Mediterranean ports feature complex layouts and exert important environmental pressures in squeezed coastal zones. They experience mild meteo-oceanographic conditions during part of the year, leading to water velocities that are close to the resolution limits of observation equipment. The paper addresses the challenge of characterising summer port hydrodynamics by designing intensive field campaigns, focused on hydrodynamic variables, such as harbour entrance fluxes. The approach was developed for three Spanish microtidal harbours with different domain sizes and one or two entrances. These elements play a key role in harbour exchanges through the entrance and the subsequent water renovation. The paper will present and discuss the meteocean data and inferred variables, such as renovation times, which is a key indicator of water quality. From this basis, the paper will discuss the changing estuarine circulation patterns and the role of upwelling and downwelling on observed water temperature peaks. The conclusions will address the role of harbour hydrodynamics in integrated coastal water quality and port engineering, particularly for ports’ environmental impacts on adjacent beaches. To assess the full hydrodynamic domain, forecasting models are helpful. The continuous observations presented in this work would also help in the implementation and validation of these models.
