Regional Analysis of Lake and Reservoir Water Quality with Multispectral Satellite Remote Sensing Images

In this research, a time-series of multispectral images acquired by Landsat 8 and Sentinel-2 satellites during 2013-2017 was combined with in situ water quality measurements to examine and analyze the spatial pattern and temporal variation of lake and reservoir water quality in the OhioKentuckyIndiana region within the Louisville District, United States Army Corps of Engineers. Reflectance values at the sampling sites for each lake were used with the in situ data collected within a 7-day time window of satellite overpass to construct empirical models to estimate water quality parameters, including turbidity, Secchi depth, and chlorophyll-a. The analysis indicated that Sentinel-2 outperformed Landsat 8 for retrieving water quality parameters, especially for chlorophyll-a. Due to the better spatial and temporal coverage of Landsat 8 for this tri-state region, the Secchi depth retrieved from the time-series Landsat 8 images was used to create lake trophic state index TSI maps in 2013, 2015, and 2017. It was observed that most lakes 75 in the study area were in mesotrophic or eutrophic classes in 2017 based on the TSI. From 2013 to 2017, the TSI range and standard deviation of lakes in Indiana region largely increased while the average TSI in this tri-state area varied slightly 1.6.