| Abstract |
Gravity observations can be used to monitor the groundwater storage variations through traditional techniques, which are very difficult due to the high cost and strong labor intensity. The system Gravity Recovery and Climate Experiment (GRACE) measures gravity anomalies on the earth to estimate changes in Terrestrial Water Storage (ΔTWS). The advantages of this technique are that it is faster and more economical than the traditional techniques, and has more extensive and continuous coverage compared with piezometer observed discrete points. GRACE data are available from 2003 to 2011for the research area. In this research, the changes in GRACE gravity data were used to monitor the Ground Water Storage changes (ΔGWS) in part of High Plains aquifer, Texas, United States, in Nile Delta aquifer and Moghra aquifer. The methodology is also applied to the majority of the Egyptian territory which extended from 22o to 32o N and 25o to 37o E. The values of ΔGWS are obtained by subtracting the soil moisture obtained from the hydrological models Global Land Data Assimilation System (GLDAS) from ΔTWS values. Maximum and minimum differences between both datasets are 45 mm and 24 mm, respectively for High Plains aquifer. Regarding the Nile Delta aquifer values of ΔGWS are validated by comparing their values extracted from GRACE versus equivalent ones taken from two piezometric maps provided by Research Institute for Ground Water (RIGW). The results indicate that maximum and minimum differences between traditional techniques from piezometric maps and GRACE satellite-GLDAS model calculations are 25 mm and -11 mm respectively with a standard deviation of about 15 mm. By applying the methodology on Moghra aquifer the results showed that the aquifer is rechargeable. |
