Chapter 13 Water Resources
Post Reading Discussion
Contents
1
b
6
a, b, c
2
a, b, c, d
7
a, b
3
a, b, c, d, e
8
a, b, c, d, e
4
a, b, c
9
a, b, c, d, e
5
a, b, c, d, e, f
10
2a. What percentage of the earth’s
freshwater is available to us?
• 0.024%
Back to Contents
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
Back to Contents
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.
Back to Contents
2d. Distinguish between surface runoff
and reliable surface runoff.
• Surface runoff we can generally rely on as a
source of freshwater.
Back to Contents
3a. How is most of the world’s water
used?
• 70%, irrigation of crops
• 20%, industry
• 10%, municipal and domestic
Back to Contents
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)
Back to Contents
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.
Back to Contents
4a. What are the advantages and disadvantages
of withdrawing groundwater?
Fig. 13-7, p. 321
Back to Contents
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.
Back to Contents
4c. Describe ways to prevent or slow
groundwater depletion.
Fig. 13-11, p. 324
Back to Contents
5a. What is a dam?
• A structure built across a river to control the
river’s water flow.
Back to Contents
5b. What is a reservoir?
• Artificial lake behind a dam.
Back to Contents
5c. What are the advantages and disadvantages
of large dams and reservoirs?
Fig. 13-12, p. 325
Back to Contents
5d. What ecological services do rivers
provide?
Fig. 11-16, p. 270
Back to Contents
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
Back to Contents
6b. Describe the Aral Sea disaster.
Back to Contents
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.
Back to Contents
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
Back to Contents
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.
Back to Contents
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.
Back to Contents
8c. List ways to reduce water waste in
industry and homes.
Fig. 13-22, p. 336
Back to Contents
8d. List ways to use water more
sustainably.
Fig. 13-23, p. 337
Back to Contents
8e. Describe ways in which you can
reduce your use and waste of water.
Fig. 13-24, p. 338
Back to Contents
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.
Back to Contents
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
Back to Contents
9e. How can we reduce the risk of
flooding?
Fig. 13-26, p. 340
Back to Contents