Hybrid forward-selection method-based water-quality estimation via combining Landsat TM, ETM+, and OLI/TIRS images and ancillary environmental data

• Published in: PloS one Vol. 13; no. 7; p. e0201255
• Main Authors: Tu, Min-Cheng, Smith, Patricia, Filippi, Anthony M
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 30.07.2018; Public Library of Science (PLoS)
• Subjects: Accuracy; Biology and Life Sciences; Calibration; Chlorophyll; Control; Data processing; Earth Sciences; Ecology and Environmental Sciences; Environmental factors; Environmental management; Health aspects; Image acquisition; Image Processing, Computer-Assisted; Landsat; Landsat satellites; Mathematical analysis; Mathematical models; Measurement; Methods; Models, Theoretical; Physical Sciences; Reflectance; Remote sensing; Research and Analysis Methods; Satellite imagery; Solid suspensions; Surface temperature; Technology application; Temperature; Texas; Total suspended solids; Water analysis; Water pollution; Water Quality; Water quality monitoring stations; Water sampling; Water Supply; Water temperature; Watersheds; Wind speed; Texas; United States > US; Pennsylvania
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0201255

A simple approach to enable water-management agencies employing free data to create a single set of water quality predictive equations with satisfactory accuracy is proposed. Multiple regression-derived equations based on surface reflectance, band ratios, and environmental factors as predictor variables for concentrations of Total Suspended Solids (TSS) and Total Nitrogen (TN) were derived using a hybrid forward-selection method that considers both p-value and Variance Inflation Factor (VIF) in the forward-selection process. Landsat TM, ETM+, and OLI/TIRS images were jointly utilized with environmental factors, such as wind speed and water surface temperature, to derive the single set of equations. Through splitting data into calibration and validation groups, the coefficients of determination are 0.73 for TSS calibration and 0.70 for TSS validation, respectively. The coefficients of determination for TN calibration and validation are 0.64 and 0.37, respectively. Among all chosen predictor variables, ratio of reflectance of visible red (Band 3 for Landsat TM and ETM+, or Band 4 for Landsat OLI/TIRS) to visible blue (Band 1 for Landsat TM and ETM+, or Band 2 for Landsat OLI/TIRS) has a strong influence on the predictive power for TSS retrieval. Environmental factors including wind speed, remote sensing-derived water surface temperature, and time difference (in days) between the image acquisition and water sampling were found to be important in water-quality quantity estimation. The hybrid forward-selection method consistently yielded higher validation accuracy than that of the conventional forward-selection approach.