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http://dx.doi.org/10.11108/kagis.2022.25.1.101

Analysis of Chlorophyll-a and Algal Bloom Indices using Unmanned Aerial Vehicle based Multispectral Images on Nakdong River  

KIM, Heung-Min (Research Institute, IREM tech. Co., Ltd.)
CHOE, Eunyoung (Monitoring and Analysis Division, Nakdong River Basin Environment Office, Ministry of Environment)
JANG, Seon-Woong (IREM tech. Co., Ltd.)
Publication Information
Journal of the Korean Association of Geographic Information Studies / v.25, no.1, 2022 , pp. 101-119 More about this Journal
Abstract
Existing algal bloom monitoring is based on field sampling, and there is a limit to understanding the spatial distribution of algal blooms, such as the occurrence and spread of algae, due to local investigations. In this study, algal bloom monitoring was performed using an unmanned aerial vehicle and multispectral sensor, and data on the distribution of algae were provided. For the algal bloom monitoring site, data were acquired from the Mulgeum·Mae-ri site located in the lower part of the Nakdong River, which is the areas with frequent algal bloom. The Chlorophyll-a(Chl-a) value of field-collected samples and the Chl-a estimation formula derived from the correlation between the spectral indices were comparatively analyzed. As a result, among the spectral indices, Maximum Chlorophyll Index (MCI) showed the highest statistical significance(R2=0.91, RMSE=8.1mg/m3). As a result of mapping the distribution of algae by applying MCI to the image of August 05, 2021 with the highest Chl-a concentration, the river area was 1.7km2, the Warning area among the indicators of the algal bloom warning system was 1.03km2(60.56%) and the Algal Bloom area occupied 0.67km2(39.43%). In addition, as a result of calculating the number of occurrence days in the area corresponding to the "Warning" in the images during the study period (July 01, 2021~November 01, 2021), the Chl-a concentration above the "Warning" level was observed in the entire river section from 12 to 19 times. The algal bloom monitoring method proposed in this study can supplement the limitations of the existing algal bloom warning system and can be used to provide information on a point-by-point basis as well as information on a spatial range of the algal bloom warning area.
Keywords
Algal Bloom; Algal Bloom indices; Chlorophyll-a; Nakdong river; Multispectral Sensor; Unmanned Aerial Vehicle;
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