Supplemental Materials for Report titled 'Evaluating water quality condition and updating monitoring strategies for the Buffalo National River'

Grantz, Erin; Haggard, Brian; Hodges, Shawn; Rodman, Ashley; Lafrancois, Brenda

This supplementary document provides an in-depth technical appendix to a comprehensive water quality and trend analysis of the Buffalo National River (BUFF) and its tributaries. It presents detailed land use and land cover data for the watershed, integrating information from the National Land Cover Database to contextualize environmental conditions. The document outlines rigorous workflows for unifying, merging, and standardizing nutrient data from multiple sources (EPA WQP, NPS, ADEQ), addressing challenges such as redundant characteristic names, inconsistent units, and ambiguous abbreviations. Translation keys and merging strategies are provided to ensure data comparability across agencies and time periods. Extensive annotated R code is included to support data cleaning, summary statistics, trend analysis (both flow-adjusted and non-flow-adjusted), and power analysis. The statistical methods are tailored for handling censored data, seasonal effects, and site-specific variability, enabling reproducibility and adaptation by other researchers. Large tables present summary statistics (e.g., median, mean, standard deviation, detection frequency) for water quality variables at each monitoring site, covering both the full period (2000–2019) and the most recent five years. Trend analysis results, using linear regression, Mann-Kendall, and seasonal Kendall tests, highlight sites and variables with significant changes over time. Power analysis tables estimate the statistical power to detect various rates of change in water quality variables under different sampling intervals and monitoring durations, informing the reliability of trend detection across the monitoring network. For each major site, narrative summaries synthesize data availability, observed trends, and notable findings, supported by time series plots and flow-adjusted analyses. Overall, this document enhances transparency in data processing, statistical methodology, and site-level interpretations, serving as a robust resource for long-term water quality monitoring and management in the Buffalo National River watershed.