EXAM 1 Flashcards
Characteristics of a lake
size based definitions: surface area, depth or zonation
Glacial lakes
74% of lakes, nutrient rich. formed from ice barriers or glacial erosion. Continental glaciers moved rocks and sediment to change the landscape.
Tectonic lakes
~5% of lakes. Often U or V shaped basins. Deep and unproductive. have GRABENS: flat bottom valleys produced by tectonic plate activity
Volcanogenic lakes
«1% of lakes. low nutrient concentrations and unproductive. deep usually old
Karst Regions
Lakes formed by soluable rocks (limestone or dolomite) that dissolves with acidic water. Small and unevenly distributed around the world
Riverine lakes
oxbow lakes: form when bends in a river become isolated due to errosive forces of rivers, usually shallow and oddly shaped
Floodplain lakes
form due to seasonal fluxes in water levels in a river basin
littoral zone
margin of lake to depth where no plants can grow
limnetic zone (palagic zone)
open water, no shore visible
benthic zone
bottom zone associated with sediments
profundal zone
deep region of the benthic, no light, fine sediments
limnetic zone
photic zone
profundal zone
aphotic zone
Epilimnion
top layer, warmer and lighter
Metamnion
medium temperature medium light
hypolimnion
dark, cold
meromictic lake
so deep that there is no single temperature, layer at the bottom never mixes
dimictic
2 mixing events per year
monomictic
mixes once a year
what enables mixing?
shallow waters, large fetch, lack of ice cover, lack of sheltering topography, large meteorological events (hurricanes)
catchment
area of land that drains into an aquatic system
seepage lakes
isolated. no inlets or outlets
drainage lakes
connected, inlets and outlet streams
lowland drainage lakes
connected, have inlets and outlets
drained lakes
no inlet streams. have an outlet
terminal lakes
has an inlet with no outlet
oligotrophic
little nutrients and phytoplankton
mesotrophic
some algae in late summer, shallow plants, some sediment buildup
eutrophic
lots of nutrients and phytoplankton, lots of chlorophyll a making it green, shallow
Trophic state index (TSI) based on what perameters
water clarity, chlorphyll a, total nitrogen, total phosphorus
water year
October 1-September 30
recharge lakes
lakes that are above the water table
flow-through lakes
lakes that receive and discharge groundwater
discharge lakes
lakes that are below the water table, only groundwater is their input
closed basin lakes
endoheric, no surface flows, long residence times
open basin lakes
exorheric, surface outflows, evaporation
el nino southern oscillation
last 9 months to two years, occurs every 3-7 years
Morphometry
quantifies the size, shape, and physical dimensions of a lake
What types of lakes are circular
caldera
what types of lakes are lunate
oxbow shape formed from river bends
what types of lakes are dendrictic
most commonly formed from dammed rivers
Bathymetric Map
Shows underwater topography using contours of equal depth (isobaths)
Historically created by sounding using a weighted line lowered until it hit the bottom
Modern methods for creating bathymetric map
echo sounding GPS, side scan sonar, dropping the boat into a large body of water
Shoreline development index
a measure of how complex the shoreline of a lake is relative to expected if the lake was a perfect circle
D= 1 means the lake is a perfect circle
Fetch
Simplest measure of fetch is the longest possible distance across which wind can blow
This can be expanded to effective fetch, which adds in the relative direction of dominant winds a lake experiences
Fetch influences wave action, which
influences bottom sediment mixing in lakes, which influences the depth of the thermocline and epilimnion in lakes`
Sieche
is a standing wave and in an enclosed body of water
