GRACE water storage estimates for the Middle East and other regions with significant reservoir and lake storage

While GRACE (Gravity Recovery and Climate Experiment) satellites are increasingly being used to monitor total water storage (TWS) changes globally, the impact of spatial distribution of water storage within a basin is generally ignored but may be substantial. In many basins, water is often stored in...

Full description

Bibliographic Details
Main Authors: L. Longuevergne, C. R. Wilson, B. R. Scanlon, J. F. Crétaux
Format: Article
Language:English
Published: Copernicus Publications 2013-12-01
Series:Hydrology and Earth System Sciences
Online Access:http://www.hydrol-earth-syst-sci.net/17/4817/2013/hess-17-4817-2013.pdf
id doaj-d828580a1ea7471e842fd4c1688964b0
record_format Article
spelling doaj-d828580a1ea7471e842fd4c1688964b02020-11-24T20:46:04ZengCopernicus PublicationsHydrology and Earth System Sciences1027-56061607-79382013-12-0117124817483010.5194/hess-17-4817-2013GRACE water storage estimates for the Middle East and other regions with significant reservoir and lake storageL. Longuevergne0C. R. Wilson1B. R. Scanlon2J. F. Crétaux3CNRS–Géosciences Rennes UMR6118, Université de Rennes 1, Rennes, FranceDGS, Jackson School of Geosciences, The University of Texas at Austin, Austin, TX, USABEG, Jackson School of Geosciences, The University of Texas at Austin, Austin, TX, USACNES/LEGOS, 14, av. Édouard-Belin, 31400 Toulouse, FranceWhile GRACE (Gravity Recovery and Climate Experiment) satellites are increasingly being used to monitor total water storage (TWS) changes globally, the impact of spatial distribution of water storage within a basin is generally ignored but may be substantial. In many basins, water is often stored in reservoirs or lakes, flooded areas, small aquifer systems, and other localized regions with areas typically below GRACE resolution (~200 000 km<sup>2</sup>). The objective of this study was to assess the impact of nonuniform water storage distribution on GRACE estimates of TWS changes as basin-wide averages, focusing on surface water reservoirs and using a priori information on reservoir storage from radar altimetry. <br><br> Analysis included numerical experiments testing effects of location and areal extent of the localized mass (reservoirs) within a basin on basin-wide average water storage changes, and application to the lower Nile (Lake Nasser) and Tigris–Euphrates basins as examples. Numerical experiments show that by assuming uniform mass distribution, GRACE estimates may under- or overestimate basin-wide average water storage by up to a factor of ~2, depending on reservoir location and areal extent. <br><br> Although reservoirs generally cover less than 1% of the basin area, and their spatial extent may be unresolved by GRACE, reservoir storage may dominate water storage changes in some basins. For example, reservoir storage accounts for ~95% of seasonal water storage changes in the lower Nile and 10% in the Tigris–Euphrates. Because reservoirs are used to mitigate droughts and buffer against climate extremes, their influence on interannual timescales can be large. <br><br> For example, TWS decline during the 2007–2009 drought in the Tigris–Euphrates basin measured by GRACE was ~93 km<sup>3</sup>. Actual reservoir storage from satellite altimetry was limited to 27 km<sup>3</sup>, but their apparent impact on GRACE reached 45 km<sup>3</sup>, i.e., 50% of GRACE trend. Therefore, the actual impact of reservoirs would have been greatly underestimated (27 km<sup>3</sup>) if reservoir storage changes were assumed uniform in the basin. Consequently, estimated groundwater contribution from GRACE would have been largely overestimated in this region if the actual distribution of water was not explicitly taken into account. <br><br> Effects of point masses on GRACE estimates are not easily accounted for via simple multiplicative scaling, but in many cases independent information may be available to improve estimates. Accurate estimation of the reservoir contribution is critical, especially when separating estimating groundwater storage changes from GRACE total water storage (TWS) changes. Because the influence of spatially concentrated water storage – and more generally water distribution – is significant, GRACE estimates will be improved by combining independent water mass spatial distribution information with GRACE observations, even when reservoir storage is not the dominant mechanism. In this regard, data from the upcoming Surface Water Ocean Topography (SWOT) satellite mission should be an especially important companion to GRACE-FO (Follow-On) observations.http://www.hydrol-earth-syst-sci.net/17/4817/2013/hess-17-4817-2013.pdf
collection DOAJ
language English
format Article
sources DOAJ
author L. Longuevergne
C. R. Wilson
B. R. Scanlon
J. F. Crétaux
spellingShingle L. Longuevergne
C. R. Wilson
B. R. Scanlon
J. F. Crétaux
GRACE water storage estimates for the Middle East and other regions with significant reservoir and lake storage
Hydrology and Earth System Sciences
author_facet L. Longuevergne
C. R. Wilson
B. R. Scanlon
J. F. Crétaux
author_sort L. Longuevergne
title GRACE water storage estimates for the Middle East and other regions with significant reservoir and lake storage
title_short GRACE water storage estimates for the Middle East and other regions with significant reservoir and lake storage
title_full GRACE water storage estimates for the Middle East and other regions with significant reservoir and lake storage
title_fullStr GRACE water storage estimates for the Middle East and other regions with significant reservoir and lake storage
title_full_unstemmed GRACE water storage estimates for the Middle East and other regions with significant reservoir and lake storage
title_sort grace water storage estimates for the middle east and other regions with significant reservoir and lake storage
publisher Copernicus Publications
series Hydrology and Earth System Sciences
issn 1027-5606
1607-7938
publishDate 2013-12-01
description While GRACE (Gravity Recovery and Climate Experiment) satellites are increasingly being used to monitor total water storage (TWS) changes globally, the impact of spatial distribution of water storage within a basin is generally ignored but may be substantial. In many basins, water is often stored in reservoirs or lakes, flooded areas, small aquifer systems, and other localized regions with areas typically below GRACE resolution (~200 000 km<sup>2</sup>). The objective of this study was to assess the impact of nonuniform water storage distribution on GRACE estimates of TWS changes as basin-wide averages, focusing on surface water reservoirs and using a priori information on reservoir storage from radar altimetry. <br><br> Analysis included numerical experiments testing effects of location and areal extent of the localized mass (reservoirs) within a basin on basin-wide average water storage changes, and application to the lower Nile (Lake Nasser) and Tigris–Euphrates basins as examples. Numerical experiments show that by assuming uniform mass distribution, GRACE estimates may under- or overestimate basin-wide average water storage by up to a factor of ~2, depending on reservoir location and areal extent. <br><br> Although reservoirs generally cover less than 1% of the basin area, and their spatial extent may be unresolved by GRACE, reservoir storage may dominate water storage changes in some basins. For example, reservoir storage accounts for ~95% of seasonal water storage changes in the lower Nile and 10% in the Tigris–Euphrates. Because reservoirs are used to mitigate droughts and buffer against climate extremes, their influence on interannual timescales can be large. <br><br> For example, TWS decline during the 2007–2009 drought in the Tigris–Euphrates basin measured by GRACE was ~93 km<sup>3</sup>. Actual reservoir storage from satellite altimetry was limited to 27 km<sup>3</sup>, but their apparent impact on GRACE reached 45 km<sup>3</sup>, i.e., 50% of GRACE trend. Therefore, the actual impact of reservoirs would have been greatly underestimated (27 km<sup>3</sup>) if reservoir storage changes were assumed uniform in the basin. Consequently, estimated groundwater contribution from GRACE would have been largely overestimated in this region if the actual distribution of water was not explicitly taken into account. <br><br> Effects of point masses on GRACE estimates are not easily accounted for via simple multiplicative scaling, but in many cases independent information may be available to improve estimates. Accurate estimation of the reservoir contribution is critical, especially when separating estimating groundwater storage changes from GRACE total water storage (TWS) changes. Because the influence of spatially concentrated water storage – and more generally water distribution – is significant, GRACE estimates will be improved by combining independent water mass spatial distribution information with GRACE observations, even when reservoir storage is not the dominant mechanism. In this regard, data from the upcoming Surface Water Ocean Topography (SWOT) satellite mission should be an especially important companion to GRACE-FO (Follow-On) observations.
url http://www.hydrol-earth-syst-sci.net/17/4817/2013/hess-17-4817-2013.pdf
work_keys_str_mv AT llonguevergne gracewaterstorageestimatesforthemiddleeastandotherregionswithsignificantreservoirandlakestorage
AT crwilson gracewaterstorageestimatesforthemiddleeastandotherregionswithsignificantreservoirandlakestorage
AT brscanlon gracewaterstorageestimatesforthemiddleeastandotherregionswithsignificantreservoirandlakestorage
AT jfcretaux gracewaterstorageestimatesforthemiddleeastandotherregionswithsignificantreservoirandlakestorage
_version_ 1716813245993451520