1. Chapter 14 Water: A Limited Resource

2. Overview of Chapter 14 o Importance of Water Hydrologic Cycle Hydrologic Cycle o Water Use and Resource Problems Too Much Water Too Much Water Too Little Water Too Little Water o Water Problems in US and Canada o Global Water Problems Sharing Water Resources Sharing Water Resources o Water Management Providing Sustainable Water Supply Providing Sustainable Water Supply o Water Conservation

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

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

5. Properties of Water o Water is never completely pure in nature o Content of seawater (left) o Many substances water dissolves cause water pollution

6. Hydrologic Cycle (units are km3 & km3 per year)

7. Hydrologic Cycle: o Evaporation – Transpiration: adds water vapor to the atmosphere o Condensation onto condensation nuclei (dust): turns water vapor into liquid water droplets (clouds) o Precipitation – large water droplets (or snow, hail, etc) fall to earth’s surface

9. Hydrologic Cycle…continued o Infiltration – water seeps into the pores in rock and soil, becomes groundwater, which flows slowly back to oceans, lakes, rivers, or wetlands o Runoff – water flows across surface into rivers & streams, wetlands, lakes, and then back to oceans. o Groundwater – the underground reservoir of water, flows due to gravity

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

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

12. Freshwater Aquifer

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

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

15. Urban vs. Pre-Urban Floodplains

16. Floodplain o Government restrictions on building Levees can fail Levees can fail o Rather than rebuild levees adjacent to rivers, experts suggest allowing some flooding of floodplains during floods (next slide) (next slide)

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

18. Case-In-Point Floods of 1993

19. Too Little Water o Typically found in arid land o Problems Drought Drought Overdrawing water Overdrawing water for irrigation for irrigation purposes purposes Aquifer depletion Aquifer depletion Subsidence Subsidence Sinkholes Sinkholes 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.

20. Too Little Water o Problems (continued) Saltwater Intrusion Saltwater Intrusion

21. Water Problems In US and Canada o US has a plentiful supply of freshwater o However, water is NOT uniformly distributed, so many areas have severe shortages Geographical variations Geographical variations Seasonal variations Seasonal variations

23. Water Problems in US and Canada o Water shortages in West and Southwest Water is diverted and transported via aqueducts Water is diverted and transported via aqueducts

24. Water Problems in US and Canada- Surface Water o Mono Lake (Eastern CA) Rivers and streams that once fed this lake are diverted to Los Angeles (275mi away) Rivers and streams that once fed this lake are diverted to Los Angeles (275mi away) Becoming highly saline Becoming highly saline Court ordered water diversion reduction Court ordered water diversion reduction o Colorado River Basin Provides water for 27-million people Provides water for 27-million people Numerous dams for Hydropower Numerous dams for Hydropower Colorado River no longer reaches ocean Colorado River no longer reaches ocean o Delaware – a state without water Use of conservation-based pricing, in which consumers are rewarded for conserving water is helping water managers meet needs Use of conservation-based pricing, in which consumers are rewarded for conserving water is helping water managers meet needs

25. Colorado River bed in Mexico

26. Water Problems in US and Canada- Groundwater o Aquifer Depletion

27. Global Water Problems o Amount of freshwater on planet CAN meet human needs BUT, it is unevenly distributed and some places lack stable runoff BUT, it is unevenly distributed and some places lack stable runoff o Problems: Climate Change Climate Change Drinking Water Drinking Water Population Growth Population Growth Sharing Water Resources Among Countries Sharing Water Resources Among Countries

28. Global Water Problems o Water and Climate Change Climate change affects the type and distribution of precipitation Climate change affects the type and distribution of precipitation Potential issues: Potential issues: Reduced snowfall will impact water resources downstream Reduced snowfall will impact water resources downstream Sea level rise will cause saltwater intrusion into drinking water supplies Sea level rise will cause saltwater intrusion into drinking water supplies

29. Global Water Problems o Drinking Water Problems Many developing countries have insufficient water to meet drinking and household needs Many developing countries have insufficient water to meet drinking and household needs The World Health Organization estimates that about 1.1 billion people lack access to safe drinking water! The World Health Organization estimates that about 1.1 billion people lack access to safe drinking water! o Population Growth Increase in population means an increase in freshwater requirements Increase in population means an increase in freshwater requirements Limits drinking water available Limits drinking water available Limits water available for agriculture (food) Limits water available for agriculture (food)

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

32. Aral Sea 19671997

33. Global Water Problems o Potentially Volatile International Water Situations Jordan River Jordan River Nile River Nile River

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

35. Dams and Reservoirs o Benefits: Ensure year-round supply of water with regulated flow for those near dam Ensure year-round supply of water with regulated flow for those near dam Generate electricity (hydroelectric power) Generate electricity (hydroelectric power) Provide recreational activities (flooded area used by boaters, fishermen, etc. Provide recreational activities (flooded area used by boaters, fishermen, etc. Can provide flood protection Can reduce flood damage Can provide flood protection Can reduce flood damage

36. Dams and Reservoirs o Disadvantages: Alter the ecosystem by: Creates a still water ecosystem rather than flowing water Creates a still water ecosystem rather than flowing water Reduce sediment load downstream, Increased sediment trapped upstream behind dam Reduce sediment load downstream, Increased sediment trapped upstream behind dam Raise temp of water behind dam Raise temp of water behind dam Lowers oxygen levels behind dam, restricts flow, etc. Lowers oxygen levels behind dam, restricts flow, etc.

37. Dams and Reservoirs o Glen Canyon Dam Regulated flow has changed ecosystem (destroyed sandbars which were bird nesting grounds) Regulated flow has changed ecosystem (destroyed sandbars which were bird nesting grounds) o To rectify situation Canyon has been flooded several times Canyon has been flooded several times Small floods compared to natural floods Small floods compared to natural floods Still helps rebuild habitat Still helps rebuild habitat

38. Dams and Reservoirs o Salmon Population in Columbia R. very low due to dams that impede migration o Fish ladders help, but are not effective enough

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

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

42. Water Conservation o Reducing Agricultural Water Waste Agriculture is very inefficient with water Agriculture is very inefficient with water Microirrigation- irrigation that conserves waster by piping to Microirrigation- irrigation that conserves waster by piping to crops through sealed crops through sealed systems systems Also called drip or Also called drip or trickle irrigation trickle irrigation

43. Water Conservation o Reducing Industrial Water Waste Stricter laws provide incentive to conserve water Stricter laws provide incentive to conserve water Recycling water within the plant Recycling water within the plant Water scarcity (in addition to stricter pollution control requirements) will encourage further industrial recycling Water scarcity (in addition to stricter pollution control requirements) will encourage further industrial recycling Potential to conserve water is huge! Potential to conserve water is huge!

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

45. Conserving at Home o Install water-saving shower heads and faucets o Install low-flush toilets o Fix leaky fixtures o Purchase high efficiency appliances o Modify personal habits o Use the dishwasher instead of washing by hand