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

In this study, subindex formulations for key water quality parameters were developed and enhanced to incorporate water quality thresholds 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 (WLEB). The modified UMWQI model integrates water quality criteria and thresholds set forth by the United States Environmental Protection Agency (USEPA) and state-level environmental agencies, to improve the water quality status. Monthly average subindex values for total suspended solids (TSS) ranged between 33 and 80 (ranking from “poor” 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 “unsuitable for all uses” 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.