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AP Enviro Sci 2013

___ % of the Earth is covered by water

70%; 97% of this is salt, 3% freshwater

Unique properties of water

1.) Strong hydrogen bonding
2.) Temperature of water changes slowly due to its high specific heat
3.) Water has a high boiling point
4.) A lot of energy is needed to evaporate water
5.) It dissolves many compounds
6.) Water filters out harmful UV radiation in aquatic ecosystems
7.) Water expends when it freezes

Formation of Lakes

1.) tectonic uplift of a mountain range that creates a depression that accumulates water
2.) advance and retreat of glaciers that scrape depressions in the Earth's surface where water accumulates
3.) salt or saline lakes that form where there is no natural outlet or where the water evaporates rapidly and the drainage surface of the water table has a higher-than-normal salt content
4.) oxbow lakes formed by erosion in river valleys
5.) crater lakes formed in volcanic craters and calderas that fill up with water more rapidly than they empty

Level of lakes

controlled by the difference between the input and output compared to the total volume of the lake;significant input sources are precipitation onto the lake, run off carried by streams and channels from the lake's catchment area, groundwater channels, and artificial sources from outside the catchment area

Lake zones

littoral zone, photic zone, deep-water benthic zone

Littoral zone

sloped area close to the land

Photic zone

sunlight is abundant

Deep-water Benthic zone

bottom of an aquatic ecosystem; consists of sand and sediment and supports its own community of organisms

Secchi disk

determines the level of turbidity or eutrophication in a lake

Oligotrophic lake

lake with a low supply of plant nutrients

Mesotrophic lake

lake with a moderate supply of plant nutrients and good clarity

Eutrophic lakes

Lakes which are oxygen-poor and nutrient-rich, and have high amounts of organic matter, algal blooms

Hypertrophic lakes

excessively enriched with nutrients; algal blooms; result of human activity such as fertilizers

the density of water _____ as temperature decreases



deep water is insulated from the sun and stays cool


the surface and water near the shore are warmed by the sun making them less dense so they form this

Seasonal turnover (lake water)

the exchange of surface and bottom water in a lake or pond that happens twice a year,

Fall turnover

During the summer, the sun heats water near the surface of lakes (which results in a well-defined warm layer of water occurring over a cooler one--stratification); as the summer continues, temperature differences between the top and bottom layers increase and a think middle layer (thermocline) develops where the rapid transition in temperature occurs; with arrival of fall and cooler air temp, water at the surface cools and becomes heavier; strong fall winds move the surface around which promotes mixing with deeper water

Spring turnover

As the winter approaches in areas where subfreezing temperatures are common, the lake surface temperatures approach the freezing mark; lake waters move toward freezing, water sinks to the lake bottom when it reaches 4 degrees Celsius, colder water remains above (maybe becoming ice), when the surface ice begins to melt the cold surface water warms until the temp of the bottom waters produce a fairly uniform temp distribution throughout the lake, winds blowing over the lake again set up a full circulation system


swamps, estuaries, marshes, and bogs; wetlands are characterized by a water table that stands at or near the land surface for long enough season each year to support aquatic plants

plant and animal life near wetlands

mangrove, water lilies, cattails, sedges, tamarack, black spruce, and cypress/many different amphibians, reptiles, birds, and mammals

Drained wetlands for

For real estate development or flooded for use as recreational lakes

Ramsar Convention (1971)

International treaty designed to address global concerns regarding wetland loss and degradation


a geologic formation that contains water in quantities sufficient to support a well or spring


unconfined aquifers have as their upper boundary the water table

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