Environment

WATER RESOURCES

Lecture 14

WHY SHOULD YOU CARE ABOUT 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 FEW YEARS

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