Abstract
Aimed at mapping time variations in the Earth’s gravity field, the Gravity Recovery and Climate Experiment (GRACE) satellite mission is applicable to access terrestrial water storage (TWS), which mainly includes groundwater, soil moisture (SM), and snow. In this study, SM and accumulated snow water equivalent (SWE) are simulated by the Global Land Data Assimilation System (GLDAS) land surface models (LSMs) and then used to isolate groundwater anomalies from GRACE-derived TWS in Pennsylvania and New York States of the Mid-Atlantic region of the United States. The monitoring well water-level records from the U.S. Geological Survey Ground-Water Climate Response Network from January 2005 to December 2011 are used for validation. The groundwater results from different combinations of GRACE products (from three institutions, CSR, GFZ and JPL) and GLDAS LSMs (CLM, NOAH and VIC) are compared and evaluated with in-situ measurements. The intercomparison analysis shows that the solution obtained through removing averaged simulated SM and SWE of the three LSMs from the averaged GRACE-derived TWS of the three centers would be the most robust to reduce the noises, and increase the confidence consequently. Although discrepancy exists, the GRACE-GLDAS estimated groundwater variations generally agree with in-situ observations. For monthly scales, their correlation coefficient reaches 0.70 at 95% confidence level with the RMSE of the differences of 2.6 cm. Two-tailed Mann-Kendall trend test results show that there is no significant groundwater gain or loss in this region over the study period. The GRACE time-variable field solutions and GLDAS simulations provide precise and reliable data sets in illustrating the regional groundwater storage variations, and the application will be meaningful and invaluable when applied to the data-poor regions.
Highlights
Groundwater is a major source of fresh water in many parts of the world
The error bars represent the standard deviations for the Global Land Data Assimilation System (GLDAS) model simulations
We present an application for estimating groundwater storage variations based on remotely sensed terrestrial water storage (TWS) changes from Gravity Recovery and Climate Experiment (GRACE) in Pennsylvania and New York States of the
Summary
Groundwater is a major source of fresh water in many parts of the world. It covers about 50%of drinking water needs, 40% of the needs of self-supplied industry, and 20% of the demand for irrigation water [1]. Groundwater is a major source of fresh water in many parts of the world. Groundwater exploitation accounts for about 70% of the urban fresh water consumption in Beijing, and this proportion is more than 60% in the North China Plain [3]. Overexploitation of groundwater, has led to water resource and environmental problems, such as unremitting decrease of water table and constant land subsidence [4,5,6]. The conventional groundwater monitoring means, like well observations, are time-and-money-consuming, and limited by their spatial coverage, which cannot produce large-scale dynamic observation and assessment due to scattered logs
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