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Chapter 18: Water Supply, Use and Management

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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

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