Chapter 11

Environmental Science

1

Water Resources Section 11.1

2

The Water Cycle Water molecules

circulating between the Earth’s surface and the atmosphere.

It involves condensation, evaporation, transpiration, and precipitation.

3

Global Water Distribution 71% of the Earth’s surface

is covered in water

97% of that water is salt water in ocean and seas

77% of the fresh water on Earth is frozen in icecaps and glaciers

Fresh water is a limited resource because there is only about 3% usable freshwater.

4

Surface Water Is fresh water on Earth’s

land surface.

Lakes, streams, rivers, and wetlands.

Water is used for drinking, agriculture, power, and transportation.

5

River Systems vs. Watersheds River Systems Watersheds

Rain and snow draining down from mountains and hills.

Small streams come together to form rivers

A river system is a flowing network of surface water.

Amazon is largest river system.

The area of land that is drained by a river.

Pollution in a watershed can pollute the river.

Amount of water varies depending on precipitation and melting snow.

6

Groundwater Water beneath the

Earth’s surface in sediment and rock formations.

Water table is where rock and soil are saturated with water.

Water table varies in wet regions vs. dry regions.

7

Aquifers An underground

formation that contains groundwater.

Consist of rock, sand, and gravel where water can accumulate.

Important water source for many cities and for agriculture.

8

Porosity vs. Permeability Porosity Permeability

Is the percentage of the total volume of a rock that has spaces or pores.

The more porous a rock, the more water it can hold

The ability of rock or soil to allow water to flow through it.

Example: granite, sandstone, and limestone are permeable but clay is impermeable.

9

The Recharge Zone An area of the Earth’s

surface from which water percolates down into an aquifer.

Environmentally sensitive

Size is affected by permeability of the surface above the aquifer.

10

Wells A hole that is dug or

drilled to reach groundwater.

Are drilled to extend below water table.

Droughts and removing groundwater faster than it is recharged leads to wells drying up.

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Water Use and Management Section 11.2

12

Global Water Use Residential (drinking,

washing, cooking, toilets)

Industrial (manufacture goods, dispose of waste, and generate power)

Agricultural (most of the fresh water used worldwide is used to irrigate crops)

13

Water Treatment Water is treated

physically and chemically to make it potable or safe to drink

Mercury, arsenic, and lead are removed by adding chlorine.

Pathogens, organisms that cause illness or disease are also removed.

14

Water Management Projects Aqueducts or huge

canals to bring water from mountains to dry areas.

Reservoirs or artificial lakes are used for recreation or drinking water

Dams are structures built across a river to control the river’s flow.

15

Benefits and Consequences of Dams Benefits Consequences

Flood control

Drinking water

Irrigation

Recreation

Industry

Electrical energy

People can be displaced

Entire ecosystems can be destroyed

Farmland below dam becomes less productive

Dam failure can lead to death.

16

Water Conservation Agriculture: drip irrigation

systems

Industry: recycling of cooling water and wastewater

Residential: shorter showers, low-flow toilets/showers, turn water off when brushing teeth, wash full loads, and water lawns sparingly.

17

Solutions for the future Desalinization:

removing salt from salt water. (very expensive)

Transporting water: ships transfer bags of fresh water or towing icebergs. (hard to find efficient way…)

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Water Pollution Section 11.3

19

Water Pollution The introduction of

chemical, physical, or biological agents into water.

Two causes are industrialization and rapid human population growth.

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Two types of sources of water pollution Point-Source Pollution Nonpoint-Source Pollution

Pollution discharged from a single source.

Easier to identify and trace.

Examples: leaking tank or unlined landfill.

Comes from many different sources

Difficult to identify and trace.

Examples: road or agricultural runoff, polluted precipitation, water runoff.

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Physical Water Pollutants Pathogens: disease causing organisms

Organic matter: feces, food wastes

Organic chemicals: pesticides, fertilizers, plastics

Inorganic chemicals: acids, bases, salts

Heavy metals: lead, mercury, cadmium, arsenic

Physical agents: heat and suspended solids

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Wastewater The water that contains

waste from homes or industry.

Most wastewater can be treated but some toxic substances require further treatment.

Sewage sludge is the solid material that remains after treatment

Hard to dispose of so sludge can be used for fertilizer and to make bricks.

23

Artificial Eutrophication Eutrophication is a

natural process but when caused by humans it is accelerated.

When phosphates and nitrates enter the water from sewage and fertilizer runoff.

Causes algal blooms that die and water becomes oxygen depleted.

24

Thermal Pollution When the temperature

of a body of water increases.

When power plants use water in their cooling systems and then discharge warm water back into lake or river.

Causes large fish kills and aquatic organisms suffocate.

25

Groundwater Pollution When polluted surface

water percolates down.

Pesticides, fertilizers, and petroleum are groundwater pollutants.

Other sources: leaking underground water tanks, septic tanks, and unlined landfills

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Cleaning Up Groundwater Pollution Most challenging

problem

Recharges very slowly

Pollution can cling to the aquifer

27

Ocean Pollution Dumped wastewater and

garbage

Majority of pollution caused by land activities

Oil spills (37 million gals)

More oil enters from nonpoint sources in cities and towns (200-300 million gals)

28

Water Pollution and Ecosystems Can have immediate

effects or lead to biomagnification (the buildup of pollutants at higher levels as it travels up the food chain).

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Cleaning up Water Pollution Clean Water Act (1972)

Marine Protection, Research and Sanctuaries Act (1972)

Safe Drinking Water Act (1975)

Comprehensive Environmental Response Compensation and Liability Act (1980)

Water Quality Act (1987)

Oil Pollution Act (1990)

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