Analysis of trends in groundwater quality across the conterminous United States for 2002–2021

This repository contains a reproducible data pipeline, implemented in R using the targets framework, that analyzes trends in groundwater quality across the conterminous United States for the period 2002–2021. The pipeline fetches monitoring well network data and constituent observations from USGS ScienceBase, formats and joins these observations with spatial information (well network centroids and hydrologic region boundaries), categorizes temporal trends by likelihood and network type, and computes composite groundwater quality scores using fuzzy logic methods and Wilcoxon-Pratt statistical tests. The analysis supports the Integrated Water Availability Assessments (IWAAs) National Water Availability Assessment, version 1b, Trends chapter.
The primary outputs of the pipeline are a suite of figures (in both SVG and PNG formats) including a graphical table of groundwater quality scores by constituent and aggregated region, trend maps showing spatial patterns of water quality change, mini-map matrices of constituent concentrations at monitoring sites, likert-style plots, and stacked bar charts of trend likelihood categories by constituent and well network type. Additionally, the pipeline produces summary CSV tables of trend statistics aggregated by hydrologic region, constituent, and likelihood category. These outputs are designed to communicate national-scale patterns in groundwater quality change for use in a USGS Professional Paper.