Fresh & Salt Water Systems
Humans depend on water supply and quality
- Earth is sometimes called the water planet because 74% of its surface is water.
- Two influences on the many variations in Earth’s water supply: Natural occurrences & Human activities
The Distribution of Water on Earth
- Earth has the most water of any planet in the solar system.
- Earth’s water exists naturally in different forms.
- Solid (ice), Liquid, Gas (vapor)
- Humans do not drink salt water. Humans drink fresh water that is potable
Potable Water :
Water that is safe for human’s to drink. Potable water also pertains to other organisms
Water on Earth
Freshwater only makes up 3% of all the Earth
Of that, only 0.003% of all the water on Earth is available for humans to drink.
Why? Rest of the water is:
- Too far below the Earth’s surface
- Located too far from human habitats (I.e. we don’t live close enough to it)
Water Quality :
A measure of the amount of substances besides water in a water sample; OR description of how pure a water sample is.
Water in nature is never pure it always contains organisms, organic material, minerals, and other chemicals.
Substances Dissolved in Water
- Most of the substances dissolved in fresh and salt water are called salts.
- Most common salt is sodium chloride, same chemical as table salt.
Amount of dissolved salt in water.
(ex) Seawater (3.5%) has a higher salinity than fresh water.
Hard Water :
Water containing a high concentration of calcium and magnesium.
- As fresh water flows from Earth’s surface and underground it dissolves minerals from the soil and rocks. One of these minerals is salt.
- These minerals can affect the taste of the water, some examples:
1) Salty fresh water in the prairies
2) Iron in the fresh water in Ontario
3) Hard water across Canada
Organisms in Drinking Water
- Fresh water also contains organisms and organic matter.
- Some organisms are harmful, but most of them are not
Escherichia coli (E. coli) can cause illness and death, but human treatment processes usually take care of this.
Water Quality Testing
- Water from a well is rarely treated because its location far underground protects it from most natural and human activities. However, airborne pathogens may still come in contact with water
- City water is always treated because it comes from surface locations (rivers and lakes) which are highly susceptible to pollution. Treating the water is important to bring up the quality so that it is potable.
Water Testing Criteria
- A simple and common method of testing is appearance and smell, but this should be used cautiously because many dangerous organisms will not be detected.
- Taste & colour
- Toxic substances
- Dissolved oxygen & solids
Changing Salt Water to Fresh Water
Due to the high salinity of most of the Earth’s water, the salt must be removed in order to make the water potable.
Removal of salts via either distillation or reverse osmosis
Technique for separating solutions that involves boiling and condensation.
Boiled water vapour leaves the salt behind, and then condensation converts the water vapour back to distilled liquid water.
- Water does not contain any undesirable contaminates like dissolved solids or chlorine.
- Contains pure water!
- Removes the dissolved gasses that give water its pleasant taste -- distilled water tastes "flat.“
- Not cheap, uses lots of energy
Reverse Osmosis :
Movement of water through a membrane from an area of lower water concentration to one of higher water concentration
- Recall Osmosis is the movement of water particles through a membrane from a high concentration to low concentration;
- Uses pressure from pumps to force a solvent through a membrane that retains the solute on one side and allows the pure solvent to pass to the other side.
- Used mainly in desalination
- Turns saltwater to potable water.
- Environmental impact. Water is filtered at the cost of large quantities of waste water. For every 20L of output, a typical residential reverse osmosis filter will send around 40 - 80 L of water down the drain.
Waves & Tides
Waves and tides are two ways in which water moves.
Are movements on the surface.
All bodies of water, even small puddles, have waves!
Are regular rising and falling of very large bodies of water.
The Movement of Water Waves
Waves are a form of energy that begin from a disturbance
In water, circular movement of water particles that cause a change in pattern that moves along the water’s surface; the pattern can move over long distances but the water particles do not.
Cause of Water Waves
Most waves are caused by the combination of a local sea and swells.
- Local seas are made by the wind :
- Wind speed increases
- Distance the wind blows over the water (called fetch)
- Time wind has blown over fetch
- Swells move away from local seas where they were produced (and continue without wind)
- In the open water the waves appear to move up and down.
Effects of Waves on Shorelines
- The force of waves can affect both a hard rock and soft sand shoreline.
- Waves regularly cause erosion on land surfaces.
Tide – daily changes in water level of the oceans.
- Tidal changes are seen regularly along the coast.
- Most places there are 2 high tides and 2 low tides a day.
- High Tide – highest water level along the coast
- Low Tide – lowest water level along the coast
The Cause of Tides
- The main cause of tides is the gravitational force of the moon.
- Water is affected by forces in space because of centripetal force
- The sun also has an influence, but not as great
- The side closest to the moon feels a strong pull from the moon creating a bulge.
- The opposite side of the Earth also has a smaller bulge due to other forces.
- The 2 bulges on both sides are the high tides.
- As the Earth rotates the points of the high tides also change.
- The movements create 2 high tides and 2 low tides every 24 hours and 50 mins (called the lunar day).
- Very similar to the 24 hour day (solar day).
- People keep track of the tides with guides called tide tables.
What is a Rip Tide ? -- When the tide is receding trough an estuary it can pull a large amount of water through a narrow gap, this can pull objects off shore very quickly!
Rip Current -- A fast narrow current running offshore and cutting through breaking waves
Erosion & Deposition
- Identifying the characteristics of a stream or river is useful because it helps:
- Scientists understand types of organisms.
- Scientists hypothesize the impact of human activities.
- Engineers use them to build bridges and dams.
- Researchers organize a river or streams characteristics with a profile.
Stream Characteristics :
Characteristics used to describe a stream or river; these include volume and rate of flow, slope and shape of bed.
Erosion and Deposition
- Moving water is a powerful force. Waves can shape a shoreline. Rivers also shape the land they flow through.
The wearing away and transporting of rocks fragments and soil.
Eroded rock fragments and soil carried by water and wind.
The laying down or depositing of sediments.
- A river’s sediment load is the amount of water-borne materials that it carries.
- The faster the water moves = the more the water can carry.
Water reacts with chemicals to dissolve rock
What makes a Watershed?
- Watershed – area of land that drains into one main lake or river.
- A watershed can contain many smaller rivers and lakes.
- Continental Divide – the highest point of land on a continent; rivers flow into different oceans depending on which side of the divide they start.
- In North America the continental divide is the Rocky Mountains.
- There are other divides in North America that contribute to the direction water flows
Processes That Shape Ocean Basins and Continental Drainage
Processes that form Ocean Basins
- The Earth is very old, and much of what we know has changed - It's 4.5 - 4.6 billion years old!
- Life started about 3.5 billion years ago w/ algae microbes
- The Lithosphere is the solid outer part of Earth, made of rock, which has broken into tectonic plates that are moving constantly and slowly due to convection currents within Earth.
Continental Drainage Systems
- The same forces that shape the ocean basins also build the continental divides.
- At the edge of the continent, two plates meet and push against each other, which cause wrinkles in the continents surfaces and pushes up.
- Plate tectonics have formed many continental divides.
Large moving body of ice; glaciers can be many meters or even kilometres thick.
- Glaciers that cover vast areas of land are called continental glaciers or icecaps.
- Glaciers form in the cold regions of Earth, they build up, and then start to move, which then are called valley glaciers because they flow between the mountains.
- The valley glaciers collect huge or small pieces of rocks, which drag on the surface and determine the form of the land.
- The movement of glaciers depends on the climate.
- Cooler – little melting, snow builds up, and the glacier moves forward.
- Warmer – more melting, snow decreases, and the glacier retreats.
Recognizing Glacial Features
- Today, few continental and valley glaciers cover the Earth.
- In the past, large areas of the Earth were covered, called the Ice Ages.
- The Ice Ages shaped most of Canada’s geography.
Glacial features include:
- Kettle lakes
Water & Climate
Average weather measured over a long period of time.
The Effect of Large Bodies of Water on Climate
- Water has a high heat capacity, so it can hold heat longer than other substances.
- It takes a long time to raise or lower the temperature of a large body of water.
- Large bodies of water influence the weather and climate in their regions.
- So land areas near large bodies of water do not usually get extreme temperatures, so temperatures differences between day and night, and summer and winter are not as great as they are on land areas surrounded mostly by land.
- Ocean currents also affect an area’s climate.
- Currents – stream of water that moves within a larger body of water.
- Carries warmer & colder water to different areas
- Currents can be caused by:
- Temperature differences in the water
- Salinity differences in the water
- Earth’s rotation
- Surface Currents
Currents and Climate
- Currents are different from waves because the water moves from place to place.
- Recall waves move the energy
- Surface currents are caused by steady winds, and can be carried great distances.
- The warm or cold currents then influence the climates on land.
Ocean Currents and Precipitation
- The temperature of an ocean current affects more than just air temperature; it also affects the amount of precipitation in an area.
- Warm air holds more moisture than cold air.
- Winds over a warm current (ex. Scotland)– carries lots of water.
- Winds over a cold current (ex. Labrodor)– carries little water.
- Warm air holds more moisture than cold air.