Spatio-temporal variability analysis of the Douro River plume through MERIS data for one hydrological year

The main objective of this study was to analyze the spatial and temporal variation of the Douro river plume (DRP) dimension, for one hydrological year, based on image segmentation of MERIS data and to modeling the plume dimension based on different environmental parameters that should be related to the DRP. The adopted methodology consisted in the development/implementation of an algorithm based on region growing approach, to automatically select the region seed and the threshold values for each image. In this algorithm two options may be used to select the seed and the threshold values. In order to relate the DRP dimension with several environmental parameters, the Douro river discharges (water flows), tide level and wind speed values were computed. The parameter that most directly influences DRP dimension is water flows. A seasonal study was also performed, considering summer and winter periods separately. The best results were obtained for the winter period with a correlation coefficient of 0.45. The plume derived from MERIS data represents DRP only when the river flow exceeds a certain threshold. Only considered the data with a corresponded water flows higher than 300 m(3)/s, a positive correlation of 0.74 was found between the DRP and water flows.