Groundwater depletion in the Middle East from GRACE with implications for transboundary water management in the Tigris-Euphrates-Western Iran region
TL;DR: Observations from the GRACE satellite mission are used to evaluate freshwater storage trends in the north-central Middle East, including portions of the Tigris and Euphrates River Basins and western Iran, from January 2003 to December 2009 to indicate that groundwater losses are the major source of this trend.
Abstract: In this study, we use observations from the Gravity Recovery and Climate Experiment (GRACE) satellite mission to evaluate freshwater storage trends in the north-central Middle East, including portions of the Tigris and Euphrates River Basins and western Iran, from January 2003 to December 2009. GRACE data show an alarming rate of decrease in total water storage of approximately -27.2 plus or minus 0.6 millimeters per year equivalent water height, equal to a volume of 143.6 cubic kimometers during the course of the study period. Additional remote-sensing information and output from land surface models were used to identify that groundwater losses are the major source of this trend. The approach used in this study provides an example of ''best current capabilities'' in regions like the Middle East, where data access can be severely limited. Results indicate that the region lost 17.3 plus or minus 2.1 millimeters per year equivalent water height of groundwater during the study period, or 91.3 plus or minus 10.9 cubic kilometers in volume. Furthermore, results raise important issues regarding water use in transboundary river basins and aquifers, including the necessity of international water use treaties and resolving discrepancies in international water law, while amplifying the need for increased monitoring for core components of the water budget.
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TL;DR: In this article, the authors argue that groundwater depletion the world over poses a far greater threat to global water security than is currently acknowledged, and propose a solution to this problem.
Abstract: Groundwater depletion the world over poses a far greater threat to global water security than is currently acknowledged.
1,053 citations
TL;DR: Analysis of 2002–2016 GRACE satellite observations of terrestrial water storage reveals substantial changes in freshwater resources globally, which are driven by natural and anthropogenic climate variability and human activities.
Abstract: Freshwater availability is changing worldwide. Here we quantify 34 trends in terrestrial water storage observed by the Gravity Recovery and Climate Experiment (GRACE) satellites during 2002–2016 and categorize their drivers as natural interannual variability, unsustainable groundwater consumption, climate change or combinations thereof. Several of these trends had been lacking thorough investigation and attribution, including massive changes in northwestern China and the Okavango Delta. Others are consistent with climate model predictions. This observation-based assessment of how the world’s water landscape is responding to human impacts and climate variations provides a blueprint for evaluating and predicting emerging threats to water and food security.
966 citations
TL;DR: In this paper, renewable groundwater stress is quantified in the world's largest aquifersCharacteristic stress regimes are defined to determine the severity of stress overstressed aquifer are mainly in rangeland biomes with some croplands.
Abstract: Renewable groundwater stress is quantified in the world's largest aquifersCharacteristic stress regimes are defined to determine the severity of stressOverstressed aquifers are mainly in rangeland biomes with some croplands.
548 citations
TL;DR: In this article, a new version of the global hydrological model WaterGAP was applied to derive groundwater depletion at the grid cell, country, and global levels, which simulates not only net groundwater abstractions and groundwater recharge from soils, but also surface water recharge from surface water bodies in dry regions.
Abstract: Groundwater depletion (GWD) compromises crop production in major global agricultural areas and has negative ecological consequences. To derive GWD at the grid cell, country, and global levels, we applied a new version of the global hydrological model WaterGAP that simulates not only net groundwater abstractions and groundwater recharge from soils but also groundwater recharge from surface water bodies in dry regions. A large number of independent estimates of GWD as well as total water storage (TWS) trends determined from GRACE satellite data by three analysis centers were compared to model results. GWD and TWS trends are simulated best assuming that farmers in GWD areas irrigate at 70% of optimal water requirement. India, United States, Iran, Saudi Arabia, and China had the highest GWD rates in the first decade of the 21st century. On the Arabian Peninsula, in Libya, Egypt, Mali, Mozambique, and Mongolia, at least 30% of the abstracted groundwater was taken from nonrenewable groundwater during this time period. The rate of global GWD has likely more than doubled since the period 1960–2000. Estimated GWD of 113 km3/yr during 2000–2009, corresponding to a sea level rise of 0.31 mm/yr, is much smaller than most previous estimates. About 15% of the globally abstracted groundwater was taken from nonrenewable groundwater during this period. To monitor recent temporal dynamics of GWD and related water abstractions, GRACE data are best evaluated with a hydrological model that, like WaterGAP, simulates the impact of abstractions on water storage, but the low spatial resolution of GRACE remains a challenge.
532 citations
Cites methods from "Groundwater depletion in the Middle..."
...The strong increase of GWD after 2007 that is estimated for the Tigris-Euphrates-Western-Iran (TEWI) region using GRACE TWS (Table 4) is assumed to be caused by intensive well construction in Iraq due to a strong drought and thus decreased surface water availability in 2007 [Voss et al., 2013]....
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TL;DR: The Gravity Recovery and Climate Experiment mission allows monitoring of changes in hydrology and the cryosphere with terrestrial and ocean applications and its contribution to the detection and quantification of climate change signals is focused on.
Abstract: Time-resolved satellite gravimetry has revolutionized understanding of mass transport in the Earth system. Since 2002, the Gravity Recovery and Climate Experiment (GRACE) has enabled monitoring of the terrestrial water cycle, ice sheet and glacier mass balance, sea level change and ocean bottom pressure variations and understanding responses to changes in the global climate system. Initially a pioneering experiment of geodesy, the time-variable observations have matured into reliable mass transport products, allowing assessment and forecast of a number of important climate trends and improve service applications such as the U.S. Drought Monitor. With the successful launch of the GRACE Follow-On mission, a multi decadal record of mass variability in the Earth system is within reach.
468 citations
References
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TL;DR: In this article, the authors constructed a 2.5° latitude-longitude grid for the 17-yr period from 1979 to 1995 by merging several kinds of information sources with different characteristics, including gauge observations, estimates inferred from a variety of satellite observations, and the NCEP-NCAR reanalysis.
Abstract: Gridded fields (analyses) of global monthly precipitation have been constructed on a 2.5° latitude–longitude grid for the 17-yr period from 1979 to 1995 by merging several kinds of information sources with different characteristics, including gauge observations, estimates inferred from a variety of satellite observations, and the NCEP–NCAR reanalysis. This new dataset, which the authors have named the CPC Merged Analysis of Precipitation (CMAP), contains precipitation distributions with full global coverage and improved quality compared to the individual data sources. Examinations showed no discontinuity during the 17-yr period, despite the different data sources used for the different subperiods. Comparisons of the CMAP with the merged analysis of Huffman et al. revealed remarkable agreements over the global land areas and over tropical and subtropical oceanic areas, with differences observed over extratropical oceanic areas. The 17-yr CMAP dataset is used to investigate the annual and interannual variab...
4,216 citations
TL;DR: The Global Land Data Assimilation System (GLDAS) as mentioned in this paper is an uncoupled land surface modeling system that drives multiple models, integrates a huge quantity of observation-based data, runs globally at high resolution (0.25°), and produces results in near-real time (typically within 48 h of the present).
Abstract: A Global Land Data Assimilation System (GLDAS) has been developed. Its purpose is to ingest satellite- and ground-based observational data products, using advanced land surface modeling and data assimilation techniques, in order to generate optimal fields of land surface states and fluxes. GLDAS is unique in that it is an uncoupled land surface modeling system that drives multiple models, integrates a huge quantity of observation-based data, runs globally at high resolution (0.25°), and produces results in near–real time (typically within 48 h of the present). GLDAS is also a test bed for innovative modeling and assimilation capabilities. A vegetation-based “tiling” approach is used to simulate subgrid-scale variability, with a 1-km global vegetation dataset as its basis. Soil and elevation parameters are based on high-resolution global datasets. Observation-based precipitation and downward radiation and output fields from the best available global coupled atmospheric data assimilation systems are employe...
3,857 citations
TL;DR: In this paper, a generalization of the single soil layer variable infiltration capacity (VIC) land surface hydrological model previously implemented in the Geophysical Fluid Dynamics Laboratory (GFDL) general circulation model (GCM) is described.
Abstract: A generalization of the single soil layer variable infiltration capacity (VIC) land surface hydrological model previously implemented in the Geophysical Fluid Dynamics Laboratory (GFDL) general circulation model (GCM) is described. The new model is comprised of a two-layer characterization of the soil column, and uses an aerodynamic representation of the latent and sensible heat fluxes at the land surface. The infiltration algorithm for the upper layer is essentially the same as for the single layer VIC model, while the lower layer drainage formulation is of the form previously implemented in the Max-Planck-Institut GCM. The model partitions the area of interest (e.g., grid cell) into multiple land surface cover types; for each land cover type the fraction of roots in the upper and lower zone is specified. Evapotranspiration consists of three components: canopy evaporation, evaporation from bare soils, and transpiration, which is represented using a canopy and architectural resistance formulation. Once the latent heat flux has been computed, the surface energy balance is iterated to solve for the land surface temperature at each time step. The model was tested using long-term hydrologic and climatological data for Kings Creek, Kansas to estimate and validate the hydrological parameters, and surface flux data from three First International Satellite Land Surface Climatology Project Field Experiment (FIFE) intensive field campaigns in the summer-fall of 1987 to validate the surface energy fluxes.
3,297 citations
"Groundwater depletion in the Middle..." refers methods in this paper
...[13] In this study, we used the results of three land surface models from GLDAS—VIC [Liang et al., 1994, 1996], Noah [Chen et al., 1996; Koren et al., 1999], and CLM2 [Dai et al., 2003]—to balance the bias of any single model....
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TL;DR: The available evidence suggests that unsustainable consumption of groundwater for irrigation and other anthropogenic uses is likely to be the cause of groundwater depletion in northwest India and the consequences for the 114,000,000 residents of the region may include a reduction of agricultural output and shortages of potable water, leading to extensive socioeconomic stresses.
Abstract: Groundwater is a primary source of fresh water in many parts of the world. Some regions are becoming overly dependent on it, consuming groundwater faster than it is naturally replenished and causing water tables to decline unremittingly 1 . Indirect evidencesuggeststhatthisisthecaseinnorthwestIndia 2 ,butthere has been no regional assessment of the rate of groundwater depletion. Here we use terrestrial water storage-change observations from the NASA Gravity Recovery and Climate Experiment satellites 3 and simulated soil-water variations from a dataintegrating hydrological modelling system 4 to show that groundwater is being depleted at a mean rate of 4.0 61.0cmyr 21 equivalent height of water (17.7 64.5km 3 yr 21 ) over the Indian states
2,198 citations
TL;DR: Geoid variations observed over South America that can be largely attributed to surface water and groundwater changes show a clear separation between the large Amazon watershed and the smaller watersheds to the north.
Abstract: Monthly gravity field estimates made by the twin Gravity Recovery and Climate Experiment (GRACE) satellites have a geoid height accuracy of 2 to 3 millimeters at a spatial resolution as small as 400 kilometers. The annual cycle in the geoid variations, up to 10 millimeters in some regions, peaked predominantly in the spring and fall seasons. Geoid variations observed over South America that can be largely attributed to surface water and groundwater changes show a clear separation between the large Amazon watershed and the smaller watersheds to the north. Such observations will help hydrologists to connect processes at traditional length scales (tens of kilometers or less) to those at regional and global scales.
2,058 citations
"Groundwater depletion in the Middle..." refers methods in this paper
...[6] Satellite observations of time-variable gravity from the Gravity Recovery and Climate Experiment (GRACE) satellite mission [Tapley et al., 2004] present a new and valuable tool to fill these gaps in data availability and water monitoring [Lettenmaier and Famiglietti, 2006; Rodell et al., 2009;…...
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...Res., 49, doi:10.1002/wrcr.20078....
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