Long-term change of water clarity in Lake Limboto derived from Landsat data

Long-term water quality data is important for supporting lake management. Performing routine in situ water quality measurement remains a challenge; thus, the available data are minimal. Long-term data archived of satellite data potentially address this data scarcity. We used Landsat TM/ETM+ images to generate a long-term water clarity or Secchi Disk Depth (SD) for Lake Limboto during 1991–2019. Pre-processing Landsat image was done before calculated SD using a selected model (i.e., removing contaminated water pixels, filtering images, and mitigating atmospheric effect). We then analyzed the long-term, temporal and spatial pattern change of SD in Lake Limboto. During the study period, linear regression showed a significant decrease in SD in Lake Limboto (R 2 = 0.21, p<0.001). The result showed Lake Limboto has seasonal change (peak= May, troughs= August - September). SD would positively and significantly correlate with monthly rainfall data if it shifted one-month later the rainfall period (R 2 = 0.46, p<0.05). Increasing population resulted in a decrease of SD during 2000-2019 (R 2 = 0.81, p<0.001). The declining trend in the SD in Lake Limboto has the potential to continue under a higher future population, land cover change, and climate change. Remote sensing can be used to capture the change tendency of water clarity in Lake Limboto. Thus, useful for evaluating the implementation of a lake management plan.