Bathing Water Quality Forecast for Chennai Coastal Waters

Risks associated with the non-compliance of bathing water quality have been increasing and becoming a challenge to maintain and manage the coastal waters. Especially, along the coastal cities, the complex nature of sources and their variation due to diverse urban runoff, industrial discharges, port activities and fluxes from different sources are deteriorating the coastal water quality which directly affects the health of beach goers, tourist, coastal communities. The Environment (Protection) Rules, 1986 has classified the seawater, class-II criteria for bathing, contact water sports and commercial fishing for Indian coastal waters. Chennai, one of the largest coastal metropolitan cities with a population of 4.65 million, is a major industrial hub having unsafe coastal waters. It's water quality faces toxic and dangerous deterioration due to domestic and industrial wastes. This paper presents an integrated modelling and forecast system developed for Chennai coastal waters through data assimilation using in situ water quality data, deterministic hydrological, hydrodynamic and water quality models. The coupled hydrodynamic-water quality model with input from catchment hydrology solves transport and dispersion of pollutants along the flow pattern. Forcing parameters were downscaled from global models to input to the local domain. 5-day forecast of sea surface temperature (SST), salinity, dissolved oxygen (DO), biological oxygen demand (BOD) and coliform are generated with confidence from validation. This predictive model and forecasting is helpful to beach managers and policy makers for better management.