Oregon Water Quality Index Methodology

2001

Oregon Water Quality Index: A tool for Evaluating Water Quality Management Effectiveness. Journal of the American Water Resources Association (JAWRA) 37(1):125-137 PDF 2mb

The Oregon Water Quality Index (OWQI) is a single number that expresses water quality by integrating measurements of eight water quality variables (temperature, dissolved oxygen, biochemical oxygen demand, pH, ammonia+ nitrate nitrogen, total phosphorus, total solids, and fecal coliform). Its purpose is to provide a simple and concise method for expressing the ambient water quality of Oregon's streams. The index allows users to easily interpret data. The OWQI improves comprehension of general water quality issues, communicates water quality status, and illustrates the need for and effectiveness of protective practices

2002

Discussion of Oregon Water Quality Index: A Tool for Evaluating Water Quality Management Effectiveness. Journal of the American Water Resources Association (JAWRA) 38(1):313-314 PDF 2mb

This report discusses concerns raised by "Oregon Water Quality Index: A Tool for Evaluating Water Quality Management
 

Reply to Discussion of Oregon Water Quality Index: A Tool for Evaluating Water Quality Management Effectiveness. Journal of the American Water Resources Association (JAWRA) 38(1):315-318 PDF 2mb

This report is the author’s response to concerns raised by "Oregon Water Quality Index: A Tool for Evaluating Water Quality Management"
 

2005

Accommodating Change of Bacterial Indicators in Long Term Water Quality Datasets. Journal of the American Water Resources Association (JAWRA) 41(1):47-54 PDF

The State of Oregon adopted a water quality standard based on Escherichia coli (E. coli) in 1996. The objective of this study was to develop a regression relationship between fecal coliform and E. coli. This relationship would fill data gaps and extend water quality models and indicators. Water quality policy is better informed by the ability of these extended water quality models to determine whether water quality meets present or would have met past bacterial standards. This relationship also allowed for the development of an E. coli algorithm for the Oregon Water Quality Index (OWQI). This study showed that changes to OWQI values (as a result of changing bacterial indicators) were minimal, and corresponded to improved characterization of water quality with respect to pathogenic potential