Conductivity as a Function of Location –

Posted by 26 May, 2013

Hypothesis: Does the time of year affect the conductivity of stagnant water in a given location? Abstract: We decided to test the conductivity levels of the water at Flat Rock Brook. If the conductivity levels are higher, it might imply higher total dissolved solid levels. We would like to see if the conductivity level changes during seasons with snowfall versus seasons without snowfall. Background:

  • Independent Variable: Time of Year (Season)
  • Independent Variable: Location
  • Dependent Variable: Conductivity Level (mg/L TDS)

The purpose of the experiment is to test the change in conductivity level throughout the year (on a seasonal basis) in various locations. While doing this experiment, it is important to keep in mind these three things:

  1. How does conductivity vary at any of the given sites during a given season.(1)
  2. What human influence might have an impact on the conductivity of the water at any given part of the year.(1)
  3. Why might this change affect the ability of organisms to live in the given test sites.(1)

This is important to Flat Rock Brook because the data could be used to do several things. For example, the change in conductivity may change the organic life in the water, thus changing the ability to safely drink it. The change may impact the ability of organisms to grow in the water, and it may change the reactive nature of the water. Conductivity can be measured by the total dissolved solids in the water. Total Dissolves Solids include the number of mineral and salt impurities in the water. (1) Ultimately, the number of minerals and salts determines how many ions in mg/L. The impurities in the water can include runoff from roads, wastewater from industrial plants, and soils and rocks. (1) The amount of total dissolved solids in the water can have a physiological effect on plants and animals living in the ponds. (2) Conductivity can be used as a way of noting changes in water conditions over short periods of time. (2) Also, the level of total dissolved solvents in water can have an effect of the ability of habitat-forming plants to grow, thus disrupting the presence of certain species. (2) Materials:

  • GPS Navigator by Magellan: We used the GPS as a way to mark off specific testing sites at McFadden’s Pond and Quarry Pond, in order to test in a precise and consistent location
  • pH/Conductivity Probe: We used the pH/Conductivity Probe to test the level of conductivity in the various locations. The conductivity was measured in mg/L (TDS), and microsiemens (µS), but due to the difficult nature of working with microsiemens, we chose to work primarily with mg/L(TDS).
  • Distilled Water: We used the distilled water to wash off the probe in between tests in order to maintain accurate readings without tainted results.
  • Map of Flat Rock Brook: We used the map of Flat Rock Brook in order to find locations from which we could test conductivity levels of water.
  • Vernier conductivity probe used with a Lab Pro interface: We used this for our May data in order to get a more accurate reading. By taking samples from Flat Rock Brook, we connected this probe to Logger Pro and recorded the conductivity which was also measured in TDS. NOTE: We used the conductivity data from these readings in our graphs and overall analysis because it provided a more accurate measurement













Methods: *Adapted from Electrical Conductivity Protocol Used by University Corporation for Atmospheric Research, Colorado State University, and NASA. (Water Temperature was not recorded.)

  • Record water temperature
  • Pour water sample into two containers (or measure in water body)
  • Rinse electrodes with distilled water, blot dry
  • Place meter in first container, 2-3 seconds
  • Remove meter, shake gently, and place in second

container, 1 minute (Do not rinse with distilled water)

  • Record value when stabilized
  • Repeat measurement with new sample water, twice
  • Average three measurements and check for accuracy

Original Protocol can be found at this link*:


Cleaning off the conductivity probe before testing the water. (Figure 2)


Testing the conductivity of the pond (Figure 3)


Results: Fall (November) : -Quarry Pond:

  • .9 mg/L

-McFadden’s Pond (site A)*:

  • 3.1 mg/L

-McFadden’s Pond (site B)*:

  • 3.05 mg/L

Spring (May): (with ph/conductivity probe) -Quarry Pond:

  • .83 mg/L

-McFadden’s Pond (Site A):

  • 2.95 mg/L

-McFadden’s Pond (Site B):

  • 2.02 mg/L

Spring (May): (LoggerPro Data) -Quarry Pond:

  • .8 mg/L

-McFadden’s Pond (Site A):

  • 3.1 mg/L

-McFadden’s Pond (Site B):

  • 2.1 mg/L

Data Graph for Quarry Pond (Figure 4)

Data Graph for McFadden’s Pond Site A (Figure 5)

Data Graph for McFadden’s Pond Site B (Figure 6)

Data Graph for all three locations (Figure 7)


Discussion: Throughout our research, there was a general shift in the conductivity level in each site we tested. At Quarry Pond, the total dissolved solids reduced from .9 mg/L to .8 mg/L from November to May. This shift can be seen in the graph shown in Figure 4. McFadden’s Pond Site B also showed a substantial shift between the November and May readings, from 3.05 mg/L to 2.1 mg/L, as seen in Figure 6. Despite these significant changes, Site A at McFadden’s Pond did not change. This could potentially be due to its close proximity to moving water. A subtle, unnoticed under-current may have existed which may have caused the water to be mixed, and therefore diluted. The figures for this measurement can be seen in Figure 5.

The changes in conductivity at Quarry Pond may be the result of runoff from the parking lot and the roads in close proximity to it. Quarry Pond, unlike the other locations was close enough to a road that run-off affects the level of total dissolved solids. Although there was a significant change in conductivity between readings, the total dissolved solids were much lower than that of McFadden’s Pond. This may explain why the presence of algae was much higher in Quarry Pond than in McFadden’s Pond. McFadden’s Pond’s conductivity may have been higher due to a larger level of mineral deposits from soil runoff. One possible explanation for this shift in conductivity is the dilution of total dissolved solids in pond water due to rainfall and melting water from snow.

Conclusion: When comparing conductivity of water at a given point of time during the year, it is clear that there are noticeable differences. During the Fall and Winter, when there is more soil and road runoff, the conductivity level is higher. Conversely, during the spring, when there is more rainwater and melted snow and ice to dilute the ponds, the conductivity level drops. This would suggest that during fall and winter, the conditions of the pond are noticeably different. This suggests the possibility that there may be a shift in population from one group of organisms to another on a seasonal basis. Knowledge of these changes may help to explain why animals would migrate to a different habitat during different seasons. Because of the nature of soil runoff and road runoff, the level of Total Dissolved Solids in the water changes on a seasonal basis, and with that, the conductivity changes as well. In conclusion, conductivity does change over time of year in stagnant water, primarily because of external conditions such as runoff and wastewater.


(1)The GLOBE Program, “Electrical Conductivity Protocol.” Hydro-Electrical Conductivity. Ed. UCAR, Colorado State University, NASA.


We used the Power Point file linked to this page as our primary source of background information as well as a standard protocol for our field tests.

(2)Conductivity And Water Quality.

<[[|<span]] We used this website as our second source of data for finding out environmental impacts of change in conductivity and overall water quality. (Note: No Author, Publisher or Editor could be found for this web page.) __ *Site A is to the right of Mystery Bridge *Site B is to the left of Mystery Bridge *Note, this protocol was implemented both in the field and in a lab dependent on the time the data was collected *If the web page is difficult to view, a link to a .ppt file is available at the top of the page. The protocol can be found on slide #12.

Study authors: Margot Bennett and Rob Schwartz

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