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%

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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.

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Fig. 13-3, p. 316

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)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.

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4a. What are the advantages and disadvantages of withdrawing groundwater?

Back to ContentsFig. 13-7, p. 321

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.

Back to ContentsFig. 13-11, p. 324

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?

Back to ContentsFig. 13-12, p. 325

5d. What ecological services do rivers provide?

Back to ContentsFig. 11-16, p. 270

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.

Back to ContentsFig. 13-17, p. 330

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 micro-

irrigation.• Rainwater harvesting• Polyculture farming, agroforestry, and fog-

cather nets.

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8c. List ways to reduce water waste in industry and homes.

Back to ContentsFig. 13-22, p. 336

8d. List ways to use water more sustainably.

Back to ContentsFig. 13-23, p. 337

8e. Describe ways in which you can reduce your use and waste of water.

Back to ContentsFig. 13-24, p. 338

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?

Back to ContentsFig. 13-26, p. 340