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...
Main Authors: | , , , |
---|---|
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 |