Water Storage Changes in Three Gorges Water Systems Area Inferred from Grace Time‐Variable Gravity Data

Abstract

AbstractTwenty‐two monthly water storage changes are predicted for the supply water systems of the Three Gorges reservoir from GRACE time‐variable gravity data. In order to assess the results, the CPC hydrological models are used to establish two benchmarks. It is found that the results are very reasonable in this area. For Gaussian averaging for 1000 km radius, the total water storage changes in the area have a peak‐to‐peak value of 14 cm, and the annual component has an amplitude of 5.8 cm and a phase of –40.8 days. The RMS difference compared with the inversion results with the same averaging radius using the synthetic gravity data from the CPC models is 1.3 cm for the total water storage changes, and the differences are 0.1 cm and 1.0 day for the amplitude and phase of the annual component. However, for checking the ability of GRACE to monitor the true water storage changes within the area, it is also necessary to compare the inversion results from GRACE gravity models with the true average results of CPC models. For this comparison the RMS difference is 2.1 cm for the total water storage changes, and the differences are 1.7 cm and 9.3 days for the amplitude and phase of the annual component. Consequently, it is found that the first comparison has overestimated the effectiveness of GRACE. Nevertheless, the second comparison shows that the monthly water storage changes can be roughly determined from GRACE data in this area.