WATER USE & DISTRIBUTION

APESCH. 21

Key HKey H220 Characteristics0 Characteristics

• Water is the prime constituent of all living organisms.

• Water moves easily-from one physical state to another, and from one place to another.

• Water slowly absorbs and releases large quantities of energy.– Creates habitable climate &

moderates world temp.

• Water is a superior solvent.

• Michael D. Lee Ph.D. Geography and Environmental Studies(Source: Wright & Nebel 2002)

The Hydrologic cycle• Driven by sunGets into the air by…• Evaporation of surface water or sublimation of snow & ice• Transpiration from plants & animals• Evaporation + transpiration = evapotranspiration• Water enters atmosphere leaving behind salts & other contaminants • Amount of water in atmosphere is humidity

– Warm air holds more water than cold• When air has all the water it can hold it has reached its saturation point.

(Relative humidity is the amount of water vapor in the air expressed as a % of max amount (saturation point) that could be held at that particular temperature.)

• When saturation point is exceeded the water molecules aggregate in process called condensation.

• Condensation nuclei (particles that water adhere to) initiate the cloud forming process

• When water droplets are too big for air currents to suspend, they fall to the ground as precipitation.

Hydrologic CycleHydrologic Cycle

When water reaches land…– Runoff- into lakes, rivers, streams– Infiltration- percolates thru soil – Temporary storage as snow and ice – Temporary storage in lakes – Temporary storage in plants (transpiration)

and animals – Chemical reactions with rocks and minerals – Source of additional water? volcanism

(steam)

www.athensclarkecounty.com/~stormwater/ SW%20Management.htm

Hydrologic CycleHydrologic Cycle

Rainfall & TopographyRainfall & Topography• Rainfall uneven over planet• Rainshadow Effect

– Air sweeps up winward side of mtn, air cools, condenses, and rains.

– As air falls down leeward side of mtn, air warms & rainfall decreases

– EX: Mt. Waialeale in Hawaii, Himalayas in south Asia, Sierra Nevada of CA, Oregon & Washington State

• Desert Belts– Located at Tropics of Cancer &

Capricorn (around 20-40 latitude)– Evaporation & precipitation

happen at equator and as air circulates toward poles it has less water and falls as hot dry air, creating deserts.

Global Precipitation PatternsGlobal Precipitation Patterns

Available WaterAvailable Water

• Total = 326 million cubic miles • 97% of Earth’s water is in

oceans• 2.997% is locked up in ice

caps and glaciers• 0.003% is easily accessible

– Soil moisture– Groundwater– Water vapor– Lakes– Streams

http://ga.water.usgs.gov/edu/waterdistribution.html

Water Supply & UseWater Supply & Use

Amount of water on planet

Amount of USABLE water on

planet

From Water Exhibit @ Natural History Museum in New York

Major Water Reservoirs

OceansOceans

• Regulates earth’s temp by absorbing and releasing heat

• Too salty for human use- without expensive distillation process

• 90% of earth’s living biomass is in the ocean• Warm & cold water occurs in layers

– Sun warms surface, colder water is denser so sinks. Warm water sits on cold water

• Average life of a water molecule in the ocean is 3000 years

Glaciers, Ice & SnowGlaciers, Ice & Snow

• Glaciers- rivers of ice flowing downhill very slowly

• Make up 2.4% of freshwater on earth

• Made of freshwater- salt is excluded during freezing

GroundwaterGroundwater• Water infiltrates thru soil and is stored

underground• Zone of aeration

– Upper soil layer where air & water mix– Contaminants may be removed here- but not all

• Zone of saturation– Lower soil layer where all spaces are occupied by water– Top of this zone is the water table

• Water table changes due to amnt of precip & infiltration rates• Aquifers- layers of porous sand, gravel or rock with underlying layer

of solid bedrock that stores water• Confined Aquifer- if crust changes due to geologic processes,

aquifer can be trapped btwn two layers of bedrock. Under pressure. Can gush out of ground as spring or artesian well.– Powder Springs use to be called Seven Springs because of the 7

mineral springs that bubbled up from ground.• Recharge zones- areas of land that allow seepage of water back

into aquifer

HOW RIVERS WORK: the role of groundwater

www.elmhurst.edu/.../chm110/ outlines/groundwater.html

Surface Water

Surface runoff flows into rivers, streams, lakes, ponds, and wetlands

Watershed- area of land that drains into a body of water

• Moving water- rivers & streams

• Standing water- lakes, ponds, wetlands

Moving WatersMoving Waters(streams & rivers)(streams & rivers)

• Originate as – Meltwater from snow or ice– Seepage from groundwater (spring)– Precipitation

• Usually headwaters of stream are in mountainous areas– Cold (elevation), highly oxygenated (gravity pulls down over rocks),

often small• As stream reaches level ground, deepens and slows & becomes a

river• Small streams that empty into river are known as tributaries

– EX: Sweetwater creek is a tributary to Chattahoochee River– EX: McEachern creek is a tributary to Noses Creek

• Not all rivers carry same amount of water• This measured as discharge- amount of water that passes a fixed

point in a given amount of time (cubic meters/second)

Standing WaterStanding Water((lakes, pondslakes, ponds, and wetlands), and wetlands)

• Ponds– Shallow enough to allow

plants to root across bottom

• Lakes– Inland depressions that hold

standing freshwater all year

• Both are relatively temporary- eventually fill in with sediment from rivers or are emptied by water diversion projects

• More accessible than groundwater or glaciers

• More plentiful than rivers & streams

Lake Lanier

West Point Lake

Walter F. George

Lake

Lake Seminole

Apalachicola River

Flint River

Chattahoochee River

Standing WatersStanding Waters(lakes, ponds, and (lakes, ponds, and wetlandswetlands))

• Wetlands– Bogs, swamps, marshes– Plant roots stabilize soil– Slow water for infiltration– Filter pollutants

• In the US, 20% of the 1 billion hectares of land were wetlands. About ½ of this has been drained (for agriculture), filled or degraded

• Results in – Reduced water holding capacity→ more flooding– Dry stream beds on other side of wetland– Reduction in biological diversity

AtmosphereAtmosphere

• Smallest major water reservoir

• Water molecule lasts 10 days in atmosphere on average

• Important in redistribution of water across planet