Watersheds &

Water Pollution

Runoff

• What is runoff?

• Review: When rain or snow falls onto the

earth, it just doesn't sit there, it starts moving

according to the laws of gravity. A portion of

the precipitation seeps into the ground to

replenish Earth’s groundwater. Most of it flows

downhill as runoff.

More on

Runoff

• Smaller

creeks/streams

flow into smaller

rivers which flow

into larger rivers

or lakes.

What is a Watershed?• A watershed is an area of

land from which all

runoff drains to the

same body of water.

•Everyone lives in a

watershed. What watershed

do we live in?

Water Pollution• Healthy watersheds are important for a

healthy environment and economy

because they provide water for

drinking, irrigation, and industry. Many

people also enjoy lakes and streams for

recreational activities like swimming,

boating, fishing, to watch wildlife, and

to check out the beautiful scenery.

Animal survival also depends on a

healthy watershed, as it provides food

and shelter.

• Contamination at any one place can

affect the overall health of the

watershed.

• How does this happen?

• Water continuously travels from

one place to another due to the

hydrologic cycle.

Evaporation

Ocean Storage Groundwater

flow to oceans

Aquifers

Infiltration

into the

ground

SpringsStreams and

rivers

CondensationPrecipitation

Lakes

Snowmelt

Types of Pollution

• Point source pollution- pollution that is

directly dumped into a body of water

• Example: A factory dumps waste in a water

• This is not as much of a problem in the United

States today. Why?

• Strict laws have been passed by the

government

Types of Pollution

• Non-point source pollution- pollution that occurs when

small amount of pollution from a variety of sources is picked

up by runoff and carried into water bodies.

• Examples:

• Excess fertilizers, herbicides and insecticides

• Oil, grease, and other chemicals leaked onto the ground

• Bacteria and nutrients from livestock, pet wastes and

faulty septic systems

• You can't point to the specific origin of the contamination; it

comes from too many places and is difficult to trace.

Types of Pollution• What activities are examples of point-source pollution

and non-point source pollution?

• Point source

pollution

• Non-Point

source

pollution

• dumping oil

into storm

drain

• fertilizer on

yard

• litter

thrown on

ground

• oil leaking

out of car

Water Treatment

• Watch the video clip How It’s Made:

Drinking Water to learn how water is

treated.

Water Treatment

• 1. Coagulation- removes dirt and

other particles suspended in water.

Alum and other chemicals are

added to water to form tiny sticky

particles called "floc" which attract

the dirt particles. The combined

weight of the dirt and the alum

(floc) become heavy enough to sink

to the bottom during

sedimentation.

• 2. Sedimentation- The heavy

particles (floc) settle to the bottom

and the clear water moves to

filtration.

Water Treatment

• 3. Filtration- The water passes through

filters, some made of layers of sand,

gravel, and charcoal that help remove

even smaller particles.

• 4. Disinfection- Water is placed in a

closed tank or reservoir in order for

disinfection to take place. A small

amount of chlorine is added or some

other disinfection method is used to

kill any bacteria or microorganisims

that may be in the water.

• 5. Storage- The water then flows

through pipes to homes and businesses

in the community.