EPA/600/A-96/029
l
Regional Lake Quality Patterns: Their Relationship to Lake Conservation
and Management Decisions
S.A. Peterson1, R.M. Hughes2, D.P. Larsen1, S. G, Paulsen1, J.M. Omernik1
lUS EPA, NHEERL/WED, 200 SW 35th Street, Corvallis, OR 97333, (541) 754-4457
FAX (541) 754-4716, EMAIL: peterson@mail.cor.epa.gov
2ManTech Environmental Research Services Corp., c/o US EPA, NHEERL/WED
200 SW 35th Street,Corvallis, OR 97333
Abstract
Understanding regional lake quality patterns is important to lake restoration. It puts specific lake
conditions into perspective, provides a basis for establishing lake quality goals, identifies lakes
most likely to benefit from restoration and forms a framework for assessing restoration success.
We describe two techniques used to characterize regional lake quality patterns. Combining the two
approaches provides an effective means to describe lake regions, management goals and restoration
success. Case examples illustrate the significance of regional lake quality to specific lake
restoration projects.
Key words
Lake restoration, Survey Sampling, Ecoregions, Phosphorus
INTRODUCTION
Scientific and public interest in lake restoration chlorophyll a. relationship and Vollenweider's
owe much to several key events including	(1975) phosphorus loading and residence time
Dillon and Rigler's (1974) phosphorus/	relationships. The passage of the Clean Water

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Regional Lake Quality Patterns
Act of 1972 with the so called "Clean Lakes"
section, ultimately was responsible for
launching the first formal and orchestrated
movement to protect and improve lake quality
in the U.S. The Clean Lakes Program
provided federal funds to lake associations for
diagnosis and "restoration" efforts.
Restoration is a misleading term frequently
envisioned to mean pristine. In practice, a more
accurate definition is that coined by Sven Bjork
in 1968, to reflect a recreation of conditions in
such a way that acceptable environmental
conditions are reestablished. As a rale this
recreation of acceptable or suitable conditions
reflects a local or regional perspective relative
to uses for which the lake was once suitable
before its degradation (Bjork 1994).
Based on the phosphorus limitation
phenomenon in most freshwater lakes,
restoration focused primarily on reducing this
nutrient in the lake to a level that produced
more acceptable phytoplankton species
composition and biomass. Many techniques
were employed for this purpose with little
consideration for regional lake water quality
relative to that of the "special interest lake". It
has become apparent that prediction of the
effectiveness of lake restoration improves if
regional lake quality is considered in the
evaluation of potential success. Thus, in this
paper we describe two approaches for
developing regional late quality patterns and
explain, through the use of case examples, why
they are significant to conservation and
management ("restoration") decisions.
ECOREGIONS
One approach for characterizing regional lake
quality patterns is to integrate existing surrogate
landscape level information pertaining to
surface water quality in a fashion such as
Omernik's ecoregions (1987, 1995). The
concept of regional variability, while not new
to limnologists, was formally recognized on a
national scale by Omernik's (1987) description
of 76 ecoregions of the conterminous United
States. Omernik's original ecoregions are
based on regional similarities in a combination
of spatial characteristics that influence aquatic
resource condition, including soils, geology,

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Regional Lake Quality Patterns
land surface form, climate, potential natural
vegetation, and land use. These ecoregions,
coupled with data on lake characteristics,
provide a basis for delimiting current
conditions and expectations for lake quality,
assessing deviations from the expected,
establishing reasonably attainable conditions,
and estimating the success of restoration
treatments. Many states are adopting an
ecoregional approach to manage water quality
(Hughes et al. 1994).
Heiskary and Wilson (1989) used Omemik
ecoregions (Figure 1) to define Minnesota lake
management goals based on differences in
regional lake quality. They characterized total
phosphorus by ecoregion from 1,400 lakes
sampled state-wide by various investigators
between 1970 and 1985 (Figure 2A). The
State itself, monitored 90 reference lakes
between 1985 and 1989 (Figure 2B), defined
as those lakes minimally affected by point and
nonpoint sources of pollution and in
watersheds with regionally predominant
landscapes. It is clear from these box-plots that
lake total phosphorus concentrations differ
Figure 1. Location of 1400 state-wide total
phosphorus lake sample sites within the four
primary ecoregions [Northern Lakes and
Forests (NLF); North Central Hardwood
Forests (CHF); Western Com Belt Plains
(WCP); and Northern Glaciated Plains (NGP)]
of Minnesota, USA. See Figure 3 for locator
map. (Heiskary et al. 1987),
i .-f 5-
NLF
NGP
WCP
considerably from ecoregion to ecoregion. The
Minnesota Pollution Control Agency uses data
from the regional reference lake patterns of
water quality to define reasonable goals
expressed in terms of average summer total
phosphorus, likelihood of nuisance conditions
(e.g., estimates of algal bloom frequency), and

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Regional Lake Quality Patterns
Figure 2. Total phosphorus (jig/L) box-plots for 1400 lakes in Minnesota sampled state-wide
between 1970 and 1985 (A), and 90 reference lakes sampled between 1985 and 1989 (B) by
ecoregions. Ninety-five percent confidence interval (CSj) of the median is calculated as;
CSj = ± 1.7(1.25I/1.35-/n) where I = interquartile range and n = number of observations
(redrawn from Heiskary and Wilson 1988, 1989).
(A)
(B)
500-
400-
S
3
co 300-
Q.
8
-C
CL
H
O
100-
90
75
50
25
T»
Percentile
Relative -j-
sampla size
200-

NLF CHF WCP NGP
Ecoreglon
400

300-
a.
at
o
.c
Q.
200
100:
NLF CHF WCP NGP
Ecorsgion
likelihood of Secchi disc transparency range
exceedances relative to both lake protection and
restoration goals. Deviation of non-reference
lake conditions from the interquartile range
(25th to 75th percentiles) of conditions for
reference lakes connotes reasonable cause for
concern and possible remediation.

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Regional Lake Quality Patterns
SAMPLE SURVEYS
The ecoregional lake patterns also can be
characterized with data collected specifically for
that purpose through a well designed sample
survey. Sample surveys that incorporate
randomization in the selection of lakes to be
monitored have the advantage of avoiding
unknown biases that can arise if lakes are
selected non-randomly. This design based
approach to selecting lakes for monitoring is
more efficient (requires fewer lakes) than use
of less focused historical data and has the
added advantage of providing estimates of the
statistical confidence with which the regions are
characterized (Larsen et al. 1994).
This approach has been used by the
Environmental Monitoring and Assessment
Program (EMAP) throughout the Northeastern
United States from 1991 through 1994 (Figure
3). For example, there are about 11,089 lakes
> 1 ha in the NE U.S. Of these, a stratified
random sample of approximately 86 lakes were
selected for monitoring each year for four years
(Table 1) with results summarized by ecoregion
5
(Figure 4). Paulsen et al. (1995) demonstrated
that pattern assessment of lakes via a
probability design differs markedly from
results obtained from a much larger hand-
picked data base for the same region. Also,
they found that the hand picked data bases
underestimate the proportion of lakes that are
eutrophic or hypereutrophic. In addition,
estimates of trophic condition from yearly
probability based sample surveys are much less
variable than those from annual hand picked
samples. The combination of ecoregional
delineations with well designed sample surveys
is an effective way to characterize the regional
setting within which to evaluate lake protection
or restoration.
CASE EXAMPLES
The importance of regional lake quality
patterns, relative to restoration efforts, is
illustrated by two examples from Minnesota.
Shagawa Lake is located in the northern lakes
and forests ecoregion (Figure 1). Between
1971 and 1973, average summer total
phosphorus in the lake ranged between 50.8

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Regional Lake Quality Patterns
Figure 3. Map of the United States showing Minnesota (Figure 1) and ecoregions of the
Northeastern United States with the location of lakes sampled from 1991 through 1994 (EMAP
1991 through 1994 Northeastern Lakes Data Base).
~	Adirondacks
~	Coastal/Lowlarid Plateau
I New England Upland
Table 1. Lake size classes, target population (number of lakes) by size class and number of lakes
sampled by EMAP in the Northeastern United States from 1991 through 1994. Sample lakes were
selected using a stratified random design (EMAP 1991 through 1994 Northeast Lakes Da* a Base).
Size Class (ha)
Target Lake Population
Sample Size
1 -<5
4160
30
>5 - <20
2135
69
>10 - £50
3287
121
>50 - <500
1294
85
>500 - <5000
208
39
>5000
5
1
Total
11089
345

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Regional Lake Quality Patterns
Figure 4. Total phosphorus (ng/L) for lakes
in ecoregions of the Northeastern United States
[Adirondack^ (ADI); New England Uplands
(NEU) and the Coastal Lowlands and Plateau
(CLP).] The legend in figure 2 applies here,
(EMAP 1991 through 1994 Northeast Lakes
Data Base)
ADI	NEU	CLP
Ecoregion
and 60.9 ug/L, clearly an anomaly for the
region. Extensive use of nutrient budget and
lake loading models identified waste treatment
discharge to the lake as exceeding by nearly
four times that of natural inflows (Larsen et al
1979). Therefore, given the information at
hand and our understanding of phosphorus
dynamics in lakes at the time, Shagawa seemed
to be an excellent candidate to benefit from
nutrient diversion; actually advanced waste
treatment. The advanced waste treatment began
in 1973 and immediately reduced the total
external phosphorus inflow from 6,200 - 7,200
kg/yr to between 900 -1,500 kg/yr, an amount
sufficient to reduce the average inflow
phosphorus concentration from 60- 100 ug/L
to less than 20 ug/L (Larsen 1979). In the
absence of internal phosphorus supplies,
Shagawa Lake should achieve lake total
phosphorus levels typical of the region.
However, in-lake total phosphorus remained
high (34.6 - 35.7 ug/L) from 1974 through
1976. Mass balance analyses identified a large
seasonal internal pulse of phosphorus from the
sediments that prevented Shagawa Lake from
achieving a regionally expected condition.
The Fairmont Lakes are located in the
Western Com Belt Plains (Figure 1). Stefan
and Hanson (1981) report total phosphorus in
surface waters of these lakes to be 30 to 150
ug/L while that in the hypolimnion ranges from
30 to 1,500 ug/L. Spring snow melt runoff to
the lakes typically is 10 to 50 ug/L. By late

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Regional Lake Quality Patterns
8 July total phosphorus runoff rises to 150 to
200 ug/L, but occasionally reaches 500 ug/L.
Clearly, these lakes are among the most
eutrophic in all of Minnesota. Stefan and
Hanson concluded that the Fairmont Lakes,
like Shagawa, have significant amounts of
internal nutrient recycling from the sediments.
s
sediments, algal resistance to copper and shifts
from green to blue-green species,
disappearance of macrophytes, shifts from
game fish to nongame fish and reductions in
macroin vertebrates.
CONCLUSIONS
A major difference between Shagawa and the
Fairmont Lakes is the pattern of lake quality in
the surrounding region. The phosphorus
concentration in Shagawa Lake is a clear outlier
in a region of otherwise high quality lakes.
The phosphorus concentration in the Fairmont
Lakes is among the highest in a region of high
phosphorus concentrations. Consequently, the
Fairmont Lakes, are unlikely to ever achieve
the quality of lakes in the Northern Lakes and
Forest ecoregion. Despite this, the Fairmont
Lakes have been subjected to over 60 years of
well intentioned "restoration efforts", including
copper sulfate and partial dredging (Hanson
and Stefan 1984). The result has produced
little if any lasting improvement and a host of
adverse side effects including oxygen
depletion, fish kills, copper accumulation in
At the time of the Shagawa and Fairmont Lake
projects, the extensive Minnesota data bases
did not exist Retrospectively, the Shagawa
project was of the right kind, for the right
reasons given regional lake quality patterns, but
produced less than expected results. While
modeling had predicted significant internal
nutrient cycling, there was no way of knowing
what time would be required for recovery. The
Shagawa example, along with others, alerted
the limnological and lake management
communities to the importance of internal
phosphorus supplies, even in regions of high
quality lakes.
The Fairmont Lakes projects resulted in
frustrations and unrealized expectations, many
of which could have been avoided had regional
lake quality data bases been available and

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Regional Lake Quality Patterns
considered. For example, the location of the
Fairmont Lakes among a population of lakes
with very high trophic levels should have
alerted late managers and government officials
to the low potential for substantial recovery.
Among more recent lake restoration efforts,
two treatment techniques stand out for their
success. These are phosphorus inactivation
and dredging (Cooke et al. 1993). However,
even these highly successful techniques are not
failsafe. They cannot be implemented without
regard for, and an understanding of regional
lake quality patterns relative to the condition of
specific lakes destined for restoration.
ACKNOWLEDGEMENTS
The authors are most grateful to Danny Kugler,
Sue Pierson and Patti Haggerty for statistical
analyses and development of the graphics for
this paper and to Steve Heiskary who provided
us with the Minnesota Lakes data. We thank
Marge Hails who word processed, reformatted
and generally cleaned-up the manuscript Drs.
G.D. Cooke, Eugene Welch and Dixon
Landers provided helpful comments on a draft
version of the manuscript Data collection and
analysis for the Northeastern lakes and
preparation of this manuscript was funded by
the U.S. Environmental Protection Agency,
National Health and Ecological Effects
Research Laboratory at Corvallis, OR, USA.
The manuscript has been subjected to the
Agency's peer and administrative review and
approved for publication. Mention of trade
names or commercial products does not
constitute endorsement or recommendation of
use.
REFERENCES
Bjork S. (1994). Overview. In: M. Eiseltova
(ed.). Restoration of Lake Ecosystems: A
Holistic Approach. IWRB Pub. No. 32.
IWRB, Slimbridge, Glocester, GL2 7BX
UK. 182 pp.
Cooke D.G., Welch E.B., Peterson S.A., &
Newroth P. R. (1993) Restoration and
Management of Lakes and Reservoirs: 2nd
Ed. Lewis Publishers, Boca Raton, FL.
548pp.

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Regional Lake Quality Patterns
Dillon P.J., & Rigler F.H. (1974) The
Phosphorus-Chlorophyll Relationship in
Lakes. Limnol. Oceanog. 19(5)767-773.
Hanson M.J., & Stefan H.G. (1984) Side
Effects of 58 Years of Copper Sulfate
Treatment of the Fairmont Lakes, Minnesota.
Water Res. Bull.. 20(6),889-900.
Heiskary S.A., & Wilson C.B. (1988)
Minnesota Lake Water Quality Assessment
Report. Minnesota Pollution Control Agency.
St. Paul, MI. 148pp.
Heiskary S.A., & Wilson C.B. (1989) The
Regional Nature of Lake Water Quality
Across Minnesota: An Analysis for
Improving Resource Management, J. Minn.
Acad. Sci.. 55(l),71-77.
Heiskary S.A., Wilson C.B., & Larsen D.P.
(1987) Analysis of Regional Patterns in Lake
Water Quality: Using ecoregions for Lake
Management in Minnestoa. Lake Reserv.
Manage, 3,337-344.
10
Hughes R.M., & Larsen D.P. (1988)
Ecoregions: An Approach to Surface Water
Protection. J. Water Pollut. Control Fed.,
60(4),486-493.
Hughes R.M., Heiskary S.A., Matthews
W.J., & Yoder C.O. (1994) Use of
Ecoregions in Biological Monitoring, pp 125-
151. In: S.L. Loeb and A. Specie (eds.)
Biological Monitoring of Aquatic Systems.
Lewis Publishers, Baca Raton, FL. 381pp.
Larsen D.P., Thornton K.W., Urquhart N.S.,
& Paulsen S. G. (1994) The Role of Sample
Surveys for Monitoring the Condition of The
Nation's Lakes. Environ. Monitor, and
Assess. 32,101-134.
Larsen D.P., VanSickle J., Malueg K.W., &
Smith P.D. (1979) The Effect of Wastewater
Phosphorus Removal on Shagawa Lake,
Minnesota: Phosphorus Supplies, Lake
Phosphorus and Chlorophyll A. Water
Research 13,1259-1272.

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Regional Lake Quality Patterns
Omemik J.M. (1995) Ecoregions: A Spatial
Framework for Environmental Management
In: W.S Davis and T.P. Simon (eds)
Biological Assessment and Criteria: Tools for
Water Resource Planning and Decision
Making. Lewis Publishers. Boca Raton, FL,
415pp.
Omemik J.M. (1987) Ecoregions of the
Conterminous United States. Annals Associ.
Ameri. Geog. 77,118-125.
Paulsen S.G., Larsen D.P., & Hughes R.M.
(1995) A Perspective on the Role of
Probability Surveys for Assessing the
Condition of Aquatic Systems. (In
preparation.) EPA, 200 SW 35th Street,
Corvallis, OR 97333.
Stefan H.G., & Hanson MJ. (1981)
Phosphorus Recycling in Five Shallow
Lakes. J. Environ.Engin. Division, ASCE,
107 (EE4),713-730.
Vollenweider R.A. (1975) Input-Output
Models with Special Reference to the
Phosphorus Loading Concept in Limnolog
Schweiz. Z Hydrol. 37,53-84.

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TECHNICAL REPORT DATA
(Please read instructions on the reverse before completingj
	
1 REPORT gf»A/600/A_g6/02g |2
3. RE<
4. TITLE AND SUBTITLE
Regional lake quality patterns: Their relationship to
lake conservation and management decisions
5. REPORT DATE
6. PERFORMING ORGANIZATION CODE
7i2^HS?°P^erson, 2R.M. Hughes, 'D.P. Larsen,
'S.G. Paulsen, 'J.M. Omernik
8. PERFORMING ORGANIZATION REPORT NO.
9. PERFORMING ORGANIZATION NAME AND ADDRESS
'U.S. EPA, NHEERL, Corvallis, OR,
2MERSC, U.S. EPA, NHEERL, Corvallis, OR
10. PROGRAM ELEMENT NO.
11. CONTRACT/GRANT NO.
12. SPONSORING AGENCY NAME AND ADORESS
US EPA ENVIRONMENTAL RESEARCH LABORATORY
200 SW 35th Street
Corvallis. OR 97333
13. TYPE OF REPORT AND PERIOO COVERED
Symposium Paper
14. SPONSORING AGENCY CODE
15. SUPPLEMENTARY NOTES, ,
1996. International Lake Environment Committee (ILEC) Journal, Lakes
and Reservoirs: Research and Management, Special Edition.
16. ABSTRACT
Understanding regional lake quality patterns is important to lake
restoration. • It puts specific lake conditions into perspective,
provides a basis for establishing lake quality goals, identifies lakes
most likely to benefit from restoration and forms a framework for
assessing restoration success. Two techniques used to characterize
regional lake quality patterns are discussed. Combining the two
approaches provides an effective means to describe lake regions
management goals and restoration success. Case examples illustrate the
significance of regional lake quality to specific lake restoration
projects.
17. KEY WORDS AND DOCUMENT ANALYSIS
a. DESCRIPTORS
b. IDENTIFIERS/OPEN ENDED TERMS
c. COSATI Field/Group
Lake restoration, survey sampling,
ecoregions, phosphorus, dredging


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