Transcript Surface water - MHS ENVIRONMENTAL SCIENCE

Chapter 14
Water: A Limited Resource
Hydrologic Cycle
Freshwater Terminology
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Surface water
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Runoff
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Movement of surface water to lakes, rivers, etc.
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Land area that delivers water into a stream or river system
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Freshwater under the earth’s surface stored in aquifers
Watershed (drainage basin)
Groundwater
Aquifer
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Precipitation that remains on the surface and does not seep
into soil
Porous layers of sand, gravel and rock in which groundwater
is stored
Aquifer Depletion
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Removal of groundwater more rapidly than it can be
recharged by precipitation or melting snow.
Freshwater Aquifer
Water Use and Resource Problems
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Fall into Three Categories
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Too much water
Too little water
Poor quality/contamination (discussed in
Chapter 22)
Which problem do we have?
Too Much Water
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Flooding
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Floodplain
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Both natural and human-induced
Area bordering a river channel that has the
potential to flood
Modern floods are highly destructive because
humans:
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Remove water-absorbing plant cover from soil
Construct buildings on floodplains
Floodplain
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Government restrictions on building within
flood plains
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Levees can fail
Rather than rebuild
levees adjacent to
rivers, experts
suggest allowing
some flooding of
floodplains during
floods
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(next slide)
Left:
Traditional
levees adjacent
to river
Right:
Suggested levee
style, set back
from river
100 year flood?
Recurrence interval: average number of years
between floods of a certain size.
The actual number of years between floods of any given
size varies a lot because of the naturally changing climate
Recurrence intervals and probabilities of occurrences
Recurrence interval, in
years
Probability of
occurrence in any
given year
Percent chance of
occurrence in any
given year
100
1 in 100
1
50
1 in 50
2
25
1 in 25
4
10
1 in 10
10
5
1 in 5
20
2
1 in 2
50
Floodplains are lands bordering a river that can become
inundated during flooding. They are considered part of
the river channel during high flows.
Too Little Water
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Typically found in arid land
Problems
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Drought
Overdrawing water
for irrigation
purposes
Aquifer depletion
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Subsidence
Sinkholes
Global Water Problems
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Amount of freshwater on planet CAN
meet human needs … BUT
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it is unevenly distributed and some places
lack stable runoff
Global Water Problems:
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Climate Change
Drinking Water
Population Growth
Sharing Water Resources Among Countries
Global Water Problems
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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; less
snow which stores water, less water in rivers
when temp warms and snow melts.
Sea level rise will…
cause saltwater intrusion into drinking water
supplies (next slide)
Too Little Water
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Aquifer Depletion
Saltwater Intrusion
Global Water Problems
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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
Sharing Water Resources Among Countries
o Rhine River Basin (right)
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Countries upstream
discharged pollutants
into river
Countries downstream
had to pay to clean the
water before they could
drink it
Aral Sea
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(next slide)
Water diversion for
irrigation has caused sea
to become too saline
1973
1986
1999
2001
Water Management
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Main Goal: Provide sustainable supply of
high-quality water
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Requires humans to use resource carefully
Dams and Reservoirs
Water Diversion Projects
Desalinization
Benefits:
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Ensure year-round supply of
water with regulated flow
Generate electricity
Provide recreational activities
Disadvantages
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Alter the ecosystem
(go-to answer:
• HABITAT DESTRUCTION)
Reduce sediment load (so
what?)
Sediments contain nutrients
and create habitat
Dams and
Reservoirs
Dams and
Reservoirs
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Glen Canyon Dam
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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
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Salmon Population in
Columbia R. very low
due to dams that
impede migration
Fish ladders allow
access to water
behind the dam.
They help, but are
not effective
enough
Water Diversion Projects
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Requires diverting water
to areas that are
deficient by pumping
through a system of
aqueducts
Much of CA receives its
water supply from
diverted water from
Northern CA
Controversial and
expensive
Water is diverted and transported via
aqueducts
Desalinization
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Removal of salt from ocean or brackish water
Two methods:
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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
• Most efficient method:
Micro-irrigation: irrigation that conserves
waster by piping to
crops through sealed
systems
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Also called drip irrigation
or trickle irrigation
Water Conservation
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Reducing Industrial Water Waste
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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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Reducing Municipal
Water Waste
Gray Water
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Can be used to flush
toilets, wash car or
water lawn
Water saving
household fixtures
Government
incentives
Conserving at Home
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Install water-saving shower heads and
faucets
Install low-flush toilets
Fix leaky fixtures
Purchase high efficiency appliances
Modify personal habits
Use the dishwasher instead of washing by
hand