Estimating Of Water Quality Parameters Based On Landsat Multispectral Images

Liao River Basin in Jilin Province is located in the southwest of Jilin Province.It is a region of water shortage and seriously affected by water pollution.The water pollution control work in this region has been carried out.How to quickly determine the water quality parameters in the basin has also become an important problem to determine the water pollution.In this study,Erlonghu reservoir in Liao River Basin of Jilin Province is taken as the study area.Erlong Lake considers one of the largest lakes in Midwest Jilin,China,and a drinking water source in neighboring cities.The present study explores that Landsat TM5,ETM7,and OLI8 images could assess water quality（V-Phenol,Dissolved Oxygen,NH₄-N,NO₃-N）in Erlong lake,Jilin province,Northeast China.Thirteen multispectral images have been used in this study（May,July,August,September）in（2000,2001,2002）,and 19th October 2020.Radiometric and atmospheric corrections have been applied to all images.All the in-situ water quality parameters were strongly correlated to each other,except DO.In-situ measurements（V-Phenol,Dissolved Oxygen,NH₄-N,NO₃-N）were statistically correlated with various spectral band combinations（Blue,Green,Red,and NIR）derived from the all Landsat imagery.Regression analysis reported that there are strong relationships between water quality and equations created from Landsat images.Moreover,in Calibrations,the highest value of coefficient of determination R²≥0.85 with（RMSE）=0.038,and（SEE）=0.013,the lowest value of R²=（>0.30）with RMSE=0.752,SEE=0.811.All models were validated in different statistical indices;R² was up to 0.95 for most cases,RMSE and SEE ranging from（1.390 to 0.050）and（0.863 to 0.006）,respectively.Finally,the empirical algorithms were successfully assessed（V-Phenol,Dissolved Oxygen,NH4-N,NO3-N）in Erlong Lake,through Landsat images with high accuracy.The results from in situ and models showed the same trends with simple differences.September of2000,2001,2002,and October of 2020 was selected to show the spatial distributions of（V-Phenol,DO,NH₄-N,NO₃-N）in the lake.Be-sides this,V-Phenol,NH₄-N,and NO₃-N were low in shallow water but high in deep water,while DO was high in shallow water but low in deep water in the lake.Domestic sewage,agricultural,and urban industrial pollution are the most common sources of pollution in the Erlong Lake.This study is of great significance for the rapid determination of water quality parameters and water resources management of Liao River Basin in Jilin Province.