Water: A Limited Resource

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 • 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 Total volume is down by 80% and all 24 fish species are gone 1967 1997

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: • 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 • 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