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Presented to:
Reitz Lake Open HouseJuly 12, 2005
Randy AnhornPrinciple Environmental Scientist
Metropolitan Council Environmental [email protected]
651.602.8743
Lake Ecology and Water Quality and
Reitz Lake
Metropolitan CouncilEnvironmental Services
Minnesotans are passionateabout their lakes and rivers
“Look! What a Peach I Landed–and How!”
Greetings from Big Sandy Lake
Metropolitan CouncilEnvironmental Services
Ecologyand Biology
of Lakes
Minnesota EcoregionsSummer Average Water
Quality Values
North Central Hardwood Forest
TP Cla SecchiPercentile (g/l) (g/l) (m)
25-75 23-50 5-22 1.5-3.2
Western Corn Belt Plains
TP Cla SecchiPercentile (g/l) (g/l) (m)
25-75 65-150 30-80 0.5-1.0
Physiographic Lake Regionsin the Twin Cities Metropolitan Area
Metropolitan CouncilEnvironmental Services
Generalized Lake Ecosystem(Summertime Average Conditions)
Diagram not to scale
Epilimnion (Mixed Layer) warm, light water
Hypolimnion(cool, heavy water)
Thermocline(prevents mixing)
Metalimnion
0-4 meters
4-17 meters
Lake Communities
Limnetic Community
Profundal Community
Area of open water;habitat of algae, zooplankton and fish
Area of no light penetration;domain of bacteria and fungi
Littoral CommunityAquatic plants dominant
Reitz Lake is in
the Carver Creek
Watershed.
Carver Creek
discharges to the
Minnesota River
Metropolitan CouncilEnvironmental Services
More Development
(impervious surface)
= More Runoff
Water Quality
The idea of lake water quality is tied to a concept of aging
or “Eutrophication”
Lake Aging Process
Mesotrophic lake:sedimentation, increased nutrient levels,more abundant aquatic vegetation
Eutrophic lake:basin nearly filled with sediment, high nutrient levels, dense aquatic vegetation
Oligotrophic lake:few nutrients, little aquatic vegetation
De
cad
es
Ce
ntu
riesNautral Eutrophication, caused
by nutrient-rich nonpoint source runoff and growth and decay of aquatic vegetation
Cultural Eutrophication accelerates the aging process by introducing nutrient-rich point source and additional nonpoint source runoff from human activities
General TrophicClassification of Lakes
Oligotrophic Mesotrophic Eutrophic Reitz LakeReitz Lake
TotalPhosphorus(g/l)
Chlorophyll-a(g/l)
SecchiTransparency(m)
<12 13-25 >26 ~100~100
<3 3-7 >8 ~ 45~ 45
>4 2-4 <2 ~ 2~ 2
Relative Costs of Lake Restoration versus Prevention
Co
sts
Corrective Measures0
Lake Restoration afterSerious Degradation
Extensive Lake Management
Limited Lake Management
Simple Prevention and Protection
DNR ID # 10-0052Surface area: 79 acresWatershed area: 3,600 acresW-to-S ratio 46:1Maximum depth 11.0 m (36 ft)Mean depth 4.0 m (13 ft)Volume of water 1,027 ac-ft% littoral 58%Thermocline Yes
Reitz Lake
Reitz Lake Summer Total Phosphorus Mean
020406080
100120140160180200
Tota
l Pho
spho
rus
(ug/
l)
MinLEAPPredicted Value
Reitz Lake Summer Chlorophyll-a Mean
0
20
40
60
80
100
120
Chl
orop
hyll-
a (u
g/L)
MinLEAP Predicted Value
Reitz Lake Summer Secchi Transparency Mean
-10
-9
-8
-7
-6
-5
-4
-3
-2
-1
0
Se
cc
hi t
ran
sp
are
nc
y (
ft)
MinLEAP PredictedValue
Lake QualityReport Card System
Grade Percentile TP (g/l) CLA (g/l) Secchi (m)
A <10 <23 <10 >3.0
B 10-30 23-32 10-20 2.2-3.0
C 30/70 32-68 20-48 1.2-2.2
D 70-90 68-152 48-77 0.7-1.2
F >90 >152 >77 <0.7
Reitz Lake Water Quality Grades Based on Summer Means
Year 1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991
Total Phosphorus D D
Chlorophyll a F D
Secchi Depth D C
Overall D D
Year 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004
Total Phosphorus D C C D D D D
Chlorophyll a C B C D C D C
Secchi Depth D C C F C B C
Overall D C C D C C C
Source: Metropolitan Council and STORET data
2004 Lake GradesCAMP and Metropolitan Council Monitored Lakes
Using Satellite Technology to Assess Regional Water Quality on an Annual Basis
Invasive SpeciesCurly-leaf Pondweed Purple LoosestrifeZebra Mussels
Eurasian Watermilfoil
www.co.carver.mn.us/water/ (Carver County Environmental Services)www.metrocouncil.org/environment/index.htm (Metropolitan Council) annual lake report- /environment /RiversLakes/Lakes/index.htm
annual WQ Summary- /planning/environment/environment/LWQ2004.pdf
annual Satellite Summary- /planning/environment/environment/TCWaterClarity2004.pdf
www.pca.mn.us (Minnesota Pollution Control Agency)
www.dnr.state.mn.us/lakefind/ (Minnesota Dept. of Natural Resources)
www.bwsr.state.mn.us (Board of Water and Soil Resources)
www.mnlakes.org (Minnesota Lakes Association)
www.shorelandmanagement.org
Randy Anhorn [email protected] 651.602.8743
Some Internet Sites of Note