The application of PlanetScope imagery to map out the trophic state of Cirata Reservoir, West Java']Java

Cirata Reservoir is one of the cascade dams in the Citarum Watershed located in three regencies of West Bandung, Cianjur, and Purwakarta. Surface water condition of the Cirata Reservoir is occupied by floating net cages, thus the waste from those activities could affect its trophic state. The purpose of this study is to assess the ability of PlanetScope imagery to map out trophic state parameters and trophic state condition during the rainy season using the Trophic State Index (TSI) method by Carlson (1977). The Carlson's TSI parameter contains water transparency (Secchi depth) chlorophyll-a, and total phosphorus based on the empirical formula generated from the regression model between image bands with field survey data. Results of the analysis showed that water transparency is strongly correlated with the red band (R-2 = 0.60) with an accuracy level of 77.51-81.62%. Chlorophyll-a is strongly correlated with green band (R-2 = 0.71) with an accuracy level of 34.69-58.31%, and the total phosphorus is strongly correlated with red band (R-2 = 0.65) with an accuracy level of -66.71-5.11%. The result of the three parameters combination reveals that the trophic state of Cirata Reservoir is in the medium eutrophic to hypereutrophic with the largest distribution in the heavy eutrophic class. The results of the accuracy-test indicated that the PlanetScope imagery is able to be used to estimate the parameters of water transparency and chlorophyll-a, whereas the total phosphorus parameter got low accuracy.