**2.1 Early Warning System for sanitary risk: Hydrometeorological operational forecasted tool**

The outcome of the feasibility study carried out during the CapRadNet project [41] had shown that an Early Warning System (EWS) for the sanitary risk assessment could be set up operationally, given the existing relationship between discharge overflow and *E. coli* concentration increases in bivalves' harvested area, in the Pescara River mouth. In general, rainfall is the most referred environmental factor influencing microbial contamination in coasts and estuaries affected by stormwater runoff and long sea and shoreline outfalls [42–44]. Rainfall-induced contamination could persist in molluscs as much as 6 days after the rainfall event [45, 46], even if a shorter lag time (<3 days) has been reported in the literature [43, 47]. The differences are often associated with the hydrogeology of the catchment (i.e., concentration time) and residence times in the receiving water [46]. Being recognised as an important predictor of microbial contamination of bivalve harvesting areas [48], river flows are explicitly mentioned in the EU legislation on official controls of bivalve molluscs intended for human consumption. In the study proposed by Campos et al. [46], the highest levels of *E. coli* were detected when total rainfall exceeded 2 mm and water levels in the main tributaries exceeded the mean flow.

Few published studies have considered the contribution of river flows in informing official public health controls for bivalve mollusc fisheries [48, 49], but the scientific literature has shown that catchment-scale microbial dynamics determining bathing water compliance are often determined by hydrological events [50–52].
