Adapting to Low Lake Levels and the Implications of a Changing Climate

Bass Patterson Lake, Washburn County (E. Cook)Susan Knight May 24, 2014

Mildred Lake 

Facts & Figures

Name Mildred Lake

Waterbody ID (WBIC) 1004600

Area 168 Acres

Maximum Depth 45 feet

Bottom 65% sand, 10% gravel, 20% rock, 5% muck

Hydrologic Lake Type Seepage

County Oneida

Lake Organizations Lake Mildred Property Owners Association

Fish Musky, Panfish, Largemouth Bass and Walleye

Lake Health

Invasive Species Chinese Mystery Snail

Trophic Status Oligotrophic

Mildred Lake 2013 Results

sampled 9 days in 2013

water clarity ● temperature ● total phosphorus ● chlorophyll

Secchi disk (summer average) =18.5 feet Northeast Georegion (summer average) = 10.6 feet

Chlorophyll (summer average) = 2.1 µg/l Northeast Georegion (average) = 12.3 µg/l. Total Phosphorus (summer average) = 6.1 µg/l.

Trophic State Index* = 40 = oligotrophic. *based on chlorophyll

Declining Lake Levels

Why are some lakes more vulnerable to declining water?

What are the effects on water quality?What are the effects on plant and animal

habitats?Why is this happening here? now?

What factors affect water levels?

• Lake morphology and hydrology

• Landscape position

• Natural variability (weather)

• Short term drought (and wet) cycles

• Water level control structures (dams)

• Climate change

• Human water use (i.e. water withdrawals)

Lake Types Seepage Groundwater Drainage Drainage Impoundments Oxbow

Seepage LakeNatural LakeWater Source

GroundwaterPrecipitationRunoff

No Stream Outlet/ Inlet

Drainage Lake

• Water Source•Streams•Groundwater•Precipitation•Runoff

• Stream Drained

Landscape Position

Magnuson et al. 2006

Response of Lakes to Drought

Seepage lakes

Drainage lake

Seepage lakes much more vulnerable to drought.

LAKE BASIN SHAPE:• The shallower the grade, the

more littoral zone exposed

DEEP versus SHALLOW•Deep parts may be unaffected•Shallower parts highly affected

Black Oak Lake, Vilas County

What factors affect water levels?

• Lake morphology and hydrology

• Landscape position

• Natural variability (weather)

• Short term drought (and wet) cycles

• Water level control structures (dams)

• Climate change

• Human water use (i.e. water withdrawals)

Current USGS Drought Watch Map

Much below normal

Evaporation Increasing

Fewer rainy days more sunny days More sunny days more evaporation Later ice-on, earlier ice-off more days

of open water for evaporation Warmer air temperatures more

evaporation Lakes shallower lake water warmer in

summer Warmer lake water more evaporation

Declining Lake Levels

Why are some lakes more vulnerable to declining water?

What are the effects on water quality?What are the effects on plant and animal

habitats?Why is this happening here? now?

Consequences of Low Lake Levels on Water Quality

Shallow lakes have water quality issues that may become problems for lakes with declining water levels such as: more mixing and more

nutrient re-suspension because shallow lakes do not stratify

more mixing and increased turbidity from disturbance of bottom sediments by boat motors

lower oxygen concentrations due to more plant growth and subsequent plant decomposition

Declining Lake Levels

Why are some lakes more vulnerable to declining water?

What are the effects on water quality?What are the effects on plant and animal

habitats?Why is this happening here? now?

Declining water levels and habitat changes

• Plants

• Wetlands

• Invertebrates

• Fish and wildlife

Lake Habitat Zones

Lake Littoral Zone

FunctionsIntercepts

NutrientsRefuge from

PredatorsNursery for Fish

Declining water levels and woody habitat: Wood left above the water line may lead to:

• Loss of habitat for fish (feeding, hiding, spawning)

• Slower growth rates for fish

• Loss of food chain associated with wood including algae, zooplankton and other invertebrates

• Loss of habitat for vertebrates and invertebrates that rely on wood

Declining water levels and invertebrates

• Many invertebrates are mobile and can move to deeper habitat

• Inverts relying on wood and emergent plant stems will lose habitat

• Some inverts will have trouble with different, perhaps softer substrates deeper in water

• Potential for huge loss of invertebrates with declining water levels

Declining water levels and Fish

• Reproduction will be the biggest challenge for fish in dealing with changing water levels.

• Preferred substrate for spawning may not be available

Declining Lake Levels

Why are some lakes more vulnerable to declining water?

What are the effects on water quality?What are the effects on plant and animal

habitats?Why is this happening here? now?

Many factors affect water levels

• Natural variability (weather)

• Short term drought (and wet) cycles

• Lake morphology and hydrology

• Landscape position

• Water level control structures (dams)

• Climate change

• Human water use (i.e. water withdrawals)

Global Warming Is Unequivocal:• The recent IPCC

report has clearly stated that “warming of the climate system is unequivocal” and it is “very likely” caused by human activities.

•

Evidence of Climate Change in the Great Lakes

RegionTemperatures are rising, especially

in winter.Extreme rainfall events (24-hr and

7-day) are becoming more frequent.

Winters have become shorter.Spring is coming earlier.Duration of ice cover is shorter, especially on smaller lakes.

Sou

rce; E

dg

e o

f the W

ildern

ess S

cen

ic Byw

aysSOURCE: UCS/ESA, 2003

Declining Water Levels: Vulnerable Lakes, Water Quality & Habitat Changes

Summary

• Drought and increased evaporation responsible for declining water levels

• Seepage lakes most vulnerable

• As lakes become shallower, may experience: more mixing higher nutrient levels more turbidity more vegetation lower oxygen concentrations

• Plants growing near shoreline must retreat with water line

• Woody habitat exposed, no longer part of lake ecosystem

• Fish: reproduction affected by changes in water levels

• Climate change real and causing: increased lake evaporation changes in fish species composition

Declining Water Levels: What You Can Do

• Understand your lake: Be especially careful in sensitive areas

• Do not to disturb shores, especially if muddy

• Do not move wood – leave it so it is present• when water levels come back

• Watch boat speeds: GO DEEP

• Watch for and remove invasive species, especially on shore

• Remove plants on exposed shore by hand only, unless you have a permit

Anvil Lake water levels, with evident periodicity of high and low levels

Acknowledgements

John Magnuson, Barbara Benson, Tim Kratz, UW Madison

Tim Asplund, Scott Provost, Pamela Toshner, Dick Lathrop, Frank Koshere, Carl Watras, Paul Garrison, WDNR

Sandy Gillum, Vilas Co. Lake Association

Brian Ewart, Berry Lake Association

Bill Rose, Dale Robertson, USGS

George Kraft, Samantha Kaplan, UWSP