RADAR SATELLITE (INSAR) MONITORING OF GROUNDWATER DYNAMICS NEAR THE ALL-AMERICAN CANAL (CALEXICO/MEXICALI REGION, RIO COLORADO)

Dispute settlement over groundwater issues is hampered by the fact that groundwater is not discussed in existing bilateral treaties between Mexico and the United States whereas aquifers frequently span the border zone. Accurate, international data on groundwater resources and dynamics are therefore needed to assist formulation of binational groundwater policy, particularly in the Colorado River delta region. We will present our preliminary InSAR (Interferometric Synthetic Aperture Radar) measurements of cm-scale vertical displacements of the surface above the Mexicali Valley aquifer, using these as a proxy for aquifer depletion and recharge events. It is anticipated that this InSAR monitoring will allow characterization of aquifer behavior across the border zone over the past decade, and prior to (or during) both the proposed lining of the All-American canal and the federal reductions in Colorado River surface water allocations to urban and/or rural California consumers. Either action could seriously alter a major aquifer recharge zone, and, consequently, groundwater volumes in Mexico (655 private and federal pumping sites) and southeastern California. We will present deformation maps for a roughly 650 km2 area of the Mexicali-Calexico region that illustrate both regional and local subsidence signals.