QUAL2Kw – A Water Quality Modeling Tool for Rivers and Streams: A Review

The QUAL2Kw is a widely used one-dimensional water quality model designed for rivers and streams under steady-state flow conditions. This review critically assesses the input data requirements, applications, recent advancements, strengths, and limitations of the model. Numerous studies have used QUAL2Kw to model the impacts on water quality of both point and non-point pollution sources, to assess pollution load capacity, and to frame control strategies for water quality management of rivers and streams. Its flexible kinetic structure, genetic algorithm-based calibration, and compatibility with Microsoft Excel make it a preferred tool for researchers and policymakers. However, limitations such as the model’s steady-state flow assumption, simplified hydrodynamics, and challenges in representing temporal variability are also addressed. This paper provides an overview of recent enhancements and hybrid approaches that combine QUAL2Kw with other models and tools to enhance prediction accuracy and support informed decision-making. The review aims to enable users to understand the model’s compatibility and its various applications in achieving the sustainable management goal of river water sources.