Transcript ch. 13 – water as a limited resource

Chapter 13
Water: A Limited Resource
Overview of Chapter 13
 Importance of Water
 Hydrologic Cycle
 Water Use and Resource Problems
 Too Much Water
 Too Little Water
 Water Problems in US and Canada
 Global Water Problems
 Sharing Water Resources
 Water Management
 Providing Sustainable Water Supply
 Water Conservation
Importance of Water
 Cooking
 Washing
 Use large amounts for:
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Agriculture
Manufacturing
Mining
Energy production
Waste disposal
 Use of freshwater is increasing
Properties of Water
 Composed of 2 Hydrogen and 1 oxygen
 Exists as solid, liquid or gas
 High heat capacity – absorbs a lot of solar
energy without increasing in temperature
much.
 Earth’s temperature matches temperature
for water as a liquid.
 “universal solvent” allows dissolved gases
and minerals in water, including
pollutants
 Colder water is more dense until 4
Celsius, then becomes less dense (ice
floats and allows living things beneath)
Hydrologic Cycle
Distribution of Water
 Only 2.5% of water on
earth is freshwater
 2% is ice!
 Only ~0.5% of water
on earth is available
freshwater
Check for understanding
 4 - I can explain to my peers at least 5 properties of
water and how water is distributed on earth.
 3 - I understand 3-4 properties of water and how
water is distributed on earth.
 2 - I can explain at least 2 properties of water and how
water is distributed on earth.
 1 - huh? I know 1 property of water.
Freshwater Terminology
 Surface water
 Precipitation that remains on the surface and does not
seep into soil
 Runoff
 Movement of surface water to lakes, rivers, etc.
 Watershed (drainage basin)
 Land area that delivers water into a stream or river system
 Groundwater
 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
 Unconfined and confined (artesian)
 Water table
Freshwater Aquifer
Check for understanding
 4 - I can explain to my peers the difference between a
confined and unconfined aquifer, what a water table is
and the difference between groundwater, surface
water, runoff, and a watershed is.
 3 - I understand the difference between a confined
and unconfined aquifer, but might not fully
understand the difference in one of the following
terms: a water table, groundwater, surface water,
runoff, and watershed
 2 - I am confused about at least 2 of the above terms
 1 - I am confused about at least 3 of the above terms
Water Use and Resource Problems
 Fall into Three Categories
 Too much water
 Too little water
 Poor quality/contamination (discussed later)
Water Use
 Mostly for irrigation for agriculture: 68%
 Even arid (deserts) & semiarid land grow crops with enough H2O
 Asia uses most
 Industry
 Domestic/municipal: 8.6%
 xeriscaping
Too Much Water
 Flooding
 Both natural and human-induced. Causes???
 Modern floods are highly destructive because humans:
 Remove water-absorbing plant cover from soil
 Construct buildings on floodplains
 Floodplain
 Area bordering a river channel that has the potential to flood
 Naturally leave behind organic matter in soil – good.
 Flood consequences???
Urban vs. Pre-Urban Floodplains
Floodplain
 Government restrictions on building
 Levees can fail
o
Rather than rebuild levees
adjacent to rivers, experts
suggest allowing some
flooding of floodplains during
floods
o Less damage if flooded
o Replenish soil
o Save money
Left:
Traditional
levees adjacent
to river
Right:
Suggested levee
style, set back
from river
NEW ORLEANS: HURRICANE KATRINA: AUGUST 2005
Case-In-Point Floods of 1993:
Mississippi River
Worsened due to:
1. Draining
wetlands for
farms and
homes
2. Building levees
(can force more
surge upstream)
3. Building on
floodplains
Similar to New
Orleans
Check for understanding
 4 - I can explain to my peers the causes and
consequences of flooding and the problems associated
with flooding and why modern societies suffer more
damage from them.
 3 - I understand the causes and consequences of
flooding and the problems associated with flooding
and why modern societies suffer more damage from
them
 2 - I need to reread my notes, but I understand
 1 - I don’t fully understand flooding.
Too Little Water
 Typically found in arid land (40% of population – Africa/Asia)
 Women may walk to get water instead of school
 Problems
 Drought
 Remove native water absorbing plants and replace with
crops/livestock overgraze  more runoff, less water in soil
 Overdrawing water
for irrigation purposes  saltier estuaries, dried wetlands (loss of
bird breeding grounds)
Too Little Water
 Problems (continued)
 Aquifer depletion
 Subsidence – sinking of land on porous rock
 Sinkholes – eroded limestone
 Saltwater Intrusion (coasts)
Problems (continued)
Aquifer depletion
Saltwater Intrusion
(coasts)
Water Problems
In US
 US has a plentiful supply
of freshwater
 Many areas have a severe
shortages
 Geographical variations
 Seasonal variations
Water Problems in US
 Water shortages in West and Southwest
 Historically for irrigation, now more water for industrial and
municipals due to increased population
 Water is diverted and transported via aqueducts
Water Problems in US Surface Water
 Mono Lake (Eastern CA)
 Rivers and streams that once fed this lake are diverted to Los
Angeles (275mi away)
 Becoming highly saline due to water diversion  disrupt food
chain
 Court ordered water diversion reduction
 LA efforts to use more reclaimed water
 Colorado River Basin
 Provides water for 27-million people – Colorado, California,
Arizona, into Mexico
 Numerous dams for Hydropower; also create resevoirs
 Colorado River no longer reaches ocean
HOOVER DAM: BETWEEN ARIZONA AND NEVADA
SALMON FISH LADDER
Colorado River bed in Mexico
Check for understanding
 4 - I can explain to my peers how water diversion and
dams can disrupt the amount of water in effected areas.
 3 - I understand how water diversion and dams can
disrupt the amount of water in effected areas
 2 - I need to reread my notes, but I understand
 1 - I don’t fully understand the impact of water
diversion projects and dams.
Water Problems in US and Groundwater
 Aquifer Depletion – especially Arizona, California, High
Plains
Case study: Ogallala Aquifer
 High Plains
 Largest groundwater in
world
 Uses 30% of irrigation
water in US – corn, wheat,
soybean, livestock (6% of
land)
 Water table down 100 ft in
some areas (rate of
recharge less than rate of
extraction) cost money
to deepen wells, lose $ on
dead crops
Global Water Problems
 Amount of freshwater on planet CAN meet human needs
 BUT, it is unevenly distributed and some places lack
stable runoff
Global Water Problems
1. Water and Climate Change
 Climate change affects the type and distribution of precipitation
 Potential issues:
 Reduced snowfall will impact water resources downstream
 Sea level rise will cause saltwater intrusion into drinking water
supplies
Global Water Problems
2. Drinking Water Problems
 Many developing countries have
insufficient water to meet
drinking and household needs
(1.1 billion lack safe water, 2.6
billion no good disposal of
wastewater/fecal waste) 
illness Ex: Cholera
 Ex: Sahel region of Africa
 Help: World Bank, US Agency
for International Development
(AID)
3. Population Growth
 Increase in population means an increase in freshwater
requirements
 Limits drinking water available
 Limits water available for agriculture (food)
 Ex: Northern China –Yellow River, Indus River in Pakistan,
Mexico (aquifer)
Global Water Problems
4. 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
 Kazakhstan and surrounding countries
 Water diversion for irrigation has caused
sea to become too saline  decreased
biodiversity
Aral Sea
1967
1997
Check for understanding
 4 - I can explain to my peers how climate change,
pathogens, a growing population, and water diversion
can reduce water availability.
 3 - I understand how climate change, pathogens, a
growing population, and water diversion can reduce
water availability
 2 - I need to reread my notes, but I understand
 1 - I don’t fully understand the impact of climate
change, pathogens, a growing population, and water
diversion can have on water availability.
Global Water Problems
5. Potentially Volatile
International Water
Situations
 Jordan River – supplies
many middle Eastern
countries
 Nile River (NE Africa) –
Sudan and Ethiopia using
more (increased
population) and affecting
Egypt’s supply
Water Management
FUN FACT: For every kilogram of animal
protein produced, livestock are fed nearly
6 kg of plant protein. Every kilogram of
beef produced takes 100,000 liters of
water. A kilogram of wheat requires 900
liters of water.
Water Management
 Main Goal: Provide sustainable supply of high-quality water
 Requires humans to use resource carefully
 Dams and Reservoirs
 Water Diversion Projects
 Desalinization
THREE GORGES DAM - CHINA
Dams and Reservoirs
 Benefits:
 Ensure year-round supply of water
with regulated flow
 Generate electricity
 Provide recreational activities
 Disadvantages
 Alter the ecosystem
 Reduce sediment load downstream
 Displace humans
 Disrupt salmon migration for
breeding
Dams and Reservoirs
 Glen Canyon Dam
 Regulated flow has changed ecosystem
 To rectify situation
 Canyon has been flooded several times
 Small floods compared to natural floods
 Still helps rebuild habitat
Water Diversion Projects
 Diverting water via
aquaducts/canals
 Ex: Mono Lake, Aral Sea
 Controversial and expensive
ARAL SEA: Kazakhstan-Uzbekistan border
Desalinization
 Removal of salt from ocean or brackish water
 Two methods:
 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 due to large energy input
 What to do with left over salt?
Check for understanding
 4 - I can explain to my peers how dams/reservoirs,
desalinization, and water diversion makes water
available for human use and the consequences of each.
 3 - I understand how dams/reservoirs, desalinization,
and water diversion makes water available for human
use and the consequences of each
 2 - I need to reread my notes, but I understand
 1 - I don’t fully understand how dams/reservoirs,
desalinization, and water diversion makes water
available for human use and the consequences of each
Water Conservation
 Reducing Agricultural Water Waste
 Drip Irrigation- irrigation that conserves water by piping to
crops through sealed systems
 Also called microirrigation or
trickle irrigation
Water Conservation
 Reducing Industrial Water Waste
 EX: paper, petroleum, food processing
 Stricter laws (and enforcement of those laws) provide incentive
to conserve water
 EX: 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
 Reducing Municipal Water
Waste : reduce, reuse, recycle
 GrayWater (reclaimed water)
 Can be used to flush toilets,
wash car or water lawn
 Water saving household
fixtures
 Raising costs to reflect real
cost
 Government incentives
Conserving at Home
 Install water-saving shower



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heads and faucets
Install low-flush toilets
Fix leaky fixtures
Purchase high efficiency
appliances –
dishwasher/washing
machine
Modify personal habits
 Shorter showers, showers
not baths
 Use the dishwasher instead
of washing by hand
Check for understanding
 4 - I can explain to my peers ways for agriculture,
industry, and homes can conserve water.
 3 - I understand ways for agriculture, industry, and
homes can conserve water
 2 - I need to reread my notes, but I understand
 1 - I don’t fully understand ways for agriculture,
industry, and homes can conserve water.