Download Introduction - Lake Mildred

Adapting to Low Lake Levels and the
Implications of a Changing Climate
Susan Knight May 24, 2014
Bass Patterson Lake, Washburn County (E. Cook)
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 Lake
Natural Lake
 Water Source

Groundwater
 Precipitation
 Runoff


No Stream
Outlet/ Inlet
Drainage Lake
•
•
Water Source
•Streams
•Groundwater
•Precipitation
•Runoff
Stream Drained
Landscape Position
Response of Lakes to Drought
Drainage lake
Seepage lakes
Seepage lakes much more
vulnerable to drought.
Magnuson et al. 2006
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

Functions
Intercepts
Nutrients
 Refuge from
Predators
 Nursery 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 Region
Temperatures 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.

Source; Edge of the Wilderness Scenic Byways
SOURCE: 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