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Chapter 20: Water Supply, Use and Management


Chapter 20: Water Supply, Use and Management Wetlands Freshwater wetlands are threatened in many areas. Over the past 200 years 50% of all wetlands have disappeared ... – PowerPoint PPT presentation

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Title: Chapter 20: Water Supply, Use and Management

Chapter 20 Water Supply, Use and Management
Properties of Water
  • To understand water, we must understand its
    characteristics, and roles
  • Water has a high capacity to absorb and store
  • 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.
  • Water is basis of earths weather

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
  • 3 fresh water
  • Most fresh water frozen (70)

The Hydrologic Cycle
At Earths surface water can be found in liquid,
solid or gaseous form. Residence time varies from
a few days to thousands of years
A Brief Global Perspective
  • Amount of water for which all people compete is
  • Industrial production increases water use
  • Irrigation increases water use

Groundwater and Streams
  • Groundwater refers to the water below the water
    table where saturated conditions exist
  • Recharge zones - locations where surface waters
    move into the ground
  • Discharge zones - places where water flows or
    seeps out are (example streams and rivers)
  • Vadose zone - unsaturated zone above water table)

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Groundwater and Streams
  • Aquifer - underground zone from which groundwater
    can be obtained
  • When water is pumped from an aquifer forms a cone
    of depression

  • Effluent stream (gaining stream)
  • Perennial stream
  • Influent stream (losing stream)
  • Ephemeral stream

Interactions Between Surface Water and Groundwater
  • Should be considered part of the same resource.
  • Nearly all surface water environments are
    connected w/ ground water
  • E.g. withdrawal of groundwater can lower stream
    flow or lake levels
  • Pollution can spread from one source to the other

Your water quality depends on what is upstream
Water Supply US
  • Water budget
  • A model that balances the inputs, outputs, and
    storage of water in a system.
  • Precipitation - evaporation runoff

What happens to water across the US?
Managing WaterPrecipitation and Runoff Patterns
  • Developing water budgets for water resources
    management you must consider
  • - Annual precipitation and runoff patterns.
  • Potential problems can be predicted in areas
    where average runoff is high and precipitation
    is low.
  • Total storage of runoff not possible because of
    evaporative losses.

  • Unique to location and unpredictable
  • Because there are large annual and regional
    variations in stream flow, even areas with high
    precipitation and runoff may suffer from droughts.

Groundwater Use and Problems
  • 30 of all precipitation enters surface or
  • 50 of people in the US use groundwater as a
    primary source of drinking water
  • In many parts of the country withdrawal from
    wells exceeds natural inflow
  • Why?
  • Overdraft
  • Nonrenewable resource
  • Problems include damage to river basins and land

Land subsidence
Salt water intrusion
Overdrafting of ground water in Arizona
Colorado River Basin the politics of water
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Desalination as a Water Source
  • Seawater is 3.5 salt
  • Desalination- a technology to remove salt from
  • Must be reduces to 0.05 to be fresh water
  • Requires large amount of energy, tied to fuel
  • Has place value- price increases quickly with
    transport distance
  • Discharge may affect local salinity

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

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

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Water Use
  • Another problem with off stream use is how much
    water can be removed w/o damaging the stream
  • E.g. Aral Sea. Diverting water for agriculture
    caused sea to dry up
  • Surface area of sea reduces 90 in 50 years

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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

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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
  • E.g. California moves water from north to south
  • E.g. New York City has had to obtain water from
    farther and farther away

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

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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
  • due to better irrigation efficiency, crop type
    and higher energy costs.

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

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Water Conservation
  • The careful use and protection of water resources
  • Involves the quantity of water used and the
  • Important component of sustainable water use
  • Expected that a number innovations will reduce
    the total withdrawals

Agricultural Use
  • Improved irrigation could reduce agricultural
    withdrawals by 20 to 30
  • Tremendous savings because ag is the biggest user

Agricultural Use
  • Suggestions for conservation
  • Price agricultural water to encourage
  • 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

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.

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

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.

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

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
  • Use reclaimed water

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

Perception and Water Use
  • Perception of water is based partly on its price
    and availability.
  • If water is abundant and inexpensive, we dont
    think much about it.
  • If water is scarce or expensive, it is another
  • E.g. people in Tucson pay about 100 more for
    water than people in Phoenix.
  • Tucson residence use less water per person per day

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.

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.

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
  • Gradually eliminate water pricing policies that
    subsidize the inefficient use of water.

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

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

Water Management
  • Options for minimizing potential problems
  • Alternating water supplies and managing existing
    supplies better
  • Towing icebergs
  • As price goes up many innovative programs are

Variable-water-source approach
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
  • During dry years, specific plans to supply water
    on an emergency basis must be in place and ready
    to use.

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
  • In wet years pump excess surface water
    underground to recharge groundwater

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

  • 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

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  • 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
  • Hydrology
  • Type of vegetation
  • Type of soil.

Natural Service Functions of Wetlands
  • Freshwater wetlands are a natural sponge for
  • Reducing flooding.
  • 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
  • Wetlands are natural filters that help purify

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.

  • Freshwater wetlands are threatened in many areas.
  • Over the past 200 years gt 50 of all wetlands
    have disappeared, 90 of freshwater wetlands
  • Diked, drained or filled
  • SF bay estuary considered the most modified by
    human activity

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  • Mississippi River delta includes major coastal
  • 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

Restoration of Wetlands
  • Number of projects have attempted to restore
  • 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

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 dont damage
    the Everglades.

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

Dams and the Environment
  • The environmental effects of dams include the
  • 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.

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
  • Restrict movement upstream and downstream or
    organic material, nutrients and aquatic

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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 dont
    want tax dollars spent on subsidized water.

  • 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
  • schistosomiasis

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.

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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.

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

Channelization and the Environment
  • Adverse environmental effects, including the
  • Degradation of the streams 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
  • Damage or loss of wetlands.
  • Aesthetic degradation.

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.

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
  • Major river of the southwestern US
  • Ends in the Gulf of California

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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
  • No water allowed for environmental purposes
  • Water rarely flows into the Gulf, all stored and
    used upstream.
  • Damaged delta

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
  • Changing hydrology of the river changed other
  • Rapids, sediment load, and vegetation

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

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.

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 waterfor example, the Aral
    Seaare 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.

Global Water Shortage Linked to Food Supply
  • As human population grows there is growing
    concern that there wont be sufficient water to
    grow the food to feed 8-9 billion people.
  • Food shortage linked to water resources a real
  • Water also linked to energy (fuel to pump) as
    energy cost goes up so does cost of food.

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.
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