1. Water: A Limited Resource

2. Overview Water Unit Importance of Water
Hydrologic Cycle
Water Use and Resource Problems
Too Much Water
Too Little Water
Water Problems in US and Canada
Global Water Problems
Sharing Water Resources
Water Management
Providing Sustainable Water Supply
Water Conservation

3. Importance of Water Cooking Washing Use large amounts for:
Agriculture
Manufacturing
Mining
Energy production
Waste disposal
Use of freshwater is increasing

4. Composition/Properties of Water
Composed of 2 Hydrogen and 1 oxygen
Exists as solid, liquid or gas
High heat capacity
Polar
One end has (+) charge, one end has (-) charge
Forms Hydrogen bond between 2 water molecules
H-bonds define water’s physical properties

5. Properties of Water Water is never completely pure in nature
Seawater (left) contains many dissolved ions
Majority being Na+ and Cl- which is why it is “salty”

6. Recall Water circulates around the earth through the Hydrologic Cycle

7. Distribution of Water Only 2.5% of water on earth is freshwater
2% is in the form of ice!
Only ~0.5% of water on earth is available freshwater

8. Freshwater Terminology
Surface water
Precipitation that remains on the surface and does not seep into soil
Runoff
Movement of surface water to lakes, rivers, etc.
Watershed (drainage basin)
Land area that delivers water into a stream or river system
Groundwater
Freshwater under the earth’s surface stored in aquifers
Aquifer
Underground caverns and porous layers of sand, gravel and rock in which groundwater is stored

9. Freshwater Aquifer

10. Water Use and Resource Problems
Fall into Three Categories
Too much water
Too little water
Poor quality/contamination (discussed in Chapter 22)

11. Too Much Water Flooding
Both natural and human-induced
Modern floods are highly destructive because humans:
Remove water-absorbing plant cover from soil
Construct buildings on floodplains
Floodplain
Area bordering a river channel that has the potential to flood

12. Effects of Urbanization: Urban vs. Pre-Urban Floodplains

13. Floodplain
Government restrictions on building based on the fact that
Levees can fail…(ex. New Orleans)
Rather than rebuild levees adjacent to rivers, experts suggest allowing some flooding of floodplains during floods
(next slide)

14. Left: Traditional levees adjacent to river
Right: Suggested levee style, set back from river

15. Case-In-Point Floods of 1993 (pg286)
Extreme flooding of the mississippi brings back the age old debate. Should the Govt. restore old levees or allow the areas to return back to a more normal state in order to mitigate the flooding?

16. Too Little Water Typically found in arid land (duh) Problems Drought
Overdrawing water
for irrigation
purposes
Aquifer depletion
Subsidence
Sinkholes

17. Too Little Water (coastal)
Problems (continued)
Saltwater Intrusion

18. Water Problems In US and Canada
US has a plentiful supply of freshwater
But many areas have a severe shortage there are also
Geographical variations
Seasonal variations

19. Water Problems in US and Canada
B/C of Water shortages in West and Southwest
Water is diverted and transported via aqueducts

20. Water Problems in US and Canada- Surface Water
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
See pg. 291

21. Colorado River bed in Mexico

22. Water Problems in US and Canada- Groundwater
Aquifer Depletion
Aquifer depletion is a wide-spread problem in the US, particularly in the high plains, California and Southern Arizona

23. Global Water Problems
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

24. 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 and coastal migration inward which will tax those sources of water

25. Global Water Problems Drinking Water Problems Population Growth
Many developing countries have insufficient water to meet drinking and household needs
Population Growth
Increase in population means an increase in freshwater requirements
Limits drinking water available
Limits water available for agriculture (food), which is needed more to feed the increased population

26. Global Water Problems Sharing Water Resources Among Countries
Rhine River Basin (right)
Countries upstream discharged pollutants into river
Countries downstream had to pay to clean the water before they could drink it
Aral Sea (next slide)
Water diversion for irrigation has caused sea to become too saline

27. Aral Sea in Kazakstan
Similar to the problems which face Mono Lake
1967
1997
Total volume is down by 80% and all 24 fish species are gone

28. Global Water Problems
Potentially Volatile International Water Situations
Jordan River
Supplies water to Israel, Jordan, the West Bank and the Gaza Strip
Increased population growth in the area is straining the resource
Nile River
Ten nations share the Nile River including Egypt, Ethiopia, and Sudan
Ethiopia and Sudan are expanding in population
Almost all of Egypts water comes from the Nile so they are becoming imperiled

29. Water Management
Main Goal: Provide sustainable supply of high-quality water
Requires humans to use resource carefully
Three main techniques:
Dams and Reservoirs
Water Diversion Projects
Desalinization

30. Dams and Reservoirs Benefits: Disadvantages
Ensure year-round supply of water with regulated flow
Generate electricity
Provide recreational activities
Disadvantages
Alter the ecosystem
Reduce sediment load

31. Dams and Reservoirs Glen Canyon Dam To rectify situation
Regulated flow has changed ecosystem
To rectify situation
Canyon has been flooded several times
Small floods compared to natural floods
Still helps rebuild habitat

32. Dams and Reservoirs
Salmon Population in Columbia R. very low due to dams that impede migration
Fish ladders help (right slide), but are not effective enough

33. Water Diversion Projects
Requires diverting water to areas that are deficient by pumping through a system of aqueducts
Much of CA’s receives its water supply from diverted water from Northern CA
Controversial and expensive

34. Desalinization
Definition: Removal of salt from ocean or brackish water
Two methods:
Distillation- salt water is evaporated, and water vapor is condensed into freshwater (salt left behind)
Reverse Osmosis- involves forcing salt water through a membrane permeable to water, but not salt
Very expensive

35. Distillation Example

36. Reverse Osmosis Example

37. Water Conservation 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

38. Water Conservation Reducing Municipal Water Waste Gray Water
Can be used to flush toilets, wash car or water lawn
Water saving household fixtures
Government incentives

39. Conserving at Home: What you can do
Install water-saving shower heads and faucets (Eco-shower)
Install low-flush toilets
Fix leaky fixtures
Purchase high efficiency appliances
Modify personal habits
Use the dishwasher instead of washing by hand