The application of remote sensing technology to water quality monitoring has special significance for lake management at regional scale. Water clarity expressed in terms of Secchi disk transparency (SDT) is a highly useful indicator of trophic status and ecosystem health. In this study, we related Landsat TM and ETM+ data with ground observations to develop a model for the estimation of SDT which can be used as a standardized procedure for regional-scale lake clarity assessment in the central region of Argentina. Samples were taken from two reservoirs of the region. Pearson correlation coefficients and step-wise multiple regression analysis were used to evaluate correlation between Landsat bands and measured SDT. Results suggested that Landsat band 3 plus the ratio 1/3 was a consistent and reliable predictor of SDT (R2 = 0.80). The algorithm was validated (R2 = 0.81) and applied to the November 10, 2010 ETM+ image obtaining a map that characterized water clarity of reservoirs within the study area. The procedure presented here could become a low cost measurement tool for water management authorities and decision-makers, obtaining simpler and practical results for regional water clarity monitoring.

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