Abstract
Regional groundwater storage changes in Illinois are estimated from monthly GRACE total water storage change (TWSC) data and in situ measurements of soil moisture for the period 2002–2005. Groundwater storage change estimates are compared to those derived from the soil moisture and available well level data. The seasonal pattern and amplitude of GRACE‐estimated groundwater storage changes track those of the in situ measurements reasonably well, although substantial differences exist in month‐to‐month variations. The seasonal cycle of GRACE TWSC agrees well with observations (correlation coefficient = 0.83), while the seasonal cycle of GRACE‐based estimates of groundwater storage changes beneath 2 m depth agrees with observations with a correlation coefficient of 0.63. We conclude that the GRACE‐based method of estimating monthly to seasonal groundwater storage changes performs reasonably well at the 200,000 km2 scale of Illinois.
Highlights
Introduction andBackground[2] Terrestrial groundwater storage, a fundamental component of the global water cycle, is of great importance for the management of water resources, agriculture, and ecosystem health
The seasonal pattern and amplitude of Gravity Recovery and Climate Experiment (GRACE)-estimated groundwater storage changes track those of the in situ measurements reasonably well, substantial differences exist in month-to-month variations
In spring, when soil moisture is close to saturation, the gain in total water storage is largely due to recharge to the shallow water table from rainfall, while in summer, its loss is largely caused by groundwater depletion by evapotranspiration
Summary
[2] Terrestrial groundwater storage, a fundamental component of the global water cycle, is of great importance for the management of water resources, agriculture, and ecosystem health. [4] In a prelaunch feasibility study, Rodell and Famiglietti [2002] explored the potential detectability of groundwater storage variations in the High Plains aquifer (United States) using GRACE They used observed hydrological measurements and prelaunch estimates of GRACE errors to demonstrate the feasibility of removing the contribution of soil moisture from future GRACE observations of total water storage change (TWSC) to isolate groundwater storage changes. Regional-scale groundwater storage changes were estimated from monthly GRACE TWSC data by removing the soil moisture signal using the Illinois data for 36 consecutive months during 2002 – 2005. These estimates were compared to those derived from in situ well measurements in Illinois. Swenson et al [2006] recently demonstrated that GRACE TWSA estimates closely match in situ observations in Illinois, while Rodell and Famiglietti [2001] highlighted
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