Integration of passive and active microwave remote sensing to estimate water quality parameters

Abstract

In this paper, a new method has been presented to estimate of the Water Quality Parameters (WQPs) such as Electrical Conductivity (EC), salinity and Total Dissolved Salt (TDS). This method is mainly depended on the thermal and SAR images as an active and passive input satellite data. A Small Perturbation Method (SPM) using the Elfouhaily spectrum has been used as a physical model to calculate the electromagnetic scattering by the river surface. This method is basically used in the inversion process to find the physical parameters of water. The inversion process is fallen into three steps: first step includes, the estimation of the reflectivity coefficients via SAR image; then, the second step, the polarization coefficient (in VV or HH polarizations) is used to find the water dielectric constant; finally, the Debye formulation is used to find the salinity value. In this study, the thermal band is used to obtain the temperature of the water surface which we used in our proposed method. Total Dissolved Salts (TDS) is estimated by calculation of the electrical conductivity (EC) which is directly derived from the salinity value. To validate our methodology, a dataset of in situ data is used and the comparison between the WQP estimated using the proposed method and those obtained from in situ data is achieved. The obtained results shows, that the using of thermal image is helped to estimate salinity ranges close to in situ, consequently, enhance the produced TDS. The results also show that the thermal-TSX is helpful to improve the estimation and mapping of WQP for the practical use in the study area with high accuracy. Keywords-active and passive microwave; salinity; in situ water quality; SAR images; thermal images; SPM method.I.

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