Monitoring water quality in the coastal area of Tripoli (Lebanon) using high-resolution satellite data

Water quality in the coastal area of Tripoli (Lebanon) was assessed using Landsat 7 ETM+ data, to provide a first baseline for coastal resources management. The data were geometrically rectified to a standard geographical grid and brightness values were converted to reflectance through radiometric correction. Sea-truth data, collected in the field within 6 hours before/after the time of the satellite overpass, were used to derive empirical algorithms for chlorophyll-a concentration, Secchi disk depth and turbidity. Then, maps of the distribution of the selected water quality parameters were generated for the entire area of interest, and compared with analogous results obtained from SeaWiFS data. The maps indicate that the Tripoli coastal area is exposed to moderate eutrophic conditions, along most of its shoreline (in particular along the northern stretch), in correspondence with fluvial and wastewater runoff sources. The Landsat 7 ETM+ data proved useful for the intended application, and will be used to start a national database on water quality in the Lebanese coastal environment.