Water is a vital component for life on Earth and is a crucial natural resource for environmental survival. In India, water quality modeling research is conducted in various ecosystems, including freshwater to marine environments. Examples of such studies include the Tehri reservoir, Chilka lake, Oatcake in Kashmir, Kodaikanal lake, Ooty lake in Tamil Nadu, the rivers Ganges, Narmada, and Kaveri, and coastal regions such as the Hoogly estuary, Paradip, Vishakhapatnam, Kakinada, Chennai, Mangalore coast, Konkan coast, and Gujarat coast. Water quality modeling is of significant importance in water quality studies, and numerical models must be properly calibrated and applied to improve our understanding of the intricate interactions between various parameters, such as temperature, biological oxygen demand, dissolved oxygen, salinity, and eutrophication, in both freshwater and seawater environments.

1. Introduction 2. Water Quality Modeling: Basics 3. Modeling: Processes and Development 4. Modeling: Applications 5. Modeling: Methodologies 6. Modeling: Rivers and Streams 7. Modeling: Coastal and Estuaries 8. Modeling: Lakes and Reservoirs 9. Modeling: Oceans and seas 10. Water Quality Modeling: BOD and DO 11. Salinity and Temperature Modeling 12. Nitrogen and Phosphorus Modeling 13. Eutrophication Modeling 14. Oil Spill Modeling 15. Tsunami Modeling 16. Littoral Drift modeling 17. An Ecohydrology Model 18. Commercially Available Models