1. Chapter 18: Water Supply, Use and Management

2. Overview Water Water Supply - A US Example Water Use
Water Conservation
Sustainability and Water Management
Wetlands
Dams and the Environment
Global Water Shortage Linked to Food Supply

3. Water Water’s characteristics: High capacity to absorb and store heat
Universal solvent
High surface tension
Only compound whose solid form is lighter than its liquid form
Permits sunlight penetration water, allowing photosynthetic organisms to live below the surface

4. A Brief Global Perspective
We are facing a growing global water shortage
Linked to the food supply
Global hydrologic cycle
Water can be liquid, solid or gas
Transfers water from the atmosphere, to land, to oceans, and back to atmosphere
Residence time varies from a few days to thousands of years

6. The Hydrologic Cycle

7. A Brief Global Perspective
Where is water globally?
97% in oceans, 2% in ice, 0.001% in atmosphere
99% of all water on earth is unavailable or unusable (salt) to plants and animals
Water is the most use resource on earth
Mass of water used 1000x the total production of minerals
This is only increasing with greater industrial production and technology

8. Groundwater and Streams
Water located below the water table
saturated conditions
Recharge zones
Locations where surface waters move into the groundwater
Discharge zones
Locations where water flows or seeps out of groundwater
Vadose zone
Area where water seeps through pore spaces

9. Groundwater and Streams
Aquifer
Underground zone from which groundwater can be obtained
Cone of Depression
Forms in water table elevation when water is pumped from an aquifer

11. Streams Effluent stream Influent stream
Flow is maintained during the dry season by seepage into channel from subsurface
Perennial stream - flows all year
Influent stream
Entirely above the water table and flows only in direct response to precipitation
Ephemeral stream
A stream can have reaches that are both of these, or intermittent at varying times of year

12. Interactions Between Surface Water and Groundwater
Should be considered part of the same resource
Nearly all surface water environments have linkages with ground water
Ex: withdrawal of groundwater can lower stream flow or lake levels
Pollution can spread from one source to the other

14. Water Supply: A US Example
Water supply depends on several factors in the hydrologic cycle
Rates of precipitation, evaporation, transpiration
Stream flow
Subsurface flow
Water budget
Model that balances the inputs, outputs, and storage of water in a system
Precipitation – evaporation = runoff

16. Water Supply: A US Example
Amount of water vapor passing over the US every day ~ 152,000 million m3
10% falls as precipitation
66% of which is evaporated or transpired
Only 34% enters surface or groundwater

18. Precipitation and Runoff Patterns
Useful in developing water budgets for water resources management
Potential problems can be predicted in areas with:
Low average runoff
Low precipitation
Total storage of runoff not possible because of evaporative losses

19. Droughts
Areas with high precipitation and runoff may suffer from droughts
Large annual and regional variations in stream flow

20. Groundwater Use and Problems
Half the US population use groundwater as a primary source of drinking water
Groundwater accounts for 20% of water used in US
In many parts of the US, withdrawal from wells exceeds natural inflow
Overdraft
Mining a nonrenewable resource
Problems include damage to river basins and land subsidence

22. Water Use Off-stream use
Refers to water removed from its source for use
May be returned to source after use
Consumptive use- water is not returned to its source
Plant or animals water use (evaporates in the tissue, or is used to make new organs)
Industrial use

23. Water Use In-stream use Water left in its source for use
Navigation, hydroelectric power, fish and wildlife habitats, and recreation
Multiple uses can create controversy

24. Water Use Problem with off-stream use
How much water can be removed without damaging the stream ecosystem?
Ex: Aral Sea
Diverting water for agriculture caused sea to dry up
Surface area of sea reduced 90% in 50 years

27. Aral Sea Salt content of the water has increased
Dust storms from dry salt flats
Climate changes
Winters colder, summers warmer
Loss of fishing and decline of tourism

28. Transport of Water Ancient civilizations In modern civilization
Constructed canals and aqueducts to transport water
In modern civilization
Water moved from areas of abundant rain and snow fall to areas of high usage
Examples
California moves water from north to south
New York City has imported water from nearby areas for more than 100 years

29. Some Trends in Water Use
Withdrawal of surface water far exceeds withdrawal of groundwater
Since 1980 use has decreased and leveled off
Suggests improvement in water management and conservation

31. Some Trends in Water Use
Trends in freshwater withdrawals by water-use categories suggests:
Major uses of water are for irrigation and the thermoelectric industry
Water use for irrigation increased from 1950–1980, but decreased and leveled off from 1985–2000
Due to better irrigation efficiency, crop type and higher energy costs

32. Some Trends in Water Use
Water use by thermoelectric industry decreased slightly in 1980, and stabilized in 1985.
Due to recirculating water for cooling
Water for public and rural supplies continued to increase through the period from 1950 to 2000
Presumably related to the increase in human population

34. Water Conservation Careful use and protection of water resources
Involves both quantity and quality of water
Important component of sustainable water use
Three components
Agricultural Use
Domestic Use
Industrial Use

35. Agricultural Use Agriculture is biggest user of water
Improved irrigation could reduce agricultural withdrawals by 20 to 30%
Suggestions for conservation
Price agricultural water to encourage conservation
Use lined or covered canals that reduce seepage and evaporation

36. Agricultural Use Suggestions for conservation (cont’d)
Use computer monitoring and schedule release of water for maximum efficiency
Integrate the use of surface water and groundwater to more effectively use the total resource
Irrigate at times when evaporation is minimal

37. Agricultural Use Suggestions for conservation (cont’d)
Use improved irrigation systems that more effectively apply water to crops
Sprinklers or drip irrigation
Improve the soil to increase infiltration and minimize runoff
Encourage the development of crops that require less water or are more salt tolerant

38. Agriculture in 1990

39. Agriculture in 2020

40. Domestic Use
Accounts for about 10% of total national water withdrawals
But concentrated in urban areas
May pose major local problems

41. Domestic Use Ways to reduce water use
In semiarid regions, replace lawns with decorative gravels and native plants
Use more efficient bathroom fixtures
Turn off water when not needed
Flush the toilet only when necessary
Fix all leaks quickly

42. Domestic Use Ways to reduce water use (cont’d)
Purchase efficient dishwashers and washing machines
Take a long bath rather than a long shower
Sweep sidewalks and driveways
Using gray water to water vegetation
Water lawns and plants at cool times to reduce evaporation

43. Domestic Use Ways to reduce water use (cont’d)
Use drip irrigation and place water-absorbing mulch around garden plants
Plant drought-resistant vegetation
Use the water meter to monitor for unobserved leaks
Use reclaimed water

44. Industry and Manufacturing Use
Water conservation measures that can be taken by industry
Using cooling towers that use little or no water
In-plant water treatment and recycling

45. Sustainability and Water Management
Sustainable water use definition
Use of water resources by people in a way that allows society to develop and flourish into an indefinite future
Use of water without degrading the various components of the hydrologic cycle or the ecological systems that depend on it

46. Sustainable Water Use General criteria
Develop water resources in sufficient volume to maintain human health and well-being
Provide sufficient water resources to guarantee the health and maintenance of ecosystems
Ensure minimum standards of water quality for the various users of water resources

47. Sustainable Water Use General criteria (continued)
Ensure that actions of humans do not damage or reduce long-term renewability of water resources
Promote the use of water-efficient technology and practice
Gradually eliminate water pricing policies that subsidize the inefficient use of water

48. Groundwater Sustainability
Sustainability involves a long term perspective
For groundwater even longer
It takes a long time to regenerate groundwater
Effects of pumping might not be seen immediately
Long-term approach involves balancing withdrawal with recharge

49. Water Management Management of water resources is a complex issue
Will become more difficult as demand for water increases
Options for minimizing potential problems
Alternating water supplies and managing existing supplies better
Towing icebergs
As price goes up many innovative programs are possible

50. Variable-water-source approach

51. Master Plan for Water Management
New management philosophy: surface water and groundwater are both subject to natural flux with time
In wet years
Plenty of surface water
Near-surface groundwater resources are replenished
During dry years
Specific plans to supply water on an emergency basis must be in place and ready to use

52. Master Plan for Water Management
Advanced planning may include
Drilling to wells that are presently isolated
Reuse of waste water
Develop surface water and use groundwater in dry years
In wet years pump excess surface water underground to recharge groundwater

53. Water Management and the Environment
Often a good deal of controversy surrounds water development
Dams, canals, wetlands modification
Resolution of development involves input from a variety of government and public groups

54. Virtual Water
Virtual water- amount of water needed to create a product or a crop
Amount of water in the product or crop itself is much smaller than the amount of water it took to create it
Ex: How much water does it take to make a cup of coffee?
40 gallons!

55. Virtual Water Concept of virtual water
Promotes efficient use of water from local to global scale
Offers regions greater water security
Helps us to understand relationships between water consumption patterns and their environmental economic and political impacts

57. Wetlands
Term for landforms such as salt marshes, swamps, bogs, prairie potholes, and vernal pools
Shallow depressions that seasonally hold water
Common feature is that they are wet at least part of the year

59. Wetlands
Areas that are inundated by water or where the land is saturated to a depth of a few cm for at least a few days per year
Three major components used to determine the presence of wetlands are:
Hydrology
Type of vegetation
Type of soil

60. Natural Service Functions of Wetlands
Freshwater wetlands are a natural sponge for water - reducing flooding
Freshwater wetlands can act as areas of groundwater recharge or discharge
Wetlands are one of the primary nursery grounds for fish, shellfish, aquatic birds, and other animals
Wetlands are natural filters that purify water

61. Natural Service Functions of Wetlands
Wetlands are often highly productive and are places where many nutrients and chemicals are naturally cycled
Coastal wetlands provide a buffer for inland areas from storms and high waves
Wetlands are an important storage site for organic carbon
Wetlands are aesthetically pleasing to people

62. Wetlands Freshwater wetlands are threatened in many areas
Over the past 200 years > 50% of all wetlands have disappeared, 90% of freshwater wetlands
Diked, drained or filled
San Francisco bay estuary considered the most modified by human activity

64. Wetlands Mississippi River delta includes major coastal wetlands
Historically maintained by flooding
Accretion processes counter natural subsidence
If accretion decreases area of open water increases and wetland in reduced
Levees block sediments and costal wetlands are being lost

65. Restoration of Wetlands
Number of projects have attempted to restore wetlands- varied success
Freshwater marshes recovery
Linked to availability of water at the site
Salt marshes more complex
National Environmental Policy Act of 1969
If wetlands destroyed by development must be replaced elsewhere

66. Restoration of Wetlands
Constructing wetlands to clean up agricultural waste
Natural ability to remove excess nutrients, break down pollutants, and cleanse water
In Florida, human-made wetlands designed to intercept and hold nutrients so they don’t damage the Everglades

67. Dams and the Environment
Dams and their accompanying reservoirs generally designed to be multifunctional structures
Recreational activities
Generating electricity
Providing flood control
Ensuring a more stable water supply
Often difficult to reconcile various uses at a given site

68. Dams and the Environment
Environmental effects of dams
Loss of land, cultural resources, and biological resources in the reservoir area
Larger, dams and reservoirs produce a potential serious flood hazard should they fail
Storage behind the dam of sediment that would otherwise move downstream to coastal areas

69. Dams and the Environment
Environmental effects of dams
Downstream changes in hydrology and in sediment transport change river ecosystem
Fragmentation of ecosystems above and below a dam
Restrict movement upstream and downstream or organic material, nutrients and aquatic organisms

71. Dams and the Environment
Many people vehemently against building new dams
But if present water use practices continue we will need new dams
Few acceptable sites for dams
Expensive to build and operate, many people don’t want tax dollars spent on subsidized water
Three Gorges Dam in Yangtze R.

72. Removal of Dams Recent dam removals include
Edwards Dam in Maine
Marmot Dam in Oregon
After removal both river saw return of fish as they migrated upstream
Large fish runs transport nutrients upriver from ocean to forest ecosystems

74. Removal of Dams
Trapped sediment behind dams must be dealt with in dam removal
If released quickly it could damage downstream ecosystem and fill pools
Slower release minimizes damage
Matilija Dam in Ventura County cost $300,000 to build but 10 times that to remove
Removing dams is simple in concept but involves complex problems relating to sediment and water

75. Global Water Shortage Linked to Food Supply
Both surface water and groundwater are being stressed and depleted
Groundwater in the United States, China, India, Pakistan, Mexico, and many other countries is being mined
Used faster than it is being renewed
Large bodies of water (Ex: Aral Sea) are drying up
Large rivers, including the Colorado in the US and the Yellow in China, do not deliver any water to the ocean in some seasons or years

76. Global Water Shortage Linked to Food Supply
Growing concern that there won’t be sufficient water to grow the food to feed 8–9 billion people.
Food shortage linked to water resources a real possibility
Water also linked to energy (fuel)
As energy cost goes up so does cost of food

77. Global Water Shortage Linked to Food Supply
Solution
Control human population growth
Conserve and sustain water resources
Be proactive now before significant food shortages develop