A GPS hydro-geodesy dataset for monitoring changes in terrestrial water storage during drought and flood periods in California: assessment, validation, and application

The continuously distributed changes in water storage in hydrosphere deform the shape of the Earth’s surface, which can be recorded by GPS position time series. However, GPS stations that exhibit poroelastic behavior located on aquifer systems are excluded from largely previous studies so that terrestrial water storage variations can be estimated by elastic loading, which leads to biases in results. We proposed a novel approach to classify GPS stations whose vertical displacement time series are significantly correlated with hydrological loading variations to construct hydro-geodesy datasets, including elastic response (positive), poroelastic response (negative), and aquifer compaction. Using the wavelet analysis method, we further identified 569 GPS vertical displacement time series from California provided by the Nevada Geodetic Laboratory between 2007 and 2017 into the pre-defined temporal-scales of long-term, seasonal, and short-term. We calculated and evaluated elastic deformation induced by hydrological loading variations, including GRACE, WaterGAP, GLDAS, NLDAS, ERA5, and ERA5-land, and the HYDL product provided by GFZ. The results show that most/several GPS stations located outside/within the Central Valley are under the control of the elastic response. We also used a poroelastic half-space model to validate that most GPS stations located within the Central Valley are simultaneously affected by surface subsidence and controlled by poroelastic response. Our results show that the hydro-geodetic datasets we constructed enable the use of previously and widely neglected GPS stations, such as those that may observe poroelastic response and those affected by surface subsidence, to accurately monitor changes in terrestrial water storage during droughts and floods.