Hydrodynamic simulation of river water quality dynamics

Excessive water use and improper waste disposal are significantly degrading water quality, posing risks of rendering water sources unsuitable for future use. The field/lab and remote sensing-based methods of water quality assessment have their own advantages and disadvantages. The hydrodynamic (HD) models are primarily used for flood simulations, however, with their present capabilities one can overcome the limitations of water quality assessment in a river system. This study investigates a 63 km stretch of the Subarnarekha River in India, between Ghatshila in Jharkhand and Jamsholaghat in Odisha, where industrial effluents and agricultural runoff are the primary pollution sources. A one-dimensional (1D) unsteady HD model integrated with a water quality module was setup to simulate pollutant transport and dispersion along this river stretch. In the initial phase, i.e., river flow simulation, the model yielded an excellent result during both calibration (RMSE < 1 m in stage and 191.33 m 3 /s in discharge) and validation (RMSE = 0.53 m in stage and 218.29 m 3 /s in discharge). The model effectively simulated seven key water quality parameters- Biochemical Oxygen Demand, turbidity, water temperature, dissolved oxygen, total solids, nitrate, and phosphate concentrations. The simulated water temperature, nitrate concentration and turbidity were highly concurrent to the observed with coefficient of determination of 0.62, 0.72, and 0.72, respectively; depicting the model’s robustness. This approach may provide a near-real-world representation of pollutant behaviour and flow interactions within the river, offering critical insights into the spatiotemporal dynamics of water quality. The findings support enhanced decision-making for sustainable water resource management and pollution control strategies.