WQI Mapper

README


  1. DEP’s Water Quality Index (WQI) uses concentrations of 21 physicochemical parameters to index an overall score from 1-100 (poor-good). The results are based on how similar a site’s water quality is to water quality dominated by one of four major land use/covers, referred to as Sub-WQI (SWQI) scores. The lowest SWQI of the four is considered “most similar” and subsequently is used to drive the WQI score.


  1. Data are presented at 3 hierarchical levels. These levels represent a backward process or general deconstruction of the WQI to provide additional information:
    • Level I is at the parameter level, where we make relative inferences regarding each parameter based on ranges within the overall dataset (e.g., percentile, quartile) using the IPV. This first level is useful for communicating spatiotemporal change of individual parameters and determining which parameters are influencing the WQI score.
    • Level II is at the sample level, where the WQI and SWQI scores provide insight into stressors and easily communicate general water quality by indexed results. This level is useful for acute measures (or discrete snapshots) of stress that are influenced by sampling conditions.
    • Level III is at the site-year level. This level consolidates much of the variability associated with sampling conditions into a measure more appropriate for spatiotemporal trend analysis. Level III aggregation could also be useful for pre-/post-treatment studies or bracketed stressor studies (e.g., upstream and downstream of a landscape stressor).


  1. WQI Categorical scores are: Good >=80, Average 60-80, Fair 40-60, or Poor <=40.


  1. Data included in this version are collected through 2025-04-30.


  1. This document contains an interactive map of Level III (site-year) data.


Map - Level III