Fig. 1. True color image of Qingcaosha reservoir (composite from L8/OLI bands 4, 3, and 2) acquired on 12 February, 2017 by the Landsat-8 (row 118, path 38)

Fig. 2. Scatter plot of the measured and estimated SPM concentration (The black line is the 1∶1 line. The L8 images were acquired on 22 September, 2016 and 4 March, 2018). (a) SPM concentration measured in situ versus SPM estimated from the calibrated mode; (b) scatter plots of comparisons between L8/OLI measured SPM concentration in-situ and estimated concentration made within 24 h time window

Fig. 3. Average distribution of SPM concentration derived from 2013 to 2019. (a) Average distribution of SPM concentration obtained based on the L8/OLI inversion, in which three sections (labeled L, M and N) are used to analyze the SPM concentration distribution at different locations, L, M, and N represent the upper part, the middle part and the lower part, respectively, and the position of the inlet gate of the reservoir is marked as A; (b) corresponding standard deviation

Fig. 4. Spatial distributions of SPM concentration derived from 2013 to 2019 L8/OLI measurements. (a) Spatial distributions of maximum; (b) spatial distributions of minimum

Fig. 5. Comparison between mean SPM concentrations and standard deviation (STD) along the three sections, where mean SPM concentration and STD are derived from 2013 to 2019 L8/OLI measurements, and the grey areas represent the latitude ranges of the Qingcaosha reservoir

Fig. 6. Spatial distributions of SPM concentration derived from L8/OLI measurements. (a) January 23, 2015; (b) March 12, 2015; (c) August 24, 2016; (d) October 30, 2018

Fig. 7. SPM distribution at L, M and N sections, where different lines represent inversion values of L8/OLI SPM concentration at different time and the grey areas represent the latitude ranges of the Qingcaosha reservoir

Fig. 8. Comparison of SPM concentration in three sections based on 20 scenes L8/OLI estimation (the gray area represents the latitude range of Qingcaosha reservoir; from top to bottom, the sections are L, M and N, respectively)