What Is the Most Accurate Water Quality Index for Stream Water Assessment: a Case of Five Headwater Streams in Bald Eagle State Forest

Elaine Langone Center, Terrace Room

Water quality index (WQI) uses many weighted, measurable parameters to give one number that reflects how good the water is. WQI is a standard approach to evaluate and compare results of different streams because of its concise form. The correct WQI expression for a specific stream can be challenging and requires a good stream water quality knowledge. In this study, five Penns Creek headwater streams in the Bald Eagle State Forrest, PA were selected and assessed with five different WQI to evaluate the specific expression that can be used for these streams. A set of water quality data from each stream was collected from June 2015 to July 2017, has been used and the correct expression was identified. Using different WQI expressions, revealed a range of values from 80 to 100 making it ranked between good and excellent quality. Since the WQI is meant for drinking water, the normalization factors of some of the parameters, pH, temperature, and Biochemical Oxygen Demand (BOD5), are excessively lowered. Due to the nature of the natural headwater characteristics, some parameters do not need to be assessed. Using this experimental site that is known to have a high water quality, with little to no human impact, the WQI has been rearranged taking in consideration the following factors: 1) the range of the pH has been expanded to more acidic and basic water 2) the range of temperature lowered for colder water 3) excess parameters, like BOD5 and ion concentration removed to lower cost of assessment.