Learn More: Quality Assurance Codes

What does this mean?

Quality Assurance (QA) Codes are used to alert data users to the presence of anomalous conditions or caveats associated with a particular sampling event or value. Another term for QA codes is "data qualifiers". Some sample values in data that are downloaded from the Water Atlas may have been flagged with one or more of these codes. These codes, if present, are found in the "QACode" or "ValueQualifier" column of your download file.

How are the data collected? (Methods)

Most agencies that provide data to the Water Atlas use a standardized set of codes approved by the NELAC Institute, a national organization that certifies environmental labs. Non-NELAC-certified laboratories may use a different set of QA codes. The Water Management Districts and U.S. Geological Survey have their own QA codes for hydrologic and water quality data.

QA codes may be attached by the laboratory processing the sample material, either as a result of the lab processing itself or in response to information provided by the person who collected the sample being processed. Examples:

  • From lab: "The laboratory analysis was from an improperly preserved sample. The data may not be accurate."
  • From data collector: "Secchi disk visible to bottom of waterbody. The value reported is the depth of the waterbody at the location of the Secchi disk measurement."

QA codes may also be added to data by USF Water Institute staff during routine quality assurance checking of data, if an out-of-range value is detected. Data that has been flagged in this way is not removed from Water Atlas databases but is not displayed on water resource pages.


Caveats and Limitations