f Gravity-measured Water Storage Change and Subsurface Hydraulic Properties at a Managed Recharge Facility in Tuscon, AZ, USA

The storage of subsurface water is central to Arizona’s future sustainable water supplies. Presently large amounts of water delivered from the Colorado River by Central Arizona Project canals (over 400,000 acre-feet/year permitted capacity) are stored underground at artificial recharge facilities to augment future water supplies. As the demand for Colorado River water increases and the energy required to transport, store, and recover this water becomes more costly, the importance of proper management and siting of recharge facilities increases. In this study, we combine different gravimeters (superconducting, absolute, and spring gravimeters) and advanced analysis methods to improve monitoring of subsurface storage and the characterization of subsurface hydraulic properties at Tucson Water’s Southern Avra Valley Storage and Recovery Project (SAVSARP) infiltration basins. Waterstorage changes will be monitored continuously with two iGrav™ superconducting gravimeters. These observations will be supported by time-lapse monitoring of spatial gravity variations with an A-10 absolute gravimeter and spring gravimeters. We will test novel approaches to gravity monitoring network design that make intelligent use of different gravimeter types for hydrological applications. These data will be analyzed in a coupled hydrogeophysical inverse framework to estimate groundwater-storage changes and to constrain effective hydraulic properties at the field scale. Here we will present the study concept, preliminary measurements, and modelling results.