Analysis of the water quality of Lake Hachiro, Japan, using time-series UAV and satellite data

In recent years, water pollution in rivers and lakes has worsened due to industrial activities and modern lifestyle trends. To mitigate this issue, water quality surveys are routinely conducted, primarily using direct sampling and laboratory analysis. However, this method captures only localized data, hindering a comprehensive assessment of the entire water body. To overcome this limitation, remote sensing technologies have been proposed for large-scale water quality monitoring. Our study group previously performed high-resolution water quality estimation for Lake Hachiro, Japan, using data obtained by unmanned aerial vehicles (UAVs). However, the study focused only on the visible spectrum and not on the near-infrared (NIR) spectrum, which is highly reflective in vegetated areas. Moreover, changes in pollution levels in Lake Hachiro over time have not been examined using UAV data. In this study, we analyzed water pollution using time-series data obtained by UAVs and satellite systems. We evaluated the water quality from data obtained by a UAV in 2023 using visible and NIR spectra compared it with field survey data from 2024. Additionally, satellite data corresponding to UAV observation dates were analyzed to compare the estimation results. Collectively, our findings elucidate the pollution dynamics of Lake Hachiro.