Making up a mere .2% of the world’s freshwater supply, streams hold an important role in our ecosystems. All 3.5 million miles of rivers and streams that stretch across the U.S. vary in temperature, turbidity, biodiversity and overall quality of the water. These variables not only affect the specific body of water, but influence all the streams and rivers that are connected to it. Since each river or stream ultimately flows into an adjoining one, water further upstream will influence the water downstream. Therefore, should there be any contamination upstream, it will ultimately end up in the larger body of water. The farther downstream one looks to assess water quality, the more contamination is present as water is constantly picking up rocks and sediment as it flows from upstream to downstream. The photo below visualizes the relationship between a large body of water and those that flow into it. This collection of connected rivers and streams is called a watershed. The depressions and formations that are visible in the picture show the impact that streams have on geography as well, for the flow of water cuts into the rock and soil of the earth; molding and reforming as it continuously flows across it. Rivers also provide a habitat for many organisms, transfer nutrients and help to drain rainwater. However, although streams have such a large scaled impact, it is still easy to see the varied qualities of them in a stream in your own backyard (Nature Works) (United States Environmental Protection Agency) (“Rivers and Streams: Biological Indicators of Watershed Health).
Since streams hold such an important role in our ecosystems, it is important to assess and potentially control the varied quality of these bodies of water. There are many factors that can affect water quality, both natural and human influenced. Therefore, it is always difficult to pinpoint the cause of contamination. However, in 1991, the EPA issued the Clean Water Act, which ensured that biological assessments of bodies of water would incorporate not only observing the organisms living in the water but collecting the physical and chemical properties of the water as well. This therefore assesses all possible influencers of water quality (“Using Biological Data as Indicators of Water Quality”).

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Biological indicators are always assessed when testing water quality. These indicators include the fish, plants, algae, bacteria and insects that are present in the body of water. The number and health of these organisms indicates the overall health of the stream because certain organisms thrive only at certain qualities of water (“Using Biological Data as Indicators of Water Quality”).

To assess physical characteristics of a body of water, one would start by measuring the stream flow, which is the amount of water that moves past a specific point during an interval of time. The swiftness of the stream has a direct relationship with the volume of water in the stream; as volume increases, stream speed will increase as well. This speed will determine the kinds of organisms that can live there, as some prefer fast moving water and some thrive in calm areas, and will also affect the concentration of silt or sediment that is able to settle in water. If the stream is slow moving, sediment will easily settle to the floor. But in swift waters, sediment will be kept suspended in the water. In order to determine stream flow, dimensions such as width and depth will have to be calculated. However, the velocity of the water can also easily be affected by factors such as day-to-day weather and seasonal fluctuations (“Stream Flow”).

The temperature of the water is another important chemical characteristic to measure as it is affected by a variety of factors and can be influential in the dissolved oxygen levels, photosynthesis rate and the types of organisms present in the water. If outside sources cause an increase of temperature in a body of water, this is considered thermal pollution. Often, in local streams, this affects small cold-water fish as water often runs off of hot, black asphalt into the stream. Temperature change also affects dissolved oxygen levels as cooler water can hold more oxygen than warmer water. Dissolved oxygen represents the concentration of oxygen that is present in the water. Should the temperature of the water increase, oxygen levels will decrease; preventing aquatic organisms from thriving and in some cases killing them. In warmer waters the rate of photosynthesis also decreases, depleting the health and stability of the organisms in this body of water (“Temperature”)(“How to Determine the Health of Our Waters”)(“DO”).

The conductivity of the water is also measured when assessing water quality. The conductivity of a water sample expresses how easily an electric current can pass through it and is dependent on the number of charged particles in the water. Conductivity of a body of water is measured with instruments that measure the concentration of dissolved solids such as nitrate, sulfate chloride, magnesium, sodium and calcium. However, conductivity can also be affected by temperature. Warmer water will have higher conductivity and cooler water will have lower conductivity. Therefore, should a body of water have high conductivity, one could assume that this water is at least somewhat polluted with potential dangerous chemicals, as this is water that individuals use in their everyday lives (“Conductivity”).

Since solids, both suspended in water and dissolved, affect water quality they are also included in the assessment of water quality. Dissolved solids are those that can pass through a filter, such as calcium, sodium bicarbonate, nitrogen, phosphorus, iron, sulfur and a variety of other ions. Suspended solids cannot pass through a filter and can include sediment, plankton, industrial waste and sewage. When testing, one may take a sample of water and evaporate off the water, in order to leave behind the solids. Determining the weight of this residue can give you the amount of residue per specified volume of water. Should this concentration be too high, the habitat can be severely affected by pollution and water balance issues, but low concentrations can also cause problems as well because nitrogen and phosphorus are essential dissolved solids to an aquatic habitat for the natural growth of algae and organic material (“Total Solids”) (“Nitrates”) (“Phosphates”).

The pH of the water is also tested to determine quality, as it measures how acidic or basic the water is. Ranging from 0 to 14, with 0 being most acidic and 14 being most basic, streams on average have a pH of 7. In streams, it is typical to find higher pH’s downstream than upstream, as contamination concentration increases as water flows downstream (“pH”).

The final test that one must perform when assessing a body of water is simply the act of observation. Should a stream have a turbid, off-color or murky appearance, such as the one in the picture below, it is a clear indicator that pollution is present. Also looking at the surrounding area to determine if aspects of it could be an influence to the health of the stream. For instance, streams near industrial areas may be negatively affected by the pollutants that are deposited (“How to Determine the Health of Our Waters”).

In order to engage in the assessment of streams and understand the affects that outside factors can have on water quality, the class visited Ridley Creek State Park. Stretching over 2,606 acres of Delaware County, Pennsylvania, Ridley Creek State Park serves as an excellent site for hiking, running, and fishing. It includes only one stream, Ridley Creek, and consists of gently rolling hills. The source of Ridley Creek is located at Frazer in Chester County and its mouth empties into the Delaware River (“Chester-Ridley-Crum Watershed Association”).

In our visit to Ridley Creek, classes collected data from three points along the stream: Gradyville, Sycamore and Yale Dam. The purpose of this was to compare and contrast the types of organisms present, and the physical and chemical characteristics of each site. In our testing, we also found that Sycamore had an average pH of 8.11, meaning that it is slightly above neutral, but should not cause any concern regarding the quality of the water (“pH”). We also tested for the stream flow, which was found to be on average .598 m/s. This is a slightly moderate flow and this site therefore would be expected to have a moderate concentration of dissolved oxygen. Faster moving water also allows for any pollution in the water, to quickly be diluted. This is much more advantageous in comparison to slow moving streams, where pollution has time to affect the ecosystem for the long term. Stream depth is an influential factor to water velocity, as deeper streams will have a more difficult time pushing large amounts of water quickly. At Sycamore, the depth was calculated to be on average 37.83 cm. This indicates that the stream was not very deep, and correlates with our data on stream flow (“Steam Flow”). The temperature of the water was on average 17.4°C. Being a fairly cool temperature, this indicates that dissolved oxygen levels must be high, allowing the water to sustain a healthy ecosystem. In relation to the temperature of the water, the dissolved oxygen level was tested to be on average 9.96 mg/L. This is consistent with our temperature data, as this is considered a healthy level of dissolved oxygen for the ecosystem (“Temperature”). Lastly, we tested the turbidity of the water, by seeing how deep we could clearly see a specific object. The object could still be seen past a meter, and therefore, the stream is very clear and would be considered healthy.

In addition to these physical and chemical characteristics, we also looked at the organisms present in the water. In looking for organisms, we used many different kinds of methods of collection. One was picking up loose rocks and examining the bottom for any organisms because many will grip onto the rock in fast running water. Also, we used square-shaped screens held under the water as we kicked dirt and rocks toward it. This would push any organisms burrowed into the ground onto the screen, and would also collect any small organisms that were riding the current of the stream. When analyzing the organisms found at a site, it is important to know the tolerance to pollution that that organism has. Knowing this will be a helpful indicator of the water quality. The graph below shows the number of Caddisflies, Mayflies, Stoneflies and Water pennies found at each site. The graph shows these organisms as a set because all of these organisms are considered to be intolerant to polluted water, therefore they will only thrive in cleaner waters (“Taxonomic Key to Benthic Macroinvertebrates”). On average, Yale dam had consistently lower numbers of these intolerant organisms present. Therefore, one can deduce that its water quality is worse than that of Sycamore and Gradyville because these intolerant organisms can simply not thrive in the waters’ condition.

In reflection of all of the different types of variables collected to assess water quality, Sycamore can be considered as a clean body of water. This is an appropriate conclusion not only because of the pollution intolerant organisms that thrive in it, but also because of its fast moving stream flow and cool water temperature. However, further downstream, the water quality may be greatly affected by the minor quality effectors that had little influence over the water quality of the Sycamore site. This is seen in the Yale Dam site, which had little presence of pollution intolerant organisms, conveying that this body of water was affected by pollution.

  • Bazelak, Danielle. “Conductivity.” Bio161ffall2012. Widener University, 29 009 2012. Web. Web. 7 Oct. 2012. .
  • Cenophat, Andrew. “Nitrates.” Bio161ffall2012. Widener University, 26 009 2012. Web. Web. 7 Oct. 2012. .
  • “Ridley Creek Watershed.” Chester-Ridley-Crum Watershed Association. Chester-Ridley-Crum Watershed Association, 2006. Web. 7 Oct 2012. .
  • Englert, Brianna. “Total Solids.” Bio161ffall2012. Widener University, 25 009 2012. Web. Web. 7 Oct. 2012. .
  • Gilette, Nicole. “Temperature” Bio161ffall2012. Widener University, 09/26/2012. Web. 10/7/2012.
  • Henderson, Robert. “pH.” Bio161ffall2012. Widener University, 26 009 2012. Web. Web. 7 Oct. 2012. .
  • Henderson, Robert. “Phosphates.” Bio161ffall2012. Widener University, 26 009 2012. Web. Web. 7 Oct. 2012. .
  • “How to Determine the Health of our Waters.” United States Environmental Protection Agency. Environmental Protection Agency, 2012. Web. 7 Oct 2012. .
  • McLaughlin, Maria. “DO” Bio161ffall2012. Widener University. October 26, 2012. Web. 7 Oct 2012.
  • “Rivers and Streams: Biological Indicators of Watershed Health.” United States Environmental Protection Agency. Environmental Protection Agency, 2012. Web. 7 Oct 2012.
  • “Rivers and Streams.” Nature Works. New Hampshire Public Television, 2012. Web. 7 Oct 2012. .
  • “Rivers and Streams.” United States Environmental Protection Agency. Environmental Protection Agency, 2012. Web. 7 Oct 2012. .
  • “Stream Flow.” United States Environmental Protection Agency. Environmental Protection Agency, 2012. Web. 7 Oct 2012. .
  • “Taxonomic Key to Benthic Macroinvertebrates.” Hoosier Riverwatch. Hoosier Riverwatch, n.d. Web. 28 Oct 2012. .
  • “Using Biological Data As Indicators of Water Quality.” United States Environmental Protection Agency. Environmental Protection Agency, 2012. Web. 7 Oct 2012. .