The imperative for sustainable water resource management is growing in significance as a result of escalating environmental concerns and human activities. This study presents a thorough examination of approaches used to calculate the Water Quality Index (WQI) and how they are incorporated into the management of water resources. This text explores the development of WQI models, emphasising important progress and the incorporation of other water quality factors throughout the years. The article analyses the fundamental structure and operation of WQI, with a focus on the significance of parameter selection, weight assignments, and their mathematical representations. Additionally, it examines the integration of Multi-Criteria Decision Making (MCDM) methods to improve the precision and dependability of Water Quality Indices (WQIs). Analysing various approaches for Water Quality Index (WQI) is done to comprehend the differences and similarities across different geographical regions. The paper highlights the potential of sophisticated technologies, such as artificial intelligence (AI) and the Internet of Things (IoT), in strengthening assessments of water quality index (WQI). It also offers future research paths aimed at refining these models to effectively address a wide range of environmental situations.