Water Systems and Quality

10.0 Getting Started

The St. Lawrence River serves as a highway to the world, stretching over 3000 km from the Great Lakes to the Atlantic Ocean, passing through Ontario and Quebec.
It has supported human life for thousands of years, from First Nations to European settlers.
Millions of people live near the river, with large cities, factories, and industrial areas along its banks.
Many depend on the river for drinking water.
In the 1950s, canals and locks were constructed to allow large freighters to navigate safely between the river and the Great Lakes, overcoming rapids and shallow areas.
Over the past century, high pollution levels have affected the river due to human activities like oil spills and chemical waste dumping.
The beluga whale population is affected by the river's pollution, with high levels of toxins like mercury and lead found in their bodies.
Scientists believe the whales are ingesting contaminated food, such as eels polluted by industrial waste from the Great Lakes and upper river.
Efforts have been ongoing for nearly two decades to help the beluga population recover by addressing the pollution problem.

D3 Quick Lab: Would You Drink It?

This lab demonstrates that diluting pollutants in large bodies of water does not solve the pollution problem.
The lab involves diluting cornstarch in water across multiple test tubes and observing color variations after adding iodine solution.
Iodine turns purple in the presence of starch. The varying color intensities in the test tubes indicate different concentrations of cornstarch.
The activity emphasizes that even diluted toxic substances would still make water unsafe to drink.

10.1 Earth's Supply of Water

Water exists on Earth in three states: liquid, solid, and gas, constantly changing in a cycle.
About 70% of the planet is covered with water, mostly salt water in oceans.
Fresh water exists on the surface, under the surface, and in the atmosphere.
A watershed is an area where all water drains into one main water body.
The concentration of dissolved salts in ocean water averages 3.5 percent, while fresh water contains less than 1 percent.
Salinity refers to the amount of salt dissolved in water.
97% of the Earth’s water is salt water, while only 3% is fresh water.
Most of the fresh water is stored as ice and snow or found underground.

Three States of Water

Water exists as liquid, solid (ice), and gas (water vapor).
Adding heat to liquid water causes evaporation (to gas), while removing heat causes freezing (to solid).

Liquid Water

Liquid water is found both above and below the ground.
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Surface Water

Oceans are massive bodies of surface salt water, averaging 3.2 km in depth and acting as the planet's water reservoirs.
Surface fresh water is common in rivers, streams, lakes, ponds, and wetlands.
Fresh water is also collected in human-made reservoirs, such as artificial lakes and water towers, replenished by precipitation.

Underground Water

More of Canada's fresh water exists underground than on the surface; scientists estimate that one-third of the world's fresh water lies underground.
Rainwater soaks into the soil and flows downward until it reaches an impermeable layer of rock or clay.
The groundwater zone is the area where water fills all air spaces in the soil and cracks in the rock.
The water table is the upper surface of the groundwater zone.
Aquifers are underground freshwater reservoirs where large amounts of water collect.
Rural homes and small farms often drill wells into aquifers to obtain fresh water.
Ground water moves slowly and eventually reaches a wetland, river, lake, or ocean, or it flows to the surface as a natural spring.
An oasis forms where ground water reaches the surface in a desert.

Solid Water

All solid (frozen) water on Earth is fresh water.
Salt water requires a lower temperature to freeze than fresh water (average freezing temperature for ocean water is -1.8^{\circ}C).
Ocean ice becomes frozen fresh water because the salt does not freeze with the water.
Most fresh water exists as ice and snow in Earth's polar regions and on the tops of high mountains. Glaciers and ice sheets contain more than 40 \text{ million } km^3 of frozen fresh water.
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Mountain Glaciers

In mountain regions, snow accumulates and compacts over centuries, turning into a solid mass of ice.
A glacier is a mass of ice and overlying snow that moves slowly down a mountain slope due to gravity.

Ice Sheets

An ice sheet is a particularly large glacier that covers the land, with only two existing on Earth: one in Greenland and one in Antarctica.
The term polar icecap is sometimes used to refer to these big ice masses at the poles.
The Antarctic ice sheet has an average thickness of more than 2 km.
Ice shelves are floating ice that may form when an ice sheet reaches the ocean.
Icebergs are large sections of an ice shelf that break off and float, eventually melting and becoming part of the ocean water.

Gaseous Water

Water exists in a gaseous state as water vapor in the atmosphere, formed through evaporation from oceans, lakes, and rivers.
Warm air can hold more water vapor than cold air, leading to humidity.
As water vapor rises, it cools and condenses into water droplets, forming clouds.
Plants release water vapor through transpiration, and animals exhale water vapor during respiration.

The Cycling Nature of Water

Water on Earth is always changing state; about 5 L of every 100,000 L cycles into another state at any given moment.
The water cycle involves processes such as freezing, melting, and evaporation.
The Sun provides the thermal energy that drives the water cycle.

Watersheds

A watershed is an area of land where all the water eventually drains into one main water body, such as a stream, river, wetland, lake, or ocean.
Activities that affect water in one part of the watershed have an effect downstream.
North America has five ocean watersheds: Arctic, Atlantic, Gulf of Mexico, Hudson Bay, and Pacific.
High points in the land, such as mountain ridges, create natural divides that direct water flow.
The Rocky Mountains act as a divide and are often referred to as the Great or Continental Divide.

10.2 Water's Influence on Weather and Climate

Water has a higher heat capacity than land or air, heating up more slowly but staying warm longer.
Oceans and large lakes moderate the air temperature of coastal areas, keeping them warmer in winter and cooler in summer compared to inland areas.
The interaction of large water surfaces and the atmosphere can produce severe storms.

How Water Moderates Air Temperature

Large bodies of water moderate atmospheric temperatures and climate in nearby regions, preventing extreme temperatures.
Earth is surrounded by an atmosphere that absorbs heat from the Sun.

Heat Capacity

Water has a higher heat capacity than air or land, meaning it takes longer to heat up and cool down.

Moderation in Action

During the day and in summer, land heats up faster than water, causing cooler air from the water to blow in, maintaining lower temperatures in coastal areas.
At night and in winter, the air over land cools faster, and warmth from the water provides heat to the cooler land.

Water Bodies and Regional Climate

The presence of large water bodies is a major contributor to climate differences from region to region.
The Great Lakes moderate temperatures and provide moisture to the air, resulting in heavy snowfalls in some areas.

Microclimates

Farmers near the Great Lakes experience longer frost-free periods due to warmer air from the lakes.
A microclimate is a small, localized climate variation that differs from the larger climate area around it.

10.3 The Effects of Ice on Water Systems

The global climate has undergone natural periods of cooling and warming, affecting the size of glaciers and ice sheets.
Changes in the size of glaciers and ice sheets influence local and global water systems.

Factors Affecting Mountain Glaciers and Ice Sheets

Glaciers form where temperatures are below freezing, and precipitation falls as snow, building up over time.
Rising temperatures and changing precipitation patterns cause glaciers to shrink.
Receding or retreating occurs when glaciers get smaller in size.

Weather's Effects on Ice

Glaciers undergo short periods of shrinking or growing due to normal seasonal weather variations.

Climate's Effects on Ice

Glaciers have been receding at a steady rate, and Arctic ice is melting, reflecting a warming trend.
Human activities that increase carbon dioxide and other gases in the atmosphere contribute to rising temperatures through the greenhouse effect.
The greenhouse effect traps heat above the Earth's surface.
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How Ice Changes Affect Water Systems

When glaciers and ice sheets increase in size, less water is available in oceans, atmosphere, and other water systems.
Ice sheet expansion lowers sea levels; during the last expansion, sea levels were more than 100 m lower.
Shrinking glaciers release frozen water in liquid and gaseous states, adding fresh water to streams, rivers, and lakes, diluting the salinity of ocean water.

11.1 Natural and Human Factors Affecting Our Water Supply

Natural occurrences such as flooding, droughts, and earthquakes can cause changes in the height of the water table.
Overuse of wells has the potential to alter groundwater supplies permanently.
How much water we take from our environment and how we alter it before disposing of it can affect both the supply and the quality of water.

The Rising and Falling Water Table

If more water leaves a watershed than enters it, a shortage will result, causing water levels in lakes and rivers to drop.
On the other hand, if more water fills a watershed than can leave it, flooding may occur.
Flooding may not only damage property but also cause drinking water to become contaminated.

Natural Water Table Changes

Floods, droughts, and earthquakes are natural occurrences that affect water supply.

Flooding

Flooding can be brought on by heavy rainfall, ice-jams, sudden spring thaws, and storms.
Flash floods are floods that come without much warning and are caused by heavy, concentrated rainfall such as the kind you would see during a thunderstorm.

Drought

Droughts are long periods of little or no precipitation, causing a watershed to gradually lose water.
Communities must restrict water use during these drought periods.

Earthquakes

In earthquake-prone areas, scientists have noticed a drop in the water table by as much as 1 m after a quake.
A disruption in the water table can also cause ground water to become cloudy, affecting its potability.

Human Causes of Water Table Changes

Human activities can also affect the water supply.

Overuse of Wells

More than 25 percent of Canadians rely on ground water for their water needs.
Overuse of wells can deplete underground aquifers, often for long periods.

Farming and Industry Practices

Many large-scale farms and industries need immense quantities of water in their operations.
After the water is used, it is discharged back into the environment.
Often, the water that is put back is not as clean as it was when it was taken out of the environment.
Examples of large-scale water use include crop irrigation, power generation other than hydroelectric, and industries such as pulp and paper production and mining.

Water Diversion and Export

The bottled water industry also removes large quantities of water from our water supply.
If more water is removed than replaced, the height of the water table will be affected.

11.2 Obtaining Water Quality

Water quality can be affected by physical, biological, or chemical contaminants.
We obtain the water we need from underground and aboveground sources.
Water that is removed from our water systems must be treated and tested before it is safe to drink.

Factors Affecting Water Quality

Whatever human activities or natural events affect the water systems in your watershed will affect the water that reaches your home.
Contaminants are contents that are harmful to humans, other animals, and the environment.

Types of Contaminants

biological: both visible (such as zebra mussels) and microscopic organisms (such as bacteria and viruses)
chemical: dissolved substances that come from natural processes (such as dissolving limestone) or human activity (such as dissolved road salt)
physical: all materials that do not dissolve in water (such as animal waste and plant debris)

Treating Groundwater Sources

For the many Canadians who get their water from a well, the water is usually filtered before drinking to remove contaminants.

Treating Aboveground Water Sources

We generally cannot drink the water as it exists in our freshwater systems.
The water from aboveground water sources needs to be treated before it becomes drinking water.
Boiling water before drinking it will kill harmful organisms, but it will not remove chemical or physical contaminants.

The Water Treatment Plant

A first stage in the treatment process is to pass the raw water through extremely fine membrane filters to remove contaminants.
The filters are so fine that they can remove an organism called Giardia, which causes an illness called "beaver fever."

Basic Treatment Stages

Water comes into the system through screens that filter out large solids (such as plastic bottles and litter), plants, and fish.
Water is pumped into a large holding tank where a chemical is added to make small solids clump together and settle to the bottom.
Water is passed through a special membrane filter to take out any remaining tiny solids. Instead of a membrane filtration system, some cities use filters made of gravel, fine sand, and charcoal.
Chlorine, a disinfectant, is added to kill any microorganisms that have not been removed by filtering alone. Also at this stage, some facilities add fluoride, a chemical used to prevent tooth decay.
The drinkable water is pumped out to storage sites such as water towers and underground reservoirs. Pipes from these storage sites distribute the water to all the businesses and homes in the community.

Testing Water Quality

Water samples from treatment plants are sent to scientists in laboratories to test. In larger communities, the tests might be done inside the water treatment plant itself.
Drinking water samples are also taken from sites that receive the processed water, such as hospitals and schools.
Water is tested for biological, chemical, and physical contaminants, and results are compared with government standards for safe limits.