Presented to: Reitz Lake Open House July 12, 2005 Randy Anhorn Principle Environmental Scientist Metropolitan Council Environmental Services [email protected]651.602.8743 Lake Ecology and Water Quality and Reitz Lake Metropolitan Council Environmental Services
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Presented to: Reitz Lake Open House July 12, 2005 Randy Anhorn Principle Environmental Scientist Metropolitan Council Environmental Services [email protected].
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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