Dynamics of the turbidity plume in the Guadalquivir estuary (SW Spain): a remote sensing approach

Estuarine environments are characterized by very complex and varied morphodynamics and are one of the most critical coastal zones for the exchange of sediment and pollutants. The fertilization role of the continental shelf of the Gulf of Cadiz (SW Iberian Peninsula) in which the estuary of the Guadalquivir and other rivers play an influential role, is the major factor determining the productivity of the basin and is the main source of sediment for the adjacent coast. The work presented here was undertaken to analyze the spatial and temporal (seasonal-to-annual) variability of the turbidity plume in relation to the meteorological and oceanographic processes controlling the plume. To achieve this goal, we have processed Moderate Resolution Imaging Spectroradiometer (MODIS) level L2 images covering a period of 8 years (2003 - 2010). Validation of at-sensor retrieval against in situ data was performed and showed good correlation; this demonstrates the potential of satellite synoptic observations as a powerful tool for operational monitoring of water quality within the region. The first preliminary results confirm that the development of the estuarine plume is mostly associated with the increase in river discharge during the rainy seasons (negative North Atlantic Oscillation index), and this, therefore, affects the seasonality of chlorophyll distribution. By the approach described here, turbidity patterns in the estuary have been successfully mapped; the incorporation of MODIS observations in the approach is recommended, since this should improve knowledge of both the physical oceanography and the marine biology aspects of the phenomenon studied. This approach has potential application to a wide variety of coastal research.