Quality Assurance/Quality Control

Water Quality QA/QC

As part of an existing long-term monitoring project, citizen scientists measured dissolved oxygen, water temperature, and Secchi depth at locations in several stream, river, and estuary sites. Starting in 2003, a data logger and sensor were installed at the river site to record data at 15 minute intervals. The citizen science sampling at that river location continued to 2009.

A poster with further analysis is being presented at the National Water Monitoring Conference, April 28 - May 1, 2014. The poster will be available here after the conference presentation.

Key Results

  • Water temperature differences were very small (mean .03 degrees C) suggesting well mixed river water since the volunteer samples were from a bucket collected near the surface and the automated sensor was .3 m above the bottom at a depth of approximately 1.5 m.
  • Air temperature differences revealed an occasional erroneous use of Fahrenheit instead of Celsius that could be easily identified and corrected but one outlier (out of 98 comparisons) could not be explained.
  • Comparison of dissolved oxygen percent saturation showed the greatest variability with a larger than desired 95% confidence interval. Further analysis was performed to investigate this variability. There was no consistent pattern over time that would suggest instrument calibration issues. There was no apparent seasonality to the differences. There were apparent differences attributable to who was doing the manual sample. An improvement in mean difference and standard deviation was detected after the replacement of the DO meter, especially after allowing time for volunteers to learn and apply the revised DO measurement procedures.
  • Salinity and pH differences were explainable by the difference in the manual and automated procedures. The automated sensor for salinity reported to 2 decimal places while the handheld meter used by the volunteers only provided one decimal place. The automated pH values were accurate to .1 pH while the volunteers used color test strips. However, there was a mean difference of .7 pH meaning the volunteer-read surface pH was lower than the automated values.

2014 poster will appear here after the conference.