Time-Series Model, Statistical Methods, and Software Documentation for R–QWTREND—An R Package for Analyzing Trends in Stream-Water Quality

Open-File Report 2020-1014
Prepared in cooperation with the International Joint Commission, North Dakota Department of Environmental Quality, and Minnesota Pollution Control Agency
By:  and 

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Abstract

As part of a U.S. Geological Survey water-quality study started in 2018, in cooperation with the International Joint Commission, North Dakota Department of Environmental Quality, and Minnesota Pollution Control Agency, a publicly available software package called R–QWTREND was developed for analyzing trends in stream-water quality. The R–QWTREND package is a collection of functions written in R, an open source language and a general environment for statistical computing and graphics. The package uses a parametric time-series model to express logarithmically transformed concentration in terms of flow-related variability, trend, and serially correlated model errors. Flow-related variability captures natural variability in concentration on the basis of concurrent and antecedent streamflow. The trend identifies systematic changes in concentration in terms of potential step trends, piecewise monotonic trends, or user-specified trends. Maximum likelihood estimation is used to estimate model parameters and determine the best-fit trend model. This report describes the time-series model and statistical methodology behind R–QWTREND and provides formal documentation for installing and using the package.

Suggested Citation

Vecchia, A.V., and Nustad, R.A., 2020, Time-series model, statistical methods, and software documentation for R–QWTREND—An R package for analyzing trends in stream-water quality: U.S. Geological Survey Open-File Report 2020–1014, 51 p., https://doi.org/10.3133/ofr20201014.

ISSN: 2331-1258 (online)

Table of Contents

  • Acknowledgments
  • Abstract
  • Introduction
  • Purpose and Scope
  • Time-Series Model
  • Statistical Methods
  • R–QWTREND Software Documentation
  • Summary
  • References Cited
  • Appendix 1 R–QWTREND Software Package

Additional publication details

Publication type Report
Publication Subtype USGS Numbered Series
Title Time-series model, statistical methods, and software documentation for R–QWTREND—An R package for analyzing trends in stream-water quality
Series title Open-File Report
Series number 2020-1014
DOI 10.3133/ofr20201014
Year Published 2020
Language English
Publisher U.S. Geological Survey
Publisher location Reston, VA
Contributing office(s) Dakota Water Science Center
Description Report: viii, 52 p.; Appendix; Dataset
Online Only (Y/N) Y
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