The satellite derived optical information for the comparative assessment of lacustrine water quality

Abstract

The objective of this research is to define the support that can be derived from satellite optical remote sensing to monitor the trophic status of lake waters, even in the absence of corroborating in situ measurements. An analysis was conducted on Lake Garda (Italy), where sub-basins showing different water quality conditions can be delineated. For this purpose, two Landsat-TM images, taken in April and August 1985, at specific seasonal situations of the limnological cycle were used. Image processing provided radiance-derived quantities, such as reflectance and chromaticity, in the form of digital transects drawn from the margin of the lake to cross the pelagic environment. In order to make the multi-temporal analysis possible, a method for compensating the differential haze effect between the two images, based on the darkest object technique was adopted. Results demonstrated the suitability of satellite remote sensing observations as a fast and relatively low cost effective tool for early and expeditious assessment of both the spatial and temporal variability of lake water quality conditions.