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Water Quality

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Is your drinking water safe? Is this lake safe for swimming? You can answer these questions by investigating the quality of the water in the surface source. Join other "Citizen Scientists" to study the quality of the surface water in a given area. Are you ready to jump in?

Planning and Carrying Out Investigations

Water Quality Brochure

Water Quality Brochure

What are surface waters?

Surface water is any body of water that has an opening at the surface of ground level. Rivers, lakes, and ponds are all examples of surface water. Ground water does not have an access point directly to the surface of the land. However, many ground water supplies are connected to surface water. For instance, much of the Florida aquifer has above ground connection points in the forms of springs and rivers where the underground river appears at surface level.

How does temperature affect water quality?

Temperature affects the quality of water quality primarily through its impact on the concentration of the oxygen dissolved in the water. As the temperature increases, the concentration of the dissolved oxygen in water decreases. High water temperatures have resulted in many fish kills in water due to the decrease in oxygen levels in the water. Large-scale fish kills rarely occur during the winter months because the oxygen levels in water are typically higher during cold weather.

How does pH affect water quality?

Aquatic organisms function within narrow pH levels. A pH of 7 is considered to be neutral. Most surface waters have a pH between 6 and 8. Trout, bass, and perch thrive in a pH that is slightly acidic. However, when the pH drops below 4, the fish are stressed and can die. Fish eggs and young fish are particularly susceptible to extreme pH values.

How does the phosphate level affect water quality?

Phosphorus in the form of phosphates is required for plant and animal growth. Phosphates primarily enter surface water through animal and human waste, fertilizers, and cleaning products. However, levels of phosphates higher than normal can lead to uncontrolled growth of plants which can "choke" the aquatic environment. The rapid plant growth is followed by rapid plant death. The natural decomposers in the surface waters cannot keep up with the large-scale plant death and undecomposed material builds up in the water and ages the body of water unnaturally.

How does the nitrogen level affect water quality?

Plants and animals require nitrogen for proper growth. Nitrogen takes many forms in aquatic environments including ammonia, nitrates, and nitrites. Fertilizers, pesticides, and human and animal wastes are the largest contributors of nitrogen to surface waters. Though plants and animals need nitrogen, large concentrations of these different forms of nitrogen in surface waters can be toxic to aquatic organisms.

How does the bacteria level affect water quality?

Fecal coliform bacteria are dangerous bacteria that exist in surface waters. Improper water treatment, septic tanks, and animal and human waste are major ways that these bacteria enter the water. People can get infections and illnesses as a result of exposure to fecal coliform bacteria. High bacteria levels can also decrease the amount of dissolved oxygen in the water, which can lead to fish kills.

How does the dissolved oxygen concentration affect water quality?

Fish and other aquatic organisms require oxygen in the water to undergo respiration. As the oxygen concentration in water increases, the rate of respiration in fish decreases since they have to breathe less frequently to take in the required amount of oxygen. The concentration of dissolved oxygen in water is closely associated with the water temperature. As the temperature of the water increases, the concentration of dissolved oxygen in water decreases. The amount of bacteria in the water can also directly impact the amount of oxygen in the water.

How does the contour of the land affect water quality?

Water tends to run downhill. As the rainwater runs over the land in its downhill movement, materials on the land are moved downward with the water. Particulates and dissolved pollutants can be moved to the surface water that collects precipitation as it moves down the contour. The steeper and less porous the ground, the more pollutants will be moved down into the surface water collection areas since the precipitation has less time to soak into the land.
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Assessment Question 8 Figure