A framework for assessing the adequacy of Water Quality Index - Quantifying parameter sensitivity and uncertainties...

Area of Science:

• Environmental Science
• Water Resource Management
• Analytical Chemistry

Background:

• Water quality monitoring is crucial for water resource management but is resource-intensive, particularly for developing nations.
• Traditional Water Quality Indices (WQI) summarize water quality but lack comprehensive assessment of their utility, flexibility, and practicality.
• Existing WQI frameworks have limitations in handling missing data and adapting to local water quality conditions.

Purpose of the Study:

• To introduce an adjusted Water Quality Index (WQI_ADJUSTED) framework to effectively manage missing data and utilize available information.
• To develop a Sub-WQI for addressing specific local water quality conditions.
• To establish a novel procedure for assessing WQI adequacy through sensitivity analysis and uncertainty quantification of missing parameter values.

Main Methods:

• Development of an adjusted WQI (WQI_ADJUSTED) incorporating a method for handling missing values.
• Comparison of WQI results derived from Multivariate Linear Regression (WQI_MLR) and Principal Component Analysis (WQI_PCA) for parameter optimization.
• Application of Monte Carlo probabilistic simulation to optimize sampling frequency based on user-defined acceptable WQI change.

Main Results:

• WQI_MLR demonstrated superior performance in explaining general water quality compared to WQI_PCA for weighted parameters.
• Optimized sampling frequency for the Johor River Basin suggests approximately 130 samples are needed for a 2% acceptable change in WQI.
• Total coliform was identified as the most sensitive parameter to missing values in the Johor River Basin study.

Conclusions:

• The proposed WQI_ADJUSTED framework enhances WQI development by effectively handling missing data and improving information utilization.
• The developed methodology provides a robust approach for assessing WQI adequacy and optimizing monitoring strategies.
• The case study in the Johor River Basin highlights the practical application of the framework for effective water resource management.