Chapter 14 Water

Aquifers:• Porous, water-saturated layers of sand, gravel,

or bedrock that can yield an economically significant amount of water.

Desalination:• Purification of salt water or brackish, (slightly

salty) water by removal of dissolved salts.

Floodplain:• Flat valley floor next to a stream channel. For

legal purposes, the term often applies to any low area that has the potential for flooding, including certain coastal areas.

Groundwater:• Water that sinks into the soil and is stored in

slowly flowing and slowly renewed underground reservoirs called aquifers; underground water in the zone of saturation, below the water table.

Natural recharge:• Natural replenishment of an aquifer by

precipitation, which percolates downward through soil and rock.

Reliable runoff:• Surface runoff of water that generally can be

counted on a stable source of water form year to year.

Surface runoff:• Water flowing off the land into bodies of

surface water.

Surface water:• Precipitation that doesn’t infiltrate the ground

or return to the atmosphere by evaporation or transpiration.

Water table:• Upper surface of the zone of saturation, in

which all available pores in the soil and rock in the earth’s crust are filled with water.

Watershed/ Drainage basin:

• Land area that delivers water, sediment and dissolved substances via small streams to a major stream (river).

Zone of saturation:• Area where all available pores in soil and rock

in the earth’s crust are filled by water.

Why is water so important, how much freshwater is available and how much of it are we using?• Water keeps us alive, moderates climate, sculpts the land,

removes and dilutes wastes and pollutants, and moves continually through the hydrologic cycle. Only about .024% of the earth’s water supply is available. We currently use more than half of the world’s reliable runoff of surface water.

What causes freshwater shortages and what can be done about it?

• Main factors causing water scarcity are dry climate, too many people using and wasting the reliable supply of water, lack of money to drill deep wells and build dams, storage reservoirs and water distribution systems. We can help prevent shortages of freshwater by not wasting water and having private companies buy and manage the water.

What are the advantages and disadvantages of withdrawing groundwater?

Advantages• Useful for drinking and irrigation• Available year-round• Exists almost everywhere• Renewable if not over-pumped or

contaminated• No evaporation losses• Cheaper to extract than most

surface waters

Disadvantages• Aquifer depletion from over-

pumping• Sinking of land from over-

pumping• Polluted aquifers for decades or

centuries• Saltwater intrusion into drinking

water supplies near coastal areas• Reduced water flows into surface

waters• Increased cost and contamination

from deeper wells

What are the advantages and disadvantages of using dams and reservoirs to supply more water?

Advantages• Produce cheap electricity• Reduce downstream

flooding• Provide year-round water

for irrigating cropland

Disadvantages• Displace people• Disrupt aquatic systems

What are the advantages and disadvantages of transferring large amounts of water from one place to another?

Advantages• Makes unproductive areas

more productive• Turns water-poor areas into

suitable places for growing food, grazing and other business activities. This will make businesses more likely to invest in the area and the econoomy with be strengthened.

Disadvantages• Encourages unsustainable

use of water in areas where water is not naturally supplied

Can removing salt from seawater solve our water supply problems?

• This method cannot really solve our problem. Current methods of desalination are very expensive due to the high amount of energy needed to desalinate the water. Also, a large amount of briny wastewater is produced and it must be safely disposed of. Currently, desalination is practical only for water-short wealthy countries and cities that can afford its high cost.

How can we waste less water?

• Redesign manufacturing processes• Repair leaking underground pipes• Landscape yards with plants that require little water• Improve irrigation techniques• Use drip irrigation• Fix water leaks• Use water meters• Raise water prices• Use waterless composting toilets• Require water conservation in water-short cities• Use water-saving toilets, showerheads and front-loading clothes washers• Collect and reuse household water• Don’t waste energy

How can we use the earth’s water more sustainably?

• Cut waste• Raising water prices• Preserving forests and wetlands in water basins• Slow population growth

What causes flooding and what can we do about it?

• Flooding is causes by heavy rainfall, rapid snowmelt, removal of vegetation and destruction of wetlands. We can reduce flood risks by controlling river flows, protecting mountainside forests, preserving and restoring wetlands, identifying and managing flood-prone areas and, if possible, choosing not to live in flood-prone areas.