Chapter 14
Water: A Limited Resource
Importance of Water
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o
o
Cooking
Washing
Use large amounts
for:
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•
•
•
o
Agriculture
Manufacturing
Mining
Energy production
Waste disposal
Use of freshwater
is increasing
Properties of Water
o
o
o
o
Composed of 2 Hydrogen
and 1 oxygen
Exists as solid, liquid or gas
High heat capacity
Polar
•
o
One end has (+) charge, one
end has (-) charge
Forms Hydrogen bond
between 2 water molecules
•
H-bonds define water’s
physical properties
Properties of
Water
o
o
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Water is never
completely pure
in nature
Content of
seawater (left)
Many
substances
water dissolves
cause water
pollution
Hydrologic Cycle
Distribution of
Water
o
o
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Only 2.5% of water
on earth is
freshwater
2% is in the form
of ice!
Only ~0.5% of
water on earth is
available
freshwater
Freshwater Terminology
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Surface water
•
o
Runoff
•
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Land area that delivers water into a stream or river
system
Groundwater
•
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Movement of surface water to lakes, rivers, etc.
Watershed (drainage basin)
•
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Precipitation that remains on the surface and does not
seep into soil
Freshwater under the earth’s surface stored in
aquifers
Aquifer
•
Underground caverns and porous layers of sand, gravel
and rock in which groundwater is stored
Freshwater Aquifer
Water Use and Resource Problems
o
Fall into Three Categories
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Too much water
Too little water
Poor quality/contamination (discussed in
Chapter 22)
Too Much Water
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Flooding
•
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Modern floods are highly destructive
because humans:
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o
Both natural and human-induced
Remove water-absorbing plant cover from soil
Construct buildings on floodplains
Floodplain
•
Area bordering a river channel that has the
potential to flood
Urban vs. Pre-Urban Floodplains
Floodplain
o
Government restrictions on building
•
o
Levees can fail
Rather than rebuild
levees adjacent to
rivers, experts
suggest allowing
some flooding of
floodplains during
floods
•
(next slide)
Left:
Traditional
levees adjacent
to river
Right:
Suggested levee
style, set back
from river
Case-In-Point Floods of 1993
Too Little Water
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o
Typically found in arid land
Problems
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Drought
Overdrawing water
for irrigation
purposes
Aquifer depletion
•
•
Subsidence
Sinkholes
Too Little Water
o
Problems (continued)
•
Saltwater Intrusion
Water
Problems In
US and Canada
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o
US has a
plentiful supply
of freshwater
Many areas have
a severe
shortages
•
•
Geographical
variations
Seasonal
variations
Water Problems in US and Canada
o
Water shortages in West and Southwest
•
Water is diverted and transported via aqueducts
Water Problems in US and CanadaSurface Water
o
Mono Lake (Eastern CA)
•
•
•
o
Rivers and streams that once fed this lake are
diverted to Los Angeles (275mi away)
Becoming highly saline
Court ordered water diversion reduction
Colorado River Basin
•
•
•
Provides water for 27-million people
Numerous dams for Hydropower
Colorado River no longer reaches ocean
Colorado River bed in Mexico
Water Problems in US and CanadaGroundwater
o
Aquifer Depletion
Ogallala Aquifer
Global Water Problems
o
Amount of freshwater on planet CAN meet
human needs
•
o
BUT, it is unevenly distributed and some places
lack stable runoff
Problems:
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•
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Climate Change
Drinking Water
Population Growth
Sharing Water Resources Among Countries
Global Water Problems
o
Water and Climate Change
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•
Climate change affects the type and
distribution of precipitation
Potential issues:
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•
Reduced snowfall will impact water resources
downstream
Sea level rise will cause saltwater intrusion into
drinking water supplies
Global Water Problems
o
Drinking Water Problems
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Many developing countries have insufficient
water to meet drinking and household needs
Population Growth
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Increase in population means an increase in
freshwater requirements
Limits drinking water available
Limits water available for agriculture (food)
Global Water Problems
o
Sharing Water Resources
Among Countries
•
Rhine River Basin (right)
•
•
•
Countries upstream discharged
pollutants into river
Countries downstream had to
pay to clean the water before
they could drink it
Aral Sea (next slide)
•
Water diversion for irrigation
has caused sea to become too
saline
Aral Sea
1967
1997
Global Water Problems
o
Potentially Volatile International Water
Situations
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•
Jordan River
Nile River
Water Management
o
Main Goal: Provide sustainable supply of
high-quality water
•
o
o
o
Requires humans to use resource carefully
Dams and Reservoirs
Water Diversion Projects
Desalinization
Dams and Reservoirs
o
Benefits:
•
•
•
o
Ensure year-round supply
of water with regulated
flow
Generate electricity
Provide recreational
activities
Disadvantages
•
•
Alter the ecosystem
Reduce sediment load
Dams and Reservoirs
o
Glen Canyon Dam
•
o
Regulated flow has changed ecosystem
To rectify situation
•
•
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Canyon has been flooded several times
Small floods compared to natural floods
Still helps rebuild habitat
Dams and Reservoirs
o
o
Salmon Population in
Columbia R. very low
due to dams that
impede migration
Fish ladders help,
but are not
effective enough
Water Diversion Projects
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o
o
Requires diverting
water to areas that
are deficient by
pumping through a
system of aqueducts
Much of CA’s receives
its water supply from
diverted water from
Northern CA
Controversial and
expensive
Desalinization
o
o
Removal of salt from ocean or brackish
water
Two methods:
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•
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Distillation- salt water is evaporated, and
water vapor is condensed into freshwater (salt
left behind)
Reverse Osmosis- involves forcing salt water
through a membrane permeable to water, but
not salt
Very expensive
Water Conservation
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Reducing Agricultural Water Waste
•
•
Agriculture is very inefficient with water
Microirrigation- irrigation that conserves
waster by piping to
crops through sealed
systems
•
Also called drip or
trickle irrigation
Water Conservation
o
Reducing Industrial Water Waste
•
Stricter laws provide incentive to conserve
water
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Recycling water within the plant
Water scarcity (in addition to stricter
pollution control requirements) will encourage
further industrial recycling
Potential to conserve water is huge!
Water Conservation
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o
Reducing Municipal
Water Waste
Gray Water
•
o
o
Can be used to flush
toilets, wash car or
water lawn
Water saving
household fixtures
Government
incentives
Population Increases (1990-2000)
Population increases
from 1990-2000 in %
Annual electricity
consumption growth
rates from 1988 to
1998 (%)
Source: California
Energy Commission,
Electricity Analysis
Office
Population Projections
Population
Projections
(2000-2030)
Greatest
increases
expected in the
driest states.
Source: U.S.
Census Bureau
NEEDS: FRESH
WATER!
Snow Survey and Water Supply
Forecasting Program
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12 western states
including Alaska
60 FTE
(36 Field, 24 NWCC)
25.5M acres of
irrigated agriculture
$51.1B in annual market
value
(Ag. Census, 2002)
NRCS SNOTEL Network
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SNOTEL network
• 12 western states
• 730+ sites
• 16 million observations
(2005)
• 16.1 million downloads
920 manual snow courses
Meteor-burst Technology
SNOTEL Site Augmented Data Array
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Snow water content
Precipitation
Temperature
Snow depth
Relative humidity
Wind speed/direction
Solar radiation
Soil moisture /
temperature
NWCC Webpage
Mt. Rose SNOTEL Data
Water Supply Forecasts
o
Water Year 2006
• 740 locations
forecast Jan-Jun
with NWS
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Over 11,534
forecasts issued by
states to users
Over 1.9M visits to
WSF pages
New Products - WSF
Rapid changes in snowpack affect water supply forecasts
New Products – Climate Maps
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Maps of
snowpack,
precipitation,
temperature
Oregon State University
http://www.ocs.orst.edu/prism/