Aquatic Systems and their Catchments

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Aquatic Systems and their Catchments
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Small Catchments, steeper slope
Large Catchment, low slope
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Water Residence Time vs. Hydraulic Water
Residence Time
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Water Residence Time vs. Catchment AreaLake Area
ratio
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Predicting WRT
WRT
Catchment Area Lake Area
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Drainage Area/ Surface Area

• Land Drainage Area/ Lake Surface Area for the
  Great Lakes.

Superior Michigan Huron Erie Ontario 1.6 2.0 2.2
3.0 3.4
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WRT and Streams
WRT increases with Stream Order
Shorter WRT (hours)
Longer WRT (days)
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WRT and Trophic State
Phosphorus loading
WRT
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WRT and Trophic State
Primary Production
WRT
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Some of the lakes with the longest WRT and
clearest water are becoming more productive Lake
Tahoe (development) Crater Lake (atmospheric
Deposition)
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WRT and Biota

• If Flushing Rate (1/WRT) is high, planktonic
  communities can be affected.
• Macrozooplankton has higher growth rates than
  phytoplankton, therefore they will be more
  affected by rapid flushing (especially in the
  epilimnion).

Weeks
Months
Days
Days
Calanoid copepod
Phytoplankton
rotifers
Daphnia
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Temperature Cycles Lake Stratification

• Most lakes mix during some seasons and become
  stratified during other seasons.
• These terms refer to the vertical circulation of
  water Mixing circulation, Stratification
  lack of mixing (development of layers)
• The mixing pattern has a large effect on lake
  chemistry and the biota
• Lakes have traditionally been classified
  according to their annual mixing pattern or
  mixing regime (amictic, monomictic, dimictic,
  etc.)

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Temperate zone Dimictic Lake
Mixing
Stratified
Stratified
Mixing
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Thermal zones in a stratifed lake
Metalimnion
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Allens Lake, MISept 7, 2007
Epilimnion
Metalimnion
Hypolimnion
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Seasonal Cycle in a Temperate Dimictic Lake

• After ice melts in spring, the lake is cold and
  isothermal (same temperature from top to bottom)

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Z
Zmax
Temperature
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Seasonal Cycle in a Temperate Dimictic Lake

• As air temperature and solar radiation increase,
  there may be a period of isothermal warming,
  where warmer surface waters are mixed downward by
  wind and wave energy

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Z
Zmax
Temperature
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Seasonal Cycle in a Temperate Dimictic Lake

• Eventually, the heating of the surface water will
  outpace the capacity of wind and waves to mix the
  heat downward

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Z
Zmax
Temperature
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Seasonal Cycle in a Temperate Dimictic Lake

• The warm surface layer (epilimnion) floats on the
  colder, denser layer (hypolimnion)

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Z
Zmax
Temperature
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Seasonal Cycle in a Temperate Dimictic Lake
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Seasonal Cycle in a Temperate Dimictic Lake

• Over the summer the epilimnion may continue to
  warm, but the hypolimnion temperature will change
  very little

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Z
Zmax
Temperature
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Seasonal Cycle in a Temperate Dimictic Lake

• In the fall, the epilimnion begins to cool, and
  the process goes in reverse. The thermocline
  will deepen.

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Z
Zmax
Temperature
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Seasonal Cycle in a Temperate Dimictic Lake

• Fall Overturn followed by isothermal cooling

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Z
Zmax
Temperature
4
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Seasonal Cycle in a Temperate Dimictic Lake

• Inverse stratification and ice formation

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Z
Zmax
Temperature
4
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Seasonal Cycle in a Temperate Dimictic Lake
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Seasonal Cycle in a Temperate Dimictic Lake

• Wind from strong storms can have a effect on the
  thermal profile, causing storm thermoclines.

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Z
Zmax
Temperature
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Mixing Regimes

• Dimictic Mixes in spring and fall
• Monomictic
• Cold high latitudes or elevation, Mixes all
  spring summer and fall. Stratified under winter
  ice.
• Warm never freeze in winter. Mixes all fall,
  winter, spring. Stratified in the summer. (Great
  Lakes as well)
• Amictic never mix. Antarctic lakes always ice
  covered and inversely stratified
• Polymictic Mix many times annually. Usually
  shallow lakes

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Lake Thermal Isopleths
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Other Mixing Categories

• Meromictic Incomplete mixing because of salts
  or gases that increase the density of the bottom
  waters.

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Mono Lake, CA (meromictic)
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Mono Lake, CA (meromictic)

• Water was diverted from Mono Lake to feed Los
  Angeles.