Transcript Drip Irrigation

Mrs. Sealy - APES
BLACK
TURKEY
SEA
GEORGIA
ARMENIA
AZERBAIJAN
TURKMENISTAN
CASPIAN
SEA
MEDITERRANEAN
SEA
LEBANON
WEST BANK
GAZA
SYRIA
IRAN
IRAQ
JORDAN
EGYPT
OMAN
KUWAIT
Aswan
High Dam
Lake Nasser
SAUDI
ARABIA
BAHRAIN
QATAR
UNITED ARAB
EMIRATES
SUDAN
OMAN
YEMEN
SOMALIA
ETHIOPIA
Fig. 13.1, p. 294
How much freshwater is available
and where is it?
• 97.4% of water is in the ocean, 2.6% is
freshwater and of that amount, Most is
locked in icecaps leaving .014%
available for use
Freshwater
Readily accessible freshwater
Groundwater
0.592%
Biota
0.0001%
Lakes
0.007%
Rivers
0.0001%
0.014%
Ice caps
and glaciers
1.984%
Soil
moisture
0.005%
Atmospheric
water vapor
0.001%
Fig. 13.2, p. 296
United States
Power
cooling
38%
China
Agriculture
41%
Industry 11%
Public 10%
Agriculture 87%
Public 6%
Industry 7%
Fig. 13.5, p. 298
5,500
Water use (cubic kilometers per year)
5,000
Total use
4,500
4,000
3,500
3,000
2,500
2,000
Agricultural use
1,500
Industrial use
1,000
Domestic use
500
1900
1920
1940
1960
Year
1980
2000
Fig. 13.4, p. 298
1 automobile
400,000 liters
(106,000 gallons)
1 kilogram
cotton
10,500 liters
(2,400 gallons)
1 kilogram
aluminum
9,000 liters
(2,800 gallons)
1 kilogram
grain-fed beef
7,000 liters
(1,900 gallons)
1 kilogram
rice
1 kilogram
corn
1 kilogram
paper
1 kilogram
steel
5,000 liters
(1,300 gallons)
1,500 liters
(400 gallons)
880 liters
(230 gallons)
220 liters
(60 gallons)
Fig. 13.6, p. 298
What
causes
water
shortages?
• Dry climate
• Drought
• Desiccation
• Water stress (low per capita availability due to
population growth)
• 30 countries containing 500,000 million people
have chronic water shortages
• There is enough water, but often it is wasted,
polluted, is in areas where it is hard to get to.
• Two-thirds of the world live in water poverty
where they do not have water coming into the
home.
Competition for the World’s
Water
• Cities are outbidding farmers for water
supplies from rivers and aquifers
• Some countries are importing grain as a
way to reduce their water needs
• More crops are being used for biofuels
increasing water demand.
Average annual precipitation (centimeters)
0-25
0-25
25-50
25-50
50-75
50-75
Fig. 13.7a, p. 299
Acute shortage
Adequate supply
Shortage
Metropolitan regions with population
greater than 1 million
Fig. 13.8b, p. 299
Europe
North
America
Asia
Africa
South
America
Stress
High
Australia
None
Fig. 13.8, p. 300
How can water supplies be
increased?
•
•
•
•
•
Building dams and reserviors
Importing water
Withdrawing groundwater
Desalination
improved efficiency
Dams and reservoirs
•
•
•
•
•
•
Pros:
Can capture and store water
The water can be released as desired
Control flooding downstream
Supply irrigation water year around
Provide electricity
Large losses
of water through
evaporation
Downstream
cropland and
estuaries are
deprived of
nutrient-rich silt
Flooded land
destroys forests
or cropland and
displaces people
Downstream
flooding is
reduced
Provides water
for year-round
irrigation of
cropland
Reservoir is
useful for
recreation
and fishing
Can produce
cheap electricity
(hydropower)
Migration and
spawning of
some fish are
disrupted
Fig. 13.9, p. 301
• Cons:
• Silting behind the dam robs the
downstream of nutrients
• Loss of silt destroys deltas
• Causes flooding behind the dam
• They can fall down
• Disturbs species like salmon
• Causes landslides and earthquakes
Case Study: The Colorado River
• Water laws in the Western United States are
governed by prior appropriation: “First in
time, first in right”, which means the first to
use the water has the first rights. On the
Colorado River the Indians and the Ranchers
were the first.
• The Colorado is divided into two parts:
* Upper Basin: Wyoming, Utah, Colorado,
New Mexico
* Lower Basin: Arizona, Nevada and
Case Study: The Colorado River
• In 1922 water was allocated to these
states by the Colorado River compact,
in 1944 Mexico was allocated water
• The problem was that the amount of
water was overestimated by 33%, so
when all the states start taking their
water, there will not be enough
IDAHO
WYOMING
Dam
Aqueduct
or canal
Salt Lake City
Grand Junction
Upper Basin
Denver
Lower Basin
UPPER
BASIN
UTAH
COLORADO
Lake
Powell
Grand
Canyon
Las Vegas
Glen
Canyon
Dam
NEW MEXICO
Boulder City
ARIZONA
CALIFORNIA
Los
Angeles
Albuquerque
LOWER
BASIN
Palm
Springs
Phoenix
San Diego
Yuma
Mexicali
All-American
Canal
Golf of
California
Tucson
0
100 mi.
0
150 km
Fig. 13.10, p. 304
MEXICO
The Science of Groundwater
• Groundwater: rain that infiltrates the ground
and percolates downward through spaces in soil,
water and rock
• Below a certain level the spaces are completely
filled with water, called the zone of saturation .
The top of this zone is the water table.
• Aquifer: porous layers of sand, gravel and rock
through which water flows (from which water
can be extracted).
• Recharge rate: how fast an aquifer can refill.
Can take thousands of years.
Tapping Groundwater
•
•
•
•
Pros:
Supplies 50 % of drinking water
Supplies 40% of irrigation
Usually very high quality
Tapping Groundwater
• Aquifer depletion: currently US is
withdrawing groundwater at 4x it’s
replacement rate
• Aquifer subsidence: sinking of land due
to water removal
• Salt water intrusion: removing too much
groundwater causes salt water to seep
into aquifers
Flowing
artesian well
Unconfined Aquifer Recharge Area
Evaporation and transpiration
Well requiring a pump
Precipitation
Evaporation
Confined
Recharge Area
Runoff
Aquifer
Infiltration
Stream
Water table
Lake
Infiltration
Unconfined aquifer
Less permeable material
such as clay
Confined aquifer
Confining permeable rock layer
Fig. 13.3, p. 297
Major irrigation
well
Well contaminated
with saltwater
Water
table
Sea Level
Salt
water
Fresh
groundwater
aquifer
Interface
Interface
Saltwater
Intrusion
Normal
Interface
Fig. 13.17, p. 308
Original
water table
Initial water table
Cone of
depression
Lowered
water table
Fig. 13.15, p. 307
Groundwater
Overdrafts:
High
Moderate
Minor or none
Fig. 13.16a, p. 308
Subsidence:
High
Moderate
Minor or none
Fig. 13.16b, p. 308
Case Study: Ogallala Aquifer
• The Ogallala aquifer stretches from
Texas north to North Dakota. It was
deposited over several thousand years
duirng the last ice age. It is the largest
aquifer in North America. It is nonrenewable because it has a very slow
recharge rate. One quarter of it will be
depleted by 2020. This is because the
farmers get tax breaks for depleting it.
In the Midwest there is no such thing as
water conservation.
Less than 61 meters (200 ft)
WYOMING
SOUTH DAKOTA
61-183 meters (200-600 ft)
More than 183 meters (600 ft)
(as much as 370 meters or 1,200 ft.
in places)
NEBRASKA
KANSAS
COLORADO
OKLAHOMA
NEW MEXICO
TEXAS
Miles
0
100
0
160
Kilometers
Fig. 13.18, p. 309
Water Transfer
• Pros:
• Using tunnels, aquaducts and pipes to
transport water from watersheds to
water poor areas
• Allows for year-around irrigation of
cropland in arid regions
• Has allowed L.A. to become what it is
(Owens Valley water transfer).
Water Transfer
• Robs other areas of water
• Can be environmentally harmful to areas
where the water is being removed
• Threatens fisheries
• Causes rivers to flow backwards
• Takes away the flushing action of rivers
• Lowers the level of inland seas and lakes
• Causes inland seas to become more salty and
produces salt rain from blowing salt
• Hard on native species
Areas already harmed:
• Aral Sea in Russia
• Mono Lake in California
• Sacramento River delta
KAZAKHSTAN
2000
ARAL
SEA
1989
1960
UZBEKISTAN
TURKMENISTAN
Fig. 13.12, p. 305
CALIFORNIA
NEVADA
Shasta Lake
Sacramento
River
Oroville Dam and
Reservoir
Feather
River
North Bay
Aqueduct
UTAH
Lake Tahoe
Sacramento
San Francisco
Fresno
South Bay
Aqueduct
Hoover Dam
and Reservoir
(Lake Mead)
Colorado
River
Los Angeles
Aqueduct
San Luis Dam
and Reservoir
ARIZONA
California Aqueduct
Colorado River
Aqueduct
Santa Barbara
Central Arizona
Project
Los Angeles
Salton Sea
Phoenix
San Diego
Tucson
Fig. 13.13, p. 306
MEXICO
Desalination
• Removing salt from ocean water by
distillation or reverse osmosis
• Problem is that it requires large
amounts of energy and it is very
expensive
Improved Efficiency
• 60-70% of water is
wasted worldwide
• Why is water wasted:
* artificially low prices in the US
* government subsidies
* outdated laws governing water supplies
* water management in watersheds is
divided into too many different hands.
Wasting Less Water in
Irrigation
• Currently we use flood irrigation or
gravity flow, which wastes 50% of
water
• Drip irrigation delivers water directly to
plants with a 80-90% efficiency
• Center-pivot-mobile boom moves over
crops 70-80% efficient
Gravity Flow
Drip Irrigation
Center Pivot
(efficiency 60% and 80% with surge valves)
(efficiency 90–95%)
(efficiency 80% with low-pressure
sprinkler and 90–95% with LEPA sprinkler)
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. 13.19, p. 311
• Lining canals bringing water to irrigation ditches
• Leveling fields with lasers
• Irrigating at night to reduce evaporation
• Using soil and satellite sensors and computer systems to
monitor soil moisture and add water only when
necessary
• Polyculture
• Organic farming
• Growing water efficient crops using drought-resistant
and salt-tolerant crop varieties
• Irrigating with treated urban waste water
• Importing water intensive crops and meat
Fig. 13.20, p. 313
Wasting Less in Industry
• Recycling water in the manufacturing
process
• Many companies already do this
because it saves them money and they
do not get government kickbacks on
water like farmers do
• Also companies have to pay for the
amount of stuff that goes down the
sewer
Wasting Less in Businesses and
Homes
• Low flush toilets
• Low flow shower heads
• Xeriscaping
• Fix leaky pipes
• Reusing gray water in
homes and to water
lawns
Too much water-Floods
• Floodplain: the natural overflow area of
a river, these are very productive areas
with nutrient rich soils
• Floods are natural thing- they enrich
the soil, recharge groundwater and refill
wetlands
• Humans make flooding worse by
removing vegetation, draining wetlands
and living on floodplains
Reservoir
Dam
Levee
Floodplain
Flood
wall
Fig. 13.22, p. 314
Oxygen
released by
vegetation
Diverse
ecological
habitat
Evaporation increases
Trees reduce soil
erosion from heavy
rain and wind
Steady
river flow
Agricultural
land
Leaf litter
improves
soil fertility
Tree roots
stabilize soil and
aid water flow
Forested Hillside
Vegetation releases
water slowly and
reduces flooding
Fig. 13.24a, p. 316
Tree plantation
Evapotranspiration decreases
Roads
destabilize
hillsides
Ranching
accelerates
soil erosion by
water and wind
Winds remove
fragile topsoil
Agriculture land
is flooded and
silted up
Gullies and
landslides
Heavy rain leaches
nutrients from soil
and erodes topsoil
After Deforestation
Silt from erosion blocks
rivers and reservoirs and
causes flooding downstream
Rapid runoff
causes flooding
Fig. 13.24b, p. 316
Extremely severe
Very severe
Moderately severe
Somewhat severe
Fig. 13.25, p. 317
Not severe
• Not depleting aquifers
• Preserving ecological health of aquatic
systems
• Preserving water quality
• Integrated watershed management
• Agreements among regions and
countries sharing surface water
resources
• Outside party mediation of water
disputes between nations
• Marketing of water rights
• Wasting less water
• Decreasing government subsides for
supplying water
• Increasing government subsides for
reducing water waste
• Slowing population growth
Fig. 13.26, p. 317