Upload
joaquin-haisley
View
222
Download
0
Tags:
Embed Size (px)
Citation preview
Water
Chapter 14
Essential Question #1
Why is water so important, how much fresh water is available to us, and how much of it are we using?
Why is Water Important
• Major part of organisms (60%)– Without water, chemical
reactions can’t occur
• Affects Climate
• Carves the Land
• Removes and dilutes wastes & pollutants
• Cycles continuously
Where is Freshwater Available?
• 97.4% salt water, 2.6% freshwater
• Of that 2.6% freshwater:– 75% is frozen– 90% of melted
freshwater is in lakes, soil & air
Fig. 11-2, p. 238
All water Fresh water Readily accessible fresh water
Oceans andsaline lakes97.4%
Fresh water2.6%
Groundwater0.592%
Ice capsand glaciers1.984%
Soilmoisture0.005%
Biota0.0001%
Rivers0.0001%
Atmosphericwater vapor0.001%
0.014%
Lakes 0.007%
Earth’s Water Budget
Only about 0.024% of water is available as accessible, liquid freshwater!
Fig. 14-2, p. 307
ContinentPercent of world's water resources and population
Asia60.5%
36%
Africa10%
8%Europe
North and Central America 7.3%
South America and Caribbean 6.4%
26%
15%
5%Oceania
11.3%
0.5%
14%
GlobalAvailability of
Water Resources
Ground Water
• Water below the earth’s surface, stored in spaces in soil, gravel, sand & rock
– Water table – top of ground water layer (zone of saturation)
• Rises & falls w/ precipitation changes
– Aquifers – deep layers of porous rock holding water• 1/3 of world pumps water from aquifers
Evaporation and transpiration Evaporation
Stream
Infiltration
Watertable
Infiltration
Unconfined aquifer
Confined aquifer
Lake
Well requiring a pump
Flowingartesian well
Runoff
Precipitation
ConfinedRechargeArea
Recharge Unconfined Aquifer
Lesspermeable materialsuch as clay Confining impermeable rock layer
Unconfined Aquifer Recharge Area
Fig. 11-3, p. 239
Groundwater Systems
Accessing Aquifers
Aquifers
• Renewable Aquifers
– Natural Recharge – precipitation percolates down to refill (slow process)
– Lateral Recharge – refilled from side by streams/rivers
• Nonrenewable Aquifers– Receive little to no recharge
Surface Water• Surface Runoff
– Precipitation that doesn’t evaporate or soak into ground
– 2/3 lost to seasonal flooding
• Watershed / Drainage Basin– The region where runoff flows into
water bodies
• Reliable Runoff– The amount of runoff we can count
on as a stable source of fresh water *(1/3 of surface runoff)
Water Withdrawal• Consumptive Use
– Does not return water to original source– ~70% of withdrawn water
• Nonconsumptive Use– Temporarily removes water from source– Ex: Power plant using water for cooling
How much water do we use?
• 70% = Irrigation
• 20% = Industrial Use
• 10% = Cities & Residencies
(1lb of beef = 6 months of showers!)
How much water do we use?
• We currently withdraw 34% of reliable runoff.
• But to meet demands of growing population we may be using 70-90% by 2025.
Fig. 11-4a, p. 240
Annual Precipitation
determines who has & does not
have water resources
Freshwater Resources in the United States
17 western states by 2025 could face intense conflict over scarce water needed for urban growth, irrigation, recreation and wildlife.
Figure 14-5Figure 14-5
Cooperation?• No cooperative
agreements exist for 158 of 263 watersheds shared by two or more countries
• Conflicts likely to increase as population & demand continue to rise
Question #2
What causes freshwater shortages, and what
can be done to increase freshwater supplies?
Causes of Freshwater Shortages
• Dry Climate
• Drought
• Large Population
• Poverty
Stress on the World’s River Basins1 in 6 don’t have access to adequate & affordable supply of
clean water.
Buy 2050 this could be 1 in 4.
Hydrological Poverty
• Could you live on 1 gallon of water/day for all your needs?
Ways to Increase Freshwater Supplies
• Dams & Reservoirs
• Water Transfers
• Using Groundwater
Ways to Increase Freshwater Supplies
• Desalination– Distillation &
reverse osmosis
• Import food
• Waste Less
Essential Question #3
What are the advantages and
disadvantages of withdrawing
groundwater?
Withdrawing Groundwater To Increase Supplies
Aquifers are Renewable as long as NOT:OverpumpedContaminated
Groundwater depletion for Irrigation is a growing problem
At least one-fourth of the farms in India are being irrigated from overpumped aquifers.
Effects of Groundwater Overpumping
Contaminates freshwater aquifers near coastal areas with saltwater.
Sinkholes form when drained aquifers collapse
Groundwater Contamination• Example: Contamination from fracking
Fig. 14-7, p. 313
Trade-Offs
Withdrawing Groundwater
Advantages Disadvantages
Useful for drinking and irrigation
Aquifer depletion from overpumping
Available year-round
Sinking of land (subsidence) from overpumping
Exists almost everywhere
Polluted aquifers for decades or centuries
Renewable if not overpumped or contaminated
Saltwater intrusion into drinking water supplies near coastal areas
Reduced water flows into surface waters
No evaporation losses
Cheaper to extract than most surface waters
Increased cost and contamination from deeper wells
Groundwater Depletion: A Growing Problem
The Ogallala, the world’s largest aquifer, is most of the red area in the center (Midwest).
Areas of Areas of greatest aquifer greatest aquifer depletion from depletion from groundwater groundwater overdraft in the overdraft in the continental U.S.continental U.S.
Figure 14-8Figure 14-8
Fig. 14-12, p. 316
Solutions
Groundwater Depletion
Prevention Control
Waste less water
Raise price of water to discourage waste
Subsidize water conservation
Ban new wells in aquifers near surface waters Tax water pumped from
wells near surface watersBuy and retire
groundwater withdrawal rights in critical areas
Do not grow water-intensive crops in dry areas
Set and enforce minimum stream flow levels
Essential Question #4
What are the advantages and disadvantages of using dams to supply
more water?
Beaver’s are Fans
Fig. 14-13a, p. 317
Provides water for year-round irrigation of cropland
Flooded land destroys forests or cropland and displaces people
Large losses of water through evaporation
Provides water for drinking Downstream
cropland and estuaries are deprived of nutrient-rich silt
Reservoir is useful for recreation and fishing
Risk of failure and devastating downstream flooding
Can produce cheap electricity (hydropower)
Downstream flooding is reduced
Migration and spawning of some fish are disrupted
Fig. 14-13b, p. 317
Powerlines
Reservoir
Dam
PowerhouseIntake
Turbine
River
The Colorado Basin – an Overtapped Resource
The Colorado River has so many dams and withdrawals that it often does not reach the ocean.
14 major dams and reservoirs, and canals.
Water is mostly used in desert area of the U.S.
Provides electricity from hydroelectric plants for 30 million people (1/10th of the U.S. population).
The Colorado River Basin
The area drained by this basin is equal to more than one-twelfth of the land area of the lower 48 states.
Figure 14-14Figure 14-14
Dam Removal
• Since 1998, U.S. Army Corps of Engineers no longer building dams / water diversion projects in US
• Many dams being removed b/c of age or ecological reasons– Difficult & Expensive
Essential Question #5
What are the advantages and disadvantages of
transferring large amounts of water from one place to another?
Advantages of Water Transfer
• Makes unproductive areas more productive
• Promotes investment / jobs / economy
Disadvantages of Water Transfer
• Encourages unsustainable use in water scarce areas
• Reduces water availability from source
• Examples: – Aral Sea Disaster
– California Water Project
– South-to-North China Water Diversion Project ($58 billion)
Essential Question #6
How can removing salt from water solve our
water supply problems? Why or why
not?
Desalination
Disadvantages
• Not Practical
– High cost / High Energy
– Disposal of waste salts / minerals / toxins
Other Ideas: Unlikely
• Cloud Seeding
• Towing Icebergs
• Giant Water Bags
Essential Question #7
How can we waste less water?
Water Waste
• 65-70% of water used is lost to evaporation, leaks, & other losses
• About 60% of water used for crop irrigation is lost due to inefficient methods
Center pivotCenter pivot
Drip irrigationDrip irrigation
Gravity flowGravity flow(efficiency 60% and
80% with surge valves)
Above- or below-ground pipes or tubes deliver water to individual plant roots.
Water usually comes from an aqueduct system or a nearby river.
(efficiency 90–95%)
(efficiency 80%–95%)
Water usually pumped from underground and sprayed from mobile boom with sprinklers.
Improving Irrigation
Reducing Water Waste• Charge more to increase
conservation
• Improve irrigation techniques (drip irrigation)
• Give financial incentives (subsidies) for improving water conservation in agriculture / industry
Reducing Water Waste
• Fix leaks in homes, businesses, infrastructure
• Install low-flow toilets, showers, etc
• Used recycled water (gray water) for watering home
• Plant drought tolerant plants
Rain Water Recycling Systems
Fig. 14-21, p. 327
Solutions
Reducing Water Waste
• Redesign manufacturing processes
• Repair leaking underground pipes
• Landscape yards with plants that require little water
• Use drip irrigation
• Fix water leaks
• Use water meters
• Raise water prices
• Use waterless composting toilets
• Require water conservation in water-short cities
• Use water-saving toilets, showerheads, and front loading clothes washers
• Collect and reuse household water to irrigate lawns and nonedible plants
• Purify and reuse water for houses, apartments, and office buildings
• Don't waste energy
Essential Question #8
What causes flooding, and what can we do to
reduce flood risks?
What is a flood?
• When water leaves its normal channel and spills into its adjacent floodplain
What causes flooding?
• Heavy Rain
• Rapid Snow Melt
• Removing Plants
• Destroying Wetlands
• Impervious Structures– Pavement / Buildings
Fig. 11-23, p. 253
Flooding After Deforestation of a Hillside
How can we reduce flood risks?
• Straighten & deepen rivers/streams
• Build Levees
• Build Dams
– These solutions have ecological problems• Can increase erosion• Can be overwhelmed by excess flood water
How can we reduce flood risks?
• Preserve & Restore Wetlands (best solution)– Act as a natural sponge for flood waters
• Better identify flood plains & think about where we live
Fig. 14-24, p. 331
Solutions
Reducing Flood Damage
Prevention Control
Preserve forests on watersheds
Strengthen and deepen streams (channelization)
Preserve and restore wetlands in floodplains
Tax all development on floodplains
Build levees or floodwalls along streams
Use floodplains primarily for recharging aquifers, sustainable agriculture and forestry, and recreation
Build dams
Essential Question #9
How can we use the earth’s water more
sustainably ?
Sustainable Water Use• Improve monitoring of water sources to improve
management
• Protect ecosystems involved in water cycle
• Regulate withdrawals
• Change subsidies to promote water conservation
• Improve wastewater treatment
• Slow population growth & thus demand
Fig. 11-21, p. 251
• Use water-saving toilets, showerheads, and faucet aerators
• Shower instead of taking baths, and take short showers.
• Repair water leaks.
• Turn off sink faucets while brushing teeth, shaving, or washing.
• Wash only full loads of clothes or use the lowest possible water-level setting for smaller loads.
• Wash a car from a bucket of soapy water, and use the hose for rinsing only.
• If you use a commercial car wash, try to find one that recycles its water.
• Replace your lawn with native plants that need little if any watering.
• Water lawns and garden in the early morning or evening.
• Use drip irrigation and mulch for gardens and flowerbeds.
• Use recycled (gray) water for watering lawns and houseplants and for washing cars.
What Can You Do?Water Use and Waste
What Can We Do?
The Awesome Water Bottle
• http://www.youtube.com/watch?v=pzdBCxZhKpQ