Chapter 11 Water

World Water Distribution Total: 97% salt water 3% freshwater Freshwater: 70% glaciers 29% aquifers 1% lakes, rivers, streams

Water is unequally distributed across Earth’s surface Different regions possess vastly different amounts of groundwater, surface water, and precipitation Many areas with high population density are water- poor and face serious water shortages

Surface Water Lakes, rivers, streams, wetlands, estuaries Watershed: the area of land that is drained by a river River system: the flowing network of water draining a river basin

Watersheds of the world (see pgs. 270-271)

Groundwater Groundwater: water that is beneath the earth’s surface Water table: the upper level of water underground Aquifer: underground formation that contains groundwater

Aquifers Most are made of materials like rock, sand, gravel with spaces in which the water can be held like a sponge (see pgs. 274-275) Water can be tapped from aquifers for use by people; if used too much and too quickly, it can go dry (Ogallala Aquifer case study, pgs. 272-273)

Aquifers Aquifers can be refilled as water percolates down through the recharge zone, may take a long time Porosity – amount of space between particles of the rock Permeability – ability of the rock or soil to allow water to flow through it Pollution can enter the groundwater through the recharge zone (think about Silent Spring) – it can then travel to other places through the underground water system, even showing up years later

The Ogallala Aquifer The world’s largest known aquifer Underlies the Great Plains of the U.S. Its water has allowed farmers to create the most bountiful grain-producing region in the world

Water Use Which category has the highest use overall in the world?

Water Use 1. Industrial – manufacturing, producing power (including reservoirs by dams), cooling of power plants

Global Water Use: Industry How does water use compare in developing and developed countries? Which countries have more than 50% of their water used by industries?

Water Use 2. Agricultural – irrigation of crops

Global Water Use: Agriculture Which countries have the highest percent of their water use dedicated to agriculture?

Water Use 3. Residential (=municipal) – drinking, cooking, cleaning

Residential Water Use

Guess the gallons it takes to… Take a shower: 50 gallons Flush the toilet: 6 gallons Large load of laundry: 60 gallons Brushing teeth, water running: 2 gallons Dishwasher load: 10 gallons Washing face/hands: 5 gallons

Water Use Caculator http://www.tampagov.net/dept_Water/information_resources/Saving_water/Water_use_calculator.asp

Drinking Water Treatment Steps (pgs. 276-277): 1. First filtration – removes large trash, objects, large organisms like fish and mussels

Drinking Water Treatment 2. Coagulation or flocculation – chemicals are added to the water; bacteria and other small impurities stick together to form flocs and settle out of the water

Drinking Water Treatment 3. Second filtration – layers of sand, gravel, coal used to filter remaining impurities

Drinking Water Treatment 4. Chlorination – chlorine added to stop bacterial growth

Drinking Water Treatment 5. Aeration – removes unwanted gases, improves odor and taste

Drinking Water Treatment 6. Additional Treatments - depends on the community: may include addition of fluoride which is good for teeth, addition of chemicals to soften hard waters

Drinking Water Treatment 7. Potable (=drinkable) water is pumped to homes for residential use.

Water Treatment Plant Virtual Tour http://www.teachersdomain.org/resources/ess05/sci/ess/watcyc/h2otreatment/index.html

Water management Water diversion projects bring water to areas that need it Central Arizona Project Aqueduct – brings water from the Colorado River to dry areas of Arizona, multiple uses (drinking water, recreation, power, etc.)

We divert – and deplete – surface water People have long diverted water to farm fields, homes, and cities The once mighty Colorado River has been extensively dammed and diverted

The Colorado River is heavily diverted What water is left after all the diversions comprises just a trickle into the Gulf of California On some days, water does not reach the gulf Diversion has drastically altered the river’s ecology

The Aral Sea Once the fourth-largest lake on Earth It has lost more than 80% of its volume in just 45 years The two rivers leading into the Aral Sea were diverted to irrigate cotton fields Consequences of a shrinking sea 60,000 fishing jobs are gone Pesticide-laden dust from the lake bed is blown into the air The cotton cannot bring back the region’s economy

Can the Aral Sea be saved? People may have begun saving the northern part of the Aral Sea

Water management Dams – purposes: flood control hydroelectric power creation of reservoirs for drinking water, irrigation and recreation Only a few major rivers remain undammed In remote regions of Canada, Alaska, and Russia

A typical dam

Water management Case Study: Glen Canyon Dam, AZ List pros and cons http://video.nationalgeographic.com/video/player/environment/going-green-environment/conservation-in-action/glen-canyon.html

Water management Case Study: Three Gorges Dam, China http://www.youtube.com/watch?v=NwFGyzllCJg&eurl=http://www.theworldisnotflat.com/three-gorges-dam List pros and cons

Benefits and drawbacks of dams Power generation Emission reduction Crop irrigation Drinking water Flood control Shipping New recreational opportunities Drawbacks: Habitat alteration Fisheries declines Population displacement Sediment capture Disruption of flooding Risk of failure Lost recreational opportunities

Are we running out of water? Do you think water is a renewable resource? It is a renewable resource because it can be replenished by nature (water cycle) However, if it is made unusable by pollution or removed from the ground faster than nature can replenish it, then it is considered nonrenewable

Will we see a future of water wars? Freshwater depletion leads to shortages, which can lead to conflict 261 major rivers cross national borders Water is a key element in hostilities among Israel, Palestinians, and neighboring countries Many nations have cooperated with neighbors to resolve disputes

Consequences of overuse of water resources: Groundwater is easily depleted Aquifers recharge slowly 1/3 of world population relies on groundwater As aquifers become depleted Water tables drop Salt water intrudes in coastal areas Sinkholes = areas where ground gives way unexpectedly Some cities (Venice, Mexico City) are slowly sinking Wetlands dry up

Solutions can address supply or demand Increasing supply Water can be transported through pipes and aqueducts It can be forcibly appropriated from weak communities Can we “make” more usable water?

Desalination Desalination is the process of removing salt from salt water – may be answer to providing more water to a growing human population It is expensive, requires fossil fuels, and produces concentrated salty water

Solutions can address supply or demand Best solution is to lower demand, that is to CONSERVE WATER Politically difficult in the short term Offers better economic returns Causes less ecological and social damage

Water conservation Agriculture – drip irrigation system

Water conservation Industry – recycle water

Residential demand can be reduced outside Water lawns at night, when evaporation is minimal Xeriscaping = landscaping using plants adapted to arid conditions Don’t wash driveways and sidewalks with water

Water conservation in the home Residential – how can you conserve water? Awareness of water use and conscious decisions to reduce water use (shorter showers, turn off water when brushing teeth, etc.) Low flow faucets, shower heads and toilets Don’t use toilet as a waste basket Run dishwasher and washing machine only when full Fix leaky plumbing