Abstract
This study examined long-term, natural (i.e., excluding anthropogenic impacts) variability of groundwater storage worldwide. Groundwater storage changes were estimated by forcing three global-scale hydrological models with three 50+ year meteorological datasets. Evaluation using in situ groundwater observations from the U.S. and terrestrial water storage derived from the Gravity Recovery and Climate Experiment (GRACE) satellites showed that these models reasonably represented inter-annual variability of water storage, as indicated by correlations greater than 0.5 in most regions. Empirical orthogonal function analysis revealed influences of the El Niño Southern Oscillation (ENSO) on global groundwater storage. Simulated groundwater storage, including its global average, exhibited trends generally consistent with that of precipitation. Global total (natural) groundwater storage decreased over the past 5–7 decades with modeled rates ranging from 0.01 to 2.18 mm year−1. This large range can be attributed in part to groundwater’s low frequency (inter-decadal) variability, which complicates identification of real long-term trends even within a 50+ year time series. Results indicate that non-anthropogenic variability in groundwater storage is substantial, making knowledge of it fundamental to quantifying direct human impacts on groundwater storage.
Highlights
Groundwater is crucial for meeting agricultural, industrial and municipal water needs, especially in arid, semi-arid and drought impacted regions where other types of fresh water are scarce[1]
We investigate variations in global groundwater storage simulated by three global-scale hydrological models, the Catchment land surface model[20] (CLSM), the WaterGAP21 and PCRaster Global Water Balance[22] (PCR-GLOBWB) water resource models
Because Catchment land surface model20 (CLSM) does not simulate human impacts such as groundwater abstraction, this study focuses on the temporal variability of natural groundwater storage changes associated with atmospheric effects
Summary
Groundwater is crucial for meeting agricultural, industrial and municipal water needs, especially in arid, semi-arid and drought impacted regions where other types of fresh water are scarce[1]. It was predicted that climate change would reduce recharge in the southern and mountainous parts of the western U.S, while recharge would be largely unchanged in the northwestern U.S15 These studies suggest that land evapotranspiration (ET), in addition to precipitation, may be www.nature.com/scientificreports/. To better predict the future, we need to improve our understanding on how groundwater has responded to changes that have occurred in the climate system over the past several decades Such studies are noticeably lacking and limited to small spatial[17] or short temporal scales[18,19]. Forced with multiple decades of meteorological data that reflect changes in the climate system, these models are able to generate spatially and temporally continuous groundwater estimates suitable for studying climate change impacts on groundwater at regional to global scales[21,23,24,25]. Modeled groundwater storage was evaluated using long-records of in situ data in the U.S and modeled terrestrial water storage (TWS) was evaluated using TWS derived from Gravity Recovery and Climate Experiment (GRACE) satellites
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