1. Water: A Limited Resource
Chapter 14

2. Chapter 14 Water: A Limited Resource
Domestic water in Lagos, Nigeria: in many less developed countries, access to safe, clean water use is limited and expensive. Poor residents of large towns often pay more for water than do the wealthy, spend a much larger fraction acquiring it
And use part of their limited
supply boiling it.

3. 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

4. Importance of Water Cooking Washing Use large amounts for:
Agriculture
Manufacturing
Mining
Moderates our climate
Allows organisms to survive
Energy production
Waste disposal
Use of freshwater is increasing

5. Properties of Water Composed of 2 Hydrogen and 1 oxygen
Exists as solid, liquid or gas
Polar
One end has (+) charge, one end has (-) charge
Forms Hydrogen bond between 2 water molecules
H-bonds define water’s physical properties
High heat capacity
High melt/freeze pt, high boil
Universal solvent
Adhesive and cohesive (cohesive sticks to other water molecule and adhesive is attaches to other surface)

6. Hydrologic Cycle

7. Major Water Compartments
Glaciers, Ice, and Snow
2.6% of world’s water is classified fresh.
0.5 % is groundwater
0.014% readily accessible freshwater
(lakes, rivers, groundwater).
As recently as 18,000 years ago, one-third of continental landmasses were covered by glacial ice sheets.
Now, Antarctic glaciers contain nearly 85% of all ice in the world.
Sea ice comes from ocean water, but salt is excluded during freezing.

8. MAJOR WATER COMPARTMENTS
Oceans
Together, oceans contain more than 97% of all liquid water in the world.
Contain 90% of world’s living biomass.
Moderate earth’s temperature.
Average residence time of water in the ocean is between 100 days to 3,000 years. (range)

10. Major Water Compartments
Groundwater- water below the water table
Second largest reservoir of fresh water.
Infiltration - Process of water percolating through the soil and into fractures and permeable rocks.
Zone of Aeration - Upper soil layers that hold both air and water.
Zone of Saturation - Lower soil layers where all spaces are filled with water.
Water Table - Top of Zone of Sat.

11. Major Water Compartments
Wetlands
Play a vital role in hydrologic cycle.
Lush plant growth stabilizes soil and retards surface runoff, allowing more aquifer infiltration.
Disturbance reduces natural water-absorbing capacity, resulting in floods and erosion in wet periods, and less water flow the rest of the year.

12. WATER AVAILABILITY AND USE
Renewable Water Supplies
Made up of surface runoff and infiltration into accessible freshwater aquifers.
About two-thirds of water carried in rivers and streams annually occurs in seasonal floods too large or violent to be stored effectively for human use.
Readily accessible, renewable supplies are 400,000 gal /person/year.

13. Major Water Compartments
The Atmosphere
Among the smallest water reservoirs.
Contains < 0.001% of total water supply.
Has most rapid turnover rate.
Provides mechanism for distributing fresh water over landmasses and replenishing terrestrial reservoirs.

14. 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

15. Distribution of Water Only % of water on earth is freshwater
% is in the form of ice!
Only ~% of water on earth is available freshwater

16. Seawater Properties of Water Water is never completely pure in nature
Many substances water dissolves cause water pollution

17. Aquifers
In unconfined aquifers, the layers of rock above are porous and allow surface water directly above them to seep downward, replacing the aquifer content. The upper limit of an unconfined aquifer, below which the ground is saturated with water, is the water table.
A confined aquifer or artesian aquifer is a groundwater storage area between impermeable layers of rock. The water in a confined aquifer is trapped and is often under pressure. Its recharge area may be hundreds of kilometers away.

18. Water use and Resource Problems
The greatest use of water worldwide is agriculture
Irrigation accounts for 71% of the world’s total consumption
Industry 20%
Domestic and Municipal use 9%

19. Water Resource Problems
Three categories
Too much
Too little
Poor quality/contamination

20. 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

21. Role of Forests
Forests trap and absorb precipitation to provide nearby lowlands with some protection from floods. If woodlands are cut it can result in floods and also erosion.
What the soil cannot absorb, spill over its banks onto the flood plain.
When an area is developed for human use, much of the water-absorbing plant cover is removed. Buildings and paved roads do not absorb water so runoff is greater.

22. Case in Point The Floods of 1993
Refer also to page number 314 and 315 in your text book.

23. 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)

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

25. Recent Floods
where
SLIDESHOW
River cresting figures

26. Too Little Water Typically found in arid land Problems Drought
Overdrawing water
for irrigation
purposes
Aquifer depletion
Subsidence
Sinkholes
Aquifer depletion from porous sediments causes subsidence or sinking of the land above it. Some areas of the San Joaquin Valley in California have sunk almost 10m. In the past 50 years.
The limestone bedrock of Florida erodes as groundwater moves through it, sometimes causing a sinkhole, a large surface cavity or depression where an underground cave roof has collapsed.
Saltwater intrusion occurs along coastal areas when groundwater is depleted faster than it recharges. Well water in these areas becomes too salty for human consumption.

27. Too Little Water
Problems (continued)
Saltwater Intrusion

28. Water Problems In US and Canada
US has a plentiful supply of freshwater
Many areas have a severe shortages because of
Geographical variations
Seasonal variations

29. Water Problems in US and Canada
Water shortages in West and Southwest
Water is primarily used for irrigation, municipal, commercial and industrial uses.
Water is diverted and transported via aqueducts

30. Mono Lake
Rivers and lakes that are largely formed from snowmelt in the Sierra Nevada Range replenish Mono Lake.
Mono lake is becoming saltier as water is removed by evaporation.
Beginning in 1941, much of the surface water that fed Mono Lake was diverted to Los Angeles 442 km away. As the water level dropped increased salinity adversely affected brine shrimp and alkali fly population. This in turn affected the bird population which fed on the shrimp and flies.
Dust storm from the exposed lakebed began to pose health hazard and violation of federal air pollution standards.

31. Mono lake

32. Solution –Mono Lake Problem
A court order halted water diversions from Mono Lake in 1989, and in 1994, the state of California worked out an agreement on Mono Lake- less water will be diverted to Los Angeles, and Mono Lake will be allowed to return to about 72% of its original volume.
The city of Los Angeles is using state funds to develop water conservation and reclaimed water projects to replace water supplies from Mono lake.

33. Colorado River Basin

34. Colorado River Basin Provides water for 27-million people
Numerous dams for Hydropower
As a result of diversion for irrigation and other uses in the United States, the Colorado river Usually dries up before reaching the Gulf of California in Mexico.
The lower Colorado is increasingly saltier as it flows toward Mexico.
Colorado River no longer reaches ocean
In 2003 California agreed to withdraw no more water from the Colorado river than the Colorado River Compact Permits.

35. Delaware: A State without water?
Delaware has no water source that originate within its boundaries and no major lake to serve its inhabitants. It shares Christina River Basin, which provides water for both Newark and Wilmington, with parts of Pennsylvania and Maryland. There are restriction as to how much water can be withdrawn from Christina River Basin.
Conservation-based pricing: water supply pricing structures that reward consumers for using less water. these often come in the form of low prices for water use up to some level, and stepped up prices as use increases.

36. Water Problems in US and Canada- Groundwater
Aquifer Depletion

37. Aquifer depletion
In certain areas of Louisiana and Texas, removal of too much groundwater resulted in intrusion of salt water from the Gulf of Mexico.
Saltwater intrusion from the Pacific Ocean has occurred along parts of the California coast, along coastal areas of Puget Sound in Washington State and in certain areas of Hawaii.
Florida and Northeast and Mid-Atlantic states also have saltwater intrusion.

38. Ogallala Aquifer
Farmers on the High Plains rely on water from the Ogallala aquifer the largest groundwater deposit in the world..
In some areas farmers are drawing water from the Ogallala Aquifer 40 times faster than nature replaces it, which has lowered the water table more than 30 m. in these places higher pumping costs have made it too expensive to irrigate.
Population decline as farms fail during dry spells

39. 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
Stable run off: the share runoff from precipitation that can be depended on every month and is low in India.

40. Water and Climate Change
Climate change affects the type and distribution of precipitation. It is expected to increase in some areas while it drops in others.
Potential issues:
Reduced snowfall will impact water resources downstream
Sea level rise will cause saltwater intrusion into drinking water supplies

41. Drinking Water Problems
Many developing countries have insufficient water to meet drinking and household needs
Population Growth and water problems
Increase in population means an increase in freshwater requirements
Limits drinking water available
Limits water available for agriculture (food)

42. 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
In 1950 the five countries(France, Switzerland, Luxemburg, Germany and Netherlands) formed the International Commission for Protection of the Rhine (ICPR) to deal with water issues related to the Rhine River.

43. Contd..
In 1986 a severe chemical spill in Switzerland dumped 30 tons of dyes herbicides, fungicides, insecticides and mercury into the river. the spill galvanized the ICPR, which initiated a 15-year Rhine Action Plan.
As a result long-absent fishes have returned to the river, including Atlantic Salmon which returned in 1990 after a 30-year absence. ICPR is now working on bank restoration, flood control, and cleaning up remaining polutants.

44. Aral Sea
Water diversion for irrigation has caused sea to become too saline
The Soviet Union diverted water from Amy Darya and the Syr Darya –1950
In 1960 the Aral sea, once the largest freshwater lake, declined in area and the total volume is down by 80% its biological diversity disappeared.
Health problems-tuberculosis to anemia, kidney disease and cancers.

45. Aral Sea
1967
1997
As water was diverted fro irrigation, the sea level subsided.

46. Potentially Volatile International Water Situations
Mekong River Basin shared between Pakistan and India.
India and Bangladesh quarrel over the Ganges river.
Slovakia and Hungary both depend on the Danube River.

47. Jordan River
It supplies water to Israel, Jordan, the West Bank, and Gaza Strip. Water use is increasing because of population growth and economic activity in the region,
Differential access between Israeli settlers on the West Bank, who use four to five times as much water as do neighboring Palestinians, may be a significant source of conflict.

48. Nile River
Egypt uses most of the Nile’s water even though 10 nations share the Nile River Basin. Ethiopia and Sudan are expanding their use of the Nile River’s flow to meet the demands of their supply at a time when its population is increasing.
The United Nations engineered an international water-use agreement among the Nile River countries to help diffuse this potentially dangerous water situation.

49. Water Management
Main Goal: Provide sustainable supply of high-quality water
Requires humans to use resource carefully
Dams and Reservoirs
Water Diversion Projects
Desalinization
Seeding Clouds
Condensation Nuclei (addition of chemicals)
Towing Icebergs
Cost

50. 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

51. Dams and Reservoirs
Salmon Population in Columbia R. very low due to dams that impede migration
Fish ladders help, but are not effective enough. They help migratory fishes to bypass dams in their migration upstream.
Read page numbers to have better understanding on the impact of dam on ecosystem and organisms

52. 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

53. 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

54. 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

55. 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

56. 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!

57. 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

58. 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
Read You can make a difference: Page number 332 Conserving water at home