Transcript APES 13 Soil and Waterx

In the end, we will conserve only what
we love, we will love only what we
understand, and we will understand
only what we are taught.“
Baba Dioum
( Senegalese conservationist)
Soil and Water
Unit 13
Flashback-Soil: Foundation for Land
Ecosystems
Types of soil vary due to:
• geography
• parent material (rock)
• climate
• age
• presence of soil organisms
FYI: Soil Formation
• takes thousands of years to form
• often transported far from source
• results from weathering of parent rock:
-sedimentary: compacted, cemented sediment
-igneous: “fire-formed”, cooled magma, lava
-metamorphic: form by heat, pressure in earth
Rock Cycle
Soil Characteristics
• horizon: horizontal layers
O- humus, leaf litter
A- topsoil: weathered
rock and organic
matter
E- zone of leaching
B- subsoil: clay, iron,
C- weathered parent
rock:
R- bedrock; regolith
(See handout from
previous chapter)
Soil Characteristics
• profile: vertical layers
Soil Texture
Classified according to particle size (large to
small):
• sand
• silt
• clay
Soil Triangle
Diagram used to classify soil type
1. Clay side: extend a line
across from the % clay
2. Silt side: extend a line
diagonally downward from
% silt
3. Sand side: extend a line
diagonally upward and to
the left from % sand
ex. If soil is 30% clay, 30% silt
and 40% sand, the texture is
clay loam
FYI: Soil Statistics
• Soil is produced naturally at a rate of 1mm/
200-400 years
• Full soil profile takes 2000-10,000 years to
develop
• Agricultural soil is lost at a rate 10-40 times faster
than is natural replaced
-global loss is 6 million hectares (ha) per year
(I ha = 10,000 m²) from a total of 1200 million
ha
Human Impact on Soil
• See notes from Unit 9: Food, Soil and Pest
Management
Water: Importance, Availability, and Renewal
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Essential for chemical reactions within organisms
Moderates climate; sculpts the land
Removes and dilutes wastes, pollutants
Moves continually through the hydrologic cycle.
≈ 0.02% of the earth’s water is available as liquid
freshwater.
Water: Importance, Availability, and Renewal
• Comparison of
population sizes and
shares of the world’s
freshwater among the
continents.
Figure 14-2
Core Case Study: Water Conflicts in
the Middle East - A Preview
of the Future
• Middle East has one
of the world’s
highest population
growth rates
• Faces water
shortages.
Figure 14-1
Water Conflicts in the Middle East: A
Preview of the Future
• Most water comes from the Nile, Jordan or Tigris
rivers.
• Countries disagree as to who has water rights.
• No cooperative agreements for use of 158 of the
world’s 263 water basins shared by two or more
countries.
Water is Abundant, But Usable Water
is Rare
Location of Water
Main sources:
1. Surface water: bodies of water on surface
2. Groundwater: accumulated water below the
surface; most important source
Surface Water
• lakes, rivers, wetlands, estuaries, ocean
• recharged from surface runoff: snow melt,
precipitation that doesn’t infiltrate soil
• watershed (drainage basin): all land that
drains into a body of water
Surface Water (cont’d)
• floodplain: land adjacent to rivers; receive
nutrient-rich deposits from flooding
FYI World’s Largest Rivers
• Amazon in South America (4,000 miles/6,437 km)
• Congo in Africa (2,920 miles/4,700 km)
• Yangtze in China (3,915 miles/6,300 km)
(Civilizations grew along water rivers due to the fertile
soil in riparian zones and access to trade)
Lakes
• Large bodies of freshwater
• Formed from precipitation, runoff from
streams or rivers, seepage from groundwater
Flashback:Lake Classifications
Lake are classified according to nutrients and
PPD:
• oligotrophic: deep, clear, low plant nutrients
and PPD
Lake Classifications (cont’d)
• eutrophic: shallow, murky, high plant
nutrients and PPD
-cultural eutrophication: acceleration of lake
eutriphication due to human activity
(pollution from atmosphere, runoff)
• mesotrophic: falls between nutrient extremes
Groundwater
• Occurs when precipitation infiltrates the
ground, percolates through soil, hits an
impermeable rock layer and stops
Groundwater Zones
• Zone of aeration: first layers beneath Earth’s
surface, filled with air
• Zone of saturation: subsurface layers, porous,
filled with water
• Water table: upper limit of saturation zone
-height fluctuates due to drought, overwithdrawal (by humans), seasonal rains
Groundwater Zones (cont’d)
• Aquifer: layer of porous rock, sand, silt, clay
through which water flows (acts like a sponge for
freshwater); holds more water than Earth’s
surface waters
-natural recharge: replenishing aquifer by
precipitation
-lateral recharge: replenishing from side from
nearby streams, lakes, etc
-nonrenewal aquifers: get little (if any) recharge
Unconfined Aquifer Recharge Area
Evaporation and transpiration
Precipitation
Confined
Recharge
Area
Evaporation
Runoff
Flowing
artesian
well
Infiltration
Water
table
Recharge
Unconfined
Aquifer
Infiltration
Stream Well
requiring a
pump
Lake
Fig. 14-3, p. 308
Global Water Usage
• 70%: agriculture
• 20%: industry, manufacturing
• 10%: cities, residences (more affluent the area,
the more water used)
• Currently humans are using ≈ 50% of globe’s
reliable runoff of surface water
• Projected increase by 2050: 70-90%
• ≈70% of water taken from surface and
groundwater is not returned
Case Study: Freshwater Resources in
the United States
• by 2025, 17 western
states could face
intense conflict over
scarce water needed
for urban growth,
irrigation, recreation
and wildlife.
Figure 14-5
Wash.
Montana
N.D.
Oregon
Idaho
Wyoming
Nevada
S.D.
Neb.
Utah
Colo.
California
Kansas
Oak.
N.M.
Texas
Highly likely conflict potential
Substantial conflict potential
Moderate conflict potential
Unmet rural water needs
Fig. 14-5, p. 310
Average annual precipitation (centimeters)
Less than 41
81–122
41–81
More than 122
Fig. 14-4a, p. 309
Acute shortage
Shortage
Adequate supply
Metropolitan regions with population greater than 1 million
Fig. 14-4b, p. 309
Water in the
United States
• Average
precipitation (top)
in relation to waterdeficit regions and
their proximity to
metropolitan areas
(bottom).
Figure 14-4
Freshwater Resources in the United
States (cont’d)
• Shortage of runoff in western states due to
drought, high rates of evaporation
• Water tables are dropping due to depletion of
aquifer
• 2013: 36 states (not just in west) faced
shortages due to urban sprawl, water use and
waste- in addition to drought.
Water Shortage Is…
• Global health issue: 1/3900 children die yearly
from waterborne diseases
• Economic issue: vital for reducing poverty,
producing food, energy
• Gender, child issue: poor women, girls are
responsible for daily water supply to family
• National/global security issue: increasing
tensions over access to limited supply
• Environmental issue: removal of water from
environments creates degradation of natural
services (reduces biodiversity)
Stress on the World’s River Basins
• Comparison of the amount of water available
with the amount used by humans.
Figure 14-6
Case Study: Who Should Own and
Manage Freshwater Resources?
• controversy exists over whether water supplies
should be owned and managed by governments
or by private corporations.
• European-based water companies aim to control
70% of the U.S. water supply by buying up water
companies and entering into agreements with
cities to manage water supplies.
How Would You Vote?
• Should private companies own or manage most of
the world's water resources?
a. No. Democratically elected governments, which are
accountable to the voters, should own and manage
water resources.
b. Qualified yes. Governments should own the
water, but expert private companies should manage
it.
c. Depends. Each case must be decided
independently. The record on private versus public
ownership is mixed.
d. Yes. Private companies have more expertise and
experience in managing water resources than most
government bureaucrats.
Increasing Freshwater Supply
• Cities are outbidding farmers for water supplies
from rivers and aquifers.
• Countries are importing grain as a way to
reduce their water use.
• More crops are being used to produce biofuels.
• Water options are:
– pump water from aquifers and rivers
– desalinate ocean water,
– waste less water.
Trade-Offs
Withdrawing Groundwater
Advantages
Useful for drinking and
irrigation
Disadvantages
Sinking of land from
overpumping
Available year-round
Exists almost
everywhere
Renewable if not
overpumped or
contaminated
Saltwater intrusion into
drinking water supplies
near coastal areas (Ga!)
Reduced water flows
into surface waters
No evaporation losses
Cheaper to extract than
most surface waters
Increased cost and
contamination from
deeper wells
Aquifer Depletion: Land Subsistence
• Sinkholes form when
the roof of an
underground cavern
collapses after being
drained of
groundwater
Figure 14-10
Groundwater Overdrafts:
High
Moderate
Minor or none
Fig. 14-8, p. 314
Aquifer Depletion: Saltwater Intrusion
•Along the coast,
water table is
shallow; sea water
is drawn into
aquifer as too
much freshwater
is taken out
FYI: Aquifer Depletion in Saudi Arabia
(1986 – 2004)
• Irrigation systems from the nonrenewable aquifer
appear as green dots. Brown dots are wells that
have gone dry.
Figure 14-9
Solutions to Depletion
• Subsidize water conservation
• Raise price of water to discourage waste
• Do not grow water-intensive crops in dry
areas
• Set and enforce minimum stream flow levels
• Implement conservation practices in
residences
Increasing Water: Dams and
Reservoirs
• Dam: structure built across a river to control
river flow
• Reservoir: an artificial lake behind a dam
• Main goals of damming: hydroelectricity,
irrigation for towns/cities
FYI: Hydroelectric Power: Advantages
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No CO₂ emissions
Provides irrigation, drinking water
Can provide flood control
Provides cheap electricity
Reservoir can be used for recreation
Hydroelectric Power: Disadvantages
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Displaces people, wildlife behind/below dam
Decreases nutrient-rich silt downstream
Loss of water due to evaporation, seepage
Disrupts migration of some fish; decreases
fish harvest below dam
Major Dams
Colorado River Basin: Colorado River-Gulf of
California
• Water flow from Rocky Mtn snowmelt
• Provides drinking water to L.A., San Diego, Las
Vegas (desert, arid regions)
• Supplies irrigation to 15% of nation’s crops
• 14 dams; reservoirs- Hoover and Glen Canyon
• Excessive withdrawals reduce river flow to Gulf;
increased salinity due to farm runoff
The Colorado River Basin
• The area drained
by basin more
than one-twelfth
of the land area
of the lower 48
states.
Figure 14-14
The Colorado River Basin
• Lake Powell, is the
second largest
reservoir in the
U.S.
• It hosts one of the
hydroelectric
plants located on
the Colorado River.
Figure 14-15
Major Dams (cont’d)
Three Gorges Dams: Yangtze River in China
• World’s largest hydroelectric dam
• Controls flooding (1998 flooding from Yangtze
killed 4000)
• Displaced 1.5 million people
• Produces same energy as 22 coal-burning plants
• Reservoir will receive 265 billion gallons of raw
sewage normally dumped into ocean
• Dam is built over seismatic fault and already has
small cracks.
Three Gorges Dam
FYI: Lake Lanier
• Above Atlanta; major source of
water for that city
•Formed by Buford Dam on the
Chattahoochee
•Covers 38,000 sq miles
•Water rights are being argued in
the Supreme Court for control by
Georgia, Alabama, Florida
(federal judge ruled against
Georgia in water rights fight)
FYI: Dam Removal
• Some dams are being removed for ecological
reasons and because they have outlived their
usefulness.
– In 1998 the U.S. Army Corps of Engineers
announced that it would no longer build large
dams and diversion projects in the U.S.
– The Federal Energy Regulatory Commission has
approved the removal of nearly 500 dams.
– Removing dams can reestablish ecosystems, but
can also re-release toxicants into the environment.
Increasing Water: Water Transfer
Projects
Transferring water can make unproductive areas
more productive
• Promotes investment, jobs and strong economy
• Encourages unsustainable use of water in areas
water is not naturally supplied
• Can cause environmental harm
Water Transfer Projects
California Water Project : northern to southern
Ca.
• One of world’s largest transfers
• Degraded river, lake ecosystems, including
Mono Lake, major feeding stop for migratory
birds
• Resulted in water waste
• Some diversions are now illegal
Case Study: The California Experience
Figure 14-16
Water Transfer Projects (cont’d)
Aral Sea: inland Aral Sea to cotton, rice fields in
Asia (formally Soviet Union)
• Reduced size of sea; increased its salinity
• Eliminated ≈ 85% of wetlands; 50% of local
birds and mammals
• Caused extinction of 20/24 fish species
• Altered climate: hotter in summer; colder in
winter
The Aral Sea Disaster
• The Aral Sea was once the world’s fourth largest
freshwater lake.
Figure 14-17
Water Transfer Projects (cont’d)
China’s South-North Water Transfer: Yangtze
River basin to populated northern provinces
• Will provide drinking water to cities such as
Beijing (12 million people)
Increasing Water: Desalination
Desalination: removal of dissolved salts from
saltwater:
• Reverse osmosis/microfiltration: external
pressure pushes saltwater through
membranes to separate salts from water
Desalination (cont’d)
• Distillation: heats saltwater until evaporation
begins, steam is collected and condensedfreshwater; salt is left behind
Disadvantages of Desalination
• Produces large amounts of briny wastewater
• Extremely expensive: 10 x cost of aquifer
water
• Not realistic for developing countries
Increasing Water: Water Conservation
About two-thirds of the water used is wasted, but
waste could be cut to 15%
• 65-70% of global water used is lost through
evaporation, leaks
• Reduce government subsidies for cost of water
• Increase government subsidies for water
conservation
Water Conservation (cont’d)
• ≈ 60% of irrigation water does not reach crops
• Types/effectiveness of irrigation:
1. flood: water flows through fields
-60% efficiency (most wasteful)
-used on 97% of China’s irrigated land
2. center pivot: pumps move water through
sprinklers
-80-90% efficiency
Water Conservation (cont’d)
3. Drip/micro-irrigation: delivers small
amounts of water to roots of plants
-90-95% efficiency
-reduces salt buildup in soil
(used on 1% of global lands- 13% Ca, 66%
Israel, 90% Cyprus)
Drip irrigation
(efficiency 90–95%)
Gravity flow
(efficiency 60% and
80% with surge
valves)
Center pivot
(efficiency 80%–95%)
Water usually comes from an
aqueduct system or a nearby
river.
Above- or below-ground
pipes or tubes deliver
water to individual plant
roots.
Water usually pumped from
underground and sprayed
from mobile boom with
sprinklers.
Fig. 14-18, p. 325
Reducing Irrigation Waste
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•
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Line canals bringing water to fields
Irrigate at night (reduces evaporation)
Add water to soil only when needed
Polyculture
Organic farming
Use treated waste water
Import water-intensive crops and meat
Reducing Waste in Business and
Industry
• Recycle water (95% of water recycled in steel)
• Fix leaks- 30-60% of water loss in cities
(especially developing countries)
• Use water meters; raise price of water
• Require water conservation
• Purify and reuse water for office buildings
• Use wastewater as fertilizer for nonfood
crops
Reducing Waste in Homes
• Use low-flow toilets, showerheads, faucets
• 5-7 minute showers (no baths)
• Wash full loads of clothes, store and use gray
water for nonfood plants
• Xeriscape- replace lawns with native plants
• Repair leaks
• Use commercial car wash
• Turn off faucet for while brushing teeth
Bottom Line: Sustainable Water Use
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Waste less; subsidize water conservation
Don’t deplete aquifers
Preserve water quality
Protect wetlands, watersheds that store and
release water
• Raise water prices
• Slow population growth
Too Much Water: Flooding
Causes: Heavy rainfall, rapid snowmelt, removal
of vegetation, destruction of wetlands
• Floodplains: areas adjacent to rivers
-provide flood, erosion control
-maintain water quality
-recharge groundwater
Flooding
• Comparison of St. Louis, Missouri under normal
conditions (1988) and after severe flooding
(1993).
Figure 14-22
Flooding Benefits
• Deposits nutrient-rich silt on floodplain (good
farming)
• Refills wetlands; supports biodiversity
Reducing Flood Risks
• Preserve forests on watersheds
• Restore wetlands (absorbs excess water)
• Limit development, use for sustainable
farming
• Build levees, dams
TOO MUCH WATER
• Human activities have contributed to flood
deaths and damages.
Figure 14-23
Exam Focus
• Main stages of water movement through
hydrologic cycle
• % freshwater on earth (not including glaciers)
• Location of freshwater
• Definition of infiltration, zones of aeration and
saturation, water table, aquifer
• Natural forces that effect surface water
• Greatest global use of water
• Results of overdrafting aquifer (land subsistence,
saltwater intrusion, contamination from toxins,
runoff)
• Sources of excessive nutrients entering surface
water/solutions to curb those sources
Exam Focus
• Solutions to aquifer depletion
• Specific economic and social benefits of
damming
• Environmental disadvantages of damming
• Colorado River Basin, Aral Sea disaster
• Methods to increase freshwater
• Methods to reduce irrigation waste
• Greatest use of water in home/ methods to
conserve water at home
• Methods to reduce flooding
FRQ
Ex: Based on total use, how many gallons of water is
available to each person
total water: 300 billion gallons
total population: 100 million people
gallons available: 3 x 10¹⁰ = 3 x 10² gal/person
1 x 10⁸
Find % of type of water used:
type of water x 100
total water