A MAJOR COMPONENT OF THE OVERALL WATER MASS BUDGET AND AN INDICATOR FOR WATER RESOURCES AVAILABILITY FOR A REGION ARE TERRESTRIAL WATER STORAGE (TWS) VARIATIONS. A DEPLETION OF WATER RESOURCES WOULD BE REFLECTED IN A REDUCTION IN TWS. HENCE MONITORING AND QUANTIFYING THE TWS VARIATIONS IS ESSENTIAL FOR PRACTICAL APPLICATIONS SUCH AS EFFICIENT DROUGHT FORECAST [HOUBORG ET AL. 2012] AND WATER RESOURCES MANAGEMENT [RAMILLIEN ET AL. 2014]. ESPECIALLY IN CALIFORNIA A PROPER WATER MANAGEMENT THAT INCLUDES ALL FRESHWATER RESOURCES IS CRITICAL [FAMIGLIETTI 2014]. A VARIETY OF SPACE-BORNE OBSERVATIONS HAVE BEEN USED TO MONITOR VARIATIONS OF TERRESTRIAL WATER STORAGES. IN SPECIFIC DATA FROM THE GRAVITY RECOVERY AND CLIMATE EXPERIMENT (GRACE) SATELLITES DETECTING CHANGES IN THE EARTH S GRAVITY FIELD HAVE BEEN WIDELY USED TO OBSERVE TWS VARIATIONS (E.G. LETTENMAIER AND FAMIGLIETTI [2006] FRAPPART ET AL. [2012] FAMIGLIETTI [2014] LONG ET AL. [2015] SCANLON ET AL. [2015] AND CHEN ET AL. [2016]). GRACE YIELDS SENSITIVITY TO THE MASS CHANGE EQUIVALENT TO A ~1 CM THICK DISK OF WATER ON THE LAND SURFACE WITH DIMENSIONS OF A FEW HUNDREDS OF KILOMETER OR LARGER. NUMEROUS STUDIES HAVE DEMONSTRATED THAT SUCH SENSITIVITY ALLOWS GRACE TO CONTRIBUTE SIGNIFICANTLY IN UNDERSTANDING TWS VARIATIONS IN LARGE BASINS WITH DIMENSIONS OF MANY HUNDREDS TO THOUSANDS OF KILOMETER [TAPLEY ET AL. 2004A LONGUEVERGNE ET AL. 2010]. HOWEVER AS THE SPATIAL SCALE OF THE INVESTIGATED PROBLEM APPROACHES A COUPLE OF HUNDRED KILOMETERS USING GRACE DATA BECOMES PROBLEMATIC DUE TO THE LIMITED SPATIAL RESOLUTION [LONGUEVERGNE ET AL. 2010]. WATER MASS BUDGET VARIATIONS IN ADDITION TO CHANGING THE GRAVITY FIELD CAUSE AN ELASTIC RESPONSE OF THE SOLID EARTH WHICH RESULTS IN A LARGE SCALE INSTANTANEOUS DEFORMATION [FARRELL 1972]. FLUCTUATIONS IN GROUNDWATER SOIL MOISTURE SURFACE WATER (BOTH IN LIQUID FORM AND AS SNOW AND GLACIAL ICE) CAUSE VARIATION IN SURFACE LOADING AND DEFORM THE EARTH S CRUST. THE TEMPORALLY VARIABLE LOADING RATE LEADS TO THE SURFACE REBOUND AT ANY GIVEN SITE DEPENDING ON THE TOTAL SURFACE LOAD AVERAGED OVER A FEW HUNDRED KILOMETERS OF THAT LOCATION [VAN DAM AND WAHR 1998]. THIS MAINLY VERTICAL ELASTIC RESPONSE TO THE VARIABLE LOADING OCCURS AT GLOBAL REGIONAL AND LOCAL SCALES [BEVIS ET AL. 2004]. THUS SIMILAR TO GRACE GRAVITY DISPLACEMENTS DUE TO LOADING REFLECT THE CHANGES IN ALL HYDROLOGICAL COMPONENTS. WHILST THE DISPLACEMENTS CAN PROVIDE INFORMATION ABOUT CHANGES IN TWS AT SCALES MUCH SHORTER THAN A FEW HUNDRED KILOMETERS [BORSA ET AL. 2014]. RECENT WORKS HAVE USED OBSERVATION OF GLOBAL POSITIONING SYSTEM (GPS) FOR ESTIMATING SPATIOTEMPORAL EVOLUTION OF TWS AT ~ 100 KM OR BETTER RESOLUTION [ARGUS ET AL. 2014 BORSA ET AL. 2014 FU ET AL. 2015].