Presented to: Reitz Lake Open House July 12, 2005 Randy Anhorn Principle Environmental Scientist...

Presented to:

Reitz Lake Open HouseJuly 12, 2005

Randy AnhornPrinciple Environmental Scientist

Metropolitan Council Environmental Servicesrandy.anhorn@metc.state.mn.us

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 randy.anhorn@metc.state.mn.us 651.602.8743

Some Internet Sites of Note