United States
Environmental Protection
Agency
Office Of Water
(WH-553)
EPA841-F-92-011
December 1992
Number 6
TMDL Case Study
The Lower Minnesota River
Key Feature:
Project Name:
Location:
Scope/Size:
Land Type:
Type of Activity:
Pollutants:
TMDL Development:
Data Sources:
Data Mechanisms:
Monitoring Plan:
Control Measures:
Program Integration:
A TMDL undergoing assessment as
part of a basinwide river assessment
project
Lower Minnesota River
EPA Region V/Southern Minnesota
Minnesota River Watershed,
16,770 mi2; Lower Minnesota River
drainage area, 320 mi2
Irregular plains
Agriculture
CBOD, ammonia
PS/NPS
STORET, Reach Files, PCS
QUAL H, kMA-12, HSPF
Yes
BMPs, NPDES permits
State/local/Federal
FIGURE 1. Location of the Minnesota River watershed
Summary: The water and sandy white riverbeds of the
Minnesota River (Figure 1) have turned murky brown and
muddy. Soil, pesticides, fertilizers, oil and grease, toxic
chemicals, and septic system wastes have all found their way
into the river, causing a variety of water quality problems that have impaired the river's ability to support fishing and
swimming. Today, the lower 25 miles of the Minnesota head the State's §303(d) list of water quality-unpaired waters. In
1985, the Lower Minnesota River Waste Load Allocation Study (MPCA, 1985a) recommended limitations on carbonaceous
biochemical oxygen demand (CBOD5) and ammonia effluent, citing frequent violations of water quality standards for these
two parameters in the lower Minnesota River. However, the study also stated that a basinwide nonpoint source control
program would be necessary to achieve ultimate water quality objectives. In 1988, the Minnesota Pollution Control Agency
(MPCA) established total maximum daily loads (TMDLs) for ultimate CBOD (CBODU) and ammonia nitrogen, allocating
waste loads to the Blue Lake and Seneca wastewater treatment facilities, which discharge effluent into the river, and
allocating loads to nonpoint headwater and tributary sources. These headwater and tributary load allocations represent
current loads reduced by 40 percent.
Since establishment of the TMDLs, the Blue Lake and Seneca WWTPs have upgraded to advanced secondary treatment to
meet their waste load allocations. However, implementation of a watershed-based nonpoint source control program is still
under way. The Minnesota River Assessment Project (MRAP), managed by MPCA, is a multi-agency effort that is
assessing the water quality, sediment chemistry, aquatic communities, and current land uses in the Minnesota River
watershed. The information collected will be used to develop specific water quality goals and to identify programs and
best management practices (BMPs) that will help reduce nonpoint source pollution. The assessment phase of the 4-year
project that was begun in 1989 is scheduled to be completed in July 1993. At that time an implementation program that
includes targeted application of BMPs and public education will begin. The Legislative Commission on Minnesota
Resources has allotted $1.1 million for the implementation program in addition to the $1.4 million that has been spent on
the assessment phase to date.
Contact: Ron Jacobson, Minnesota Pollution Control Agency, Water Quality Division, 520 Lafoyette Road, St. Paul,
MN 55155, phone (612)296-7252; Tim Larson, MPCA MRAP Coordinator, (612)296-7356" " ' ' -
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^
W^^ i^ i* i ill! I ^Aim
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BACKGROUND
'': i iil'i, I'1* '!'!!' SWIM'* l; :J.| l«! Ill IIP! I'lPII !' iifll '41 rill « li|::iiililr
ift'lilliiiiiilfll''ffil HH''
i1'"i1"" "i""'• "i1 s1 if'"'"!•'™i|»''1 "ni i'1 '""".i!'""" i '''" i;'i l!l-IEH'if""i'.3''i^tfe
JJ^aiuk Li :LJ Itf: iiiJKLdilK[£ .J!:!!!:!!!
In 1987, after DO and un-ionized ammonia were
ir the"
Programmatic Issues
liliFlill'llfIIIiillilnlll:lilllliiffi ;, if THj;,! iHilW : , :
he 320-SQuare-mile area that drains to the lower
l|^j^^^i]£'^^.''||'jjgg^'l^f agnoJiltun} —jj roaSentiaT
lijagiw,,,,,, ,,» :,l.,,ii: ^ju^yuunercial p«yyp_gment.' The Minnesota River is
^iiiifiiaiiiSL'iii ejllgifiel lor specific" uses "'and' coverecf f>y" water qjiafijy'"
'"""^ ' "', coniaine| inj^innesota^^
,,.„„„ ije lower ^linnesota River, the use classification
!IM 'Ifl'lli^
feE£^s*;;J3!SffiSe? at nver mile 22, Upstream from nver mile 22,
::'^
water quality must permit the propagation and
....... ......
^'maintenance ...... oFcooT ...... or
mus
'''•" '< ''"
._iT.rr(S|T.i7, ^ of all kinds, Including
i, t T , „ swinuning." '^wnstream' 'from "nver "mile' 22 to "the
i| iiiiii imppjljj.'in1 'tiie^^reacfi "generally accessible to commercial""
lower Mmnesota River, 'MPCA established preliminary
m Jj2r^p|£i§SE?j S^, S™?,!1?^ m'^PSern, 3p5f, in^u,?£d
tiem in"tneuiState's Water-^ualiity 'Management'Plan"
(MPCA, 1987). The Blue Lake and Seneca Road
WWTPs and headwater and benthic loads were listed as
the primary point sources and nonpoint sources of the
problem, respectively. The Lower Minnesota River
, Waste Load Allocation Study provided the basis for the
i modeling work during the initial stages of TMDL
. development (MPCA, 1985a). The study recommended
CBOD5 and ammonia effluent limitations at point sources
and the implementation of a basinwide nonpoint source
• program to reduce headwater CBOD loads and sediment
oxygen demand in order to achieve ultimate water quality
objectives.
||;:f:- ;• ~:--••-;!;;; ; barge traffic, the river is classified as a 2C water,
i11!' n' •': r;''!: ¥ Jndicatuig its' status" as "aroug^ fishery "water suitable "for
I! I
I..! ti
i^' :irl "1:: ::f "" :%aj!ng out"not' recOTimen'ded' fof'swimmmg. The entire
'fjf^ " f H* ^inncsota Riyer is classified as^SB (industrial
'""" ^^$Giffiiiipn| which ^1^5' usage' for""' general" uiaustrial
sr " m" "
I" i :i'i ill1 •' Ill I!"! i; '3 ' "" 'ft'' :" "1 R" SM" » ""T "I '"
|lit^iii iiiijjii; indegree pf treatment), 3C (industo
I T!: rT^rfr jpSmlts" usage fot industrial cooling and material!
j^juin usage for irrigation, livestock, and VYUUUI.W
lij^t*^ i:^i»!;-iiii||^
jj^^frS^ depiplnl'1 tn'at"t£e" water quality must'K'lSSeScailyi"1
I'•''jl^j'!""'_, "'ii 'Sui^le^iEor's^enic'eiyoymentj mifs't nbTmte^ere"with""
'i" ' a, and'must'nave"'no damaging "effects "on"
;"For tie lower Minnesota' River Se water Quality
In 1989, MPCA organized MRAP to address the water
quality problems of the Minnesota River, especially those
problems associated with nonpoint sources. MRAP is a
4-year multi-agency effort involving more than a dozen
local, State, and Federal organizations working in concert
with local governments in the Minnesota River
watershed. The agencies involved include the U.S.
Geological Survey, the U.S. EPA Environmental
, Research Lab-Duluth, Mankato State University, the
Minnesota Department of Natural Resources, and 37
Minnesota counties and Soil and Water Conservation
Districts. The Legislative Commission on Minnesota
Resources provided a State grant of $700,000 to fund the
initial phase of the study.
tBBBBIItl
ow 5 mg/L and ammonia nitrogen should
I i 5 SLl&ft ^fcfi^a 0.04 mg/L (un-ionized as N).
.*'- »«I- •iBKfWra?«!ra'iffi(SiP:tf«i»'!:?!SWI§i!aJ! Ill m^mii !•
fe's nyers, In 1985,
The Minnesota River drains a 16,770-square-mile area
representing approximately 19 percent of Minnesota's
' land mass. It flows 330 miles from Big Stone Lake on
the Minnesota-South Dakota border to its confluence
iWth the Mississii River at Saint Paul (Figure 2).
Agricultural 'activcoimOT ovepercent of land ......
uses in the basin, and nonpoint source pollution is the
Hajor cause of water quality degradation.
||!|" ^uMpns'at ;fo'OFR' Part*! SOra'SffiSolpgjy^ for"
; TMM,'s fof"ffie Slii
compliance with State water quality standards
I=,_ ............ __ ...... ___ ....... ____ ...... __ .......................
•: ii <* ^i^ : mi L:1!!!! f i" iii'Siiuiii:,, ,» n, f .................. * ....... £ .......... «u ................... • ....................... .«., ...... f , ........ • ...... ..... f ............... «» ....... d.
'gj ....... JJJ ...... 1986 Water DuaUty Management
......... w'i 1' f '1'inni iiiir iiiignm^^^^^^^ ............................... A ..... ...... ..... .............................. A ......... .......... .......... ................ ,r
siu'table for TMDL assessment.
..... exlsSng'lSeral,' State, ..... OT ........
Land types in the Minnesota River watershed range from
" flat to irregular plains. The basin of the lower Minnesota
River, which covers about 25 miles between Shakopee
and the river's mouth, consists of irregular plains where
" natural vegetation tends toward maple, basswood, and
northern hardwoods (Omemik, 1987).
iijf"''v' i"1'"' i"''Ri!'" i''1'!!1!1'1' 'flcmcvc aii€* txiain 1^1 ^n ^vatfir cjuaiity sianciaros. jviirvxif\
'I:1! l!!''i''!!,' I. '','."' ''» 'i l^jiiil J i ' l*"ij'l'j|iill"''ll'ijj|" • jf"1' ' '•'"''"'"'''"' l*iliiijr f»''"'"""_ ll'""'"11"''' •j"hj"»i'«'iiJi" '• .'NLiiiiN j ,,1111,1, n, " i" •"'" '. v"1'' 'i'*'_ I'1 ' ""i"
l^^ii^jy^p^i^Lpi iKSKirMsi^sfe-ilx6! si fep^ofiiy J!*?ij of
( ||.^^^iii,:.?l!^^^2^r~1-ra?- s5'"35* 5™"?? fo.f^^,.^™-^- ., ,
m
! |i;| f, ;? '.(^' {|»:i, .iVj? ^j.
"As the Minnesota River enters the lower 25-mile reach,
the combined effect of channel dredging and the
backwater pool created by the U.S. Army Corps of
Engineers' Dam No. 2 on the Mississippi River at
Hastings transforms the Mmnesota from a shallow, free-
flowing stream to a deeper, low-velocity channel
IJSTHSIitvJi (
IS !i.ii'MiKl
-------
to zo 30 *io :o
'
3CAUC OF MILES
FIGURE 2. The Minnesota River watershed
maintained for commercial navigation (MPCA, 1985a).
River flows are monitored by the USGS with a
continuous water stage recorder located at station
05330000 near Jordan, about 39 miles upstream from the
mouth. The average discharge for the period between
1935 and 1983 was 3,520 cubic feet per second.
Average annual precipitation hi this area is approximately
28 inches, and average annual runoff ranges from 4 to 6
inches (USGS, 1985). Sixty-five to seventy-five percent
of the annual precipitation in Minnesota occurs during
the growing season of May through September, and only
15 percent occurs during December through March. As
much as 50 percent of the total runoff can occur during
the spring rain and snowmelt periods.
Water quality in the last 25 miles of the river is
frequently in violation of water quality standards,
especially during summer, low-flow conditions. Un-
ionized ammonia is especially a problem during summer
drought conditions when temperatures and pH levels are
high. To address these water quality problems, TMDLs
were established for both CBODn and ammonia nitrogen.
The Lower Minnesota River Waste Load Allocation Study
(MPCA, 1985a) provided the basis for TMDL
development in these last 25 miles.
ASSESSING AND CHARACTERIZING
THE PROBLEM
Monitoring and Data Bases
MPCA combines data from several sources and enters
them into the State's Water Quality Management Plan
data base. This data base includes water quality data
from the routine and intensive monitoring conducted by
MPCA, water quality standards for waters in Minnesota,
effluent limitations for municipal and industrial
wastewater discharges, and flow for wastewater
discharges.
MPCA routinely monitors stations and enters the data
into EPA's STORET data base. These data are linked
with Reach File data and effluent data from municipal
and industrial wastewater discharges (Discharge
Monitoring Report data from the Permit Compliance
System) to provide an overall picture of water quality in
Minnesota. After retrieving these data from EPA's
mainframe, MPCA determines where ambient violations
have occurred and whether there are discharger
violations. Next, MPCA meets with in-house point and
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:::i i ,i:, ft;, i1;,; :,:' ,„,:•:: i,;: i „, •, i h1:,i „ i: i,I'l'i vei, „'':, ss,1:1 -":,:.. f ",iii wii. i IH ."i"1,1"'»' i", 'vii:i,,iii,ra,i: 'JLE zniB!;!!!1 "ir • !IIIIIIIII,.:T::|:H „ !!WM,!:H!H!:!!:S lain;::1
nt source experts and makes judgments as to
Whether the violations are most likely point or rionpoint
KC i .Most .often ^'"problems" are "a "result '"of i
'I,,'! ;,l, '"I1:™,,! IK ":i,,li I;!,,,,!;*!!,:!
both.
Wl '"I, I !,:, Nil
parameters of concern. The model uses a finite-
Difference^'"technique"to''solve"me"mass balance"equations^1
<', «, ,|, n fill' H II I » ' ' I.T ' h •
'*6
..^l^te, analysis is part of the method used to diffusion, loci sources and sinks of water quality
;':;'::"rtargel"watef qi^iywpaued ^g5i^^ requiring xMDEs ___-_ _j ^g-g-g——-—-— _g__ __ ,__
(Sylvia McCollor, MPCA, personal communication, The time-dependent reaction kinetics for physical,
"<"•': -': October 16,1992).
.-it !•'• . 1 I 'i-ii'i i i .i,' :':, ifir;o. *! '« ii :ri!' >;i!ilUU ii liiiiilRl:: lliiiiliiiiaSlfi1!. 'tillWiiil .IWiH^^^ i'UI IKiliM
jlgjggggt^^j^^g^^gigKly for each parameter. The steady state mode
,'"„:," • :• ,.,' ,:::!•: ,
specifically for MRAP are also
;. being stored in STORET; however, at this time, only
MPCA data Lare .being used for the assessment project.
Data from other agencies may be used at a later time.
was used to simulate low stream flow conditions. Under
these conditions th
headwater, tributary, and waste inputs are held constant
over time The follbwing water quality constituents and
™ ; ph^sicalf processes "were s'imulateS'' using ' 'RMS- 12:
' .......... ...... " ............ '"' ........................ ""' ....... ........................................ ' ..... ' .......... ................. ........ ' ......................
»i;lllpSy topanklon algae
,alig ' '""chioroiphyil-fl"'
Management Plan data base to ideh'SJEy "river reaches carbonaceous BOD
where' watjar quality standards 'are" not '6eing" met As part dissolved oxygen
^ff'fefnStiSon'plwS, ^CAidentffies segmente benthic oxygen demand
Ike" the 'i^'muBes^^ atmosphenc reaeration
may pose human health threats (a fish consumption
advisory for PCBs is in place) and considers the relative
importance of the resource to the surrounding population
and the, designated uses of thg resource (e.g., for
recreation). Currently, the Minnesota River remains the
highest priority on the State's §303(d) list.
organic
ammonia nitrogen
nitrite nitrogen
nitrate nitrogen
orthophosphate
TMDL DEVELOPMENT
Under MRAP, MPCA is currently assessing the effects
of nonpoint source pollution loads on water quality in the
Minnesota River. This modeling effort should be
completed by June 1993. MPCA chose to use the HSPF
model to characterize the effects of nonpoint source
';j^ to translate .those .loads to ambient river water
communication, November 17, 1992).
I II.? II '.Mil' I H
Models
The earliest attempts to estimate the assimilative capacity
of the lower Minnesota River m order to allocate waste
loads used the classic Streeter-Phelps approach to predict
_the river's DO response to point source discharges. during summertime^ 'low:flpw conditions. [
Interpretation of the results of these modeling efforts led
to the conclusion that a 40 percent reduction in some
ty i i n i m i i r
nonpoint source loadings and the upgrading of the Blue
Lake and Seneca WWTPs would be necessary to meet
; ' | ,,, pi '.'h|r 'mi! IMJ Hnii,1 iyv'iiiiiV'ihi i ,|np|ii< '''in,! 11!,'! ,| > ii",« , v t ,<• ,„ ,,;, „, ,, ,, ,,;,,; ,,„
water quality standards in the lower Minnesota River
TMDL development included consideration of all
significant sources and sinks of DO in the aquatic
environment in order to protect the level of DO in the
river. Later studies of the lower reaches of the
Minnesota River used the original QUAL n model.
Then in 1985, a version of the QUAL H model, RMA-
12, as revised by W.R. Norton of Resource Management
Associates (Norton, 1977), was iised'to determine ^asle
load allocations for the lower Minnesota River (MPCA,
I985a). It simulated the effects of waste loads,
nitrification, sediment oxygen demand, and algal
photosynthesis. RMA-12 was used for this study
because of changes in the growth equation for algal
biomass and a redefinition of the nitrogen cycle. RMA-
^2 considers the organic and ammonia fonns of nitrogen
Separately, whereas QUAL n uses KjeldaUjiiitrojien.'
The RMA-12 model also allows for the direct uptake of
nitrogen by algae.
of the Load/Waste Load
Allocations
RMA-12 uses a one-dimensional, adyectiye-dispersive
A 1961 study by the University of Minnesota showed
that dissolved oxygen concentrations would be
maintained at 4.0 mg/L under low-flow conditions with
year 2000 predicted loadings, if 90 to 95 percent of the
organic matter hi the wastewater was removed. A 1974
study conducted by consultants for MPCA concluded that
under summer low-flow conditions, effluent standards of
17 mg/L BOD5, 4 mg/L DO, and 2.85 mg/L ammonia
nitrogen were necessary for the Blue Lake and Seneca
treatment plants under year 2000 design flows to ensure
an average instream dissolved oxygen level of 5 mg/L
(MPCA, 1985a). During a 1980 survey, the headwater
(nonpoint source loads) contributed 80.9 percent of the
CBQD load, WWTPs .about. 12.9 percent, and the
tributaries about 4.0 percent. Under future design low-
equation for a numerical solution"df tite;^^.'™^ flow conditions> at effluent concenttations averaging 25
ii^
-------
mg/L CBODS, the Blue Lake and Seneca WWTPs would
contribute about 67 percent of the projected CBOD5 load.
Consequently, the 1985 study recommended the
maximum monthly average effluent concentrations listed
in Table 1 for CBOD5 and ammonia at the Blue Lake
and Seneca WWTPs (MPCA, 1985a),
Table 2 presents the TMDLs that were established in
1988 for CBODU and ammonia nitrogen (MPCA, 1988).
The design parameters for the TMDLs at the WWTPs
were the maximum summer month flow, the CBODS
summer monthly average, and the CBOD/CBOD5 ratio.
The parameters for the headwater and tributary sources
were 7Q10 flow adjusted by a wet weather/annual
average flow ratio and the current water quality reduced
by 40 percent. Calibrated water quality models were
used to derive the relative proportions of loads
contributed by the headwater, tributaries, benthos, and
instream nitrification, A margin of safety was
incorporated into the TMDL by implicit use of
conservative approaches in the modeling and permitting
process.
IMPLEMENTATION OF POLLUTION
CONTROLS
Point Sources
The Blue Lake and Seneca wastewater treatment plants
discharge their effluent within the last 25 miles of the
Minnesota River, The upgrading and improvement of
these WWTPs was completed in August 1992 at a capital
cost of approximately $65 million at each plant. The
plants now provide advanced secondary treatment and
meet the waste load allocations set forth by the TMDLs
established in 1988, Controls on discharge limitations
were established through the NPDES permitting process
in 1987.
Nonpoint Sources
To date MRAP has received matching and cooperating
funds totaling approximately $1,4 million, and another
$1.1 million has been allotted by the Legislative
Commission on Minnesota Resources to implement the
recommendations of the project.
The main goal of the implementation phase is to
showcase certain BMPs in targeted geographic areas,
demonstrating the effectiveness of BMPs when applied in
a holistic manner throughout the watershed. These
BMPs, which appear on Minnesota's list of approved
BMPs for agriculture, include manure management,
contour cropping, stripcropping, grassed waterways,
riparian filter strips, nutrient management, integrated pest
management, and conservation tillage. Presently, only
minimal application occurs on a large scale. The
implementation project intends to show mat targeted
application of these BMPs will improve water quality
more effectively.
In addition to continued monitoring and application of
BMPs on a watershed basis, the implementation phase of
the project will include public education programs
targeted at homeowners and farmers, such as the
Midwestern Rivers Program and the Manure Treatment
Management Project The multi-agency effort instituted
with MRAP will continue throughout the implementation
phase.
FOLLOW-UP MONITORING
Monitoring, an important component of the TMDL
process, helps to determine whether allocated loads and
waste loads have unproved water quality. MRAP
includes three major monitoring components that will
permit an assessment of the TMDLs established in 1988.
Physical/chemical monitoring, biological/lexicological
monitoring, and land use assessment in the Minnesota
River watershed each provide information on susjjended
solids, oxygen demand, nutrients (nitrogen and
phosphorus), and bacteria (animal and human waste),
which are the pollutants of greatest concern (MPCA,
1991).
Although variability hi the year-to-year weather and flow
data since 1988 has prevented a pre-assessment of the
TABLE 1. Recommended maximum monthly average
effluent concentrations of CBOD5 and ammonia for the
Blue Lake and Seneca wastewater treatment plants
CBOD5
Ammonia
Season
Summer (June-Sept.)
Winter (Dec.-Mar.)
Spring (Apr,-May)
Fall (Oct-Nov.)
Month(s)
Dec.-Apr.
May
June
July-Sept
October
November
Max Monthly
Avg (mg/L)
12 (Blue Lake)
15 (Seneca)
25
25
25
Max Monthly
Avg (mg/L)
No specified
limit
9
12
2
5
7
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established TMDLs, the initial assessment phase of
MRAP should be finished by July 1993 when nonpoint
source load modeling is completed. It will be
determined then whether the TMDLs established in 1988
for the lower Minnesota River are sufficient to protect
water quality. Monitoring will continue after BMPs are
implemented until July 1995. A final report is due at the
end of that year.
The physical/chemical monitoring program consists of a
twofold approach. First, sampling is being conducted at
the mouths of the major tributaries to assess the pollutant
loads each is carrying. Second, sampling is being
conducted at the mainstem of the Minnesota River to
measure the cumulative effect of all sources entering the
river. The major objectives of this portion of the study
are to identify sources and loadings of nutrients,
suspended sediment, BOD, and organic carbon in the
river; to calculate the movement of sediment and
associated pollutants between various points along the
river, and to identify areas of bank erosion and
associated deposition of sediment to determine whether
loadings of sediment within the river channel have a
more negative effect on water quality than sources of
pollution coming from upland areas. Additional
emphasis has been placed on studying the Blue Earth
River and determining its effect on the Minnesota. This
river is thought to contribute the largest loadings of any
tributary in the river system.
TABLE 2. TMDLs for oxygen demand and ammonia
nitrogen in the lower Minnesota River
Source
Blue Lake WWTP - CBOD.
Seneca WWTP - CBOD.
Headwater - CBOD,
Tributaries - CBOD,
Sediment Oxygen Demand
Nitrogenous Oxygen Demand
TMDL
Source
Blue Lake WWTP
Seneca WWTP
Headwater
Tributaries
Bcnthic Ammonia
TMDL
Oxygen
Demand,
Ibs/day
*14,600
*15,100
13,600
1,200
6,700
2,200
53,400
Ammonia
Nitrogen,
Ibs/day
*617
*634
415
37
445
2,148
Percent
of
TMDL
27.3
28.3
25.5
2.2
12.6
4.1
100
Percent
of
TMDL
28.7
29.5
19.4
1.7
20.7
100
» NPDES pennitted loading
The biological/toxicological monitoring program consists
of fish studies, algal studies, toxicity testing, and
macromvertebrate studies. The fish studies involve
assessing the health of fish communities in the river
using the Index of Biotic Integrity (IBI). This tool
examines the condition of the fish habitat, the number of
fish species found, the population of each species, and
the availability of food sources at sampling sites. Forty-
five sites on the river were sampled to select reference
sites that represent the best attainable conditions for the
river. These reference streams will serve as the goal for
improving more degraded reaches. Researchers are also
studying several fish species to understand the impacts of
organic chemicals, oil, and farm pesticides. Because
algal communities provide an important food source for
invertebrates and fish, MRAP is studying the abundance
and diversity of algal populations within representative
streams hi the river basin. Toxicity tests are being used
to identify problem areas in the river. At 26 sites,
MRAP used two standard test procedures, using a small
microscopic animal and a green algae, to check toxicity
levels. An additional test examines the effect of
sediment pore water on mitochondria. Aquatic
macroinvertebrates, consisting largely of insect larvae,
are important indicators of water quality.
Macroinvertebrate communities were assessed at 19 sites
during the first 2 years of MRAP. Samples were
collected by using a kick net, by hand-picking specimens
from natural river bottom materials, and by placing
artificial substrate samplers at the sites.
The land use assessment program considers the
connection between land use practices and water quality
within the Minnesota River watershed. MRAP has
determined that any strategy to solve water quality
problems must include the watershed protection
approach. The Minnesota River basin consists of 1,208
minor watersheds. Thirty-two of these sub-basins have
been selected for the study and four different methods of
land use assessment are being used. Land Use Level I
assesses the nonpoint source pollution potential of the 12
major watersheds in the basin using the ecoregions
concept to characterize each watershed. Land Use Level
II, managed by USDA-SCS, involves identifying and
recommending the most cost-effective Resource
Management Systems (RMSs) or BMPs that will prevent
water quality problems caused by agricultural practices.
Ten minor watersheds will be studied using this method.
Land Use Level III, managed by several Soil and Water
Conservation Districts, is assessing the nonpoint source
as well as small point sources of pollution within the 32
minor watersheds. This method includes collecting field
data in each watershed, interviewing landowners within
the watershed to determine land use practices, developing
detailed land use maps for each watershed, and storing
all of the collected information in a data base. Land Use
Level IV involved using infrared aerial photography to
help interpret land use practices in some of the minor
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•watersheds. These aerial photos were used to distinguish
landscape features, which were mapped on mylar and
then digitized.
During the final phase of the study these monitoring
programs will focus on studying more reaches of the
river. The physical and chemical component will study
the effects of the Blue Earth River on the tributary
loadings to the Minnesota and the effects of streambank
erosion on sediment contribution to the river. The
biological and toxicological component also will study
the Blue Earth River, using the IBI developed from
reference sites. Additional toxicity tests will be applied
to the upper reaches of the river's tributaries.
Information from the Level I, II, and III components will
be refined to predict nonpoint source pollution and
provide recommendations for improving water quality.
REFERENCES
MPCA. 1985a. Lower Minnesota River Waste Load
Allocation Study. Minnesota Pollution Control Agency,
Division of Water Quality, Monitoring and Analysis
Section.
MPCA. 1985b. Office Memorandum - Total Maximum
Daily Loads (TMDLs): U.S. EPA Requirements and
Proposed Methodology. Minnesota Pollution Control
Agency, Division of Water Quality, Monitoring and
Analysis Section.
MPCA. 1987. Minnesota Surface Water Quality
Management Plan: Point Source Element. Minnesota
Pollution Control Agency, Division of Water Quality,
Program Development Section.
MPCAl 1991. Understanding the Minnesota River
Assessment Project.
Norton, W.R. 1977. Operating Instructions and
Program Documentation for the Computer Program
RMA-12. Resource Management Associates, Lafayette,
CA.
Omernik, J.M. 1987. Ecoregions of the Conterminous
United States. Annals of the Association of American
Geographers 77(1):118-125.
USGS. 1985. National Water Summary 1985 -
Hydrologic Events and Surface-Water Resources. U.S.
Geological Survey. Water-Supply Paper 2300.
sase study wt$ prepared Ijy Tetta Tecfe, Inc>,
VA, ia etttij«n<;lan.wifli EPA's Office, of Wetlands,
and. Watersheds, Watershed Maaagemeat Section,
obtaia "copies, contact y««t l^PA Regional
Coordinator,
To
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