Water

WaterEB

Lecture 112008 Spring

Agenda• Understand freshwater systems• Use of water• Depletion of water• Water Pollution• Marine water• Ocean Impact• Marine Conservation

Case Study 1Aral Sea

Aral Sea

• Location: Asia• Type: Freshwater• Issue: Overuse• What was the

fourth biggest inland sea is now mostly desert

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Too much use• Soviet Union diverted two rivers which

fed the Aral Sea• to grow cotton in the desert• However, they created an ecological and

human disaster– Disease and cancer are rife in the population.– 60,000 fishing jobs are gone– Cotton fields are down– The fresh water is contaminated with salt

Case Study 2Colorado River

Colorado River



Nevade• Southern Nevada gets nearly 90 percent

of its water supply from the Colorado River.

• The river begins as snowmelt in the Rocky Mountains.

• The snowmelt travels through a series of tributaries into the river, which winds its way south for 1,400 miles and empties into the Gulf of California

Seven States• The Colorado River is one of the most

controlled and litigated rivers in the world.

• Seven western states and Mexico share the water, which serves about 25 million people

• The river is divided among Arizona, California, Colorado, Nevada, New Mexico, Utah and Wyoming according to a 1922 Colorado River Compact.

Where is my water?

• Most times not a single drop empties into the Gulf of Mexico.

• Every drop is used now.• What of the future?• Disputes have already started.• What alternatives exist?

Freshwater Systems

Two types of water

• Fresh water - low in minerals• Sea water - high in salt and other

minerals

• How much of each type is there on Earth?

Hydrologic Cycle

• Water circulates between the different sources

• Constantly moving physical and organic elements

• Key to life

Rivers and Streams• These begin life from

– Rainfall– Snowmelt– Springs

• Tributaries flow into each other and then rivers, then to either lakes or oceans

• Key in spreading silt - vital for organic life• Floodplains also receive silt.

Lakes and Ponds

• Bodies of standing water• Demarcation to;

– Littoral zone - where plant life grows to emerge from water

– Benthic zone - bottom surface– Limnetic zone - where light penetrates– Profundal zone - no light - it is dark!

Marshes, Swamps, Bogs

• Mix of dryland and freshwater = wetlands• Marsh

– Shallow water covering• Swamp

– As marsh but with forests• Bog

– Water covered with thick vegetative mats

Wetlands

• Extremely important– Buffers– Pollution controls– Over 50% of US wetlands are gone!– Most made into farmland, or– developments

Groundwater• Water not sequestered elsewhere will

percolate into the ground to form groundwater

• Aquifers - porous rocks containing water

• Water table - boundary between water saturated rock and layer above.

Groundwater

• Fresh water• Slow to form• Most aged at 1,400 years• Large deposits• Ogallala Aquifer - largest in the world• Reduced by 10%



Water distribution is uneven

• Different regions have differing rainfall• Differing groundwater• Differing surface water• Some regions have more water than

other per head– Most in Hawaii– Least in Chile

Water Usage

We depend on water

• 70% for agriculture• 20% for industry• 10% for residential and municipal use

• Consumptive use - not returned• Non-consumptive use - returned

I’ll be DAMMED• Humans have erected dams on nearly

every water way in the world.• Why?

– Drinking water– Irrigation– Hydroelectric energy– Colorado River extensively dammed.

Water ‘mining’

• Extraction of water faster than replacement is leading to problems– Subsidence– Falling water tables– Salt water intrusion– Drying wetlands

Water Wars

• As water becomes limiting there will likely be conflict

• Middle East - started• Even current treaties such as India and

Pakistan will be faces with strains as the demand for clean fresh water increases

Water woes• One can• Ship it in - from other places• Make it - from sea water - desalination

– Expensive and energy intensive• Reverse osmosis• Filtration• Distillation

Solutions

• Reduce demand– Better irrigation - drip irrigation– Match plants to region– Genetically improve plants– Reduce amount of meat eaten!

• Increase supply– From where?

Water Pollution

Water Quality

• Amount is one aspect• The other is quality

• Polluted water has a cost– Disease– Poisonous

Point source pollution• Point source pollution comes from a single

defined source - factors• Non-point source pollution comes from

multiple sources– Farm runoff– Fertilizer use– Winter salting– Oil leaks– Animal waste

Eutrophication

• Fresh water can suffer from this too• Phosphorus causes issues of overgrowth• Hypoxia results from bacterial activity• Biological pollution is the major issue• Contaminated water - from sewage• Spinach anyone???????

Toxic outcomes

• Heavy metals in water• Acid rain• Water erosion• Sediment release• Temperature pollution• Water treatment facilities

Marine Systems

• Complex interactions exist.

Human Impact

On the Oceans

• Nets• Plastics• Oil• Nutrients• Red tides

Overfishing

• On the brink• Over fishing

– Smaller fish– Younger fish

• Non-target kills• Market driven fisheries management

Help is coming

• From the UN• From each country• From the community• MPAs• Marine Reserves

– Data suggests that they may work!!!

Water

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