Streams contribution on bathing water quality after rainfall events in Costa do Estoril- a tool to implement an alert system for bathing water quality

VIEGAS , C., NUNES , S., FERNANDES , R., NEVES , R., 2009. Streams contribution on bathing water quality after rainfall events in Costa do Estoril- a tool to implement an alert system for the bathing water quality, SI 56 (Proceedings of the 10th International Coastal Symposium), pg – pg. Lisbon, Portugal, ISBN Bathing waters of Costa do Estoril are located near urban and rural areas, crossed by streams discharging into the sea/estuary. In order to evaluate the contribution of these streams on bathing water quality after rainfall events, a monitoring program financed by SANEST, SA was established. The final aim of this work is to be able to provide bathing water quality information from the automatic monitoring of water levels in streams. To achieve this goal, the relationship between water level, flow and contamination must be determined. The monitoring program included sampling of water quality indicators (e.g faecal coliforms) in streams and beaches, water level and discharge measurements in streams and the implementation of models capable of explaining local trends, and ultimately forecast hydrodynamics and water quality. Also, automatic hydrometric stations were installed in Marianas and Sassoeiros streams. These stations automatically measure water level and send real–time alerts to a central workstation when the water level rises above predetermined values. In addition, currents along the beaches were measured using acoustic profilers. These data provide a better comprehension of local hydrodynamics and information to validate models. Results show correlation between water level and flow that allow estimating stream outflow from water level. Numerical predictions were made using MOHID Water Modelling System. Simulations using measured stream discharge show that the model can accurately simulate dispersion and evolution of the streams plume and bathing water quality.