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.