Wildlife Work Group, a sub-group of
the U.S. Army Corps of Engineers St. Paul District’s River Resources Forum.
I: Basin Description
A: Overview
The Lower Mississippi River Basin, which includes the Cedar River
Basin for planning purposes, is located in southeastern Minnesota. It includes
all or part of 17 counties and has 12 major watersheds covering about 7,266
square miles (4,650,100 acres). Land use is diverse. On the western side lands
are primarily cultivated, while the eastern landscapes are dominated by steep
forested hill slopes. About two-thirds
of the land in the basin is under cultivation, while about 13 percent is
forested. Roughly 17 percent of the land use is open or pasture lands. Major
agricultural crops include corn, soybeans and hay. Animal production includes
dairy and beef cattle, hogs, sheep and lambs. Major population centers include
the southern Metropolitan area of Dakota County in addition to Austin, Albert
Lea, Faribault, Owatonna, Rochester, Red Wing and Winona. These and other urban areas are experiencing
rapid population growth and commercial development.
The basin’s population grew 11.9 percent between 1990 and
1998, from 539,787 to 603,997, according to Minnesota Planning. Most of the
growth has been in Dakota (23.3 percent), Dodge (10 percent), Olmsted (11.8
percent) and Rice (10 percent) counties.
Beautiful bluffs, springs, caves and numerous trout streams
abound in the eastern basin, where steep topography and erosive soils increase
the potential for pollutant runoff and sedimentation of streams. Sinkholes and
disappearing streams highlight the close connection between surface water and
groundwater in this part of the basin. The presence of fractured limestone
bedrock lying close below the land surface, which is often referred to as karst
topography, presents a widespread risk of groundwater
contamination in the eastern basin. In the southwestern basin, Mississippi
tributaries emerge as small streams out of a prairie landscape once rich in
wetlands but now extensively drained to support a productive agriculture.
Further to the north, in the western Cannon River Watershed, remnants of the
Big Woods hardwood forest intermingle with mixed crop and livestock farming in
a rolling terrain interspersed with lakes and wetlands. On the basin’s eastern
border, the Mississippi River is shaped by the lock-and-dam system, which
converted a free-flowing meandering river into a series of navigation pools
with a nine-foot-deep channel for barge traffic.
The character of rivers and streams in the Lower Mississippi
River Basins changes considerably along the main direction of flow, west to
east. The Cannon River originates in
the lake area of eastern Le Sueur and western Rice County, a farming region of
glacial drift and moraines. A major tributary, the Straight River, has its
marshy beginnings near Owatonna. The headwater tributaries of the Zumbro, Root
and Cedar Rivers ooze from till plains and moraines of Steele, Dodge, Mower and
Freeborn counties once rich in wetlands, now extensively drained for
agriculture.
The extent of presettlement wetlands in Lower Mississippi
Basin counties has been estimated to be approximately 880,000 acres. Good
estimates of remaining wetland acreage are not available, but considerably less
than half of the original wetlands are believed to exist today (Anderson and
Craig, 1984). The vast majority of original wetland acreage is located on the
western side of the basin in Dodge, Freeborn, Mower, Steele and Waseca
counties. Seventy-nine percent of the landscape in southeastern Minnesota is
classified as well-drained, and much of the land that was poorly drained has
been tiled for agricultural production.
After leaving the till plains, the Cannon, Zumbro and Root
drop down into deeper valleys starting near Northfield (Cannon), Zumbrota
(Zumbro) and Spring Valley (Root).
Hereafter the network of rivers and tributaries is fed by ever-deeper
reserves of ground water. In certain streams, a combination of swiftly moving
current, streambeds formed of boulders, cobble and gravel, and stable flows of
cool, oxygen-rich waters support trout and the aquatic insects on which they
feed. Deep pools and undercut banks provide refuge during sunny days and low
waters, while riffles provide a continuing source of food.
Stream gradients become steeper as the rivers approach the
Mississippi Valley. The upper stream valleys in this driftless area, which the
last glaciation did not reach, are formed by vertical limestone bluffs, the
product of millenia of erosion through highly soluble limestone. Snowmelt and
heavy rainfall can induce flash floods in this topography. Finally, the rivers near the Mississippi
Valley begin to slow down, lose energy and drop their load of sediment in
alluvial floodplains that have been inching higher ever since glacial times. In
recent decades, however, dikes along the lower reaches of the Root and Zumbro
have disconnected the rivers from their alluvial floodplains, making farming of
the rich soil possible, at the cost of increased sedimentation of the
Mississippi and the degrading of a rich ecosystem.
B: History
The Mississippi River valley is the product of thousands of
years of glacial activity and water and wind erosion. The first people that lived along the Upper Mississippi River
Valley (the stretch between Lake Itasca and the confluence with the Missouri
River above St. Louis) arrived 12,000 years ago. These early inhabitants were followed by a succession of native
cultures that lived near the Mississippi and relied on the river for food.
Some later
cultures also farmed on the Mississippi floodplains and islands. For example, early European explorers wrote
of native farming practices on Prairie Island, Minnesota. These early explorers also documented the
bounty of the Mississippi River in terms of fish and game:
“Radisson went with hunting parties,
and traveled "four months...without doing anything but go from river to
river." He was enamored of the beauty and fertility of the country, and
was astonished at its herds of buffaloes and antelopes, flocks of pelicans, and
the shovel-nosed sturgeon, all of which he particularly described. Such was the
first year, 1655, of observations and exploration by white men in Minnesota,
and their earliest navigation of the upper part of the Mississippi River.”
(Collections of the Minnesota Historical Society, Volume 10, Part 2, pp.
462-463)
Following the early exploration of the Mississippi River in
what is now Minnesota, additional Europeans began to trickle into this part of
the continent. Eventually that trickle
became a flood, and European settlers became the predominant residents of the
river valley.
Land-Use Changes
As European immigrants advanced across the U.S., they left
changing landscapes in their wake. In
Minnesota, settlers plowed under the prairie and cut down the forests. Outposts, then towns, then cities grew up on
riverbanks. Industry was established on
the banks of the Mississippi in St. Anthony/Minneapolis, then in St. Paul. All of these activities took their toll on
the health of the Mississippi River.
European settlers weren’t the only sources of landscape
changes in the Lower Mississippi River basin, however. Pollen analysis of sediment cores taken from
Lake Pepin shows an increase in “Big Woods” plant species such as sugar maple
and basswood trees long before the arrival of most Europeans. This landscape change is associated with a
climatic shift to cooler, wetter conditions that occurred several hundred years
before Europeans began to settle this part of the continent.
During European settlement, the landscape changed
again. Pollen analysis (again on Lake
Pepin sediment cores) shows a shift from primarily pine, oak, birch, and big
woods species to greatly increased amounts of pollen from plants like ragweed,
which grows well in open fields and cleared areas (Engstrom and Almendinger,
2000). While the exact timing of this
shift is not known, the co-occurrence of this change with the first appearance
of corn and wheat pollen suggests that it happened at about the same time that
widespread cultivation came to Minnesota, in the 1850’s.
At
roughly the same time that agricultural activities were changing the landscape
of southern Minnesota, logging was altering the Mississippi and St. Croix River
basins to the north, both of which flow into the Lower Mississippi. Massive logging operations were active in
the Upper Mississippi basin between about 1870 and 1915 (Sterner and Nunnally,
1999). Hundreds of thousands of board
feet of logs and lumber were sent down the Mississippi to the mills of St.
Anthony and even farther downstream each year.
The St. Croix River was also a thoroughfare for the logging industry,
and large mills were built at Stillwater and beyond. The intensive logging left the land susceptible to erosion, and waste products from the mills
were disposed of in the rivers.
Finally, the advent of commercial navigation on the Mississippi
River above St. Louis, Missouri impacted the basin as well, both directly and
indirectly. The arrival of the first
steamboat at Fort Snelling in 1823 heralded a new era in river transportation
in Minnesota, and enormous changes for the river itself.
Navigation and the River
It is difficult to over-state the impact of navigation on
the Mississippi River. The advent of
commercial navigation, and the ensuing channel modifications and lock and dam
system, transformed the Mississippi River above St. Louis, Missouri, from a
free-flowing river to a system of reservoirs interrupted by stretches of
altered river. These changes had a
profound impact on the river’s ecology.
Today, the existence of the navigation system places boundaries on the
extent to which the river can be restored and managed.
The changes wrought on the Mississippi between St. Anthony
Falls and the Minnesota-Iowa border due to navigation began almost as soon as the
first steamboat maneuvered upstream to Fort Snelling and later the falls of St.
Anthony. Wood was scavenged or cut from
the banks of the river to feed the steam engines. This activity had a significant impact on the Mississippi River
near St. Louis. On the Minnesota
stretch of the river, early steamboat traffic was limited to high-water periods
when the boats could navigate the shallow Mississippi depths. But that limitation was soon to change.
Recognizing that steamboat traffic upstream of the confluence
of the Mississippi and Missouri Rivers (below which the river became more
navigable) would increase if the river channel was “improved,” the U.S. Army
Corps of Engineers (USACE) began altering the Mississippi River channel as
early as 1838. In 1878, Congress
authorized the USACE to create a 4.5-foot navigation channel through a
combination of dredging and clearing snags from the river. According to the report Ecological Status and Trends of the Upper Mississippi River System 1998:
“Snag
clearing … contributed to the instability of the river bank because trees were
removed 100 to 200 feet (30 to 60 m) back from the shoreline to reduce future
hazards.” (p. 3-5)
Wing dams were another tool used by the USACE to enhance
navigability. These long fingers of
rock and willow mats (and later concrete) extended from the shoreline out into
the river channel, focusing much of the water flow into the center channel
where it would scour out accumulated sediment and debris. The wing dams also served to raise the water
level in the main channel. Closing dams
were also constructed on side channels, to focus the river flow into the main
portion of the river.
It didn’t take long before the 4.5-foot channel was seen as
inadequate, and in 1907 Congress authorized a six-foot channel project. This was followed by a nine-foot channel
project in 1930 that led to the system of locks and dams that exists on the
river today.
Today, 26 locks and dams aid Mississippi River navigation
between Minneapolis and the confluence of the Missouri and Mississippi Rivers
below Alton, Missouri. Eight of these
locks and dams are located in Minnesota, between Minneapolis and the
Minnesota-Iowa border.
Ecological Impacts
All of the historical changes in the Lower Mississippi River
Basin have impacted this area’s ecological systems. For example, intensive agriculture and logging left vast tracts
of bare land susceptible to soil erosion.
Wind and water erosion sent thousands of tons of sediment and associated
nutrients into the Mississippi River and its tributary streams each year.
Agriculture and logging were not the only sources of
nutrient inputs to the river. Untreated
sewage and industrial wastes from the cities of Minneapolis and St. Paul were
disposed of in the river until the Pig’s Eye Treatment Plant — now called the
Metro Plant — was constructed in 1933.
This contributed to downstream nutrient loading and other problems. For example, a 1927 report of the U.S.
Public Health Service and the U.S. Bureau of Fisheries indicated that pollution
from the Twin Cities was so severe that a 45-mile stretch of the river below
St. Paul could not support fish during August 1926 due to low dissolved oxygen
levels.
This increased flux of sediment and nutrients into the Lower
Mississippi River can be seen in sediment core samples taken from Lake
Pepin. Between shortly after the onset
of European settlement (approx. 1830) and today, sediment loading to Lake Pepin
increased by an order of magnitude, and the lake experienced a more than
15-fold increase in phosphorus accumulation in the bottom sediments. These changes are also reflected in a shift
in diatoms, a type of algae, from species associated primarily with clear water
to those more commonly seen in nutrient-enriched lakes. These changes began during European
settlement and have continued at varying rates into the present, with the
greatest changes in nutrient and sediment loading occurring after 1940
(Engstrom and Almendinger, 2000).
The burgeoning population living along the river took its
toll in other ways, as well.
Over-fishing led to the near elimination of some large fish species
(Lubinski et. al., 1998, p. 3-6), and native mussel beds were decimated by
pearl hunting and the harvesting of shells for the active button industry that
grew up along the river. (For details
on over-harvesting of the mussel beds, see Great
River: The Environmental History of the Upper Mississippi, 1890-1950,
Philip V. Scarpino, University of Missouri Press, 1985, Chapter 3.)
Navigation, and the accompanying river channel alterations,
has also altered the ecology of the river.
The ecological impacts of first the wing dams and closing dams, and then
the lock and dam system has been dramatic.
The construction of closing dams cut off side streams and backwater
areas of the river. No longer exposed
to periodic flushing by higher water flows, the backwater areas began to fill
with sediment, a problem that was exacerbated by increased sediment loading to
the river from upstream logging and agricultural activities (USGS, 1998, p.
3-4).
Dredging was also done to increase the depth of the main
river channel. Dredge spoils were piled
to create channel border islands, and also deposited in shallow areas near the
riverbanks, covering those aquatic habitats (USGS, 1998, p. 4-11). Levees were also built to protect the
floodplains—which had become farmlands and cities—from seasonal
floodwaters.
All of this added up to habitat changes for the Mississippi
River. Fish spawning areas were lost,
and native mussel beds either scoured away or silted over. As mentioned earlier, fisheries were also
impacted. In addition, the floodplain
forests experienced a decrease in diversity and a shift to a system dominated
by silver maple (Yin and Nelson, 1995, p. 5).
The
construction of the lock and dam system in the 1930s brought more changes. The dams slowed flow velocities, raised
water levels and inundated adjacent floodplains. Many islands disappeared below the rising water levels, and those
that remained experienced increased wave erosion. Larger pool areas in the river meant a larger surface area for
the wind to blow across, spurring wave action that stirs up sediment, leading
to decreased water transparency and declines in aquatic plants.
Not all of the changes led to a decrease in habitat and
diversity. New backwater areas were
created as a result of the dams, and some now support diverse plant and animal
communities. New wetlands were created
as well. However, at least some of
these habitats are slowly filling with sediment deposited by the river, and
there is concern that eventually these areas will be lost.
The River Today
Today, advances in wastewater treatment and best management
practices have led to water quality improvements. Fish and mayflies have returned to the Mississippi River below
St. Paul, and numerous bald eagles return to the river near Lake Pepin and
Wabasha each year. However, challenges
remain. The current lock and dam system
limits the impact of “re-setting events”—like floods and droughts—that once
maintained the ecological system. Toxic
pollutants, while decreasing, still pose a threat to human health and
wildlife. Nutrient levels remain
elevated in Lake Pepin. These and other
problems must be addressed if the Lower Mississippi River Basin is to thrive
into the future.
C: Geology
The Lower Mississippi River Basin comprises an area of 5,708
square miles in southeastern Minnesota. The Vermillion, Cannon, Zumbro and Root
Rivers drain most of the basin. Annual precipitation
ranges from 28 to 31 inches and increases toward the southeast. Annual runoff
ranges from 5.5 to about 8 inches, increasing from west to east. The topography
varies from gently rolling in the west to plateaus with deeply-incised bedrock
valleys in the east. Row crop agriculture is the primary land use in upland
areas, valley slopes are forested, and river valleys have a mixture of
agriculture and forest.
Bedrock geology consists of alternating layers of shale,
sandstone, and carbonates of Paleozoic age. These deposits have been eroded
from west to east so that individual formations vary in their vertical
position. Where carbonate bedrock is the first bedrock, it may be highly
dissolved. The uppermost bedrock unit is generally fractured.
Much of the basin has been glaciated, but glacial deposits
vary in thickness from several hundred feet in the west to less than 50 feet in
the east. Bedrock is often exposed along the major rivers. Des Moines Lobe till
associated with the Bemis moraine and the Altamount moraine occur in the
extreme west. Most of the western half of the basin is covered with old gray
till. Alluvial and colluvial deposits
occur along the major rivers in the east. A loess cap occurs throughout most of
the basin.
The hydrogeology of the area has been extensively studied.
Despite this, mechanics of flow are not completely understood because of the
complexities of flow within fractures and solution channels. Aquifers are
generally recharged where they are exposed or have a thin cover of
unconsolidated material. Ground water flows toward the major rivers. Vertical
mixing of aquifers is most likely in areas where there are steep hydraulic
gradients, such as along rivers and in buried bedrock valleys. Fractured flow
and local heavy pumping also may lead to vertical mixing between aquifers.
The Cedar River Basin comprises an area of approximately
1,200 square miles in south central Minnesota.
The Cedar and Shell Rock Rivers and smaller streams drain southward into
Iowa and eventually into the Mississippi River. Annual precipitation ranges
from 30 inches in the northern part of the basin to 31 inches in the south.
Average annual runoff varies from 5.5 inches in the west to about 6.5 inches in
the east. The area consists primarily of a flat undulating plain. Row-crop
agriculture is the primary land use.
Glacial deposits overlie the entire watershed and consist of
pre-Wisconsin drift in the eastern half of the basin and Wisconsin drift in the
western half. Glacial deposits range in thickness from less than 100 feet in
the south central to more than 200 feet in the northeast and northwest. Few
wells are completed in drift materials because supplies are not dependable, the
aquifers are susceptible to contamination, and concentrations of dissolved
solids are very high, particularly in deposits of the Wisconsin drift.
The Upper Carbonate bedrock units have typically been
classified as a single aquifer. They
consist of the Cedar Valley, Maquoketa, Dubuque, and Galena formations. Upper
Carbonate deposits underlie the entire basin.
Ground water within these formations drains toward the major rivers and
streams in a general southward direction.
Recharge to the ground water system occurs in upland areas. Water
infiltrates through glacial deposits and moves into the bedrock units. Bedrock
deposits are fractured and have many solution channels. Flow can thus be very
rapid within the bedrock aquifers. The rate that water percolates through the
glacial deposits and the chemistry of glacial deposits exert strong controls on
water quality of the bedrock aquifers. Recent investigations indicate there may
be confining bedrock units within the Upper Carbonate deposits. In many
portions of the basin, the Upper Carbonate aquifer is not considered an acceptable
drinking water sources due to actual or potential contamination.
D: Land Use, Landscape Features and Water Quality
Steep-sloping land, often under intensive cultivation or
development, is located in close proximity to streams in many parts of the basin.
This is especially true of the blufflands on the eastern side of the basin and
the rolling moraine landforms on the western edge of the basin, as well as less
extensive steep areas located in between.
Approximately 11 percent of the land is next to permanent streams and
about 29 percent next to intermittent streams. This indicates a very high
potential for sediment delivery to streams as a result of erosion and
runoff.
The National Resource Inventory, a statistical land-use
survey conducted every five years by the Natural Resources Conservation
Service, indicates that soil erosion is evenly distributed across highly
erosive and moderately erosive fields. Erosion rates are described relative to
the amount of erosion that land can tolerate (T) without impairing its
productive capacity. Land eroding at “T” , which usually amounts to about 3 to
5 tons per acre, is thus able to maintain its productive capacity.
Results of the 1997 NRI indicate that 61,200 acres of
cultivated cropland in the Lower Mississippi River Basin are eroding at a rate
of 4T or greater. This land comprises only 2.2% of the cultivated cropland in
the basin, but accounts for 16% or the total water erosion in the region from
cultivated cropland. Also according to
the 1997 NRI, 154,700 acres of cultivated cropland in the Lower Mississippi
River Basin are eroding at a rate of 2T - 4T. This land comprises only 5.5% of
the cultivated cropland in the basin, but accounts for 19% of the total soil
loss from water erosion from in the region from cultivated cropland. However, the majority of soil erosion – an
estimated 65% -- comes from the remainder of cropland which erodes at moderate
and low rates of soil loss – an estimated 2,597,000 acres. Collectively, it
appears that these moderately eroding acres contribute the bulk of agricultural
sediment to the region’s streams.
Soil erosion and runoff are greatly affected by land use –
particularly, how the land use affects surface roughness and the ability to
infiltrate water. Well-managed pasture and hay land provide vast areas where
rainfall and snowmelt can infiltrate the soil and recharge shallow groundwater
rather than running off the surface and carrying high water volumes and
pollutants to streams.
Data from the NRI show a steady decline in pastureland and
erratic fluctuations in noncultivated cropland from 1982 to 1997. Together,
acreage in these two land-use categories declined from 628,000 acres in 1982 to
448,000 acres in 1997, a decline of 180,000 acres, or 28 percent. Forested acreage increased slightly over the
same period, from 574,000 to 590,000 acres.
Although reasons for declining acreage of pasture and
noncultivated cropland were not identified in the NRI study, conversion from
mixed crop/livestock farming to larger, more specialized row-crop operations
appears to be playing a major role. In Olmsted County, for example, data from
the Minnesota Agricultural Statistics Service indicate that major crop acreage
has changed significantly over the past 25 years. There has been a shift from a
forage-small grain-corn rotation to a corn-soybean rotation. From 1975 to 1998,
soybeans have replaced one-third of the alfalfa hay acres and more than eighty
percent of the harvest oats acreage. Soybean acres have increased from 29,900
in 1975 to 67,600 acres in 1998 (Wotzka and Bruening).
Sources: Section
II
Anderson, Jeffrey, and William Craig, 1984,”Growing Energy
Crops on Minnesota’s Wetlands: The Land-Use Perspective,” Center for Urban and
Regional Affairs, University of Minnesota, Minneapolis
Engstrom, Daniel R., and James E. Almendinger, 2000,
“Historical Changes in Sediment and Phosphorus Loading to the Upper Mississippi
River: Mass balance Reconstructions from the Sediments of Lake Pepin,” St. Croix
Watershed Research Station, Science Museum of Minnesota, Marine on St. Croix,
Minnesota
Hoops, Richard. 1987.
A River of Grain: The Evolution of
Commercial Navigation on the Upper Mississippi River. University of Wisconsin-Madison, College of
Agricultural and Life Sciences Research Report. Madison, WI.
Minnesota Historical Society, Collections of the Minnesota
Historical Society, Volume 10, Part 2, 1905
Minnesota Pollution Control Agency, 1999, “Baseline Ground
Water Quality Information for Minnesota’s Ten Surface Water Basins,” MPCA
Ground Water Monitoring and Assessment Program, web site at
http://www.pca.state.mn.us/water/groundwater/gwmap/gwpubs.html/#reports
Scarpino, Philip V., Environmental History of the Upper
Mississippi, 1890 – 1950, University of Missouri Press, 1985
Sterner, Robert and Patrick Nunnally. 1999.
Ecological Trends in the Upper
Mississippi Basin: A Combined Historical and Ecological Approach. Report submitted to the Minnesota Pollution
Control Agency Environmental Trends Project.
University of Minnesota, “Lower Mississippi River Basin
Information Page”, Department of Soil, Water and Climate. http://www.soils.agri.umn.edu/research/seminn/
US Army Corps of Eng., 2000.
US Department of Agriculture, Natural Resources Conservation
Service, National Resources Inventory, 1982, 1987, 1992, and 1997
Waters, Tom, 1977, Streams and Rivers of Minnesota,
University of Minnesota Press, Minneapolis
US Geological Survey, 1999, “Ecological Status and Trends of
the Upper Mississippi River System 1998: A Report of the Long-Term Resource
Monitoring Program,” LTRMP 99-T001,
Upper Midwest Environmental Sciences Center, La Crosse, Wisconsin
Wotzka, Paul and Denton Breuning, 2000, “A Small-Scale Watershed Assessment of
Nitrogen Inputs and Losses for A Southeastern Minnesota Trout Stream,”
Minnesota Department of Agriculture, St. Paul
Yin, Yao, and John T. Nelson. 1995. Modifications to the Upper Mississippi River
and Their Effects on Floodplain Forests, Long Term Resource Monitoring
Program Technical Report 95-T003.
Prepared for National Biological Service Environmental Management
Technical Center. Onalaska, WI.
III: Water Quality
A: Basinwide
Surface Water Quality Conditions and Trends
Summary:
Water quality monitoring data from the Mississippi River and
its tributaries in southeastern Minnesota present a somewhat mixed picture. The
current condition of surface water in the basin must be described as impaired
and in need of restoration with regard to several types of pollutants – mainly
those for which numerical water quality standards exist. A review of historical water quality
monitoring data in the basin has identified widespread impairments indicated by
exceedences of the water quality standards for turbidity
and fecal coliform bacteria,
and isolated exceedences of the standard for un-ionized ammonia.
Of 42 stream reach impairments on the Section 303(d) list,
20 are for fecal coliform bacteria, 19 are for turbidity, and four are for
un-ionized ammonia.
The MPCA is required under the Clean Water Act to publish a
list of stream segments which have impaired uses, and for which the MPCA
proposes to complete total maximum daily load (TMDL) studies. TMDL studies
define the maximum amount of each pollutant which can be released and
assimilated in the receiving water from point and nonpoint sources and still
allow the receiving water to achieve water quality standards. The MPCA is
required to list and prioritize stream segments. The 1998 list of impaired
waters is based on a relatively small number of monitoring stations whose
locations were determined by specific needs not necessarily related to
watershed assessment. Thus, the list of impaired waters did not result from a
comprehensive survey of water quality. Prioritization decisions are based on
problem severity, relative importance of the stream segment, and availability of
resources to conduct the TMDL work. As
the basin planning process is launched in the Lower Mississippi River basin,
water quality problems will be identified and prioritized, resulting in
possible modifications of the list below:
|
303(d) IMPAIRED WATERS 1998
LOWER MISSISSIPPI RIVER BASIN
|
|
|
|
|
|
|
|
|
Mississippi River, Pine Cr. to Root R.
|
|
|
|
|
07040006-001
|
|
Aquatic life
|
Ammonia5, 6
|
2004//2007
|
|
Mississippi River, LaCrosse R. to Pine Cr.
|
|
|
|
|
07040006-002
|
|
Aquatic life
|
Ammonia5, 6
|
2004//2007
|
|
Reach
|
River Reach#
|
Lake #
|
Affected use
|
Pollutant or stressor
|
Target start//completion 7
|
|
UPPER MISSISSIPPI RIVER BASIN, Lower
Portion (cont'd)
|
|
|
|
|
|
|
|
|
|
|
Mississippi River, Trimble R. to Cannon
R.
|
|
|
|
07040001-006
|
|
Aquatic life
|
Ammonia5, 6
|
2004//2007
|
|
Garvin Brook, Headwaters to Mississippi R.
|
|
|
|
|
07040003-023
|
|
Swimming
|
Fecal Coliform3
|
2002//2006
|
|
Root River, S. Fk. Root R. to Mississippi
R.
|
|
|
|
|
07040008-001
|
|
Swimming
|
Fecal Coliform3
|
2001//2005
|
|
***
|
07040008-002
|
|
Swimming
|
Fecal Coliform3
|
2001//2005
|
|
Straight River, Maple Cr. to Crane Cr.
|
|
|
|
|
07040002-021
|
|
Swimming
|
Fecal Coliform3
|
2003//2007
|
|
Zumbro River, South Fork, Cascade Cr. To
Middle Fk. Zumbro R.
|
|
|
|
07040004-016
|
|
Swimming
|
Fecal Coliform3
|
2000//2004
|
|
Whitewater River, South Fork, Source to Split
at 122 S. Fk. Whitewater R.
|
|
|
07040003-222
|
|
Swimming
|
Fecal Coliform3
|
2002//2006
|
|
Robinson Creek, Headwaters to N. Br. Root R.
|
|
|
|
07040008-418
|
|
Swimming
|
Fecal Coliform3
|
2001//2005
|
|
Prairie Creek, Headwaters to Cannon R.
|
|
|
|
|
07040002-033
|
|
Swimming
|
Fecal Coliform3
|
1999//2003
|
|
Salem Creek, Split at 220 to S. Fr. Zumbro
R.
|
|
|
|
|
07040004-120
|
|
Swimming
|
Fecal Coliform3
|
2000//2004
|
|
Whitewater River, North Fork, Unnamed Cr.
to Middle Fk. Whitewater R.
|
|
|
07040003-120
|
|
Swimming
|
Fecal Coliform3
|
2002//2006
|
|
Vermillion River, Headwaters to S. Br.
Vermillion R.
|
|
|
|
07040001-312
|
|
Swimming
|
Fecal Coliform3
|
2003//2007
|
|
Vermillion River, S. Br. Vermillion R. to
the Hastings Dam
|
|
|
|
07040001-212
|
|
Swimming
|
Fecal Coliform3
|
2003//2007
|
|
Cannon River, Pine Cr. To Mississippi R.
|
|
|
|
***
|
07040002-002
|
|
Swimming
|
Fecal Coliform3
|
2003//2007
|
|
|
07040002-001
|
|
Swimming
|
Fecal Coliform3
|
2003//2007
|
|
Mississippi River, La Crosse R. to Root R.
|
|
|
|
***
|
07040006-001
|
|
Swimming
|
Fecal Coliform3
|
2004//2008
|
|
|
07040006-002
|
|
Swimming
|
Fecal Coliform3
|
2004//2008
|
|
Mississippi River, Root R. to Coon Cr.
|
|
|
|
|
07060001-021
|
|
Swimming
|
Fecal Coliform3
|
2004//2008
|
|
Garvin Brook, Headwaters to Mississippi
R.
|
|
|
|
07040003-023
|
|
Aquatic life
|
Turbidity
|
2002//2006
|
|
Mississippi River, Hay Cr. to Lake
Pepin
|
|
|
|
|
07040001-204
|
|
Aquatic life
|
Turbidity
|
2003//2007
|
|
Root River, Thompson Cr. to Mississippi
R.
|
|
|
|
07040008-001
|
|
Aquatic life
|
Turbidity
|
2001//2005
|
|
|
|
|
|
|
|
|
Reach
|
River Reach#
|
Lake #
|
Affected use
|
Pollutant or stressor
|
Target start//completion 7
|
|
UPPER MISSISSIPPI RIVER BASIN, Lower
Portion (cont'd)
|
|
|
|
|
|
|
|
|
|
|
Mississippi River, L&D #3 to Trimble
R.
|
|
|
|
|
07040001-108
|
|
Aquatic life
|
Turbidity
|
2003//2008
|
|
Mississippi River, Trimble R. to Cannon
R.
|
|
|
|
07040001-006
|
|
Aquatic life
|
Turbidity
|
2003//2008
|
|
Mississippi River, Coon Cr. to L&D 8
|
|
|
|
|
07060001-217
|
|
Aquatic life
|
Turbidity
|
2004//2008
|
|
Zumbro River, Indian Cr. to Mississippi
R.
|
|
|
|
07040004-001
|
|
Aquatic life
|
Turbidity
|
2000//2004
|
|
Vermillion River, Dam to Mississippi
R.
|
|
|
|
|
07040001-112
|
|
Aquatic life
|
Turbidity
|
1999//2003
|
|
Mississippi River, Lk. Pepin to Rush
R.
|
|
|
|
|
07040001-104
|
|
Aquatic life
|
Turbidity
|
2003//2008
|
|
Cannon R, Belle Cr. to Mississippi R.
|
|
|
|
|
07040002-001
|
|
Aquatic life
|
Turbidity
|
1999//2003
|
|
Mississippi River, Root R. to Coon Cr.
|
|
|
|
|
07060001-021
|
|
Aquatic life
|
Turbidity
|
2004//2008
|
|
Whitewater River, Whitewater R.,
N.Fk. to Mississippi R.
|
|
|
|
07040003-018
|
|
Aquatic life
|
Turbidity
|
2002//2006
|
|
Whitewater River,N. Fk., Unnamed Cr. to
Middle Fk. Whitewater R.
|
|
|
07040003-120
|
|
Aquatic life
|
Turbidity
|
2002//2006
|
|
Mississippi River, Zumbro R. to Whitewater
R.
|
|
|
|
|
07040003-008
|
|
Aquatic life
|
Turbidity
|
2004//2008
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
CEDAR-DES MOINES RIVER BASIN
|
|
|
|
|
|
|
|
|
|
|
Des Moines River Below Windom Dam, Windom
Dam to Jackson dam
|
|
|
07100001-101
|
|
Aquatic life
|
Ammonia4,5
|
2004//2007
|
|
Shell Rock River, Albert Lea Lake to Goose
Cr.
|
|
|
|
|
07080202-009
|
|
Aquatic life
|
Ammonia5
|
2004//2007
|
|
Des Moines River, Windom Dam to Jackson
Dam
|
|
|
|
07100001-101
|
|
Aquatic life
|
Low Oxygen2
|
2002//2007
|
|
Cedar River, Roberts Cr. to Austin Dam
upper
|
|
|
|
|
07080201-321
|
|
Swimming
|
Fecal Coliform3
|
2004//2007
|
|
Cedar River, Rose Cr. to Woodbury Cr.
|
|
|
|
|
07080201-016
|
|
Swimming
|
Fecal Coliform3
|
2004//2007
|
|
Shell Rock River, Albert Lea Lk. to Goose
Cr.
|
|
|
|
|
07080202-009
|
|
Swimming
|
Fecal Coliform3
|
2004//2007
|
|
Des Moines River, Windom Dam to Jackson
Dam
|
|
|
|
07100001-101
|
|
Aquatic life
|
Turbidity
|
2002//2007
|
In addition, 17 lakes in the basin are impaired by severe
algae blooms that result from excess nutrients. Nutrient levels in streams are monitored,
but the lack of numeric ambient water quality standards makes it difficult to
evaluate whether monitored concentrations are causing impairments. Impairments
for both fecal coliform bacteria and turbidity frequently occur in the lower
reaches of the basin’s major tributaries as well as far upstream in the
watersheds.
On the positive side, a long-term evaluation of the MPCA’s
16 Minnesota Milestone monitoring sites in the Lower Mississippi/Cedar River
basins shows significant improvements in the concentration of certain
pollutants and no trend in others over the past three decades.
·
Un-ionized ammonia concentrations decreased at
all 16 sites.
·
Biochemical oxygen demand (BOD) concentrations
decreased at all but one site (on the Vermillion River);
·
Total Phosphorus decreased at 11 sites and
remained unchanged at 5 sites.
·
Fecal Coliform Bacteria concentrations declined
at 8 sites and showed no trend at 8 sites.
·
Total suspended Solids (TSS) concentrations
showed no trend at 11 sites, declined at 4 sites and showed an increase at two
sites (both on the Mississippi River)
·
Nitrate Nitrogen concentrations showed an
increasing trend at 12 sites and no change at four sites.
Many of these positive trends likely have resulted from the
installation of secondary (biological) or further treatment for point source
dischargers in the basin. However,
despite these positive and neutral trends, concentrations of many pollutants
remain high enough to cause widespread water quality impairments. The ubiquitous and substantial increases in
nitrate nitrogen concentrations is thought to be related to manure and
commercial nutrient applications to row-cropped fields. Many fields have been
extensively drained with subsurface tile, which act as efficient conveyors of
nitrate nitrogen to surface water. In addition, wastewater treatment facilities
with ammonia effluent limits convert ammonia to the nitrate form of nitrogen.
Water quality in the Mississippi River varies considerably
along the 146.5 river miles between confluence with the St. Croix River just
southeast of St. Paul, southward to the Iowa border. Several complicating factors make this stretch of river unique
and challenging to describe with simple measurements of water quality.
The first, and most obvious, is the lock-and-dam system that
forms nine navigation pools adjacent to Minnesota (29 for the entire Upper
Mississippi River) within which a nine-foot-deep navigation channel is
maintained to support commercial barge traffic. This system, installed in the 1930s, has fundamentally changed
the river and its potential uses by converting a free-flowing river meandering
through a broad floodplain, into a series of pools that cover the floodplain
with slackwater. Within the navigation
pools it is useful to distinguish between the flowing water of the main
channel, and the side channels and backwaters, when describing water quality
and its connection to aquatic life support.
A second structural factor that greatly influences water
quality of the Mississippi is the presence of Lake Pepin, which was formed
naturally from alluvial sediment deposits at the mouth of the Chippewa
River. Because Lake Pepin acts as a
settling basin for sediments and attached contaminants, water quality differs
quite dramatically upstream and downstream of Lake Pepin.
1.
Water Quality: Lake Pepin and
the River Upstream
Two dominant influences on water quality in the 60 river
miles between Lake Pepin and upstream through Pool 2 are the Minnesota River
and the Metropolitan Twin Cities area. The Minnesota River contributes more
than 80 percent of the average annual sediment load to Lake Pepin, and is
chiefly responsible for the filling-in of the lake at a rate roughly 10 times
that which prevailed in pre-settlement times (before 1840). Approximately 17
percent of the lake volume in 1830 has been replaced by sediment. If current
rates of sedimentation continue, Lake Pepin will fill in after approximately
340 years rather than 4,000 years without accelerated sediment loading. In less than a century the upper third of Pepin
will be filled in. The rate of
phosphorus accumulation has increased 15-fold over the same period. Currently,
the Minnesota River contributes approximately half the load of phosphorus and
viable chlorophyll a (a measure of algae) to Lake Pepin on an average annual
basis. During low flow periods of
concern, half the load of chlorophyll comes from the Upper Mississippi River
Basin. This contributes to chronic problems associated with algal production. Upstream of Lake Pepin, sediment from the
Minnesota River makes the Mississippi River much more turbid than it otherwise
would be, limiting the diversity of aquatic life including mussels and
submersed aquatic vegetation.
The Metropolitan Twin Cities area also exerts a powerful
influence on the Mississippi River through Lake Pepin. This is a result of the
density of population (more than 3 million) combined with the relatively small
discharge of the river in the metropolitan area (310 cubic meters per second on
average, compared to 520,000 cubic meters per second near the mouth of the
Mississippi River). This produces a “population stress” level of about 10,000
people per square meter of river flow per second, the highest of any point on
the Mississippi River.
The 60-mile reach downstream of the Metropolitan area was
polluted with sewage for many decades. This resulted in frequent depletion of
dissolved oxygen, which adversely affected fish and other pollution-sensitive
organisms. This situation prevailed until the mid-1980s, after which time
improvements in the Metro Plant, the state’s largest sewage treatment facility,
were introduced. The Metro Plant was
built to provide primary treatment in 1938; secondary treatment was added in
1978. More recently, additional
treatment for ammonia was added; and biological phosphorus removal is being
introduced at the Metro Plant and other facilities operated by the Metropolitan
Council in the near future. The
separation of storm water from the sanitary sewage collection system completed
in 1995 has further reduced pollution pressure by virtually eliminating the
need for sewage treatment bypasses during storm events in the Metro area.
Ammonia toxicity problems have diminished in frequency as a
result of these improvements, and it is hoped that phosphorus reductions from
the Metro Plant, combined with planned reductions from point and nonpoint
sources in the Minnesota River, will help to reduce algal bloom frequency and
duration in Lake Pepin, especially in vulnerable low-flow periods when point
sources provide the bulk of phosphorus to the river. The last such period was
summer 1988, when a severe drought resulted in very low flows, algal blooms,
oxygen depletion and resulting fish kills in Lake Pepin.
Toxic chemicals became a major pollution problem in the
Mississippi following World War II, when the synthetic-organic chemical
industry rapidly expanded and introduced thousands of new chemicals, which
eventually found their way into the nation’s rivers. By 1950, the Mississippi
River had been significantly degraded by chemicals such as mercury and
polychlorinated biphenyls (PCBs). Following the banning of PCBs in the 1970s,
concentration in sediments decreased greatly. Bed sediments deposited during
the 1950s and 1960s retain extremely high levels of PCBs (2000 to 3000
nanograms per gram) in Pool 2; thus, contaminated sediments could remain a
problem for years to come. USGS
sampling from 1987 to 1992 showed that bed-sediment concentrations of mercury
in Lake Pepin exceeded 0.18 micrograms/gram, a level that has been shown to
increase the mortality rates in fish, embryos, eggs and larvae.
In surficial bed sediments, PCB concentrations are high below the Twin Cities,
reach a peak in Lake Pepin, and decline sharply downriver.
High organic-carbon concentrations in the presence of
mercury in the bed sediments increase the methylation rate of mercury and
subsequently increase the absorption and retention of mercury in fish and human
tissues. The Mississippi River between
Lake Pepin and the Twin Cities is one of the areas where this is most likely to
occur.
Recent water quality monitoring data show that the
Mississippi River upstream of Lake Pepin is impaired by turbidity and ammonia.
The MPCA lists the Mississippi River from Lock and Dam 3 through Lake Pepin as
impaired by turbidity. The lower reach of the Vermillion River, which at higher
flows exchanges water with the Mississippi, also is listed as impaired by
turbidity. In addition, a short reach between the Trimbelle River and the
Cannon River is impaired by un-ionized ammonia.
USGS monitoring from 1987 to 1992 showed that average
concentrations of herbicides were below maximum contaminant levels of
drinking-water standards established by the US EPA. However, it is not known whether agricultural chemicals and their
metabolites adversely affect aquatic life. Concentrations of dissolved heavy
metals are well below maximum contaminant levels, but concentrations in
suspended and deposited sediment often exceed maximum contaminant levels, and
toxics accumulated in bed sediments remain a potential threat to riverine
biota.
The Wisconsin Department
of Natural Resources’ Mississippi-Lower St. Croix Team has identified positive
trends in several water quality parameters after examining two decades of
monitoring data. In the last 20 years,
significant decreasing trends were noted for fecal coliform bacteria,
un-ionized and total ammonia nitrogen in the upper study area (Lock & Dam 3
and 4). Dissolved oxygen concentrations
and dissolved oxygen saturation exhibited a small increasing trend over the
same period. Municipal point source pollution abatement activities,
particularly in the Twin Cities Metropolitan Area, were likely important
management activities influencing these positive improvements. However, nitrite+nitrate nitrogen
concentrations and loading increased significantly at Lock and Dam 3 and 4. But
when all forms of inorganic nitrogen were considered, only a small increasing
trend was observed at Lock & Dam 4.
A Water Quality Assessment Report published in 1999 by the
Wisconsin Department of Natural Resources indicates that concentrations of PCBs
have been gradually decreasing at monitoring sites near Lock and Dam 3 and Lock
and Dam 4 on the Mississippi River.
This assessment is based on long-term monitoring of suspended sediment
contaminant concentrations at these two sites since 1987. Suspended sediment
contaminant trends for lead and mercury are less obvious, although there
appears to be a decline in lead and mercury concentrations at Lock and Dam 3.
These trends in contaminant reduction were credited to past pollution abatement
efforts to reduce the use or discharge of these contaminants.
Suspended sediment in river water represents a major portion
of contaminant transport, especially in turbid rivers such as the Mississippi
River. Organic chemicals that do not dissolve readily in water (such as PCBs,
organochlorine pesticides and heavy metals) adsorb to fine-grained suspended sediment
particles, especially those high in organic matter content. Some sources of
contaminant input include runoff from urban and agricultural land use,
deposition from coal and waste incineration, resuspension of contaminated bed
sediments, and wastewater discharges.
Concentrations of PCBs, lead and mercury in suspended
sediments normally were higher in samples collected from Lock and Dam 3 than at
Lock and Dam 4. This is due to the closer proximity to the Twin Cities
Metropolitan area, a major source of these contaminants. Lake Pepin acts as a
natural sediment trap, which results in decreased transport of these
contaminants downstream.
2.
Water Quality Downstream of
Lake Pepin
In some respects the Mississippi River “starts over” at Lake
Pepin. As noted above, concentrations of heavy metals drop sharply. Nutrient
enrichment and consequent hyper-eutrophication is not a recurring, widespread
problem, as it is in Lake Pepin and further north in Spring Lake. Impairments for ammonia, fecal coliform
bacteria and turbidity are clustered toward the southern stretches of the
river, between the confluence with the LaCrosse River and the Iowa border.
Sediment is a widespread and recurring problem both in the
main channel and slackwater areas of all navigation pools. Continual deposition of large-particle
sediments (sand) in the main channel necessitate regular dredging and a massive
river channel maintenance program to maintain the 9-foot navigation
channel. Much of the large-particle
sediments originate in Chippewa River. Other tributaries and upstream river
channel scouring also are sources of large-particle sediment. Dredging itself as well as related
activities such as transport and storage and dewatering of dredge spoils within
the flood plain, are potential sources of pollution.
Finer-particle sediments (silt and clay) from tributaries
and points upstream (the Minnesota River, for example) tend to settle out in
side-channels and backwater areas where water moves very slowly. In the decades
since the Lock-and-Dam system was constructed, backwater areas that once were
lakes, old river channels, oxbows and wetlands, have been filled in with
several feet of fine-particle sediment from upstream sources. The surficial
sediments are not consolidated, and are easily resuspended by wind or
turbulence caused by recreational and commercial boat propellers.
Many backwater areas of the Mississippi supported dense beds
of aquatic plants before an abrupt decline in the late 1980s. High levels of
turbidity continue to hinder the re-establishment and recovery of submersed
aquatic vegetation in these areas by keeping light from penetrating to the
river bed. Continued deposition and resuspension of sediment in backwaters also
has tended to produce a uniform depth of water which results in a less diverse
biological community. A recent increase in submersed aquatic vegetation in
Pools 5-9 has been accompanied by an apparent decline in turbidity.
The rapid spread of zebra mussels into the Upper Mississippi
River is quickly becoming a major water quality issue. Zebra mussels were first
discovered near La Crosse in 1991. Since then, the population and distribution
of zebra mussels have expanded greatly.
The highest concentrations have been found on hard substrates in flowing
water with moderate to low suspended solid concentrations. Densities exceeding
several thousand individuals per square meter have been found in some portions
of the river. Zebra mussel populations
upstream of Lake Pepin are very low and are likely negatively affected by high
suspended solid concentrations from the Minnesota River.
Unusually low dissolved oxygen concentrations were detected
in parts of the Mississippi River where zebra mussel populations were high,
during early summer periods of 1997and 1998. Water clarity improved
dramatically in portions of the river in late summer 1997, which may have
resulted from the filter-feeding activity of zebra mussels. Perhaps the most serious impact of zebra
mussels is on native mussel populations in the river. Native mussels are being smothered by high concentrations of
zebra mussels that attach themselves to the native mussel’s shell. This greatly
reduces the ability of native mussels to filter-feed. In addition, waste products from zebra mussels may be harmful to
native mussels.
C: Water
Quality of Major Mississippi Tributaries
The major tributaries to the
Mississippi are listed north to south, accompanied by a brief summary of water
quality resource issues:
Vermillion River: This stream originates in the south
metro area near Lakeville, and discharges into the Mississippi near Redwing.
The headwaters area of the Vermillion
includes reaches classified for a trout fishery, which are threatened by urban
development, lack of shading, high temperature and unstable hydrology. The
Vermillion is impaired by excess levels of fecal coliform from the headwaters
to the dam in Hastings, and by excess turbidity in the lower reach that runs
parallel to the Mississippi River. Sediment exchange between the Vermillion and
Mississippi Rivers at high flow complicates the turbidity problem. Recent
monitoring shows that riverine lakes along the lower reach of the Vermillion
are impacted by excess phosphorus. Urbanization, stream corridor protection
from agricultural practices and development, and the Metropolitan Council’s
Empire wastewater treatment facility are among the most significant
concerns. Long-term monitoring of the
Vermillion four miles northeast of Farmington indicates decreasing concentrations
of total suspended solids and
un-ionized ammonia, and increasing concentrations of BOD5 and nitrate-nitrogen.
Cannon River: The Cannon
River enters the Mississippi River immediately upstream of Lake Pepin. Riverine reservoirs including Cannon Lake
and Lake Byllesby often suffer from hyper-eutrophication, the result of
excessive loads of phosphorus from point and nonpoint sources. The latter
include feedlots, excess fertilizer and manure use, and soil erosion. Riverine
lakes at the mouth of the Cannon also may be impacted by phosphorus. Fecal
coliform bacteria levels are high throughout the Cannon River and its major
tributaries. The northern portion of the watershed is experiencing rapid urban
development, partially a result of more Twin Cities commuters. The lower reach of the Cannon is impaired by
excess turbidity, which is likely a result of excessive soil erosion from the
surrounding hilly terrain combined with streambank erosion. The Straight River,
a major tributary that runs parallel to the developing Interstate 35 corridor,
is impaired by fecal coliform bacteria. Long-term monitoring at the mouth of
the Cannon show decreasing concentrations of BOD5 ,un-ionized
ammonia, total suspended solids, total phosphorus and fecal coliform bacteria
over past decades.
U.S. Geological Survey monitoring
from 1984 to 1993 was evaluated for the National Water Quality Assessment
Program (NAWQA) in the Cannon River.
The assessment showed that the greatest loads and yields of nitrate nitrogen
and total phosphorus in both the Straight River (near Faribault) and Cannon
River (near Welch) occurred in spring
and summer. Nitrate nitrogen concentrations exceeded the Maximum Contaminant
Level of 10 milligrams per liter on the Straight River during spring and summer
of 1990. The Straight River, a large
tributary that enters the Cannon River at Faribault, was found to contribute
disproportionately to nutrient loads in the Upper Mississippi. Yield of total
nitrite plus nitrate nitrogen was 8.22 tons per square mile per year, on
average, more than twice the amount estimated for the Minnesota River and seven
times the amount for the Vermillion River. The yield of total phosphorus was
0.30 tons/square mile/year, three times that of the Minnesota River, and six
times the level in the Vermillion River.
In an Upper Mississippi River Basin NAWQA Study of snowmelt runoff,
concentrations of nitrate nitrogen, dissolved ammonia nitrogen and total
phosphorus in the Cannon River watershed were among the highest in the study area.
Zumbro River: Like the Cannon River, the Zumbro River
is impaired throughout by excessive concentrations of fecal coliform bacteria.
Zebra mussels were detected in Lake Zumbro in September 2000, the first time
this exotic species has been found in Minnesota outside of the Mississippi
River and the Duluth-Superior harbor where it is a major nuisance. Lake Zumbro also suffers from
hyper-eutrophication, but has improved somewhat since phosphorus controls were
introduced at the Rochester Water Reclamation Plant. Additional reductions from
point and nonpoint sources are needed. The Zumbro also is considered a source
of nitrates that contribute to the contamination of the aquifer that supplies
drinking water to the City of Rochester. A Clean Water Partnership for the
South Fork was initiated to address this problem. The lower Zumbro is impaired
by high suspended sediment concentrations. Sediment and phosphorous discharged
from the Zumbro at times may impair aquatic vegetation in Weaver Bottoms in the
Mississippi. Long-term monitoring of the south fork of the Zumbro downstream of
Rochester shows decreasing concentrations of BOD5 , un-ionized
ammonia and total phosphorus, and an increasing trend in nitrate-nitrogen
concentrations over past decades.
Whitewater River: The Whitewater River supports a
healthy population of brown trout, and is the centerpiece of one of the state’s
most popular parks. Impairments from excessive sediment and bacteria limit its
uses. The MPCA, Natural Resources Conservation Service and other state and
federal agencies are assisting local government in a major watershed
improvement effort focused mainly on sediment reduction and habitat
improvement. These efforts will also
help to protect the Weaver Bottoms in the Mississippi River. Long-term monitoring indicates that average
concentrations of BOD5 and
un-ionized ammonia have been decreasing over past decades, while nitrate
nitrogen concentrations have been increasing. In the 1990s decade, the mean
concentration of nitrate nitrogen was 8.90 mg/l, the highest level recorded at
long-term monitoring stations in the basin.
Root River: The Root River originates in the Western
Corn Belt Plains ecoregion dominated by intensive agricultural land uses, and
flows into the Driftless Region which is more wooded, rolling karst terrain
where groundwater flows provide stream temperatures suitable for trout. High
concentrations of fecal coliform bacteria and sediment impair the Root River,
limiting its suitability for recreation and for aquatic life support. The mean concentration of total suspended
solids at the mouth of the river was 99 mg/l during the 1990s, more than twice
as high as any other monitored major tributary in the basin. Concentrations of
BOD5, Total Phosphorus, un-ionized ammonia and fecal coliform
bacteria have been decreasing over past decades, while nitrate-nitrogen
concentrations have been increasing.
Cedar and Shell Rock River watersheds. These two
watersheds discharge into the Cedar River in Iowa, where the vast majority of the
watershed acreage is located. Fecal coliform bacteria concentrations are high
enough to cause both streams to be impaired on the Minnesota side of the
border. The Cedar River is listed as impaired by nitrate-nitrogen and fecal
coliform bacteria by the Iowa Department of Natural Resources. Long-term monitoring has been conducted at
two sites on the Cedar River and one site on the Shell Rock River. A monitoring site north of Austin on the
Cedar shows decreasing concentrations of BOD5, total phosphorus and
un-ionized ammonia. A monitoring site south of Austin, downstream, shows
decreasing concentrations of BOD5 , total phosphorus, un-ionized ammonia and fecal coliform
bacteria, with an increase in nitrate-nitrogen concentrations. The Shell Rock River
shows decreasing concentrations of BOD5, total suspended solids and
un-ionized ammonia, and increasing concentrations of nitrate-nitrogen.
|
Cannon River at Br on CSAH-7 at Welch (CA-13)
|
1950s
|
1960s
|
1970s
|
1980s
|
1990s
|
|
overall trend
|
|
|
|
Biochemical Oxygen Demand (5-day)
|
3.3
|
---
|
---
|
2.5
|
2.5
|
|
decrease
|
|
|
|
Total Suspended Solids
|
---
|
---
|
---
|
22.8
|
15.1
|
|
decrease
|
|
|
|
Total Phosphorus
|
---
|
---
|
---
|
0.26
|
0.18
|
|
decrease
|
|
|
|
Nitrite/Nitrate
|
---
|
---
|
---
|
3.00
|
3.90
|
|
no trend
|
|
|
|
Un-ionized Ammonia
|
---
|
---
|
---
|
0.0060
|
0.0040
|
|
decrease
|
|
|
|
Fecal Coliform Organisms
|
---
|
---
|
---
|
139
|
52
|
|
decrease
|
|
|
|
|
|
|
|
|
|
|
|
|
Cedar River at CSAH-4, 3 Miles S of Austin
(CD-10)
|
1950s
|
1960s
|
1970s
|
1980s
|
1990s
|
|
overall trend
|
|
|
|
Biochemical Oxygen Demand (5-day)
|
---
|
5.2
|
5.8
|
3.1
|
2.4
|
|
decrease
|
|
|
|
Total Suspended Solids
|
---
|
31.0
|
30.5
|
23.4
|
28.8
|
|
no trend
|
|
|
|
Total Phosphorus
|
---
|
0.64
|
0.72
|
0.43
|
0.36
|
|
decrease
|
|
|
|
Nitrite/Nitrate
|
---
|
---
|
3.20
|
3.90
|
5.45
|
|
increase
|
|
|
|
Un-ionized Ammonia
|
---
|
---
|
---
|
0.0135
|
0.0070
|
|
decrease
|
|
|
|
Fecal Coliform Organisms
|
---
|
2,307
|
697
|
199
|
280
|
|
decrease
|
|
|
|
|
|
|
|
|
|
|
|
|
|
Cedar River at CSAH-2, 0.5 Miles E of Lansing
(CD-24)
|
1950s
|
1960s
|
1970s
|
1980s
|
1990s
|
|
overall trend
|
|
|
Biochemical Oxygen Demand (5-day)
|
---
|
3.3
|
3.0
|
1.9
|
1.4
|
|
decrease
|
|
|
|
Total Suspended Solids
|
---
|
23.0
|
25.5
|
18.9
|
21.1
|
|
no trend
|
|
|
|
Total Phosphorus
|
---
|
0.18
|
0.28
|
0.19
|
0.16
|
|
decrease
|
|
|
|
Nitrite/Nitrate
|
---
|
---
|
---
|
4.40
|
6.55
|
|
no trend
|
|
|
|
Un-ionized Ammonia
|
---
|
---
|
---
|
0.0060
|
0.0030
|
|
decrease
|
|
|
|
Fecal Coliform Organisms
|
---
|
409
|
589
|
302
|
374
|
|
no trend
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
Garvin Brook at CSAH-23, SW of Minnesota City
(GB-4.5)
|
1950s
|
1960s
|
1970s
|
1980s
|
1990s
|
|
overall trend
|
|
|
Biochemical Oxygen Demand (5-day)
|
---
|
---
|
---
|
1.6
|
1.4
|
|
decrease
|
|
|
|
Total Suspended Solids
|
---
|
---
|
---
|
85.8
|
35.5
|
|
no trend
|
|
|
|
Total Phosphorus
|
---
|
---
|
---
|
0.25
|
0.13
|
|
no trend
|
|
|
|
Nitrite/Nitrate
|
---
|
---
|
---
|
1.30
|
1.70
|
|
increase
|
|
|
|
Un-ionized Ammonia
|
---
|
---
|
---
|
0.0050
|
0.0040
|
|
decrease
|
|
|
|
Fecal Coliform Organisms
|
---
|
---
|
---
|
670
|
851
|
|
no trend
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
Units of Measurement
|
Biochemical Oxygen Demand (5-day)
|
(geomean in mg/l)l
|
|
Total Suspended Solids
|
(geomean in mg/l)l
|
|
Total Phosphorus
|
(geomean in mg/l)l
|
|
Nitrite / Nitrate
|
(geomean in mg/l)l
|
|
Un-ionized Ammonia
|
(geomean in mg/l)l
|
|
Fecal Coliform Organisms
|
(geomean in col/100ml)
|
Root River at Br on MN-26, 3 Mi E of Hokah
(RT-3)
|
1950s
|
1960s
|
1970s
|
1980s
|
1990s
|
|
overall trend
|
|
|
Biochemical Oxygen Demand (5-day)
|
---
|
5.5
|
2.4
|
1.8
|
1.5
|
|
decrease
|
|
|
|
Total Suspended Solids
|
---
|
58.5
|
92.6
|
81.3
|
99.1
|
|
no trend
|
|
|
|
Total Phosphorus
|
---
|
0.16
|
0.26
|
0.18
|
0.17
|
|
decrease
|
|
|
|
Nitrite/Nitrate
|
---
|
---
|
1.90
|
2.65
|
3.90
|
|
increase
|
|
|
|
Un-ionized Ammonia
|
---
|
---
|
---
|
0.0025
|
0.0020
|
|
decrease
|
|
|
|
Fecal Coliform Organisms
|
---
|
1,276
|
703
|
322
|
615
|
|
decrease
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|