Chapter 9: Water Resources

• Flooding- both natural and human induced.

• Modern floods are highly destructive because humans have:− Removed water-absorbing plant

cover from soil.− Constructed buildings on floodplains

• Floodplain- area bordering a river channel that has the potential to flood

Too much water: Flooding

Urban vs. pre-Urban Floodplains

Floodplains

• Rather than rebuild levees adjacent to rivers, experts suggest allowing some flooding of floodplains during floods

Traditional levees adjacent to river

Suggested levee style, set back from river

Too Little Water

• Typically found in arid land• Problems• Drought• Overdrawing water for irrigation purposes• Aquifer depletion• Subsidence• Sinkholes• Saltwater intrusion

NOTE: shown are center-pivot irrigation circles…each one is the

result of long pipes that extend along the radius from the center of the

circle to the edge…rotating slowly to spray the crops.

Subsidence

Subsidence- occurs when large amounts of ground water have been removed from certain types of rocks.

Sinkhole

Sinkholes- Sinkholes are depressions or holes in the land surface, they can be shallow or deep, small or large, but all are a result of the dissolving of the underlying limestone.

• Agriculture- the largest user of water around the world

~70%

Agriculture, Industry and Household Needs

• Irrigation techniques-− Furrow irrigation- a trench that is flooded

with water.

− Flood irrigation- the entire field is flooded with water.

− Spray irrigation- an apparatus that sprays water across a field.

− Drip irrigation- using a slow dripping hose that is laid on or buried beneath the soil.

− Hydroponic agriculture- crops grown in fertilized water and no soil.

Agriculture, Industry and Household Needs

• Industry- the second largest user of water worldwide.

Agriculture, Industry and Household Needs

• Households- the third largest user of water worldwide .

Agriculture, Industry and Household Needs

• US has a plentiful supply of freshwater

• However, water is NOT uniformly distributed, so many areas have severe shortages• Geographical

variations• Seasonal

variations

Water Problems in US and Canada

• Water shortages in West and Southwest• Water is diverted and transported via aqueducts

Water Problems in US and Canada

• Mono Lake (Eastern CA)• Rivers and streams that once fed this lake

are diverted to Los Angeles (275mi away)• Becoming highly saline• Court ordered water diversion reduction

• Colorado River Basin• Provides water for 27-million people• Numerous dams for Hydropower• Colorado River no longer reaches ocean

• Delaware – a state without water• Use of conservation-based pricing, in which

consumers are rewarded for conserving water is helping water managers meet needs

Water Problems in US and Canada

Colorado River bed in Mexico

Groundwater (Aquifer) Depletion

Water Problems in US and Canada

Reducing Agricultural Water Waste• Agriculture is very inefficient with water• Microirrigation- irrigation that conserves

waster by piping to crops through sealed systems• Also called drip or trickle irrigation

Water Conservation

Reducing Industrial Water Waste• Stricter laws provide incentive to

conserve water• Recycling water within the plant

• Water scarcity (in addition to stricter pollution control requirements) will encourage further industrial recycling

• Potential to conserve water is huge!

Water Conservation

• Amount of freshwater on planet CAN meet human needs− BUT, it is unevenly distributed and

some places lack stable runoff• Problems:

− Climate Change− Drinking Water− Population Growth− Sharing Water Resources Among

Countries

Global Water Problems

• Water and Climate Change− Climate change affects the type and

distribution of precipitation− Potential issues:

−Reduced snowfall will impact water resources downstream

−Sea level rise will cause saltwater intrusion into drinking water supplies

Global Water Problems

• Rhine River Basin − Countries upstream discharged pollutants into river− Countries downstream had to pay to clean the

water before they could drink it

• Aral Sea− Water diversion for irrigation has caused sea to

become too saline

Sharing Water Resources

1967 1997

• Water ownership- people can have rights to water use, but they do not own the water.

• Water conservation- using techniques such as more efficient water fixtures, faucets and washing machines.

The Future of Water Availability

• Gray water- wastewater from baths, showers, bathroom sinks and washing machines.− While not suitable for drinking, gray water is

perfectly suitable for watering lawns and plants, washing cars, and flushing toilets

Working toward Sustainability

• Install water-saving shower heads and faucets

• Install low-flush toilets

• Fix leaky fixtures

• Purchase high efficiency appliances

• Modify personal habits

• Use the dishwasher instead of washing by hand

Conserving water at Home