LIGHT & HEAT IN INLAND WATERS
Feb 23, 2016
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 = >>10-150
• 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 (Jackson Turbidity Units- JTU)
Susquehanna River at Byer’s Island
Lakes Erie and St. Claire following major runoff event
Heat Budget for LakesSources• 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
where S = storage rate of heat in the lakeRn = net radiationE = evaporationH = sensible heat transfer, conductionQ = advective heat transfers due to water
inflows and outflows
S = Rn – 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. Holomixisa. 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)
Property Rivers Reservoirs LakesTemperature variations Rapid, large Rapid in upper zone;
slow in lower portionSlow, 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