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QOD Calculate how many liters of water are wasted in 1 month by a faucet that leaks 2 drops of water per second. (1 liter of water equals about 3500 drops) How many gallons is this? (1 liter equals gallons)
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Living in the Environment
Water Resources G. Tyler Miller’s Living in the Environment 13th Edition Chapter 14
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Key Concepts The physical properties of water
Availability of fresh water Methods of increasing freshwater supplies Using water more efficiently Problems associated with flooding
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Water’s Unique Properties
Hydrogen bonding Major factor in determining water’s unique properties
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Hydrogen bonds O H + - Covalent bonds O H + - O H + -
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Water’s Unique Properties
Liquid over wide temperature range High boiling point 100°C (212°F) Low freezing point 0°C (32°F) Changes temperature slowly Helps protect organisms Moderates the earth’s climate Excellent coolant High heat of evaporation Absorbs heat as it changes into water vapor Releases heat as vapor condenses
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Water’s Unique Properties
Great dissolving power Carries dissolved nutrients into tissue Flush waste products out of tissue All-purpose cleanser Remove and dilute water-soluble wastes pH Helps maintain balance between acids and bases Adhesion and cohesion Surface tension Wetting ability Expands when it freezes Ice floats
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Water: A Vital Resource
Fresh Water 2.6% Oceans and saline lakes 97.4%
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Supply of Water Resources
Freshwater Readily accessible freshwater Biota 0.0001% Rivers Atmospheric water vapor 0.001% Lakes 0.007% Soil moisture 0.005% Groundwater 0.592% Ice caps and glaciers % 0.014%
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Available Water Total = 326 million cubic miles
Available Water Total = 326 million cubic miles 97% of Earth’s water is in oceans 2.997% is locked up in ice caps and glaciers 0.003% is easily accessible Soil moisture Groundwater Water vapor Lakes Streams
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Water Supply & Use
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Hydrologic Cycle Powered by solar energy and gravity
Evaporation and precipitation Continuous recycling of water Runoff Infiltration Evaporation Temporary storage as snow and ice Temporary storage in lakes Temporary storage in plants (transpiration) and animals Chemical reactions with rocks and minerals Volcanism also causes melting of snow caps and mudflows as melted water mixes with ash Source of additional water? volcanism (steam)
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Surface Water Surface runoff Reliable runoff
Water flowing off the land into bodies of water Reliable runoff One-third of world’s annual runoff Represents a stable source of water Watershed (Drainage Basin) Region from which water drains
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Groundwater Zone of aeration:
As precipitation infiltrates and percolates through voids in soil and rock Pores, fractures, crevices, etc. Shallow rock has little moisture Zone of saturation depth were ground is filled with water Top of zone of saturation is water table Falls in dry weather Rises in wet weather
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Groundwater Movement Groundwater moves from recharge area through an aquifer and out a discharge area well, spring, lake, geyser, artesian well, steam, ocean Normally moves downhill at only a meter per year Some aquifers get little recharge and were formed thousands of years ago Removal from these nonrenewable resources is called water mining
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Groundwater
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Evaporation and transpiration
Ground Water Fig p. 315 Flowing artesian well Unconfined Aquifer Recharge Area Precipitation Evaporation and transpiration Well requiring a pump Evaporation Confined Recharge Area Runoff Aquifer Stream Infiltration Water table Lake Infiltration Unconfined aquifer Confined aquifer Less permeable material such as clay Confirming permeable rock layer
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Use of Water Resources Agriculture Industry Domestic Power Plants
Humans use about 50% of reliable runoff United States Industry 11% Public 10% Power cooling 38% Agriculture 41% Agriculture Industry Domestic Power Plants
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Use of Fresh Water United States China 41% agriculture 87% agriculture
38% power plant cooling 11% industry 10% public China 87% agriculture 7% industry 6% public
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Water use (cubic kilometers per year)
5,500 5,000 4,500 4,000 3,500 3,000 2,500 2,000 1,500 1,000 500 1900 1920 1940 1960 1980 2000 Water use (cubic kilometers per year) Total use Agricultural use Industrial use Domestic use Year
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Water in the United States
Average precipitation (top) in relation to water-deficit regions and their proximity to metropolitan areas (bottom).
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Too Little Water Dry climate Drought Desiccation Water stress
Air circulation patterns Drought 21 days+ Precipitation <70% Increased evaporation Desiccation Drying of the soil Water stress Low per capita availability Caused by increased population Limited runoff levels Acute shortage Adequate supply Shortage Metropolitan regions with population greater than 1 million
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Too Little Water Water stressed – reliable runoff per person below 1700 cu meters per year Water scarcity – per capita availability below 1000 cu meter per year 500 million people live in countries that are either water stressed or water scarce limited access (live far away) arrives during short periods hydrological poverty Collect water from unsafe sources Purchase from private vendor
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Global Precipitation Patterns
Wright and Nebel, 2002. Michael D. Lee Ph.D. Geography and Environmental Studies
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Increasing Fresh Water Supplies
Build dams and reservoirs to store runoff Bring surface water from another area Withdraw groundwater. Convert salt water to fresh water Waste less water Import food to reduce water use
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Using Dams and Reservoirs to Supply More Water (To Dam or Not To Dam)
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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) Figure 14.13 Trade-offs: advantages (green) and disadvantages (orange) of large dams and reservoirs. The world’s 45,000 large dams (higher than 15 meters or 50 feet) capture and store 14% of the world’s runoff, provide water for almost half of all irrigated cropland, and supply more than half the electricity used by 65 countries. The United States has more than 70,000 large and small dams, capable of capturing and storing half of the country’s entire river flow. QUESTION: Which single advantage and which single disadvantage do you think are the most important? Downstream flooding is reduced Migration and spawning of some fish are disrupted Fig a, p. 317
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Ecological Services of Rivers
• Deliver nutrients to the sea which helps to sustain coastal fisheries • Deposit silt that maintains deltas • Purify water • Renew and nourish wetlands • Provide habitats for aquatic life • Conserve species diversity
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Large Dams - Pros Collect and store water from rain and snow
Produce electricity Irrigate land below the dam Control flooding Provide water to cities, towns and rural areas Provide recreational activities such as swimming, boating, fishing
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Large Dams - Cons Enormous loss of water due to evaporation
Mass of water can cause earthquakes Flooded land destroys forests or cropland and displaces people Danger of Dam collapse Downstream areas deprived of nutrient-rich soil, which will eventually clog the reservoir Migration and spawning of fish disrupted Expensive to build
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Upstream of Dams - Negative Impact
Environment Loss of terrestrial/riparian habitat and species Creation of artificial lacustrine (lakes) system exotic species introductions Reservoir/storage for contaminants Cultural / social Loss of cultural resources Displacement of families (villages, regions) Water quality hazard Economic Shift in land use / economy Water loss via evaporation Water loss via seepage Aesthetic landscape inundated
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China’s Three Gorges Dam
Beijing RUSSIA YELLOW SEA MONGOLIA CHINA Shanghai Wunan Jailing River Yichang Chongquing Yangtze River CHINA Three Gorges Dam Reservoir EAST CHINA SEA NEPAL BHUTAN BANGLADESH PACIFIC OCEAN INDIA VIETNAM BURMA LAOS China’s Three Gorges Dam
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Case Study: The Colorado Basin – an Overtapped Resource
Lake Powell, is the second largest reservoir in the U.S. It hosts one of the hydroelectric plants located on the Colorado River.
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The Colorado River Basin
IDAHO WYOMING Dam The Colorado River Basin Aqueduct or canal Salt Lake City Upper Basin Grand Junction Lower Basin Denver UPPER BASIN UTAH COLORADO Lake Powell Grand Canyon Glen Canyon Dam Las Vegas NEW MEXICO Boulder City ARIZONA CALIFORNIA Albuquerque Los Angeles LOWER BASIN Palm Springs Phoenix 100 mi. San Diego Yuma 150 km Mexicali Tucson All-American Canal Gulf of California MEXICO
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Transferring Water from One Place to Another
Watershed transfer North Bay Aqueduct South Bay California Aqueduct CALIFORNIA NEVADA UTAH MEXICO Central Arizona Project Colorado River Los Angeles Shasta Lake Sacramento Fresno Phoenix Tucson ARIZONA Colorado River San Francisco San Diego California Water Project Central Arizona Project James Bay (Canada)
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Increasing Fresh Water Supplies
Build dams and reservoirs to store runoff Bring surface water from another area Withdraw groundwater.
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Tapping Groundwater Advantages Potential Problems! Year-round use
No evaporation losses Often less expensive Potential Problems! Many
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Problems with Using Groundwater
Water Table Lowering Initial water table Cone of depression Original water table Lowered
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Problems with Using Groundwater
WYOMING SOUTH DAKOTA NEBRASKA COLORADO KANSAS OKLAHOMA NEW MEXICO TEXAS 100 Miles Kilometers Less than 61 meters (200 ft) meters ( ft) More than 183 meters (600 ft) (as much as 370 meters or 1,200 ft. in places) 160 Aquifer depletion Ogallala Aquifer
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Aquifer Depletion 95% of water removed from Ogallala Aquifer is for irrigation and the removal rate is greater than the refreshing rate
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Problems with Using Groundwater
Subsidence Sinking of land when groundwater is withdrawn
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Well casing projecting from the ground (40 years)
Aquifer Subsidence Well casing projecting from the ground (40 years) Mexico City’s aquifer has shrunk enough that land has dropped up to 7.5 m
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Other Effects of Groundwater Overpumping
Sinkholes form when the roof of an underground cavern collapses after being drained of groundwater.
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Problems with Using Groundwater
Saltwater intrusion Major irrigation well Well contaminated with saltwater Saltwater Intrusion Normal Interface Fresh groundwater aquifer Salt water Sea Level Water table
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Fresh groundwater aquifer
Major irrigation well Well contaminated with saltwater Water table Sea level Fresh groundwater aquifer Saltwater Figure 14.11 Natural capital degradation: saltwater intrusion along a coastal region. When the water table is lowered, the normal interface (dashed line) between fresh and saline groundwater moves inland, making groundwater drinking supplies unusable. QUESTION: What two things would you do to reduce the threat of saltwater intrusion? Seafloor Interface Saltwater intrusion Interface Normal interface Fig , p. 315
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Problems with Using Groundwater
Chemical contamination Reduced stream flow Tragedy of the commons
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Converting Salt Water to Fresh Water
Desalination – removing dissolved salts from ocean water or brackish water. Distillation desalination Heating salt water until it evaporates. Reverse osmosis desalination Salt water is pumped at high pressure through a thin membrane
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Converting Salt Water to Fresh Water
Desalination Cons Desalination is very expensive Larger amounts of energy needed Desalination produces large quantities of wastewater waste disposal problem
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Making it Rain Cloud Seeding Limited Success Water condensation nuclei
Silver iodide particles Limited Success Not useful in dry areas Potential pollution from cloud seeding chemicals Legal disputes: ownership of clouds
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Using Water More Efficiently
Reduce losses due to leakage 60 to75% of water people use is lost! Causes of waste Water subsidy policy Artificially low cost of water False sense of abundance
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Using Water More Efficiently
Causes of waste cont. Water laws Doctrine of riparian rights (East) Anyone owning land adjoining stream has right to water Principle of prior appropriation (West) First-come, first-served Common law governs groundwater Subsurface water belongs to whoever owns the land above it Fragmented watershed management
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(efficiency 60% and 80% with surge valves)
Drip irrigation (efficiency 90–95%) Gravity flow (efficiency 60% and 80% with surge valves) Figure 14.18 Major irrigation systems: because of high initial costs, center-pivot irrigation and drip irrigation are not widely used. The development of new low-cost drip-irrigation systems may change this situation. Center pivot (efficiency 80%–95%) Water usually pumped from underground and sprayed from mobile boom with sprinklers. Above- or below-ground pipes or tubes deliver water to individual plant roots. Water usually comes from an aqueduct system or a nearby river. Fig , p. 325
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Too Much Water: Floods Natural phenomena
heavy rain, melting snow Aggravated by human activities Renew and replenish Reservoir Dam Levee Flood wall Floodplain
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Solutions: Achieving a More Sustainable Water Future
Efficient irrigation Water-saving technologies Improving water management
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What Can You Do? Water Use and Waste
• Use water-saving toilets, showerheads, and faucet aerators. • Shower instead of taking baths, and take short showers. • Stop water leaks. • Turn off sink faucets while brushing teeth, shaving, or washing. • Flush toilets only when necessary. • Wash only full loads of clothes or use the lowest water-level for smaller loads. • Use recycled (gray) water for lawn, gardens, house plants, car washing. • Wash a car from a bucket of soapy water, and use the hose for rinsing only. Figure 14.25 Individuals matter: ways you can reduce your use and waste of water. Visit for an array of water-saving tips from the EPA and the California Urban Water Conservation Council that can be used anywhere. QUESTION: Which four of these actions do you think are the most important? • 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 and decorative gravel or rocks. • Water lawns and gardens in the early morning or evening. • Sweep or blow off driveways instead of hosing off with water. • Use drip irrigation and mulch for gardens and flowerbeds.
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