Transcript Chapter 13 Water Resources - Zamorascience

Chapter 13 Water Resources
Post Reading Discussion
Contents
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2a. What percentage of the earth’s
freshwater is available to us?
• 0.024%
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2b. Define groundwater, zone of
saturation, water table, and aquifer.
• Water that infiltrates the ground through
spaces in soil, gravel, and rock; found in the
zone of saturation below the water table.
• Zone where all available pores in soil and rock
in the earth’s crust are filled with water.
• Upper surface of the zone of saturation.
• Geological layers of underground caverns and
porous layers of sand, gravel, or bedrock
through which groundwater flows.
Fig. 13-3, p. 316
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2c. Define surface water, surface runoff,
and watershed (drainage basin).
• Freshwater from precipitation and snowmelt
that flows across the earth’s land surface and
into rivers, streams, lakes, wetlands, estuaries,
and ultimately the oceans.
• Precipitation that does not infiltrate the
ground or return to the atmosphere by
evaporation.
• Land from which surface water drains into a
particular river, lake, or other body of water.
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2d. Distinguish between surface runoff
and reliable surface runoff.
• Surface runoff we can generally rely on as a
source of freshwater.
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3a. How is most of the world’s water
used?
• 70%, irrigation of crops
• 20%, industry
• 10%, municipal and domestic
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3b. Describe the availability an use of
freshwater in the United States.
• More than enough renewable, but unevenly
distributed and much is contaminated by ag- and
industrial use.
• The East: most used for energy production, power
plant cooling, and manufacturing.
• In arid and semi-arid West: most (85%) used for
irrigation.
• Half of water come from ground; rest, from rivers,
lakes and reservoirs.
• Hotspots (see Figure 13-5, p. 318)
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3d. What is drought and what are its
causes and harmful effects?
• Condition in which an area does not get enough
water because of lower than normal precipitation
or higher than normal evaporation from higher
temperatures.
• Causes: below normal rainfall, falling water tables
(such as when ground water is overused), and
climate change.
• Dries soils, reduces stream flows, decreases tee
growth and biomass, lowers NPP, reduces crop
yields, and can shift biomes towards savannas
and deserts.
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4a. What are the advantages and disadvantages
of withdrawing groundwater?
Fig. 13-7, p. 321
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4b. Describe the problems with groundwater depletion
in the world and in the U.S., esp. the Ogallala Aquifer.
• Water tables fall
• ½ billion people fed on grain
grown with ground water
• In U.S., groundwater
withdrawn 4x faster than
recharge.
• Serious overdrafts in lower
half of Ogallala Aquifer; CA’s
Central Valley (Fig. 13-9, p.
322)
– Loses of ecological and
agricultural productivity/loss of
natural capital and ecological
services.
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4c. Describe ways to prevent or slow
groundwater depletion.
Fig. 13-11, p. 324
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5a. What is a dam?
• A structure built across a river to control the
river’s water flow.
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5b. What is a reservoir?
• Artificial lake behind a dam.
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5c. What are the advantages and disadvantages
of large dams and reservoirs?
Fig. 13-12, p. 325
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5d. What ecological services do rivers
provide?
Fig. 11-16, p. 270
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6a. Describe the California Water Project and
the controversy over this water transfer project.
• Dams, pumps and aqueducts transport water
from water-rich northern CA to water-poor
southern CA’s heavily populated ag-regions and
cities.
• Southern CA wants more water for crops and LA
and San Diego.
• Northern CA argues that Sacramento River is
degraded cause or reduced flow, threatening
fisheries and reduces river’s ability to flush
pollutants out of San Francisco Bay; much of
water sent south is wasted.
Fig. 13-17, p. 330
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6b. Describe the Aral Sea disaster.
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7a. Define desalinization and distinguish
between distillation and reverse osmosis.
• Removal of dissolved salts from ocean water
or from brackish water in aquifers or lakes or
domestic use.
• Heating saltwater until it evaporates.
• Also called microfiltration; use high pressure
to force saltwater though a membrane filter
with pores small enough to remove salt.
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7b. What are the limitations of desalinization
and how might they be overcome?
• Limitations:
– High cost and large energy footprint
– Kill many marine organisms
– Concentrated brine needs to be disposed of
• Obstacles
– New filtering technologies
– Desalinization off-shore
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8a. What percentage of the world’s water is
unnecessarily wasted and what are causes of
such waste?
• 65-70%
• Causes
– Evaporation, leaks, and other losses
– Low cost
– Lack of subsidies for improving the efficiency of
water use.
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8b. Describe four irrigation methods and describe ways
to reduce water waste in irrigation in developed and
developing countries.
• Flood irrigation, gravity flow
• Center-pivot, low pressure sprinkler
• Drip or trickle irrigation, also called microirrigation.
• Rainwater harvesting
• Polyculture farming, agroforestry, and fogcather nets.
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8c. List ways to reduce water waste in
industry and homes.
Fig. 13-22, p. 336
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8d. List ways to use water more
sustainably.
Fig. 13-23, p. 337
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8e. Describe ways in which you can
reduce your use and waste of water.
Fig. 13-24, p. 338
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9a. What is a floodplain and why do
people like to live on floodplains?
• Area adjacent to rivers where streams
overflow the normal channels.
– Include highly productive wetlands, provide
natural flood control, maintain water quality, and
recharge groundwater.
• People live there because of fertile soils,
ample water for irrigation, transportation and
recreation, and flat land suitable for crops,
buildings, highways and railroads.
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9c. List three human activities that
increase the risk of flooding.
• Removal of water-absorbing vegetation (see
Fig. 13-25, p. 339)
• Draining and building on wetlands
• Burning fossil fuels and clearing forests
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9e. How can we reduce the risk of
flooding?
Fig. 13-26, p. 340
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