A Method for Assessing and Predicting Water Quality Status for Improved Decision-Making and Management

Valeria Mijares, Purdue University


With the increasing population and demand for water, it is crucial to be able to assess its quality on a real-time basis and for predictive purposes. Water-quality Indices (WQIs) provide a means by which the water quality can be compared across space and time based on a composite indicator. Index and subindex values can be used to flag contaminants of concern, guide prioritization of management efforts, and for predictive purposes. In this study, subindex formulations for key water quality parameters were developed and enhanced to incorporate water quality targets and criteria. The enhanced subindex formulations were built into the Unweighted Multiplicative Water Quality Index (UMWQI) and tested for suitability, with a focus on the Western Lake Erie Basin. The proposed UMWQI model integrates water quality criteria and targets set forth by the USEPA and state environmental agencies, in order to improve the water quality status of the WLEB tributaries. Monthly average subindex values for total suspended solids (TSS) ranged between 33 and 80 (ranking from "fair" to "very good"), those for total phosphorus ranged between 31 and 73 (ranking "poor" to "good"), while those for soluble reactive phosphorus ranged between 13 and 78 (ranking "poor" to "good"). Overall index values ranged from 35 to 80 throughout the basin, indicating that water quality in the basin is generally "poor" to "good", consistent with existing literature and water quality reports. Of the four sites that were being assessed, the River Raisin site tended to have the highest annual overall water quality index (cleanest system), with the Tiffin and Blanchard sites ranking the worst. All four sites had soluble reactive phosphorus as the worst ranking determinant, indicating that this is the determinant of greatest concern, also consistent with existing literature. Results indicated that UMWQI and associated subindices as developed were suitable for use within the WLEB. Methodologies and approaches developed are applicable in other areas experiencing similar concerns




Gitau, Purdue University.

Subject Area

Natural Resource Management|Environmental engineering

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