Toward calibration of regional groundwater models using GRACE data

0022-1694/$ see front matter 2011 Published by doi:10.1016/j.jhydrol.2011.10.025 ⇑ Corresponding author. Present address: Bureau o School of Geosciences, University of Texas at Austi Tel.: +1 512 475 6190. E-mail address: [email protected] (A.Y. Sun). Regional groundwater models are increasingly used for shortand long-termwater resources planning, in anticipation of greater climate variability and population growth. However, many of thesemodels are subject to structural and parametric uncertainties because of the lack of field measurements. In recent years, the Gravity Recovery and Climate Experiment (GRACE) satellite mission has shown great potential for tracking total water storage changes over large regions. The pattern of groundwater storage changes inferred fromGRACEmay be incorporated as an additional regularizationmechanism for calibrating regional groundwater models. Motivated by the demonstrated success of GRACE for monitoring groundwater storage changes, this study explores the combined use of in situ water level measurements and GRACEderived groundwater storage changes for calibrating regional groundwater models. The resulting optimization problem is solved using an evolutionary optimization algorithm.We demonstrate the proposed calibration strategy for the hydraulically connected Edwards–Trinity Plateau and Pecos Valley aquifers (total area 115,000 km) in west Texas. Monthly GRACE data from 2002 to 2007 were used to recalibrate a regional groundwater model developed for the area. Our results indicate that (i) calibration using in situ data alone may yield multiple plausible solutions, a phenomenon well known to hydrologists; and (ii) GRACE data helped further constrain model parameters over the study period and, thus, may be continuously assimilated, among other sources of data, for enhancing existing regional groundwater models. 2011 Published by Elsevier B.V.