Developing algorithm for estimating chlorophyll-a concentration in the Thac Ba Reservoir surface water using Landsat 8 Imagery
Authors: Vinh Pham Quang , Ha Nguyen Thi Thu , Binh Nguyen Thanh , Thang Nguyen Ngoc , Oanh La Thi , Thao Nguyen Thien Phuong 
Published: February 2019

This study aims at developing a regional algorithm to quantify chlorophyll-a concentration (Chla) in the Thac Ba Reservoir surface-water using Landsat 8 imagery basing on in-situ data of Chla and above-water reflectance taken in both dry and rainy seasons 2018. In situ datasets obtained from 30 water sampling sites show a strong correlation (R2=0.73) with the reflectance ratio of two Landsat 8 (L8) bands, the green band (band 3: B3) versus the red band (band 4: B4), B3 / B4, by an exponential equation. The algorithm for estimating Chla using this ratio was well-matched up the validation using multiple-dates in-situ datasets (R2 = 0.82; RMSE ~ 5%) and was then applied to L8 images level 2 acquired in both dry and rainy seasons to understand the spatiotemporal distribution of Chla over the reservoir. 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