Groundwater storage is a spatial and temporal variable that represents an essential part of the global hydrological cycle. Traditionally, many wells (i.e., a large number), spatially distributed across a basin, are measured annually to monitor changes in the groundwater (GW) level. It has been shown that invasive measuring of water levels in agricultural wells during winter months is most representative because the wells are normally not in use and have had sufficient time to rebound from seasonal use. However, traditional invasive measurements are inefficient, labor-intensive, and expensive with significant regional obstacles that can inhibit good spatial representation. Thus, satellite observations of the Earth's time-variable gravity field from the Gravity Recovery and Climate Experiment (GRACE) mission provide a unique opportunity to monitor changes in groundwater storage from space (Rodell and Famiglietti, 2002; Tapley et al., 2004).