Improving Groundwater Model Calibration with Repeat Microgravity Measurements.

Groundwater-flow models depend on hydraulic head and flux observations for evaluation and calibration. A different type of observation-change in storage measured using repeat microgravity-can also be used for parameter estimation by simulating the expected change in gravity from a groundwater model and including the observation misfit in the objective function. The method is demonstrated using new software linked to MODFLOW input and output files and field data from the vicinity of the All American Canal in southeast California, USA.