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