YAKIMA VALLEY DEFORMATION DETECTION BY INTERFEROMETRIC SYNTHETIC APERTURE RADAR (INSAR)

Groundwater withdrawal can result in land subsidence and permanent reduction of aquifer capacity. The Yakima Valley, in the Columbia Plateau Regional Aquifer System (CPRAS), hosts approximately one-third of Washington’s vineyards. It is an active agricultural area that depends on both surface and groundwater resources and thus could be vulnerable to land subsidence. We use Interferometric Synthetic Aperture Radar (InSAR) data from the Sentinel-1 satellite to investigate land subsidence in the Yakima Valley from 2017 to 2022. We use the Miami InSAR Time-series software in Python (MintPy) to select 153 interferometric pairs and analyze the deformation time series. The InSAR time series reveals that the Yakima Valley has experienced land subsidence of up to 10 cm from 2017 to 2022. Groundwater usage is suspected to be a contributing factor to this ground deformation, although supporting evidence, including data on groundwater levels and shallow stratigraphy, is required to verify this claim. While the subsidence mechanism in the Yakima Valley remains unclear, the persistent nature of the subsidence signals a need for close monitoring and assessment of groundwater over-extraction in the Yakima Valley.