Satellite-based monitoring of soil moisture in catchment basins: a novel approach integrating temperature, albedo, and spectral indices

Soil Moisture Content (SMC) is a crucial parameter in the management of water resources. Due to the expansive nature of catchment basins, satellite remote sensing in optical wavelengths is identified as a vital approach for monitoring soil moisture in these basins. The main goal of this study is to develop a methodology based on a physical linear relationship that utilizes surface temperature, albedo, and spectral indices obtained from satellite imagery in both visible and thermal wavelengths to determine SMC. Considering the availability of field SMC data and the acknowledged challenge of achieving increased accuracy in estimating SMC in regions with sparse vegetation, the state of Utah in the United States was selected as the selected study area. A dataset comprising 792 SMC measurements collected by the Soil Climate Analysis Network (SCAN) on April 23, 2021, October 16, 2021, April 23, 2022, and October 16, 2022, was compiled as ground truth data. Additionally, 288 Visible Infrared Imaging Radiometer (VIIRS) and 360 Moderate Resolution Imaging Spectroradiometer (MODIS) images corresponding to the field data period were gathered. Then, a novel experimental relationship was developed to estimate SMC based on Normalized Difference Vegetation Index (NDVI), albedo, land surface temperature, and Bare Soil Index (BSI), in spatial resolutions of 375 and 250 m. Comparing the estimated SMC using this experimental approach and measured SMC to a depth of 5 cm, the Pearson’s correlation coefficient (R) achieved 0.504 for VIIRS data and 0.503 for MODIS data in the optimal scenario. The Nash-Sutcliffe criterion (NSE) for this modeling yielded approximately 0.253 for both sensors, while the Kling-Gupta criterion (KGE) was 0.278 for the MODIS data and 0.270 for VIIRS data. The Root Mean Square Error (RMSE) was also 0.023 and 0.027 for these two datasets (m3/m3). The results suggest that the method proposed in this research, compared to the established triangular method, demonstrates equivalent or superior outcomes, thus affirming the validity of the developed Relationship.