Maintaining or increasing SOC concentration is fundamental for reducing the effects of global warming and increasing soil productivity. In this paper, a method based on Landsat 8 OLI products was developed for qualitatively monitoring in the Lake Valencia basin (Venezuela) the dynamic of SOC concentration between the years 2013 to 2018. The developed method uses the Green (B3), NIR (B5) and SW1 (B6) bands of Landsat 8 OLI sensor for detecting changes in the spectral signatures of bare soils that indicate possible variations in their concentrations of SOC. It was found that for the study period, the Lake Valencia basin soils do not present spectral features of significant variation in SOC concentration. An area of 8.61Km2 (0.3% of the study area) was identified as a zone with a possible reduction of SOC concentration. In case of insufficient data for developing remote sensing based predictive models, the proposed method allows qualitatively monitoring and categorizing the dynamic of SOC concentration and identifying areas with spectral features of a possible variation in SOC concentration.

Lake Valencia is the second most important natural freshwater basin in Venezuela. The expansion of industrial and agricultural activities and population growth over the past four decades has accelerated the process of eutrophication of the lake waters at such a rapid rate that it cannot be compensated by natural processes at present. Continuous monitoring of the trophic state of the lake, including remote sensing, is mandatory for collection of hydrobiological information, which allows developing effective strategies for monitoring and improving the quality of the lake's waters. Development and validation of a model for estimating the concentration of A-chlorophyll and the trophic state of Lake Valencia through the visible and near-infrared spectrum engaged multispectral satellite images Landsat 8 OLI in the present study. The results of measuring A-chlorophyll concentration at four sampling stations conducted in 2011 were also used. The proposed model showed a positive correlation of r 2 = 0.77 for the study conditions. A-chlorophyll concentration was estimated using a grid of 778 points located within the perimeter of the lake and on the basis of the proposed model. The Achlorophyll concentration increased by 11.48% from 2013 to 2019. The eutrophic state of Lake Valencia, characterized by TSI = 68.238 at the date of the last monitoring (20 February 2019), was confirmed.