Ch 9 – Water Resources

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If all the water in the world could fit in a two liter bottle, all of the

freshwater in the world would fit in a

teaspoon

Available Water

Water residence time by Reservoir

Groundwater

Evaporation and transpiration

Evaporation

Stream

Infiltration

Water tableInfiltration

Unconfined aquifer

Confined aquifer

Lake

Well requiring a pump

Flowingartesian well

Runoff

Precipitation

ConfinedRecharge Area

Aquifer

Less permeable materialsuch as clay Confirming permeable rock layer

Groundwater• Precipitation infiltrates and percolates through

pores and fractures in soil and rock until it hits an impermeable layer

• Zone of saturation is at a depth were ground is filled with water – Top of this zone is water table

• Falls in dry weather• Rises in wet weather

• Groundwater flows slowly based on the amount of recharge and the amount of discharge

• Over pumping of groundwater can result in a variety of environmental problems

Cone of Depression• In an unconfined aquifer, there

is an actual depression of the water levels (water table drops).

• In confined (artesian) aquifers, the cone of depression is a reduction in the pressure head surrounding the pumped well.

Aquifer Subsidence •a gradual sinking of land with respect to its previous level as a result of groundwater being pumped.

•Cracks and fissures can appear in the land as sinking may not be uniform.

•Subsidence is virtually an irreversible process.•http://ca.pbslearningmedia.org/resource/ess05.sci.ess.earthsys.mexico/water-conservation-mexico

/

Salt Water Intrusion• Over pumping of freshwater

near salt water results in the movement of the salt water aquifer inward

• Creates brackish water that is unsuitable for drinking and irrigation

• Solution: injection well that pumps freshwater into the aquifer pushing the salt water out

Use of Fresh Water - US

What activity uses the most water?

A. Industrial useB. Household useC. AgricultureD. Power plants

US water usage by State

http://ebooks.bfwpub.com/friedlandapes/sections/figure

Hidden Water

If you want to know more: http://environment.nationalgeographic.com/environment/freshwater/embedded-water/

Desalination

• Removal of salts from ocean water – distillation – Reverse osmosis

• Common in the Middle East

• Performed by the US to meet water standards for water flowing into Mexico

• Currently very expensive

Where does all that salt go?• Salt is in the form of brine water (very salty

water that is dense and sinks)• Can be put back into the ocean, but

– Must meet salinity requirements– Can impact benthic organisms

Droughts• Causes

– Climate, weather patterns (low rainfall, high temperatures), less snowfall leading to less snowmelt, overusing water during normal rainfall (less storage = less water in reserve)

– Exacerbated by: • Water diversion• River channelization• Overpumping of

groundwater• Dams and aqueducts• Conversion of native

vegetation to rangeland, farmland or urban areas

• Effects– Lack of water for farming,

household use, industry etc

– Soil loss, erosion, dust storms

– Food shortages famines death

– higher food prices– Loss of habitat/biodiversity– Economic losses,

recession, depression– Water conflicts, territory

disputes, wars

Floods• Causes

– Heavy rains, rapidly melting snow, lack of water storage areas

– Exacerbated by• Living in a floodplain• Loss of wetlands• Dams and aqueducts• Native vegetation loss/root

loss due to fires, overgrazing, farming, urbanization, mining, etc

• Impermeable surfaces• Loss of top soil, erosion • Prolonged droughts• Soil compaction, waterlogged

soils

• Effects– Water bodies overflow their

boundaries and flood surrounding areas

– Property damage, loss of life– Loss of crops increased

food prices famines– Erosion, loss of top soil– Damage to wetlands and

other areas that can prevent further storm damage

– Surface water contamination (sedimenst, sewage, chemicals, etc)

– Drinking water contamination (sewage, chemicals, etc)

Media

• Farming and Flooding: http://ca.pbslearningmedia.org/resource/ess05.sci.ess.earthsys.flooderosion/flood-farming-and-erosion/

• Xeriscaping: http://www.youtube.com/watch?v=0RaxjUzFYV8

• Hurricane Katrina– New Orleans Hurricane Risk: http

://ca.pbslearningmedia.org/resource/ess05.sci.ess.earthsys.neworleans/hurricanes-new-orleans-under-threat/

– Hurricane Katrina: http://ca.pbslearningmedia.org/resource/ess05.sci.ess.watcyc.katrinavid/hurricane-katrina-a-scientists-response/

– Wetland Destruction: http://www.pbs.org/wgbh/nova/sciencenow/3214/06-wetl-video.html

• Article on CO flooding: http://www.huffingtonpost.com/2013/09/23/colorado-flood-before-and_n_3975938.html

• Ways to conserve water interactive: http://wateruseitwisely.com/100-ways-to-conserve/