Chapter 17

Question 1

Explain hydrological cycle.

Answer 1

• The Hydrologic Cycle Redistributes Water.
• Hydrologic Cycle : water evaporates from moist surfaces, falls as rain or snow, passes through living organisms and returns to the oceans. More than 90% of the water that evaporates world-wide rains back into the oceans. Some is carried over land where it renews freshwater systems. Solar energy drives the hydrologic cycle

Question 2

What drive the hydrological cycle?

Answer 2

•Solar Energy

Question 3

Name the 3 principal factors that control global water deficit d surpluses.

Answer 3

• Global atmospheric circulation.
• Proximity to water sources.
• Topography

Question 4

How do mountains act as cloud formers and rain catchers?

Answer 4

•Air sweeps up the windward side of a mountain, pressure decreases, and the air cools. Eventually saturation point is reached, and moisture in the air condenses. Rain falls on the mountaintop

Question 5

What is Rain Shadow?

Answer 5

•Cool, dry air descends from the mountaintop down the other side of the mountain (leeward side) creating dry areas with very little precipitation

Question 6

What are the percentages of water in oceans, freshwater and in atmosphere?

Answer 6

• The oceans hold 97% of all liquid water on the earth
• 2.4% of world’s water is classified as fresh of which most of it is stored in glaciers, ice caps, and snowfields
• Atmosphere contains the smallest water reservoirs (Less than 0.001% of total water supply).

Question 7

Define zone of aeration, zone of saturation, water table, recharge zones, and river discharge..

Answer 7

• Zone of aeration - upper soil layers that hold both air and water
• Zone of saturation - lower soil layers where all spaces are filled with water.
• Water table - top of zone of saturation. Groundwater Stores Large Water Resources
• Recharge zones - area where water infiltrates into an aquifer. Presently, groundwater is being removed faster than it can be replenished in many areas.
• Rivers discharge : The amount of water that passes a fixed point in a given amount of time. Usually expressed as cubic feet per second

Question 8

Define wetlands and what is the role of a wetland.

Answer 8

•Wetlands play an important role in hydrological cycle: Lush plant growth stabilizes soil and retards surface runoff, allowing more aquifer infiltration

Question 9

Renewable water supplies is made up of ___ and ___

Answer 9

1. Surface Runoff

2. Infiltration into accessible freshwater aquifiers

Question 10

Readily accessible, renewable supplies are only about ____ gal /person/year. The United Nations considers ____ gallons per person per year to be the minimum necessary to meet human needs.

Answer 10

1. 400,000

2. 264,172

Question 11

When does water stress occur?

Answer 11

•Water Stress occurs when human and ecosystem needs exceed the renewable water supplies, resulting in competition.

Question 12

Define water withdraw and water consumption.

Answer 12

• Withdrawal: total amount of water removed from a water body.
• Consumption: loss of water due to evaporation, absorption, or contamination.

Question 13

Worldwide, agriculture claims about _70%__% of total water withdrawal and 85% of consumption.

Answer 13

1. 70%

2. 85%

Question 14

What happened to Aral Sea?

Answer 14

•Once the fourth largest inland body of water in the world, it has now lost 90% of its volume since 1975, as water was diverted for irrigation of rice and cotton crops

Question 15

By 2025, the U.N. estimates that __of the word’s population will be living in water-stressed countries .

Answer 15

2/3

Question 16

Withdrawing large amounts of groundwater in a small area causes porous formations to collapse, resulting in ______________.

Answer 16

Subsidence (settling)

Question 17

How does salt intrusion occur?

Answer 17

•Saltwater intrusion can occur along coastlines where overuse of freshwater reservoirs draws the water table low enough to allow saltwater to intrude

Question 18

What are advantages and disadvantages of dams?

Answer 18

• Advantages of Dams: Provide inexpensive hydroelectric power. Provide jobs. Reduce flooding. Allow farming on lands that would otherwise be too dry
• Disadvantages of dams: Submerge farmlands and towns displacing people. Cause earthquakes. Block fish migration (e.g., salmon). Change aquatic habitats for native species. Reduce spring floods that drop sediment to enrich soils downstream. Sediment carried by rivers eventually fills up dams

Question 19

What is seeding clouds and what substances are used to seed clouds?

Answer 19

•Seeding Clouds : Using silver iodide or potassium iodide to cause condensation nuclei, resulting in rain.

Question 20

What is “ desalinization” ?

Answer 20

•Desalination - removing salt from ocean water or brackish water to get fresh water . Three to four times more expensive than most other sources. Oil-rich Middle East states produce 60% of desalinated water