water supply, use & management. water to understand water, we must understand its...
TRANSCRIPT
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Water Supply, Use & Management
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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.
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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
Video on Water Cycle: Water Cycle
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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
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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
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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
Aquifer Depletion Video: Aquifer Depletion
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Streams
Effluent stream Flow is maintained during the dry season by seepage Perennial stream
Influent stream Entirely above the water table and flows only in direct
response to precipitation Ephemeral stream
A given stream can have reaches that are both or intermittent at varying times of year.
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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
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Water Supply: A U.S. 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
stream flow subsurface flow
Water budget A model that balances the inputs, outputs, and storage of
water in a system. Precipitation - evaporation = runoff
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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
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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 precipitation low Total storage of runoff not possible because of
evaporative losses
Precipitation and Runoff Patterns
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Droughts
Because there are large annual and regional variations in stream flow, even areas with high precipitation and runoff may suffer from droughts.
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Groundwater Use and Problems
½ the people in the United States 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 Overdraft Nonrenewable resource Problems include damage to river basins
and land subsidence
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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
Desalination Video: Desalination
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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
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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 ecosystem. E.g. Aral Sea
Diverting water for agriculture caused sea to dry up
Surface area of sea reduces 90% in 50 years
Aral Sea Video: Aral Sea
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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 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
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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
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Some Trends in Water Use1. 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.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.
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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
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Agricultural Use
Improved irrigation could reduce agricultural withdrawals by 20 to 30% Tremendous savings because ag is the biggest user
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.
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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 withdrawals But concentrated in urban areas May pose major local problems
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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. 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. 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
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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
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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
without degrading the various components of the hydrologic cycle or the ecological systems that depend on it
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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.
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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.
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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
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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
Options for minimizing potential problems: Alternating water supplies and managing existing
supplies better Towing icebergs As price goes up many innovative programs are
possible.
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Variable-water-source approach
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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.
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
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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
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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
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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: Hydrology Type of
vegetation Type of soil
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Natural Service Functions of Wetlands
Freshwater wetlands are a natural sponge for water. 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 animals.
Wetlands are natural filters that help purify water.
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.
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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
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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
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.
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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
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
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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.
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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
schistosomiasis
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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.
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.
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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
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
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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
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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 1922 No water allowed for environmental purposes Water rarely flows into the Gulf, all stored and used
upstream. Damaged delta
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
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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
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