LIGHT & HEAT IN INLAND WATERS - PowerPoint Presentation

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LIGHT & HEAT

IN INLAND WATERS

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Light spectrum at the top and bottom of the atmosphere

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Measurable Properties of Light

Intensity

Quality

Both are dependent on absorption and reflection by the atmosphere

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Fates of light in water

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Shading of low order streams

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Confluence of Kotorosl and Volga Rivers

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Walker Lake

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Extinction Coefficient

ν (nu) = extinction coefficient of light through water.Examples:Crystal Lake v = 0.19Turbid Pond v = 1 – 10Muddy Stock Tankv = >>10-150

Depends on:

Light absorption by water

Light scattered and absorbed by particles

Light absorbed by dissolved substances

v ~ 1/secci depth

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Secci Disk

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Typical Secci Depths

Crater Lake 40mCastle Lake 33mLake Texoma 0.75mSusquehanna RiverWest Shore >1.2mWest Center 0.32mEast Center 0.23mEast Shore 0.18m

Secci

Depth measured with

Secci

Disk in lakes and with a

Secci

Tube in running water.

Also measured with

Turbidimeter

(Jackson Turbidity Units- JTU)

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Susquehanna River at Byer’s Island

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Lakes Erie and St. Claire following major runoff event

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Heat Budget for Lakes

SourcesSolar radiationSensible heat conductionStream InputSediment absorption of sunlightGeothermalBiogenic

Sinks

Evaporation

Sensible heat conduction

Back radiation from lake surface

Stream inputs (snow melt)

Surface outflow

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Annual Lake Heat Budget

where S = storage rate of heat in the lake Rn = net radiation E = evaporation H = sensible heat transfer, conduction Q = advective heat transfers due to water inflows and outflows

S = R

n

– E – H – Q

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Lake Tahoe, CA-NV

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Lake Tahoe, CA-NV

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Lake Mendota, WI

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Density and temperature

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Stratification

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Castle Lake Stratification

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Lake Classification Based on Thermal Stratification Patterns

Holomixis

monomictic

– mixes once per year

warm monomictic – never below 4

°C

cold monomictic – never above

4

°C

ex

: Lake Tahoe

large volume and large depth

no winter ice cover

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Fall turnover occurs when the center of gravity (M) approaches the center of the volume (X).

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Martin Lake

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dimictic – mixes twice per yearex: Castle Lake and Lake Mendotasmall temperate lakefreezes over during winter

amictic

– does not mix, permanently ice-covered

ex

: Lake Vanda, Antarctic

high latitude lake

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Lake Vanda, Antarctica

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Meromixis

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Lake Nyos

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Lakes Nyos (A&C) and Monoun (B&D)

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Lake Kivu

Lake Kivu is one of the rift valley lakes on the border between Rwanda

and Congo

2,000X the size of Lake

Nyos

Geological sources of carbon dioxide

Biological conversion of carbon dioxide to methane

Lake area on a spreading zone and subject to earthquakes (last in 2008)

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Polymixis in Clear Lake(Rueda et al. 2003)

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Property

Rivers

Reservoirs

Lakes

Temperature variations

Rapid, large

Rapid in upper zone; slow

in lower portion

Slow, stable

Stratification

Rare

Irregular

Common (

monomictic

or

dimictic

)

Spatial differences

Headwaters cooler

becoming warmer downstream

Large fluctuations in upper reservoir, more stable in main body

Stratification common

Groundwater effects

High ratio groundwater to runoff

Small

Usually small (high in seepage lakes)

Tributary effects

Can be significant

Moderate to small

Small and localized

Shading effects

Considerable, especially in the headwaters

Small to negligible

Small to negligible

Winter

ice formation

Transitory

Usually transitory

Persistent

Ice scouring effects

Extensive

Minor

Minor