Water’s Importance

Water Helps:

  • Keep us alive
  • Moderates our climates
  • Sculps the land
  • Remove and dilutes wastes and pollutants

Only ____ of the earths water supply is available to us as liquid freshwater
0.2%
Where does the water go?

  • Precipitation infiltrates the ground
  • It is stored in soil and rock (aquafer)
  • some water evaporates into the air
  • the rest runs of (surface runoff) into bodies of water

Uses of Water

  • We use greater than 50% of worlds reliable runoff and could be using 70-90%
  • 70% of the water we take out of rivers, lakes and aquafers is not returned
  • Irrigation uses 70%, Industries 20% and residences use 10%

___% of the worlds population lives in river basins that do not have enough freshwater
41%
Many parts of the world are experiencing:

  • Rivers running dry
  • Lakes and Seas shrinking
  • Falling water tables from over-pumped aquafers

Who owns the Water?
There is a controversey over whether water supplies should be owned and managed by the Government or by private corps.
European based water companies aim to control ___ of US water supplies by buying up water companies and entering into agreements with cities to manage water supplies.
70%
Cities are outbidding ________ for water supplies from rivers and aquafers
farmers
Countries are importing _____ as a way to reduce their water use.

Grain
More crops are being used to produce____.
Bio-fuels
If we need water, our options are:

  1. Get more from aquafers and rivers
  2. De-salinate ocean water
  3. Waste less water

Most aquifers are renewable unless,
Water is removed faster than it is replenished or it becomes contaminated
Advantages of withdrawing groundwater:

  • useful for drinking and irrigation
  • available year round
  • exists almost everywhere
  • renewable if not overpumped or contaminated
  • No evaporation losses
  • Costs little to extract

Disadvantages to withdrawing groundwater:;

  • Aquafer depletion from over pumping
  • sinking of land from overpumping
  • polluted aquafers for decades or longer
  • saltwater intrusion into drinking water
  • as aquafers become depleted, deeper wells cost more

Benefits of large dams and reservoirs:

  • provides water for year round irrigation and cropland
  • provides water for drinking
  • resevoir for recreational uses
  • production of cheap electricity
  • reduces downstram flooding

Disadvantages to dams:

  • Flooded land above dam can destroy cropland and forests, displace people
  • Large losses of water through evaporation
  • Cropland and estuaries downstream deprived of nutrient rich silt
  • Dams pose risk of failure
  • Migration and spawning of fish

The Colorodo River
Too many dams and water withdrawals cause most water to never reach the ocean

  • 14 major dams, resevoirs and canals
  • Water used mostly in desert areas
  • provides electricity for 30 million people (1/10 of US population)

Chinas Three Gorges Dam
There is a debate as to whether the advantages of the woulds largest dam will outweigh the disadvantages.

  • it will be 2km long (1.24 miles)
  • the electric output will be that of 18 large coal burning plants
  • it will be able to facilitate ship travel to reduce transportation costs
  • dam will displace 1.

    2 million people

  • dam is built over seismic fault and already has small cracks

Transferring water can make unproductive areas more productive but can cause _________.
Environmental Damage
Transferring water

  • promotes investment, jobs and a strong economy
  • encourages unsustainable use of water where water is not naturally supplied.

Removing salt from water is:

  • costly
  • produces large amounts of saltwater waste

2 methods to desalinate water:

  • Distillation- heating saltwater until it evaporates
  • Reverse Osmosis- uses high pressure to force saltwater through a membrane filter

Other options to desalinate water:

  • Seeding clouds to promote rainfall
  • Towing ice bergs
  • Dragging huge bags filled with freshwater

What is wrong with the other ways to desalinate water?
They are too costly and will produce insignificant amounts of water.
We waste about ___ of the water we use, but we can cut it down to ___.

2/3, 15%
____ of the water people use throughout the world is lost through evaporations, leaks and other losses.
65-70%
Water is _____ through government subsidies.
Underpriced
The lack of government subsidies for improving the efficiancy of water use contributes to:
water waste
___ of the worlds irrigation water is wasted
60%
Improved techniques could but world irrigation waste to ___.
5-20%
Some suggest that we should ____ the price of water while providing ____ rates for the poor.
increase, low
We must simply _____ our freshwater and use it wisely
conserve
Effects of too much water:

  • Heavy rain, snow melt, removal of vegetation and destruction of wetlands cause flooding.

  • Floodplains help probide natural flood and erosion control (we develop these areas)
  • develpment and other human activities have contributed to deaths.