Ranking tributaries for setting remediation priorities in a TMDL context

• Published in: Chemosphere (Oxford) Vol. 71; no. 10; pp. 1895 - 1908
• Main Author: Stringfellow, William T.
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 01.05.2008; Elsevier
• Subjects: Animal, plant and microbial ecology; Applied ecology; Biological and medical sciences; California; Carbon - analysis; Chemometric; Chlorophyll - analysis; Diffuse pollution; Ecotoxicology, biological effects of pollution; Environmental Monitoring; Environmental Restoration and Remediation - classification; Eutrophication; Freshwater; Fundamental and applied biological sciences. Psychology; General aspects; Geographic Information Systems; Marine and brackish environment; Nephelometry and Turbidimetry; Nitrates - analysis; Phosphates - analysis; Quaternary Ammonium Compounds - analysis; Rivers; Statistics, Nonparametric; TMDL; Water Pollutants - analysis; Water quality index; Wilcoxon–Mann–Whitney; California; USA, California, San Joaquin R; USA, California; USA, California, Central Valley; Diffuse pollution; Chemometric; Wilcoxon–Mann–Whitney; Water quality index; TMDL; Eutrophication; Rank statistic; Decontamination; Wilcoxon-Mann-Whitney; Priority; Trophic status; Water pollution; Chemometrics
• ISSN: 0045-6535; 1879-1298
• DOI: 10.1016/j.chemosphere.2008.01.040

The San Joaquin River (SJR) in the Central Valley of California has been designated an impaired waterbody based on its loss of fisheries-related beneficial uses and the river is now subject to regulation under total maximum daily load (TMDL) rules. For impaired waterbodies, numeric standards alone may not be sufficient to establish remediation priorities and priorities must be established by comparing drainages to each other. Data collected as part of regional water quality (WQ) studies in the SJR Valley were not normally distributed, so nonparametric methods based on ranking were used to compare the WQ of individual tributaries and drainages. Normalized rank means (NRMs) were calculated from ranked data and NRMs were mapped to identify priority drainages for WQ improvement activities. NRMs for individual parameters were combined into indexes that are useful for examining the relative importance of different drainages for multiple parameters simultaneously. Indexes were developed for eutrophication and overall WQ. This ranking approach is being proposed as an easily understood, transparent, and scientifically rigorous method to assess the relative WQ impact of individual drainages and set watershed remediation priorities.