Water Resources, Usage, and Problems from Use

Environmental Science

Chap 20 Sect 1 & 2

Essential Questions to Examine

Why is Water So Important?

Water For Life!! Helps shape our continents & moderates climate Medium by which living processes occur

– Required by chemical reactions– Dissolves important substances for life- minerals,

oxygen, nutrients– Removes wastes

Regulates body temp and global temperature Supports structures- cells 60-70% of your body is water You can only survive a few days without it

Hydrologic Cycle

Process by which Earth’s water supply is continually collected, purified, and distributed– Describes the circulation of water as it evaporates,

condenses, and falls to the Earth surface Processes involved are:

– Evaporation– Transpiration– Condensation– Precipitation– Infiltration

Hydrologic Cycle a.k.a The Water Cycle

Water as a Resource Availability of fresh, usable water is

limited. Freshwater Resources Include:

– Surface Water– Groundwater

Water Resources- Surface Water

Surface Water- above ground water Run-Off- water flowing across land from rain

or melted snow and ice into bodies of water– Creates rills- shallow grooves

Watershed (drainage basin)- land areas that drain run-off water into bodies of water– Rivers, streams, etc.

Water Resources- Groundwater Most groundwater considered a

“nonrenewable” resource Groundwater will eventually discharge into

surface water Groundwater- underground supply of

freshwater from precipitation seeping into soil– Infiltration-process where water percolates into

soil and pores of permeable rock

Groundwater: Water Table

Water Table- upper surface of groundwater, ground below is completely saturated by water– Zone of saturation- saturated rock layer

below water table– Zone of aeration- area where water enters

an aquifer– Zone of discharge- where groundwater

leaves an aquifer & becomes surface water

Water Resource- Groundwater

Aquifer-underground porous rock or caverns that contain groundwater– Confined (artesian) – storage area trapped

between 2 impermeable rock layers• Water is trapped, often underpressure• Recharge area is often miles away

– Unconfined- groundwater storage located above a layer of permeable rock

• Allows surface water to percolate and recharge (replenish)

Aquifer- Groundwater Use Problems Depletion- water withdrawn faster than

recharge– Most recharge rates are very slow– Some recharge zones “covered” by

development

UH OH SINKHOLE!!

Subsidence- Withdrawal of groundwater cause porous formations to collapse– Surface settling– Sinkholes- form when too

much water withdrawn from caverns and aquifers

– Roof of the underground cavern collapses, creates a large surface crater

Collapse of an Aquifer

Aquifer- Groundwater Use Problems Salt Water

Intrusion- occurs along coast

Withdrawal of freshwater allows salt water to enter aquifer

Water Usage and Resources Water consumption varies by country due to its

availability.– Domestic & municipal uses 9%– Industry uses 20%– The largest use of water worldwide is agriculture using

71% of total water consumption. According to the USGS- in 2005, 410,000 million

gallons per day (Mgal/d) of water was withdrawn for use – 80 % (328,000 Mgal/d) was from surface water– 20 % (82,600 Mgal/d) was withdrawn from groundwater

Domestic Use of Water Domestic water use is water used for indoor

and outdoor household purposes– drinking, preparing food, bathing, washing clothes

and dishes, brushing your teeth, watering the yard and garden, and even washing the dog

U.S. Sources: city/county water department or from a well.

Average person in U.S. uses 300 Liters/day– Personal hygiene– Home cleaning & maintenance

Industrial Water Use

Access to water a factor in short term & long term plans of industry

Water is used by Industries that produce:– metals, wood and paper products, chemicals,

gasoline and oils,– fabricating, processing, washing, diluting, cooling,

or transporting a product– incorporating water into a product; or for sanitation

needs within the manufacturing facility.

Agricultural Water Use

Single largest user of water in U.S. Approx 200 billion L/day Used for livestock and crop production Irrigation is largest form of use

– Flood irrigation– Furrow irrigation– Overhead irrigation– Subirrigation

Types of Irrigation

Flood irrigation- flooding of flat area of land, inexpensive method– Very wasteful evaporation

takes 50 % of water Furrow irrigation-

releases water into furrows/ditches dug between crop rows– Evaporation rate is up and

mineral salts accumulate

Types of Irrigation

Overhead irrigation- – Sprinkler- flat & uneven slopes

• Efficiency is decreased with strong winds

– Drip or trickle- very efficient but expensive• Uses tubing to deliver small quantities of water to plant

roots• Great for areas where water supply is low

Subirrigation- water introduced naturally or artificially beneath the soil– Effective in places where water is close to surface

Global Water Use

Global averages vary a great deal between regions. Look at the examples below, tell me what do you

think is different about these continents and how do you think that determines how they use water?

In Africa,

In Europe

–agriculture consumes 88 % of all water withdrawn for human use–domestic use accounts for 7 % –industry for 5 %.

–industry 54 %–agriculture's 33 %–domestic 13 %

Georgia Water Use In 2000, 6,490 million gallons

per day (Mgal/d) Thermoelectric power 3,310

Mgal/d from surface water.– 17 plants operate using fossil

fuels & 2 nuclear-powered plants.

hydroelectric power plants estimated to be 31,900 Mgal/d.– Most water remains in system,

not counted as “Used”

Georgia Water Use Agricultural totaled 1,130

Mgal/d (1,090 Mgal/d for irrigation and 35 Mgal/d for livestock).

17-19 % of water use Public-supply was 1,250 million gallons per day (Mgal/d),– surface-water withdrawal =

78 % – ground-water = 22 %

Water Problems: Too Much Water

Flooding- a natural event,

human activities contribute to removal of natural vegetation and floodplains (wetlands, etc.)

greater frequency of impermeable surfaces

Water Problems: Too little water3 primary reasons for freshwater shortages1)Increasing pollution of existing water

supplies- To be discussed in the next chapter must know that it’s a problem found with usage.

2) Climate- precipitation varies due to topographical effects (mountains, location on Earth i.e. latitude, near the coastline, desert belts, etc.)

Cycles of wet and dry years create temporary droughts

Water Problems: Too little water

3) Rising Demands Populations increasing

More water used for drinking, sanitation, agriculture, recreation, and industrial uses

More demand placed on surface and groundwater resources

Examples: Colorado River and Ogallala Aquifer

Rising Demands and Water Shortages- Colorado River

Begins in N. Central Colorado- Ends in Gulf of California (1450 miles long)

7 states are in its Watershed- Colorado, Wyoming, Nevada, Utah, Arizona, N.Mexico, California

– California River Compact (1922) divided up water among these states

– each would receive 7.5 million acres /yr

– all water is “spoken for” w/ population increases/development not enough water to go round

Colorado River sometimes dries out before it can make it to the Gulf of California

Ogallala Aquifer

Largest groundwater source in the world Farmers drawing water 40 times faster

than it can recharge Water table has lowered more than

30meters in some areas Feared that groundwater level in aquifer

will drop to a level to expensive to pump

Environmental Impact

Water Management

Water Management- Globally