Monitoring of reservoir CDOM degradation process by remote sensing of its surface waters signal

Abstract

Many remote sensing studies have been conducted to estimate the chromophoric dissolved organic matter (CDOM) concentrations of inland waters, but never have yet been conducted the CDOM degradation rates analyse its yearly variations. This, limits our understanding of the organic matter process that occurs in inland waters and thus the carbon cycle. With the aim of improving the knowledge of CDOM degradation rates and times, a total of 45 field samples were used to conduct this study. Twenty-three samples were used for the calibration process and other twenty-two for validation, obtaining a R2 of 0.87 and an RRMSE of 13%. Finally, all samples were used to obtain a more robust algorithm. The CDOM degradation rates calculated for reservoirs in the summer period, with a hydraulic residence time of 30–40 days, were in agreement with the rates obtained in laboratory experiments, whereas with higher residence times other autochthonous or allochthonous factors began to have influence. Annual variations in the CDOM degradation rate exhibited the maximum value in spring, simply because more degradable CDOM was present in springtime water, and the minimum values in autumn and winter, with less light degradation and the increased entry of more recalcitrant allochthonous CDOM, a result coinciding with those of other studies using laboratory experiments.