Chapter 14

Water

Water’s Unique Properties

• 1) Polar covalent molecule• 2) High heat capacity (good coolant – helps to

moderate climate)• 3) Universal solvent• 4) Expands when it freezes (helps form soil)• 5) pH = 7• 6) Adhesion – water sticks to other substances• 7) Cohesion- water sticks to itself

WATER’S AVAILABILITY

• Only about 0.02% of the earth’s water supply is available to us as liquid freshwater (97.4 % = oceans, 2.6% = fresh)

WATER’S IMPORTANCE, AVAILABILITY, AND RENEWAL

• Water stress = high demand for water (due to population), low availability

Figure 14-2Figure 14-2

Ground Water Terms• Aquifer – underground water source (porous

rock)• Recharge Area – area of porous rock where

water can infiltrate into the aquifer• Artesian Well – crack in aquifer where water

can escape• Zone of Saturation – the level of water in

the aquifer• Zone of Aeration – distance to the water

table

Ground Water Terms• Water Table – level of water retention in

the aquifer

• Confined Aquifer – aquifer surrounded by 2 layers of impermeable rock

• Unconfined Aquifer – aquifer with 1 layer of impermeable & 1 layer of permeable rock

• Saltwater Intrusion – when saltwater enters aquifer due to depletion of aquifer

Fig. 14-3, p. 308

Unconfined Aquifer Recharge Area

Precipitation Evaporation and transpiration Evaporation

Confined Recharge Area

Runoff

Flowing artesian well

Recharge Recharge Unconfined Unconfined AquiferAquifer

Stream Well requiring a pumpInfiltration Water

table LakeInfiltration

Unconfined aquifer

Confined aquiferConfining impermeable rock layer Confining impermeable rock layer

Less permeable Less permeable material such as claymaterial such as clay

WATER USAGE

• Irrigation: (70%)• Industry: (20%) • Municipal use: (10%) • Average person: 1280 gallons/day.

Water in the United States

• Average precipitation (top) in relation to water-deficit regions and their proximity to metropolitan areas (bottom).

Figure 14-4Figure 14-4

Freshwater Resources in the United States

• 17 western states by 2025 could face intense conflict over scarce water needed for urban growth, irrigation, recreation and wildlife.

Figure 14-5Figure 14-5

TOO LITTLE FRESHWATER

• Causes: dry climate, drought, dessication, water stress

• Riparian Rights (east coast)

• Common Law Rights (western)

Stress on the World’s River Basins

• Comparison of the amount of water available with the amount used by humans.

Figure 14-6Figure 14-6

Groundwater Depletion: A Growing Problem

• The Ogallala, the world’s largest aquifer, is most of the red area in the center (Midwest).

Areas of Areas of greatest aquifer greatest aquifer depletion from depletion from groundwater groundwater overdraft in the overdraft in the continental U.Scontinental U.S..

Figure 14-8Figure 14-8

Effects of Groundwater Depletion

• Subsidence• Saltwater Intrusion

Figure 14-11Figure 14-11

Effects of Groundwater Depletion

• SubsidenceFigure 14-10Figure 14-10

DAMS AND RESERVOIRS

• Advantages: produce cheap electricity, reduce downstream flooding, and provide year-round water for irrigating cropland

• Disadvantages: displace people, disrupt aquatic systems, cause erosion downstream, flooding upstream, keep silt behind the dam rather than distributing it downstream, prevent fish migration

Fig. 14-13a, p. 317

Provides water for year-round irrigation of cropland

Flooded land destroys forests or cropland and displaces people

Large losses of water through evaporation

Provides water for drinking Downstream

cropland and estuaries are deprived of nutrient-rich silt

Reservoir is useful for recreation and fishing

Risk of failure and devastating downstream flooding

Can produce cheap electricity (hydropower)

Downstream flooding is reduced

Migration and spawning of some fish are disrupted

Fig. 14-13b, p. 317

Powerlines

Reservoir

Dam

PowerhouseIntake

Turbine

The Colorado River Basin

• Watershed is equal to more than one-twelfth of the land area of the lower 48 states.

Figure 14-14Figure 14-14

China’s Three Gorges Dam

– Will be 2 kilometers long.– The electric output will be that of 18 large coal-

burning or nuclear power plants.– It will facilitate ship travel reducing transportation

costs.– Dam will displace 1.2 million people.– Dam is built over seismatic fault and already has

small cracks.

The California Water Project

• A massive transfer of water from northern California to southern California

Figure 14-16Figure 14-16

The Aral Sea Disaster

• The Aral Sea was once the world’s fourth largest freshwater lake.

Figure 14-17Figure 14-17

The Aral Sea Disaster

• Water was diverted for Irrigation

• Effects:– About 85% of the wetlands have been

eliminated and roughly 50% of the local bird and mammal species have disappeared.

– Since 1961, the sea’s salinity has tripled and the water has dropped by 22 meters most likely causing 20 of the 24 native fish species to go extinct.

Options to Increase Freshwater• Distillation: heating saltwater until it

evaporates, leaves behind water in solid form (lots of salty waste).

• Reverse osmosis: uses high pressure to force saltwater through a membrane filter

• Cloud seeding

• Towing Icebergs

• Water Baggies

INCREASING WATER SUPPLIES BY WASTING LESS WATER

• 65-70% of the water people use throughout the world is lost through evaporation, leaks, and other losses

• Water is underpriced through government subsidies

• Drip irrigation

• Center-pivot, low-pressure sprinklers

• Xeriscaping

Fig. 14-18, p. 325

Center pivotCenter pivot

Drip irrigationDrip irrigation

Gravity flowGravity flow(efficiency 60% and

80% with surge valves)

Above- or below-ground pipes or tubes deliver water to individual plant roots.

Water usually comes from an aqueduct system or a nearby river.

(efficiency 90–95%)

(efficiency 80%–95%)

Water usually pumped from underground and sprayed from mobile boom with sprinklers.

Using Less Water to Remove Industrial and Household Wastes

• Use nutrients in wastewater before treatment as soil fertilizer

• Use waterless and odorless composting toilets that convert human fecal matter into a small amount of soil material.

TOO MUCH WATER

• Comparison of St. Louis, Missouri under normal conditions (1988) and after severe flooding (1993).

Figure 14-22Figure 14-22

TOO MUCH WATER

• Human activities have contributed to flood deaths and damages.

Figure 14-23Figure 14-23

USING WATER MORE

SUSTAINABLY• Cut waste

• Raise water prices

• Preserve forests and wetlands in water basins

• Slow population growth.

Figure 14-25Figure 14-25