Estimating Groundwater Storage Changes in the Western Kansas Using Grace Data

The Gravity Recovery and Climate Experiment (GRACE) delivers monthly gravity fields since it was launched in March 2002, which provides a new way to monitor the groundwater storage variations for large regions. In this study, we attempt to apply the GRACE data combined with estimated soil moisture based on the water balance approach to estimate monthly groundwater changes in the western Kansas of approximately 100,000 km. The comparison of different Gaussian smoothing radiuses indicated that a smaller filter radius (150 km) is more appropriate for this size of the study area to get more effective gravity signals. The results are compared with in situ yearly measurements of groundwater levels and show a prominent seasonal cycle. The groundwater storage changes estimated from GRACE data agree well with the measured groundwater levels during 2003 and 2008. Both of them show a decline trend. Such observation results from GRACE data will provide regional fundamental information for water resource management.