Water Quality

Let's recap what we have covered in this chapter -- water is amazing, mostly because it can dissolve and transport other substances. Water is moving and changing states constantly. Only a very small amount of water on Earth is freshwater, and that water is exposed to all types of other substances based on the use of land in the watershed where it runs -- some of which might be helpful, some of which may be harmful.

So the next big question is how we determine the health or quality of water -- water quality.

photo by Will Parson/ Chesapeake Bay Program
photo by Will Parson/ Chesapeake Bay Program

Water Quality Testing

Water quality describes the condition of the water you're assessing, based on biological, physical, and chemical characteristics. 


We can assess the biological quality of a body of water by observing and using tools to answer a few questions:

  • What is living in this water? What does this tell us about the health of the water?
  • Is there suitable habitat for living things?
  • Are there any harmful bacteria or algae in the water?
  • What are the nutrient levels (nitrogen & phosphorus) in the water?


We can assess the physical quality of water by observing and using tools to answer these questions:

  • How much salt is in the water?
  • What is the color of the water?
  • How clear is the water?
  • What is the temperature of the water?
  • Does the water have a smell or odor?


Finally, we can use chemical tests to identify substances in the water and determine if they are harmful. A few chemical tests we would do include:

  • pH (acidic or basic water)
  • Dissolved Oxygen
  • Harmful metals like lead or mercury
  • Other harmful chemicals
watering can

Water Quality & Uses

The 'quality' of water, or the acceptable levels of some of the contaminants we may find in our water quality testing, will depend on what the water is being used for. For example, the water that we use to irrigate our garden does not have to be as clean as the water we want to drink. But it's important to know the quality of water we are swimming in, fishing in, and where our drinking water is coming from.

What are our uses of water and threats to water quality?