Ž . The Science of the Total Environment 268 2001 1929 Detecting chlorophyll, Secchi disk depth and surface temperature in a sub-alpine lake using Landsat imagery Claudia Giardino  , Monica Pepe, Pietro Alessandro Brivio, Paolo Ghezzi, Eugenio Zilioli National Research Council-Remote Sensing Department, Via Bassini 15, I-20133 Milan, Italy Abstract Some bio-physical parameters, such as chlorophyll a concentration, Secchi disk depth and water surface tempera- Ž . Ž . ture were mapped in the sub-alpine Lake Iseo Italy using Landsat Thematic Mapper TM data acquired on the 7 March 1997. In order to adequately investigate the water-leaving radiance, TM data were atmospherically corrected using a partially image-based method, and the atmospheric transmittance was measured in synchrony with the satellite passage. An empirical approach of relating atmospherically corrected TM spectral reflectance values to in situ measurements, collected during the satellite data acquisition, was used. The models developed were used to map the chlorophyll concentration and Secchi disk depth throughout the lake. Both models gave high determination Ž 2 2 . coefficients R 0.99 for chlorophyll and R 0.85 for the Secchi disk and the spatial distribution of chlorophyll concentration and Secchi disk depth was mapped with contour intervals of 1 mgm 3 and 1 m, respectively. A scene-independent procedure was used to derive the surface temperature of the lake from the TM data with a root mean square error of 0.3°C.  2001 Elsevier Science B.V. All rights reserved. Keywords: Thematic mapper; Water quality parameters; Mapping 1. Introduction Lakes are valuable water resources and are  Corresponding author. Tel.: 39-02-23699-457; fax: 39- 02-23699-300. Ž . E-mail address: claudia@irrs.mi.cnr.it C. Giardino . used for fishing, transport, agriculture, industry, recreation and tourism. Today, the water quality of a number of lakes around the world is so low that it is unrecoverable by natural means of purification. Local industrial developments and population increases have affected lake ecosys- tems and, hence, their water quality. In the future we are going to need more and more high quality 0048-969701$ - see front matter  2001 Elsevier Science B.V. All rights reserved. Ž . PII: S 0 0 4 8 - 9 6 9 7 00 00692-6