Search

The role of environmental forcings on the fecal contamination dynamics in small coastal streams was investigated, using the Aljezur coastal stream (Portugal) as a test case. An integrated modeling approach, combining hydrological and coupled hydrodynamic-fecal indicator bacteria models, was applied to selected scenarios of relevant forcings, on the basis of previously calibrated and validated model applications. The forcings investigated included: tides, winds, waves, atmospheric pressure, bathymetry, river flow, and upstream fecal bacteria concentrations; this study targeted the characterization of the relative importance of these factors on the fecal contamination dynamics, to enhance our understanding of small coastal streams water quality dynamics. Results highlight distinct patterns for dry and wet periods. Fecal bacteria transport is mainly forced by tidal propagation, in dry periods; and by freshwater flows, during wet periods. The analysis reveals a complex hydraulic and water quality dynamic resulting from the interactions between the environmental forcings and strongly dependent on their relative strength. This analysis can be extrapolated for systems with a similar balance between the environmental factors. [ABSTRACT FROM AUTHOR]

Wet weather urban discharges are responsible for bathing water contamination. The proposal for a revised EU Directive concerning the quality of bathing water imposes significantly more stringent requirements for the management of bathing water quality, with particularly important repercussions on beaches subjected to short-term pollution incidents. The paper reviews the aspects from EU legislation most directly related to the problem of wet-weather discharges, placing special emphasis on the recent revision process of the Directive on bathing water quality, and evaluates the benefits of some potential solutions based on continuous modelling of a combined sewer system. Increasing the sewer system storage capacity or the STP hydraulic capacity may substantially reduce the untreated discharge volumes, but spill frequency reductions under 2 to 3 spill days per bathing season will hardly be achieved. Results show the severe strains that local rainfall patterns would place on compliance with the Commission's proposal for a revised Directive and highlight the importance of the changes introduced in the amended proposal recently approved by the Council, making it less prescriptive if adequate measures are adopted to prevent bathers' exposure to short-term pollution incidents. [ABSTRACT FROM AUTHOR]