Estimation of nutrient concentrations in the Tri An reservoir, Dong Nai province using LANDSAT 8 OLI

Recently, using remote sensing to monitor water quality has become popular because of its outstanding advantages. Tri An reservoir, since its construction, has always played an important role in the southern provinces; however, the lake is now highly eutrophicated in which the green algae community, which causes this phenomenon, is strongly influenced by the nutrients in the lake. The aim of this research is to estimate the nutrient pollutants concentration (i.e., NO₂⁻, NO₃⁻, NH₄⁺) for the Tri An reservoir on November 14^th 2020 using Landsat 8 OLI images. The study performed correlation analysis between measured nutrient pollutants concentration and spectral reflectance values derived from Landsat 8 image bands. The result showed that they are strongly correlated with each other (Pearson coefficients are larger 0.95 between band 4 and NO₂⁻, NO₃⁻, NH₄⁺ measured concentrations). On that basis, the regression equations estimating the nutrient pollutants concentration in the lake were set up and the optimal equation was chosen (the equations estimated NO₂⁻, NO₃⁻, and NH₄⁺ concentrations had adjusted R² values 0.94, 0.93, 0.94, respectively), consequently, the nutrient distribution maps in Tri An reservoir were established to identify the high pollution areas. This study has clearly revealed the effectiveness of using satellite images for monitoring water quality.