Deriving Water Quality Parameters Using Sentinel-2 Imagery in the Sado Estuary (Portugal)

BUIGUINO, B.; SENT, G.; FAVARETO, L.; CRUZ, J.; SA, C.; DOGLIOTTI, A.I.; PALMA, C.; BROTAS, V.; BRITO, A.C.

Conferencia; CERF 2021; 2021

Over the past few decades, satellite remote sensingtechniques have increasingly been used to support environmental monitoringmainly because of their cost-effectiveness and spatio-temporal resolution. Oneof the most recent and useful tools for this type of analysis is Sentinel-2, ahigh-resolution satellite recently launched. Althoughdesigned for landapplications, some of its wavebands can be used for water applications.Its 10 mspatial resolutionmakes it particularly useful for detectinghigh spatial variationsin marine environments, as estuaries. Therefore, the present study aimed to evaluatethe potential of using Sentinel-2 observations for water quality monitoring in theSado estuary, a low inflow estuary on the west coast of Portugal. An algorithmintercomparison exercise and timeseries analysis of different water qualityparameters was performed (i.e., Colored Dissolved Organic Matter (CDOM),Chlorophyll-a(Chl-a), Suspended Particulate Matter (SPM), andturbidity) considering the period 2018–2020. Results suggest that Sentinel-2 isuseful for monitoring these parameters, however, retrieving accurate data forsome of the variables, such as Chl-a, showed to be more challenging. Spatio-temporal variabilityresults were consistent with historical data, presenting the highest values ofCDOM, Chl-a, SPM and turbidity during Spring and Summer. Moreover, it isconcluded that there is a high potential for using remote sensing methodologiesfor continuous water quality monitoring in transitional systems under the scopeof the European Water Framework Directive. This study also allowed to detect dredgingactivities conducted in the estuary, which can be potentially used to assessthe effect of such works on the quality of the water in the region.This is thefirst study in the Sado Estuary to provide an integrated water qualityassessment based on satellite high spatial resolution (10 m) data, thus representinga key contribution forthe definition of effective monitoring programs.