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Quality Assurance Process for National Lakes Assessment Surface Water Quality Parameters
Citation:
Handler, A., K. Blocksom, A. Herlihy, A. Nahlik, AND A. Trebitz. Quality Assurance Process for National Lakes Assessment Surface Water Quality Parameters. U.S. Environmental Protection Agency, Washington, DC, 2025.
Impact/Purpose:
Reproducible and documented workflows for quality assuring data is key to scientific transparency. This code package provides an example of how water quality data from the National Lakes Assessment--part of the National Aquatic Resource Survey--are quality assured. The techniques used in this code package may serve as an example to agency partners such as states, tribes, and territories that have water quality monitoring programs and seeking guidance on quality assuring data.
Description:
The purpose of this code and resulting report is to provide a reproducible framework for quality assuring the National Lakes Assessment (NLA) surface water quality data. The data are inclusive of physical and chemical parameters as well as chlorophyll a. Data are evaluated for completeness and consistency while also providing an initial data quality check. The code includes checks for data completeness based on field logs, consistency in reporting units, consistency in data quality flags, checks for internal chemical validity, and provides a comprehensive set of bivariate plots to aid identifying data quality issues. The code produces a report in HTML format for interactive use and a tabular data file with all observations flagged by the process. The tabular file can then be used to annotate further investigations and follow-up actions, providing a record of the QA process. Additional background information on water quality validation is provided in the report appendix.
