Water Trophic Status Mapping of Tecto-Volcanic Maninjau Lake during Algae Bloom using Landsat 8 OLI Satellite Imagery

摘要

Maninjau Lake is a tecto-volcanic lake that benefit its surrounding in various aspect, so it is necessary to preserve the quality of this lake. The objectives of this study were 1) Mapping out the concentration of chlorophyll-a, total phosphorus and transparency of Maninjau Lake through analysis of Landsat-8 OLI image and field survey, 2) Identifiying trophic status of Maninjau Lake using Carlson method through Landsat-8 OLI and surveys; and 3) Mapping the trophic status of Maninjau Lake using Landsat-8 OLI image analysis. Identification of trophic status are conducted using the TSI Carlson. The parameters used to determine the Carlson TSI are chlorophyll-a, total phosphorus, and Secchi Disk Transparency (SDT). The Carlson TSI parameter are modeled from Landsat 8 OLI image using stepwise regression. The variables that fulfill the prerequisite of stepwise regression is band 4 that strongly correlated with SDT data (R² = 0.82). Band 5 and 6 ratios are also strongly correlated with a-chlorophyll data (R² = 0.64). Band ratios of 3,4 and 5 are strongly correlated with total phosphorus data (R² = 0.46). The TSI Carlson mapping results show that Maninjau Lake is in a light eutrophic to hypereutrophic position with the largest distribution being heavy eutrophic. The estimated error standard (SE) SDT was 0.2 m with 74,06% maximum accuracy, SE total phosphorus maintained 0.14 mg/ l with 76,69% maximum accuracy, and SE chlorophyll-a 0.02 mg/ l with 42% maximum accuracy. Landsat-8 OLI is capable to estimate the conditions of trophic status parameter.