LIGHT & HEAT IN INLAND WATERS

Light spectrum at the top and bottom of the atmosphere

Measurable Properties of Light Intensity Quality Both are dependent on absorption and reflection by the atmosphere

Fates of light in water

Shading of low order streams

Confluence of Kotorosl and Volga Rivers

Walker Lake

Extinction Coefficient ν (nu) = extinction coefficient of light through water. Examples: Crystal Lake v = 0.19 Turbid Pond v = 1 – 10 Muddy Stock Tank v = >> Depends on: Light absorption by water Light scattered and absorbed by particles Light absorbed by dissolved substances v ~ 1/secci depth

Secci Disk

Typical Secci Depths Crater Lake 40m Castle Lake 33m Lake Texoma 0.75m Susquehanna River –West Shore >1.2m –West Center 0.32m –East Center 0.23m –East Shore 0.18m Secci Depth measured with Secci Disk in lakes and with a Secci Tube in running water. Also measured with Turbidimeter (JTU)

Susquehanna River at Byer’s Island

Lakes Erie and St. Claire following major runoff event

Heat Budget for Lakes Sources Solar radiation Sensible heat conduction Stream Input Sediment absorption of sunlight Geothermal Biogenic Sinks Evaporation Sensible heat conduction Back radiation from lake surface Stream inputs (snow melt) Surface outflow

Annual Lake Heat Budget whereS = storage rate of heat in the lake R n = 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

Lake Tahoe, CA-NV

Lake Mendota, WI

Density and temperature

Stratification

Castle Lake Stratification

Lake Classification Based on Thermal Stratification Patterns 1.Holomixis a.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

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

Martin Lake

b.dimictic – mixes twice per year ex: Castle Lake and Lake Mendota  small temperate lake  freezes over during winter c.amictic – does not mix, permanently ice- covered ex: Lake Vanda, Antarctic  high latitude lake

Lake Vanda, Antarctica

Meromixis

Lake Nyos

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

Polymixis in Clear Lake (Rueda et al. 2003)

PropertyRiversReservoirsLakes Temperature variationsRapid, largeRapid in upper zone; slow in lower portion Slow, stable StratificationRareIrregularCommon (monomictic or dimictic) Spatial differencesHeadwaters cooler becoming warmer downstream Large fluctuations in upper reservoir, more stable in main body Stratification common Groundwater effectsHigh ratio groundwater to runoff SmallUsually small (high in seepage lakes) Tributary effectsCan be significantModerate to smallSmall and localized Shading effectsConsiderable, especially in the headwaters Small to negligible Winter ice formationTransitoryUsually transitoryPersistent Ice scouring effectsExtensiveMinor