Freshwater Resources… Going…. 71% of Earth’s surface –97% saltwater –3% freshwater 2.6% ice caps and glaciers Only 0.014% of Earth’s total water supply.

Freshwater Resources…

• Going… Going…

• 71% of Earth’s surface–97% saltwater–3% freshwater

•2.6% ice caps and glaciers•Only 0.014% of Earth’s total water supply is easily accessible as freshwater for human use

Surface water:

Watersheds

• the area of land where all of the water that is under it or drains off of it goes into the same place.

• Should be a renewable resource, but….

• Examples: –South Carolina vs. North Carolina–California–Colorado River–Aral Sea (and the Salton Sea)

Groundwater

NOT underwater lakes…

• Water fills cracks, fissures, and pore spaces

Ogallala Aquifer: World’s Largest

Tapping other groundwater – problems

• Saltwater Intrusion–Normal interface between

freshwater and saltwater moves inland

• Subsidence:–Land sinks

–San Joaquin, CA (source = USGS)

– Some parts of Mexico City sinking 1 inchper month.

• Sinkholes–Roof of cavern

collapses

Water can dissolve minerals and rocks…

Pollution: more expensive and difficult to clean up

• Septic Systems• Animal “lagoons”• Fracking• Coal ash spills• Landfill leaks• Pesticides• Sewer leaks• Oil refinery “accidents”• Etc etc etc!

Water Waste

Example of water waste:

• Household leaks can waste more than 1 trillion gallons annually nationwide. That's equal to the annual household water use of more than 11 million homes.

• We use so much while much of the world suffers from Hydrological Poverty:

–Approximately 1.4 billion people (POOR) living on less than $1 a day can not afford clean drinking water.

Why do we really waste so much?

• Underpricing! We don’t really pay for that much for it!

Conventional Irrigation: #1 Use of Water World Wide

• “About 60% of the irrigation water applied throughout the world does not reach targeted crops.”–Most lost to evaporation and

run-off

Examples:

1. Flood irrigation:

2. Conventional spray irrigation:

More efficient irrigation technologies include:

1. Center Pivot/LEPA

LEPA: Low Energy Precision Application

2. Drip Irrigation, Microirrigation

Other ways to reduce water waste:

3. Xeriscaping

• Replace green lawns with vegetation adapted to the climate! (natural)

4. Gray Water System

5. Using storm run-off

This storm water system will reduce the building’s water bill by 90% and save water

resources

• In the U.S.: Flushing toilets with water clean enough to drink is the single largest use of domestic water.

U.S. Domestic Water Use

Solution: Desalination

– Reverse osmosis: forcing water through a membrane (salt stays behind)

– Distillation: boiling water (salt stays behind)

–Disadvantages: •Expensive

•Energy Intensive

•Produces Briny Water

Zones of a lake

Zones of a river

The floodplain

People settle on floodplains because…

• Fertile soil (nutrient-rich silt from floods)

• Water for irrigation

• Transport

• Flat land

“controlling” flooding

• Channelization: straighten/deepen rivers

• Build levees

• Build dams

• Preserve wetlands

Dams

• China’s 3 Gorges

Good!

• “clean” electricity

Bad…

• Controls flooding downstream but floods upstream

• Displaced over a million people

• Seismic faults

• Disrupted ecosystems (river dolphin: ecologically extinct).