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Chapter 14 Water: A Limited Resource

Chapter 14 Water: A Limited Resource. Overview of Chapter 14. 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

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Chapter 14 Water: A Limited Resource

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  1. Chapter 14Water: A Limited Resource

  2. Overview of Chapter 14 • 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. 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 • Content of seawater (left) • Many substances water dissolves cause water pollution

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

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

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

  9. 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

  10. 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

  11. Freshwater Aquifer

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

  13. 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

  14. Urban vs. Pre-Urban Floodplains

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

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

  17. Case-In-Point Floods of 1993

  18. Too Little Water • Typically found in arid land • Problems • Drought • Overdrawing water for irrigation purposes • Aquifer depletion • Subsidence • 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.

  19. Too Little Water • Problems (continued) • Saltwater Intrusion

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

  21. Water Problems in US and Canada • Water shortages in West and Southwest • Water is diverted and transported via aqueducts

  22. 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 • Delaware – a state without water • Use of conservation-based pricing, in which consumers are rewarded for conserving water is helping water managers meet needs

  23. Colorado River bed in Mexico

  24. Water Problems in US and Canada-Groundwater • Aquifer Depletion

  25. 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

  26. 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

  27. Global Water Problems • Drinking Water Problems • 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! • Population Growth • Increase in population means an increase in freshwater requirements • Limits drinking water available • Limits water available for agriculture (food)

  28. 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

  29. Aral Sea 1967 1997

  30. Global Water Problems • Potentially Volatile International Water Situations • Jordan River • Nile River

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

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

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

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

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

  36. 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

  37. Desalinization • 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

  38. 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

  39. 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!

  40. 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

  41. Conserving at Home • 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

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