WATER RESOURCES
Lecture 14
WHY SHOULD YOU CAREABOUT WATER RESOURCES?
Humans and environment depend on water
– Life made primarily of water- Survival without water a few days- Industry and agriculture use large
amounts
Water unevenly distributed on earth
– Too much floods- Too little becomes main focus of life
-Low cost encourages waste
WE ARE MANAGING FRESHWATER POORLY
• Access to freshwater a global health issue− An average of 9,300 people die each day from lack of access
to safe drinking water
• Economic issue− Water vital for producing food and energy
• National and global security issue
• Environmental issue− Excessive withdrawal
THE EARTH’S WATER SUPPLY
• LIQUID WATER COVERS 3/4 SURFACE
– MOST SALTWATER
– AVAILABLE LIQUID FRESHWATER 0.024% OF TOTAL
– SURFACE WATER (LAKES, RIVERS AND STREAMS)
– GROUNDWATER
• HYDROLOGIC CYCLE
-MOVEMENT OF WATER IN THE SEAS, LAND, AND AIR
-DISTRIBUTED UNEVENLY
• HUMANS ALTER THE HYDROLOGIC CYCLE
-WITHDRAWING AND POLLUTING WATER AND CAUSING CLIMATE CHANGE
GROUNDWATER
• ZONE OF SATURATION• SPACES IN SOIL BELOW A CERTAIN DEPTH ARE
FILLED WITH WATER
• WATER TABLE• TOP OF ZONE OF SATURATION
• AQUIFERS• RECHARGED NATURALLY BY PRECIPITATION OR BY
NEARBY LAKES, RIVERS, AND STREAMS
SURFACE WATER
• SURFACE WATER• SURFACE RUNOFF
• WATERSHED OR DRAINAGE BASIN
WATER USE IS INCREASING
• TWO-THIRDS OF SURFACE RUNOFF LOST TO SEASONAL FLOODS
• RELIABLE RUNOFF• REMAINING ONE-THIRD IS RELIABLE SOURCE OF
FRESHWATER
• WORLDWIDE AVERAGES• IRRIGATION FOR CROPS AND LIVESTOCK: 70%• INDUSTRIAL USE: 20%• CITIES AND RESIDENCES: 10%
• WATER FOOTPRINT• VOLUME OF WATER USED DIRECTLY OR INDIRECTLY
WATER USE IS INCREASING• VIRTUAL WATER
– WATER USED TO PRODUCE FOOD AND OTHER PRODUCTS
CASE STUDY: FRESHWATER RESOURCES
IN THE UNITED STATES
• MORE THAN ENOUGH RENEWABLE FRESHWATER
-UNEVENLY DISTRIBUTED AND POLLUTED
THE COLORADO RIVER BASIN• RUNS THROUGH DRY SOUTHWESTERN
U.S.
– 14 MAJOR DAMS
– MOST WATER REMOVED
– ELECTRICITY
– IRRIGATION
– PUBLIC WATER
– 15% OF U.S. FOOD PRODUCTION AND 13% LIVESTOCK
– FLOW GREATLY DECREASED
– SILTATION
FRESHWATER SHORTAGES WILL GROW
• MANY OF THE WORLD’S MAJOR RIVER SYSTEMS ARE HIGHLY STRESSED• NILE, JORDAN, YANGTZE, AND GANGES
• MORE THAN 30 COUNTRIES FACE FRESHWATER SCARCITY• ESTIMATE: 60 COUNTRIES BY 2050
• 30% OF THE EARTH’S LAND AREA EXPERIENCES SEVERE DROUGHT• RESEARCH PREDICTS THIS WILL WORSEN
GROUNDWATER DEPLETION
• GROUNDWATER WITHDRAWALS UNSUSTAINABLE IN SOME AREAS• BEING PUMPED FROM AQUIFERS IN SOME AREAS FASTER THAN IT IS RENEWED BY
PRECIPITATION
• WIDESPREAD DRILLING OF WELLS BY FARMERS• ACCELERATED AQUIFER OVERPUMPING• WATER TABLES FALLING
• IN 2008, SAUDI ARABIA ANNOUNCED THAT
IT HAD DEPLETED ITS MAJOR DEEP AQUIFER
OVERPUMPING OF THE OGALLALA AQUIFER
• OGALLALA AQUIFER—LARGEST KNOWN AQUIFER
• IRRIGATES THE GREAT PLAINS
• VERY SLOW RECHARGE
• WATER TABLE DROPPING• WATER PUMPED 10–40 TIMES FASTER
THAN RECHARGE RATE
• GOVERNMENT FARM SUBSIDIES RESULT IN FURTHER DEPLETION
• BIODIVERSITY THREATENED IN SOME AREAS
OVERPUMPING AQUIFERS CAN HAVE HARMFUL EFFECTS
• LIMITS FOOD PRODUCTION AND RAISES PRICES
• WIDENS GAP BETWEEN RICH AND POOR
• LAND SUBSIDENCE• SAN JOAQUIN VALLEY IN CALIFORNIA• MEXICO CITY
• GROUNDWATER OVERDRAFTS NEAR COASTAL REGIONS• CONTAMINATION OF GROUNDWATER WITH
SALTWATER
DEEP AQUIFERS MIGHT BE TAPPED
• MAY CONTAIN ENOUGH WATER TO PROVIDE FOR BILLIONS OF PEOPLE FOR CENTURIES
• MAJOR CONCERNS• NONRENEWABLE• LITTLE IS KNOWN ABOUT THE GEOLOGICAL
AND ECOLOGICAL IMPACTS OF PUMPING DEEP AQUIFERS
• NO INTERNATIONAL TREATIES GOVERN ACCESS
• COSTS OF TAPPING ARE UNKNOWN• WATER IS CONTAMINATED
HOW CAN WE INCREASE FRESHWATER SUPPLIES?
• LARGE DAM-AND-RESERVOIR SYSTEMS• GREATLY EXPANDED WATER SUPPLIES IN SOME
AREAS
• DISRUPTED ECOSYSTEMS AND DISPLACED PEOPLE
• MAIN GOAL OF A DAM AND RESERVOIR SYSTEM• CAPTURE AND STORE RUNOFF• RELEASE RUNOFF AS NEEDED FOR:
• FLOOD CONTROL• GENERATING ELECTRICITY• SUPPLYING IRRIGATION WATER• RECREATION (RESERVOIRS)
LARGE DAMS PROVIDE BENEFITS AND CREATE PROBLEMS
• RESERVOIRS
• INCREASE THE RELIABLE RUNOFF AVAILABLE FOR USE (33%)
• DISPLACE PEOPLE (40-80MILLION)
• IMPAIR ECOLOGICAL SERVICES OF RIVERS (NUTRIENT CYCLING, CLIMATE MODERATION, WASTE TREATMENT, GROUNDWATER RECHARGE, HABITAT)
• ENDANGER PLANT AND ANIMAL SPECIES (1 OUT OF 5 SPECIES)• FILL UP WITH SEDIMENT WITHIN 50 YEARS• GLACIERS FEEDING THE RIVERS ARE MELTING FAST
WATER TRANSFERS
• TRANSFERRING WATER FROM ONE PLACE TO ANOTHER HAS GREATLY INCREASED WATER SUPPLIES IN SOME AREAS
-HAS ALSO DISRUPTED ECOSYSTEMS
• WATER TRANSFERRED FROM WATER-RICH TO POOR REGIONS- CANALS AND PIPELINES
– BENEFITS WHERE WATER TRANSFERRED
-WATER LOSS THROUGH EVAPORATION AND LEAKS
– ECOSYSTEMS CHANGE BOTH PLACES
– CALIFORNIA WATER PROJECT
– SACRAMENTO RIVER DEGRADED
– POLLUTION PROBLEMS
CASE STUDY: THE ARAL SEA DISASTER
• LARGE-SCALE WATER TRANSFERS IN DRY CENTRAL ASIA HAVE LED TO:• WETLAND DESTRUCTION
• DESERTIFICATION• GREATLY INCREASED SALINITY• FISH EXTINCTIONS AND DECLINE OF FISHING• BLOWING SALT AND DUST DESTROYING WILDLIFE AND CROPS• INCREASED GLACIAL MELTING IN THE HIMALAYAS
CASE STUDY: THE ARAL SEA DISASTER
• SHRINKAGE OF THE ARAL SEA HAS ALTERED LOCAL CLIMATE
• HOT, DRY SUMMERS, COLDER WINTERS, AND A SHORTENED GROWING SEASON
• RESTORATION EFFORTS• COOPERATION OF NEIGHBORING COUNTRIES• MORE EFFICIENT IRRIGATION • DIKE CONSTRUCTION RAISED LEVEL OF
NORTHERN SEA BY 2 METERS
• SOUTHERN SEA MAY DRY UP WITHIN FEWYEARS
DESALINATING SEAWATER
OCEAN WATER ABUNDANT
– REMOVAL OF SALT = FRESHWATER
– DISTILLATION OR REVERSE OSMOSIS
– CURRENTLY <1% OF FRESHWATER FOR THE WORLD AND U.S.
– PROBLEMS
– VERY EXPENSIVE
– HIGH ENERGY USE
– DISPOSAL OF SALTY WATER
– MOSTLY IN MIDDLE EAST, NORTH AFRICA,
CARIBBEAN, AND MEDITERRANEAN
(18, 400 ACROSS THE WORLD)
CONSERVING WATER
• WAYS TO USE FRESHWATER MORE SUSTAINABLY- 66% OF WATER WASTED
– RAISE WATER PRICES
– SHIFT WATER SUBSIDIES
– INCREASE IRRIGATION EFFICIENCY.
– NIGHT IRRIGATION
– SEVERAL CROPS TOGETHER
– MORE WATER-EFFICIENT CROPS
– IMPORT WATER-DEMANDING CROPS
– USE TREATED WASTEWATER
– CONSERVE WATER IN INDUSTRY
– CONSERVE WATER IN HOMES
WHAT WOULD YOU DO?
• WAYS TO REDUCE WATER USE
– SHORT SHOWERS
– WASH FULL LAUNDRY LOADS
– DRIP IRRIGATION
– FIX LEAKS
– WATER SAVING DEVICES
– DON’T RUN WATER WHEN NOT USING
– REDUCE MEAT AND WATER RICH FOOD CONSUMPTION
– REPLACE LAWNS WITH LOW-WATER PLANTS
– WASH CAR BY HAND
- �Water Resources�
- Why Should You Care�About Water Resources?
- We Are Managing Freshwater Poorly
- The Earth’s Water Supply
- Slide Number 5
- Groundwater
- Surface water
- Water Use Is Increasing
- Water Use Is Increasing
- Case Study: Freshwater Resources in the United States
- Slide Number 11
- �The Colorado River Basin
- Freshwater Shortages Will Grow
- Slide Number 14
- Groundwater Depletion
- Slide Number 16
- Overpumping of the Ogallala Aquifer
- Overpumping Aquifers Can Have Harmful Effects
- Deep Aquifers Might Be Tapped
- How Can We Increase Freshwater Supplies?
- Large Dams Provide Benefits and Create Problems
- Water Transfers
- Case Study: The Aral Sea Disaster
- Case Study: The Aral Sea Disaster
- Desalinating Seawater
- Conserving Water
- What Would You Do?