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The Colorado River Basin
Fig. 13-1, p. 317
Case Study: The Colorado River Basin— An
Overtapped Resource (1)
• 2,300 km through 7 U.S. states
• 14 Dams and reservoirs
• Located in a desert area within the rain shadow of
the Rocky Mountains
• Water supplied mostly from snowmelt of the Rocky
Mountains
Case Study: The Colorado River Basin— An
Overtapped Resource (2)
• Supplies water and electricity for about 30 million
people
• Las Vegas, Los Angeles, San Diego
• Irrigation of crops that help feed America
• Very little water reaches the Gulf of California
• Southwest experiencing recent droughts
Aerial View of Glen Canyon Dam Across the Colorado
River and Lake Powell
Fig. 13-2, p. 317
Freshwater Is an Irreplaceable Resource That
We Are Managing Poorly (1)
• Earth as a watery world: 71% of surface
• Water Used for
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Drinking and cooking
Irrigation
Industry
Sewage
…
• Often a poorly managed resource =
• Water waste
• Water pollution
Freshwater Is an Irreplaceable Resource That
We Are Managing Poorly (2)
• Access to water is
• A global health issue
• Access to clean water = improved health
• An economic issue
• Needed for a strong industry and agriculture economy
• A national and global security issue
• Water locations often cross borders
• States and countries often fight over water rights
Girl Carrying Well Water over Dried Out Earth during
a Severe Drought in India
Fig. 13-3, p. 319
Most of the Earth’s Freshwater Is Not
Available to Us
• Hydrologic cycle: Movement of water in the seas,
land, and air
• Driven by solar energy
and gravity
• Changing as a result of
climate change
• People divided into
• Water haves
• Water have-nots
Most of the Earth’s Freshwater Is Not
Available to Us
• Freshwater availability: 0.024%
• Groundwater (aquifers)
• Surface water (lakes, rivers, streams)
Groundwater and Surface Water Are
Critical Resources (1)
• Aquifers
• Locations where pores or fractures in sediment or
rock have become saturated (filled) with water
Groundwater and Surface Water Are
Critical Resources (1)
• Vadose Zone (Unsaturated zone)
• Spaces in soil are filled with air or air/water mix
• Zone of saturation
• Spaces in soil are filled with water
• Water table
• Top of zone of saturation
Groundwater and Surface Water Are
Critical Resources (2)
• Surface Water
• Surface runoff: rain, snowmelt…that runs over land
surfaces, streams and rivers towards a surface water
• Watershed (drainage) basin: area of land where all
water drains towards a common end point
We Use Much of the World’s Reliable
Runoff
• 1/3 is reliable runoff = usable and consistent runoff
that can be counted on from year to year
• 2/3 of the surface runoff: lost by seasonal floods
(quickly moves through watershed)
Withdrawal and Consumption
• US water consumption averages
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Use and don’t return to watershed
Domestic: 10%
Agriculture: 70%
Industrial use: 20%
U.S. Freshwater Consumption 2005
• US water withdrawal averages
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Use and return to watershed
Electricity: 50%
Domestic: 10%
Agriculture: 35%
Industrial use: 5%
U.S. Freshwater Withdrawal 2005
Science Focus: Water Footprints and
Virtual Water (1)
• Water footprint
• Volume of water we directly and indirectly
• Average American uses 260-300 liters (70-80 gal) per
day
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Flushing toilets, 27%
Washing clothes, 22%
Taking showers, 17%
Running faucets, 16%
Wasted from leaks, 14%
World’s poorest use 19 liters (5 gal) per day
Science Focus: Water Footprints and
Virtual Water (2)
• Virtual water = Indirect water use
(ex. growing crops, manufacturing
products)
• One head of lettuce = 3.5 gal
• 1 lb Hamburger = 660 gal
• 4oz Chocolate = 1000 gal
Water Hotspots in 17 Western U.S. States
Fig. 13-5, p. 322
Water Shortages Will Grow (2)
• 30% earth’s land area experiences severe drought
• Est. rise to 45% by 2059 from climate change
• Population growth in water scarce areas
• Potential conflicts/wars over water
• Refugees from arid lands
Water Shortages Will Grow (2)
Natural Capital Degradation: Stress on the
World’s Major River Basins
Fig. 13-6, p. 323
Groundwater is Being Withdrawn
Faster Than It Is Replenished (1)
• Most “shallow” aquifers are renewable (if properly
managed)
• “Fossil” aquifers are generally non-renewable
• (Ogallala Aquifer)
• Aquifers provide drinking water for half the world
• Water tables are falling in many parts of the world,
primarily from crop irrigation
Groundwater is Being Withdrawn
Faster Than It Is Replenished (1)
Groundwater is Being Withdrawn
Faster Than It Is Replenished (2)
• Industrial Scale Grain Production
• Overpumping aquifers for irrigation of crops
• Saudi Arabia
• Aquifer depletion and irrigation
Saudi Arabia
Before and after
Natural Capital Degradation: Areas of
Greatest Aquifer Depletion in the U.S.
Fig. 13-9, p. 326
Overpumping Aquifers Effects
• Land subsidence (sinking)
• Groundwater near coastal regions
• Contamination of groundwater
with saltwater
Solutions
Groundwater Depletion
Prevention
Control
Waste less water
Raise price of water
to discourage waste
Subsidize water
conservation
Tax water pumped
from wells near
surface waters
Limit number of wells
Do not grow waterintensive crops in
dry areas
Divert surface water
in wet years to
recharge aquifers
Fig. 13-12, p. 327
Large Dams and Reservoirs Have
Advantages and Disadvantages (1)
• Main goal of a dam and reservoir system
• Capture and store runoff
• Release runoff as needed to:
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Generate electricity
Supply irrigation water
Recreation (reservoirs)
(Control Flooding)
Dworshak Dam, Idaho
Large Dams and Reservoirs Have
Advantages and Disadvantages (2)
• Advantages
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Increase the reliable (predictable) runoff available
Reduce flooding
Grow crops in arid regions
“Greener” source of electricity
Large Dams and Reservoirs Have
Advantages and Disadvantages (3)
• Disadvantages
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Loss of plant and animal species
Fill up with sediment
Can cause other streams and lakes to dry up
Concerns with climate
change (precipitation)
• Reservoir Levels Graphs
Lake Mead, Nevada
Transfering Water from Water-Rich
Areas to Water-Poor Areas
• Example – California
• Water transferred by
• Tunnels
• Aqueducts
• Pipes and Pumps
The California Water Project and the Central Arizona
Project
Fig. 13-16, p. 331
Transferring Water to Cities
• Example – New York City
• Mostly “gravity fed”
Southern California Lettuce Grown with Northern
California Water
Fig. 13-15, p. 331
Converting Seawater to Freshwater
• Desalination
• Removing dissolved salts from seawater (or groundwater)
• 14,450 plants in 125 countries
Saudi Arabia: 125 million gal/day
at this plant alone
Removing Salt from Water Is Costly,
Creates Briny Wastewater (2)
• Problems of desalination
1. High cost and energy footprint
2. Large quantity of brine wastes
Reducing Water Waste Has Many
Benefits
• One-half to two-thirds of water is wasted
• Leaks in pipes
• Evaporation
• Poor irrigation
• Subsidies mask the true cost of water
Cutting Water Waste
• Drip or low energy spray irrigation
• Irrigate with treated waste water
Cutting Water Waste
• Fix leaks in the plumbing systems (upgrade infrastructure)
• Use water-thrifty landscaping: xeriscaping
• Use gray water
Floodplains and Water
• Floodplains: area prone to regular flooding
• Highly productive wetlands
• Provide natural flood and erosion control
• Recharge groundwater
Floodplains
• Benefits of floodplains
• Fertile soils
• Nearby rivers for industry use and recreation
• Often highly populated for reasons above
Floodplains
• Channelizing
• Common in cities
• Quickly moves water
downstream to help
prevent flooding
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But…
Simply moves problem downstream
No natural habitat
No recharge of groundwater
Very expensive
Floodplains
• Managing Floodplains and development
• Control by:
• Insurance rates based upon
location in floodplain
• Return areas back to
natural habitat or create
no development zones