Water quality mapping using airborne and satellite multispectral sensors -Lake Shinji and Lake Nakaumi, Japan-

摘要

Lake Shinji and Lake Nakaumi are brackish lakes located in the western Japan. They are both suffering eutrophication although the mechanism which controls nutrient balance and water quality has not been fully understood yet. To study the horizontal distribution of water quality in these lakes and investigate the potential of remote sensing technology for such studies, we have planned and conducted almost forty remote sensing campaigns since FY1995. In FY1997, we successfully conducted two airborne-satellite joint campaigns. Also we conducted concurrent in-situ water quality surveys using research vessels as well as ground reflectance measurements for vicarious calibration of airborne and satellite data. On October 9 1997, the airborne sensor and SPOT HRV observed the lakes with 1.5 hour interval. The horizontal distribution of the algal bloom occurred in lake Shinji was clearly shown by both sensors. On March 3, 1998, the airborne sensor, Landsat TM, and SPOT HRV observed the lakes with 45-minute interval. The airborne data indicated the horizontal gradient of surface chlorophyll-a concentration which was low in the near-shore region and high in the off-shore region.