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Unit C - Water Systems on Earth. Water, water, everywhere, Nor any drop to drink. Chapter 7-The Water Cycle. 7.1 – WATER IN OUR WORLD. Water Distribution. Water covers 71% of the Earth’s surface . Water Distribution. Most of Earth’s liquid water is salt water in the oceans.

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Unit C - Water Systems on Earth

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Unit C - Water Systems on Earth

Water, water, everywhere,

Nor any drop to drink.

Chapter 7-The Water Cycle


Water Distribution

  • Water covers 71% of the Earth’s surface

Water Distribution

  • Most of Earth’s liquid water is salt water in the oceans.

Water Distribution

  • Fresh water- is water (liquid, solid or gas) that contains a low concentration of dissolved salts.

Salt Water

  • Oceans contain most of the world’s salt water. The salinity of ocean water is about 3.5%

  • Most of the salt in the water comes from land. As fresh water seeps through the soil, it dissolves some of the salt and other minerals we can’t taste the salt yet, but once the runoff (the fresh water going over the land) reaches the oceans it deposits the salt. Over millions of years the salt concentration in the oceans has built up to current levels.

Salt Water

  • Estuaries- are areas where rivers flow into an ocean.

  • Sometimes high tides cause ocean water to flow upstream into the river. This results in salt water mixing with fresh water. This mixed water is saltier than fresh water but fresher than salt water – it is called brackish water.

Fresh Water

  • Canada contains about 9% of the world’s fresh water supply although it only has 0.5% of the world’s population

  • Canada has many wetlands which: help filter and clean the water, and moderate water levels

The Three States of Matter

  • Water is the only substance on Earth that exist naturally in all three physical states; solid, liquid and gas

Chapter 7.3 -The Water Cycle

Water is always on the move. It is always changing its state and location

The movement of water and its changing of states is known as the Water Cycle- the movement of water as it changes state over, on, and in Earth

The Water Cycle

The Water Cycle

The Water Cycle

  • Heat energy from the sun causes water on Earth’s surface to change to water vapour in a process called Evaporation

  • Water can also evaporate from soil, plants and animals

  • As the air rises it cools. Cool air can not hold as much water as warm air. The cooled water vapour in the air becomes liquid again in a process called Condensation

The Water Cycle

  • Eventually so much water collects as clouds and the wind can no longer keep it aloft (floating). It then falls to Earth as Precipitation

  • Rain, hail, sleet, and snow are examples of precipitation

  • Sometimes snow and ice can turn directly into water vapour in a process called sublimation- change of state where a solid turns directly into a gas without first becoming a liquid

The Water Cycle

  • Liquid water flows along the surface of the ground (Runoff) and gathers in rivers, lakes and oceans

  • Wetlands are important reservoirs of water.

Types of Wetlands

  • Marsh-low-lying, treeless area of soft wet ground usually covered by water (fresh or salt) for part of the year. Grasses, cattails and other plants grow there.

Types of Wetlands

  • Swamp- low-lying, treed area of soft, wet ground covered with water (fresh or salt) for part of the year but contains many trees and bushes

Types of Wetlands

  • Bog- is dominated by mosses, which are wetland sponges


  • Groundwater is water that has soaked into the soil.

  • It passes through gravel, sand, soil and rock on its way back to rivers, lakes and oceans, or to longer term storage underground


  • Water in vapour and liquid form can dissolve many substances.

  • This can be a problem because along with minerals and salts, pollutants and chemicals can also be transported by ground and surface water into lakes and oceans.

Chapter 7.4- The Water Table

The Water Table

  • Water can be “sticky” that is, it shows an attraction to many other materials. This property is called Adhesion – the attractive forces between the particles of a fluid and the particles of another substance.

The Water Table

  • Water is composed of hydrogen and oxygen. Because of the way the atoms are arranged one end of a water molecule has a positive end and one has a negative end

  • This causes water molecules to act like tiny magnets and forms a cohesive force- the attractive force among particles of the same substance

Water in the Ground

  • When rain hits the ground, gravity causes it to sink. As it sinks, the water dissolves salts and minerals as it moves through the spaces between the soil particles. This process is known as Percolation.

Water in the Ground

  • As the water continues down through the ground, it eventually reaches a level where it will not go down any further. This is called the impermeable layer. Soil above this layer then becomes saturated with water. This is called the saturated zone.

  • The Upper layer of the Saturated zone is called the water table

Saturated vs Unsaturated

The Water Table

Factors Affecting the Water Table

  • Amount of rainfall

  • If no little precipitation has fallen the water table can be depleted by capillary action

  • Capillary action happens because water is adhesive and cohesive

Human Activities

  • In urban areas water percolation does not happen as much as in other areas Why?

  • Urban areas are paved, so precipitation that falls in the city runs directly into the sewers and is emptied into stream and rivers without having a chance to become ground water.

7.5 - The Power of Water

7.5-The Power of Water

  • Sediment – Weathered pieces of rock that can be carried away by erosion


  • Weathering- Weathering is the breaking down of rock into smaller and smaller pieces.


  • There are different methods by which rocks can be broken into smaller and smaller pieces

    • Mechanical

    • Chemical

    • Biological – can be both physical and biological

Mechanical Weathering

  • Mechanical Weathering occurs when rock is physically broken down into smaller pieces. The “new material” is the same as the parent material

Mechanical Weathering

  • Ice Wedging – water gets inside tiny cracks of rocks and freezes. When water freezes it gets about 9% bigger. Over time this will split the rock

Chemical Weathering

  • Rain water is slightly acidic. Also water can dissolve other chemicals that can react with minerals in the rock causing chemical weathering


  • Erosion is the movement of sediment from its place of origin

  • Erosion can be caused by

    • Gravity

    • Running water

    • Waves

    • Moving ice

    • wind


  • Sediment gets picked up by rain or running water and eventually finds its way into a river

  • When the water is moving slow enough the sediments will settle to the bottom of the river in a process called DEPOSITION.

  • Heavier sediments settle first while light sediments take longer to be deposited


  • Over time the deposited sediment can fill in lakes or can build up a delta at the mouth of a river

  • Delta-a flat area of land formed by sediment that has settled at the mouth of a river over many thousands of years

7.6 – The Human Side of Water Systems


-recycle plastic-make sure garbage goes to the right place-make strict laws to help minimize waste-Mass clean up to help pick out the trash-Using an alternative to plastic.

What Do We Do about it? Brainstorm

7.6 – The Human Side of Water Systems

  • Earth has a lot of people ( aprox. 6.8 billion) who need water for survival and recreation. Unfortunately our actions have not always have a positive impact on the water supply

  • WATER POLLUTION – any pollution that negatively affects the quality of water

Micro-organisms in Water

  • Coliforms (bacteria found in the intestines of animals) can cause a serious health issue.

  • Coliforms can be in high concentrations if raw or improperly treated sewage is discharged into the water.

  • Nausea, vomiting and diarrhea can result

Acid Precipitation

  • ACID PRECIPITATION – occurs when water vapour reacts with air borne pollutants, like sulfur dioxide and nitric oxide, to form an acid (sulfuric acid and nitric acid)

  • The water then condenses and falls to the Earth as acid rain or snow

Acid Precipitation

Acid Precipitation

7.7 – Water Treatment and Disposal

Intake and Treatment

  • Most of the water used comes from lakes and rivers through a large intake pipe

  • Screens keep out fish and garbage

  • The water is pumped into a large reservoir where large sediments can settle

  • The water then goes through more screens on its way to the water treatment plant

Water Treatment Plant

  • Chemicals (alum) are added to make sediments clump together

  • Water is then forced through layers of sand, gravel and charcoal, which filter out fine sediment

  • Chemicals or UV Light are then added to kill and micro-organisms


  • In urban areas, water is pumped through large water pipes (mains) and up into a water tower

  • The force of gravity then send water through smaller mains into houses, businesses and institutions

Disposal of Waste Water

  • There are two types of waste water

    • Sanitary Sewage

    • Stormwater

Sanitary Sewage

  • Sanitary Sewage- is water from sinks, baths, washing machines and toilets

  • A service main carries sanitary sewage to a water treatment facility

  • Stormwater- is rainwater and melted snow that runs off streets and the surface of the land

Sewage Treatment

  • Solids in sewage are sent to settling tanks. Larger particles settle to the bottom and form sludge.

  • Sludge can be burned, put in a landfill or used as farm fertilizer

  • Liquid sewage is pumped to an aeration tank where oxygen helps break down organic material

  • Water that is released back into the environment is called effluent

  • Effluent is usually treated with chlorine or other chemicals to kill bacteria

  • Make a chain diagram showing the process of Water treatment and disposal

Project Coming This Tuesday!!!

  • Making a Water Filter with simple materials

  • More information about the project will be given Tuesday after the quiz!

  • Performance based!

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