1. Unit 4
Lesson 3
Water on Earth
S8.D

2. Water Cycle
When water evaporates from a plant
Why clouds float?

3. The Sun powers the Water cycle
Water cycle for kids

4. Watershed
An area of land that drains rain or snow into a particular body of water
An area of land that water flows over to reach a river is the river’s watershed

5. Chesapeake Bay Watershed
We live in both the Susquehanna River and Chesapeake Bay watersheds
About 150 different rivers and streams flow into Chesapeake Bay
In the bay, fresh water from rivers mixes with saltwater from oceans

6. Pollution in Watersheds
Pollution anywhere in a watershed can lead to pollution in a body of water
Runoff can wash soil, fertilizers, litter, toxic chemicals, and other pollutants into creeks rivers  bay ocean
Farmers often add nutrients to soil to help crops grow
Nutrients can make their way to a body of water and cause an overgrowth of algae (Algal Bloom)
Algae depletes the water of oxygen that other organisms need to live

7. Freshwater Bodies Lentic Systems Lotic Systems
Water is still or almost still
Lake, wetlands
Lotic Systems
Creeks, streams, and rivers
Water is moving from high elevation to lower elevation
Flow rate or current rate at which water flows
Organisms have adaptations to prevent them from being swept downstream

8. Changes to Lentic Systems
Changes in flow rate, temperature ,and water quality can affect a river’s/stream’s Biodiversity (variety of organisms that can live there)
Heavy rainfall can increase flow rate
Power plants use river water for cooling
Litter and pollutants can move into a stream from the watershed
Bill Nye- Rivers and Streams

9. Wetlands Marshes, swamps, bogs
Link
Marshes, swamps, bogs
An area of land that is underwater for all or part of the year
Form when water washes over land from rivers, creeks, streams, and lakes
How they Help?
Filter pollutants, excess nutrients, and sediments out of the water that moves through them
Improve quality of water that flows to other bodies of water downstream

10. Saltwater Bodies Oceans cover 70% of Earth
Estuary- the wide part of a river where it nears the sea; fresh and salt water mix
Bay- body of water that connects to an ocean

11. Saltwater vs Freshwater
Why are oceans salty?
Salinity
Is the dissolved salt content (NaCl) in water
Measured in ppm (parts per million)
Oceans have a salinity of 35,000 ppm (35 ppt)
Freshwater has a salinity of about 500 ppm
Why are some lakes salty?
Wiki seawater

12. Saltwater vs Freshwater
Density
Saltwater is denser than freshwater
density of saltwater is 1.025g/ml
Conductivity
Pure water will not conduct electricity
Freshwater is a poor conductor of electricity (has few dissolved ions)
Saltwater is a good conductor of electricity
When salt dissolves in water Na(+) ions and Cl(-) ions form
Saltwater

13. Saltwater vs Freshwater
Freezing and Boiling point
Salt lowers the freezing point and higher the boiling point
For every 29.2g of salt per liter of water (kg), the freezing point lowers by 3.3 F
Freshwater freezes at 32 F……..Seawater freezes at ~28 F
For every 29.2g of salt per liter of water (kg), the boiling point raises 0.9 F
Freshwater boils at 212 F……..Seawater boils at ~213F
The above numbers assume seawater’s salinity is 35 ppt.
The salinity of seawater is not constant everywhere