The Science of the Total Environment 196 (1997) 229-245 The satellite derived optical information for the comparative assessment of lacustrine water quality E. Zilioli *, P.A. Brivio CNR-IRRS Telerilevamento, 56 Via Amp&e, 20131 Milano, Italy Received 2 October 1996; accepted 20 November 1996 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), wheresub-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 techniquewas adopted. Results demonstrated the suitability of satellite remote sensing observations as a fast and relatively low cost effective tool for early and expeditiousassessment of both the spatial and temporal variability of lake water quality conditions. 0 1997Elsevier Science B.V. Keywords: Satellite data; Optical remote sensing; Limnology; Eutrophication 1. Introduction The quality of most freshwater systems in the world is continuously decreasing due both to sus- pended particulate materials originating from soil erosion and to anthropogenic eutrophication phe- nomena. Lakes and reservoirs, in particular, rep- resent major freshwater resources from several __.__ * Corresponding author. points of view: water supply, aesthetic, economic and scientific. The implementation of methods for the monitoring and proper management of lakes becomes a priority in order to prevent pollution and loss of beneficial uses and to ensure that future generations can benefit from an unspoilt resource. The aim of this study is to verify current satel- lite remote sensing capabilities, in particular Landsat-TM data, for the detection of even the 004%9697/97/%17.00 0 1997 Elsevier Science B.V. All rights reserved. PII SOO48-9697(96)0541 l-3