Water. To understand water, we must understand its characteristics, and roles:Water has a high capacity to absorb and store heat. Water is the universal solvent.Water has a high surface tension.Water is the only compound whose solid form is lighter than its liquid form. Sunlight penetrates wate
1. Chapter 21: Water Supply, Use and Management
2. Water To understand water, we must understand its characteristics, and roles:
Water has a high capacity to absorb and store heat.
Water is the universal solvent.
Water has a high surface tension.
Water is the only compound whose solid form is lighter than its liquid form.
Sunlight penetrates water to variable depths, permitting photosynthetic organisms to live below the surface.
3. A Brief Global Perspective We are facing a growing global water shortage linked to the food supply.
Global hydrologic cycle
Transfers water from the atmosphere, to land, to oceans and back to atmosphere
97% in oceans
2% in ice
Only 0.001% in atmosphere
6. A Brief Global Perspective At Earth’s surface water can be found in liquid, solid or gaseous form.
Residence time varies from a few days to thousands of years
Amount of water for which all people, animals and plants compete is < 1%
Industrial production increases water use
Mass of water used 1000x total production of minerals
7. Groundwater and Streams Groundwater refers to the water below the water table
Where saturated conditions exist
Locations where surface waters move into the ground are recharge zones
Places where it flows or seeps out are discharge zones (points)
Area where water seeps through pore spaces known as vadose zone
8. Groundwater and Streams Aquifer is an underground zone from which groundwater can be obtained
When water is pumped from an aquifer forms a cone of depression
10. Streams Effluent stream
Flow is maintained during the dry season by seepage
Entirely above the water table and flows only in direct response to precipitation
A given stream can have reaches that are both or intermittent at varying times of year.
11. Interactions Between Surface Water and Groundwater Should be considered part of the same resource.
Nearly all surface water environments have linkages w/ ground water
E.g. withdrawal of groundwater can lower stream flow or lake levels
Pollution can spread from one source to the other
13. Water Supply: A US Example Water supply at any point on the land surface depends on several factors in the hydrologic cycle,
including the rates of precipitation, evaporation, transpiration
A model that balances the inputs, outputs, and storage of water in a system.
Precipitation - evaporation = runoff
15. 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
17. In developing water budgets for water resources management it is useful to consider annual precipitation and runoff patterns.
Potential problems can be predicted in areas where average runoff and precip low
Total storage of runoff not possible because of evaporative losses Precipitation and Runoff Patterns
18. Droughts Because there are large annual and regional variations in stream flow, even areas with high precipitation and runoff may suffer from droughts.
19. Groundwater Use and Problems ½ the people in the US use groundwater as a primary source of drinking water
20% of water used
In many parts of the country withdrawal from wells exceeds natural inflow
Problems include damage to river basins and land subsidence
21. Desalination as a Water Source Seawater is 3.5% salt
Desalination- a technology to remove salt from water
Must be reduces to 0.05% to be fresh water
Requires large amount of energy, tied to fuel prices
Has place value- price increases quickly with transport distance
Discharge may affect local salinity
22. Water Use Off-stream use
Refers to water removed from its source for use
May be returned to source after use
Or consumptive use- water enters tissues, product or evaporates during use and not returned
23. Water Use In-stream use
The use of the river for navigation, hydroelectric power, fish and wildlife habitats, and recreation.
Multiple uses can create controversy
25. Water Use Another problem with off stream use is how much water can be removed w/o damaging the stream ecosystem.
E.g. Aral Sea. Diverting water for agriculture caused sea to dry up
Surface area of sea reduces 90% in 50 years
28. Aral Sea Salt content of the water has increased
Dust storms from dry salt flats
Winters colder, summers warmer
Loss of fishing and decline of tourism
30. Transport of Water Ancient civilizations constructed canals and aqueducts to transport water
From distant river to where it is needed
In modern civilization water moved from areas of abundant rain and snow fall to areas of high usage
E.g. California moves water from north to south
E.g. New York City has had to obtain water from farther and farther away
31. Some Trends in Water Use Withdrawal of surface water far exceeds withdrawal of groundwater
Since 1980 use has decreases and leveled off
Suggests improvement in water management and conservation
33. Some Trends in Water Use Trends in freshwater withdrawals by water-use categories suggests that:
1. The major uses of water are for irrigation and the thermoelectric industry.
2. Water use for irrigation increased from 1950-1980. It decreased and leveled off from 1985-2000
due to better irrigation efficiency, crop type and higher energy costs.
34. Some Trends in Water Use 3. Water use by thermoelectric industry decreased slightly in 1980, and stabilized in 1985.
Due to reticulating water for cooling
4. Water for public and rural supplies continued to increase through the period from 1950 to 2000
presumably related to the increase in human population.
37. Water Conservation The careful use and protection of water resources
Involves the quantity of water used and the quality
Important component of sustainable water use
Expected that a number innovations will reduce the total withdrawals
38. Agricultural Use Improved irrigation could reduce agricultural withdrawals by 20 to 30%
Tremendous savings because ag is the biggest user
39. Agricultural Use Suggestions for conservation:
Price agricultural water to encourage conservation
Use lined or covered canals that reduce seepage and evaporation.
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.
40. Agricultural Use Irrigate at times when evaporation is minimal, such as at night or in the early morning.
Use improved irrigation systems, such as sprinklers or drip irrigation, that more effectively apply water to crops.
Improve the soil to increase infiltration and minimize runoff.
Encourage the development of crops that require less water or are more salt tolerant.
43. Domestic Use Accounts for about 10% of total national water withdrawals
But concentrated in urban areas
May pose major local problems
44. Domestic Use Water use can be substantially reduced by:
In semiarid regions, replace lawns with decorative gravels and native plants.
Use more efficient bathroom fixtures.
Turn off water when not absolutely needed.
Flush the toilet only when really necessary.
Fix all leaks quickly.
45. Domestic Use Purchase dishwashers and washing machines that minimize water consumption.
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.
46. Domestic Use Use drip irrigation and place water-holding mulch around garden plants.
Plant drought-resistant vegetation.
Learn how to read the water meter to monitor for unobserved leaks and record your conservation successes.
Use reclaimed water
47. 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
48. Perception and Water Use Perception of water is based partly on its price and availability.
If water is abundant and inexpensive, we don’t think much about it.
If water is scarce or expensive, it is another matter.
E.g. people in Tucson pay about 100% more for water than people in Phoenix.
Tucson residence use less water per person per day
49. Sustainability and Water Management From a water supply use and management perspective, sustainable water use defined as:
use of water resources by people in a way that allows society to develop and flourish into an indefinite future
W/o degrading the various components of the hydrologic cycle or the ecological systems that depend on it.
50. 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.
51. Sustainable Water Use 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.
52. Groundwater Sustainability Sustainability involves a long term perspective
For groundwater even longer
Effects of pumping might not be seen immediately
Long-term approach involves balancing withdrawal with recharge
53. Water Management Management of water resources is a complex issue that will become more difficult as demand for water increases in the coming years.
Especially in areas like the Southwestern US and other semi arid regions
54. Water Management Options for minimizing potential problems:
Alternating water supplies and managing existing supplies better
As price goes up many innovative programs are possible.
55. Variable-water-source approach
56. A Master Plan for Water Management New management philosophy is that surface water and groundwater are both subject to natural flux with time.
In wet years, there is plenty of surface water, and the 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.
57. A 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
58. 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
59. Wetlands Wetlands is a comprehensive term for landforms such as salt marshes, swamps, bogs, prairie potholes, and vernal pools.
Common feature is that they are wet at least part of the year
Have a particular type of vegetation and soil
63. Wetlands Wetlands - defined as 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:
Type of vegetation
Type of soil.
64. Natural Service Functions of Wetlands Freshwater wetlands are a natural sponge for water.
Many freshwater wetlands are important 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 help purify water.
65. 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.
66. 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
SF bay estuary considered the most modified by human activity
68. 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
69. Restoration of Wetlands Number of projects have attempted to restore wetlands.
In freshwater marshes recovery linked to availability of water
Salt marshes more complex
EPA of 1969 states if wetlands destroyed by development must be replaced elsewhere
70. Restoration of Wetlands Constructing wetlands to clean up ag 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.
71. Dams and the Environment Dams and their accompanying reservoirs generally are designed to be multifunctional structures.
Used for recreational activities
Providing flood control
Ensuring a more stable water supply
Often difficult to reconcile various uses at a given site.
72. Dams and the Environment The environmental effects of dams include the following:
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.
73. Dams and the Environment Downstream changes in hydrology and in sediment transport that change the entire river environment and the organisms that live there.
Fragmentation of ecosystems above and below a dam.
Restrict movement upstream and downstream or organic material, nutrients and aquatic organisms.
75. 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.
76. Canals Water from upstream reservoirs may be routed downstream by way of natural water ways or canals and aqueducts.
Not hydrologically the same as creeks
Smooth, steep banks; water moves fast
Canals can spread and carry disease
77. 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.
79. 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.
80. Channelization and the Environment Channelization of streams consists of straightening, deepening, widening, clearing, or lining existing stream channels.
Engineering technique that has been used to control floods, improve drainage, control erosion, and improve navigation
81. Channelization and the Environment Adverse environmental effects, including the following:
Degradation of the stream’s hydrologic qualities;
nearly all riffle flow, resulting in loss of important fish habitats.
Removal of vegetation along the watercourse, which removes wildlife habitats and shading of the water.
Downstream flooding where the channelized flow ends.
Damage or loss of wetlands.
82. Channelization and the Environment Case study in problems w/ Channelization
Kissimme River in Florida
Meandering river turned into straight ditch
Failed to provide flood protection, damaged wildlife habitat, water quality problems and aesthetic degradation.
In 1990 efforts to restore river began.
83. The Colorado River: Water Resources Management and the Environment The history of the Colorado River emphasizes linkages among physical, biological, and social systems that are at the heart of environmental science.
Major river of the southwestern US
Ends in the Gulf of California
85. The Colorado River For its size has a modest flow but is one of the most regulated and controversial bodies of water in the world.
Total flow was apportioned among various users in 1922
No water allowed for environmental purposes
Water rarely flows into the Gulf, all stored and used upstream.
86. The Colorado River Two largest reservoirs- Hoover Dam and Glen Canyon Dam
Stored about 80% of total in the basin
Represents a buffer of several years water supply.
Changing hydrology of the river changed other aspects
Rapids, sediment load, and vegetation
87. The Colorado River Record snowmelt in the Rocky Mountains in 1983 forced the release of water from Glen Canyon Dam
Three times normal but similar to spring floods before the dam was built.
Beneficial to the river, highlighted the importance of floods in maintaining a natural state.
88. The Colorado River As an experiment “flood” waters released in 1996
Two weeks at full flood
As a result 55 new sandbars formed and 75% of existing sandbars increased in size, rejuvenated marshes and backwaters.
Hailed a success; hoped that what was learned can help restore other river impacted by dams.
89. 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—for example, the 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.
90. Global Water Shortage Linked to Food Supply As human population grows there is 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 to pump) as energy cost goes up so does cost of food.
91. Global Water Shortage Linked to Food Supply Solution
Control human population growth
Conserve and sustain water resources
Need to be proactive now before significant food shortages develop.