Freshwater
 • Since 70% of Earth’s freshwater is frozen in ice, we 
  split the remaining usable freshwater into two 
  categories:  groundwater and surface water.
 • Surface water is found in lakes, streams, and rivers, 
  while groundwater is found underground in aquifers.
 • Both forms are replenished by the water cycle 
  through precipitation, however, runof water will feed 
  lakes, rivers, and their tributaries (streams that flow 
  into rivers) while water that infiltrates and drips 
  through the ground will feed the aquifers there.
     Freshwater continued…..
  • As the runoff flows over land it can pick up 
   pollutants and other materials that negatively 
   affect its quality.
  • Groundwater on the other hand, is filtered as 
   it drips through the many layers of rock that 
   lead to the aquifer.
        Water Quality
 • Because both freshwater and saltwater resources 
  are so vital to living things on Earth, it is important 
  that we maintain their quality by keeping them 
  clean.
 • In general, water quality refers to the cleanliness of 
  water and is determine by looking at a variety of 
  physical and chemical factors.
 • For example, the health of a river system is best 
  judged by nitrate levels and turbidity while a lake 
  used for freshwater, is assessed by temperature and 
  pH.
     Water Quality continued…..
 • In the United States, the Environmental Protection Agency 
  (EPA) is responsible for regulating the quality of natural 
  resources such as air and water by setting limits on the 90 
  most common pollutants and contaminants since excessive 
  amounts of tem are considered dangerous to our health.
 • Physical aspects of water quality include its temperature, 
  turbidity (how cloudy the water is), and rate of water 
  movement. 
 • Even though living things can survive in a range of 
  temperatures, aquatic animals generally need to be in cooler 
  water because at warmer temperatures, the water contains 
  less dissolved oxygen and other nutrients which are needed 
  to support them.
    Water Quality continued……
 • Because the increased temperature can kill off or 
  force the migration of a species away from the area, 
  the entire ecosystem can easily become unstable or 
  collapse. 
 • Water with higher turbidity is cloudier because there 
  are more solids and sediments suspended in it.
 • Since many of these solids come from pollutants, 
  lower turbidity is better for most living things.
 • This cloudiness can also prevent sunlight from getting 
  into the water reducing the amount of photosynthesis 
  present.