GEOPHYSICAL RESEARCH LETTERS, VOL. 38, L17401, doi:10.1029/2011GL048604, 2011

Contribution of global groundwater depletion since 1900
to sea‐level rise
Leonard F. Konikow1
Received 20 June 2011; revised 29 July 2011; accepted 30 July 2011; published 2 September 2011.

[1] Removal of water from terrestrial subsurface storage is a
natural consequence of groundwater withdrawals, but global
depletion is not well characterized. Cumulative groundwater
depletion represents a transfer of mass from land to the oceans
that contributes to sea‐level rise. Depletion is directly calculated
using calibrated groundwater models, analytical approaches,
or volumetric budget analyses for multiple aquifer systems.
Estimated global groundwater depletion during 1900–2008
totals ∼4,500 km3, equivalent to a sea‐level rise of 12.6 mm
(>6% of the total). Furthermore, the rate of groundwater
depletion has increased markedly since about 1950, with
maximum rates occurring during the most recent period
(2000–2008), when it averaged ∼145 km3/yr (equivalent to
0.40 mm/yr of sea‐level rise, or 13% of the reported rate of
3.1 mm/yr during this recent period). Citation: Konikow, L. F.
(2011), Contribution of global groundwater depletion since 1900 to
sea‐level rise, Geophys. Res. Lett., 38, L17401, doi:10.1029/
2011GL048604.

1. Introduction
[2] Water budgets form the foundation of informed water
management strategies, including design of water supply
infrastructure and assessment of water needs of ecosystems
[Healy et al., 2007]. As part of assessing water budgets,
periodic assessments of changes in aquifer storage should be
undertaken [U.S. Geological Survey, 2002]. Groundwater
depletion, herein defined as a reduction in the volume of
groundwater in storage in the subsurface, not only can have
negative impacts on water supply, but also can lead to land
subsidence, reductions in surface water flows and spring
discharges, and loss of wetlands [Bartolino and Cunningham,
2003; Konikow and Kendy, 2005]. Groundwater depletion is
becoming recognized as an increasingly serious global
problem that threatens sustainability of water supplies [e.g.,
Schwartz and Ibaraki, 2011].
[3] Water budgets are also critical in understanding sea‐
level rise (SLR) [e.g., Milly et al., 2003; Lettenmaier and
Milly, 2009]. Milne et al. [2009] note that complete closure of a globally integrated sea‐level budget contains many
uncertainties, including land‐based water storage, and further state, “… it remains important to understand better the
magnitudes and error budgets of the various processes that
contributed to sea‐level change during [the 20th century].”
[4] In a classic paper describing the source of water
derived from wells, Theis [1940] clarified that withdrawals

1

U.S. Geological Survey, Reston, Virginia, USA.

This paper is not subject to U.S. copyright.
Published in 2011 by the American Geophysical Union.

are balanced by some combination of removal of groundwater from storage (depletion), increases in recharge, and/or
decreases in groundwater discharge. Furthermore, over time,
the fraction of pumpage derived from storage will generally
decrease as a system approaches a new equilibrium condition [e.g., see Alley et al., 1999, Figure 14].
[5] The extracted groundwater can subsequently follow
any number of pathways through the hydrologic cycle, and
most pathways that don’t involve a return to the groundwater
system have relatively short travel times and relatively small
storage capacities [Alley et al., 2002; Oki and Kanae, 2006].
But because the oceanic volume is so large relative to other
pools or stocks, the ultimate volumetric sink for essentially all
depleted groundwater is the oceans. If the removal of
groundwater from storage in the continental subsurface is
sufficiently large and persistent, it can represent a substantial
transfer of water mass from the land to the oceans, and
thereby represent a measureable contributor to long‐term
SLR [Sahagian et al., 1994; Gornitz et al., 1997; Konikow
and Kendy, 2005; Huntington, 2008; Milly et al., 2010].
The principal difficulty in testing this hypothesis has been a
lack of reliable data on large‐scale, long‐term, groundwater
depletion.
[6] The goal of this study was to quantitatively assess the
magnitude of long‐term groundwater depletion by developing the first comprehensive aquifer‐based estimate of changes
in groundwater storage using direct volumetric accounting.
The results have value both for assessing freshwater resources
and to help understand, assess, and reduce uncertainty in
factors contributing to global SLR.

2. Previous Estimates
[7] Margat et al. [2006, p. 19] estimate that global
groundwater mining (i.e., depletion that is essentially nonrecoverable) occurs at a rate of 27 km3/yr (0.075 mm of SLR).
Gornitz [2001, p. 103] estimates that groundwater mining can
contribute 0.10 to 0.30 mm/yr to SLR. Wada et al. [2010]
estimate that the rate of global groundwater depletion is
283 km3/yr (∼0.8 ± 0.1 mm/yr of SLR), stating that this
represents 25% of the currently reported rate of SLR of
3.1 mm/yr.
[8] The first two estimates are based on a limited number
of direct aquifer evaluations. The estimate of Wada et al.
[2010] is derived using an indirect, flux‐based water budget approach that assumes that groundwater depletion is
equal to the difference between natural recharge and withdrawals—an approach that is not based on observations of
groundwater conditions. Recharge values are derived from
global‐scale modeling designed to estimate “diffuse” recharge
from climatic data and soil properties [Döll and Fiedler,
2008]. This methodology does not calculate recharge from

L17401

1 of 5

 L17401

KONIKOW: GROUNDWATER DEPLETION

surface‐water bodies, nor adjust depletion estimates in
accordance with Theis’ [1940] principles, which are applicable regardless of climate (Wada et al. [2010] only allow this
for humid climates). Even in the Nubian Aquifer system—the
classical example of a fossil groundwater aquifer having no
modern recharge—about 25% of the total withdrawals in
1998 were offset by (and derived from) reductions in natural
discharge from the system (such as to springs and oases)
[CEDARE, 2001]. The global modeling approach to estimating natural recharge also does not account for “non‐natural” non‐diffuse recharge, such as leakage from canals,
sewers, or pipelines, or from artificial recharge—none of
which depend on climate and soil characteristics inherent in
their recharge estimation model. Hence, the flux‐based water
budget approach of Wada et al. [2010] can substantially
overestimate groundwater depletion.
[9] Problems with the approach of Wada et al. [2010] are
illustrated by examining their results for areas in the US
where depletion data exist. Figure 2 of Wada et al. [2010]
shows highest rates of depletion in four areas in the US (red
zones, rated at 300–1000 mm/yr of depletion), which appear
to include the Los Angeles and San Diego areas of southern
California. In the Los Angeles area, depletion is closely
tracked by local agencies. These data and analyses (see
auxiliary material) indicate that from 1961 to 2008 the
cumulative change in storage was an increase of ∼0.20 km3,
and in 2000 was a decrease of ∼0.04 km3/yr.1 This corresponds to a rate of depletion of less than 20 mm over the area
of resolution of the map of Wada et al. [2010]. In the San
Diego area, there is no large‐scale development of groundwater, and no reported depletion problems of significance.
[10] The few available estimates of global groundwater
depletion rates for the end of the 20th century vary by about
an order of magnitude. The variability, weaknesses, and
uncertainties in the previous estimates support the need for a
more comprehensive analysis.

3. Sea‐Level Rise
[11] The average rate of global SLR in the 20th century
was 1.7 ± 0.5 mm/yr and the rate may be accelerating in
recent years [Church and White, 2006; Bindoff et al., 2007;
Lettenmaier and Milly, 2009]. For 1961–2003 the average
rate of SLR was 1.8 ± 0.5 mm/yr and for 1993–2003 had
increased to an estimated rate of 3.1 ± 0.7 mm/yr [Bindoff
et al., 2007]. Munk [2002] notes that after accounting for
thermal expansion and melting, there remains “a residual of
12 cm of 20th century rise to be accounted for.” Groundwater depletion is one of several anthropogenic land‐based
factors affecting SLR through mass transfers; uncertainty in
their magnitudes contribute to uncertainty in balancing the
SLR budget [Huntington, 2008]. Better numbers are needed
to constrain the residual of the SLR budget.

4. Methods
[12] Groundwater depletion cannot be measured directly,
but rather must be measured through a variety of indirect
approaches. Changes in groundwater storage can be viewed
from a perspective of either pools (volumes in storage, or
1
Auxiliary materials are available in the HTML. doi:10.1029/
2011GL048604.

L17401

stocks) or fluxes [Alley et al., 2002]. One can thus estimate
groundwater depletion directly by analyzing sequential
changes in volume stored or indirectly from the residual of
fluxes in and out of the system. The volumetric approach
typically requires estimates of changes in head (groundwater
levels) over time and of storativity coefficients, as demonstrated by McGuire et al. [2003], although gravity measurements can also be used to directly estimate changes in
water mass (and hence volume) stored in an area, as illustrated by the analyses of Rodell et al. [2009], Tiwari et al.
[2009], and Famiglietti et al. [2011]. These volumetric
approaches have the advantage that the change in hydraulic
head (water level) or mass integrates the effects of all inflow
and outflow fluxes and obviates the need to identify and
quantify specific types of fluxes. A flux‐based estimate
requires a detailed water budget approach that includes
estimates of all inflows and outflows (recharge and discharge). All such fluxes cannot be estimated with high
accuracy and precision over large areas, and the residual (the
change in storage) typically represents a small difference
between relatively large and uncertain numbers. The volumetric approach is therefore preferable, and this study
develops and primarily uses estimates based on volumetric
approaches and direct observations of aquifer characteristics. More details about the specific methods used in this
study, their reliability, and how estimates were derived for
each specific aquifer or area are included in the auxiliary
material.
[13] One or more methods are applied to specific aquifers
to estimate long‐term depletion, including:
[14] 1. Integrate measurements of changes in groundwater
levels over time and area, combined with estimates of
storativity [e.g., McGuire et al., 2003].
[15] 2. Estimate large‐scale water loss from gravity changes over time as measured by GRACE satellite [e.g., Rodell
et al., 2009].
[16] 3. Use deterministic groundwater flow models that are
calibrated to long‐term observations of heads [e.g., Faunt
et al., 2009].
[17] 4. For confined aquifer systems, apply the method of
Konikow and Neuzil [2007], estimates of specific storage,
thickness of the confining unit, and head changes in the
adjacent aquifer, to estimate the depletion from confining
units.
[18] 5. Use pumpage data in conjunction with a water
budget analysis to estimate depletion [e.g., Kjelstrom, 1995].
[19] 6. Assume that the ratio of depletion to pumpage in a
control area or time can be extrapolated to a larger area or
time [e.g., Gornitz et al., 1997].
[20] 7. If data are not available through 2008, extrapolate
rates of depletion through the end of the study period using
the observed rates calculated for the most recent multi‐year
period, and adjust rates for extrapolation accordingly if
recent observed water‐level changes or pumpage data do not
support a linear extrapolation.
[21] 8. Calculate a volume of subsidence in areas where
land subsidence is caused by groundwater withdrawals; this
serves as a cross‐check and constraint on calculated depletion volumes.
[22] In the study approach, seasonal variability is intentionally ignored to better identify the long‐term signal. The
intent was to complete as comprehensive a census as possible
(see auxiliary material for descriptions of representative

2 of 5

 L17401

L17401

KONIKOW: GROUNDWATER DEPLETION

Figure 1. Cumulative net groundwater depletion in major
aquifer systems or groups in the United States, 1900–2008.

assessments and summary results for all 46 evaluated cases),
but insufficient data were available for some areas outside the
USA where depletion is known to exist (see discussions by
Sahagian [2000], Milly et al. [2010], and in the auxiliary
material). Depletion for these areas is estimated indirectly;
efforts should continue to improve the estimates with direct
volumetric calculations.

5. Results
[23] Depletion volumes and rates in the USA (Figure 1) are
calculated in 41 separate aquifer systems or subareas using
comprehensive calibrated groundwater simulation models,
analytical approaches, or volumetric budget analyses and

Figure 2. Estimated cumulative global groundwater depletion, 1900–2008.

plotted for 8 major systems or groups (Table 1 and Table S1
in the auxiliary material). During 1900–2000, there was
∼800 km3 of net cumulative depletion of groundwater in the
USA—equivalent to a sea‐level rise of ∼2.2 mm (Table 1).
Depletion in the USA increased ∼25 percent during the next
8 years—to a cumulative total of ∼1,000 km3 (∼2.8 mm of
sea‐level rise).
[24] Estimating global groundwater depletion is more
problematic. There are five groundwater systems outside the
USA with large volumes of depletion for which there are data
to allow a reliable quantitative estimate to be made (Figure 2
and Table 1). The relative magnitudes of USA and global
withdrawals and the fraction of total withdrawals represented

Table 1. Long‐Term Cumulative Net Groundwater Depletiona

Primary
Methodsb
Atlantic Coastal Plain
Gulf Coastal Plain
High Plains (Ogallala) Aquifer
Central Valley, California
Western Alluvial Basins
Western Volcanic Systems
Deep Confined Bedrock Aquifers
Agricultural and Land Drainage
TOTAL (all USA systems)
Nubian Aquifer System
North Western Sahara Aquifer System
Saudi Arabia Aquifers
North China Plain
Northern India and Adjacent Areas
TOTAL Non‐USA Aquifer Systems
TOTAL (all evaluated systems)

1, 3, 4, 7
3, 7, 8
1
2, 3
1, 3, 5, 6, 7
1, 3, 5, 6, 7
3, 4, 6, 7
1

3, 5, 7
5
3, 5, 7
1, 3, 7
2, 6

Number of
Sub‐areas

Total Net Volumetric
Groundwater
Depletionc (km3)
1900–2008

1900–2000

1900–2008

USA Aquifer Systems
7
14.4
5
198.6
1
258.6
1
113.4
19
175.1
3
−47.9
4
33.0
1
54.0
41
799.2

17.2
266.0
353.3
144.8
177.5
−45.0
35.6
54.0
1003.0

0.040
0.550
0.716
0.314
0.485
−0.133
0.091
0.150
2.214

0.048
0.737
0.979
0.401
0.492
−0.125
0.099
0.150
2.779

Non‐USA Aquifer Systems
1
79.5
1
52.7
1
358.6
1
130.3
1
937.5
5
1559.5
46
2358.0

98.4
70.3
467.7
170.3
1361.0
2168.0
3171.0

0.220
0.146
0.993
0.361
2.597
4.317
6.531

0.272
0.195
1.295
0.472
3.770
6.004
8.783

3371.0

4534.0

9.339

12.560

TOTAL GLOBAL ESTIMATE
a

1900–2000

Total Net Depletion as
Equivalent Sea‐Level
Rised (mm)

A more detailed breakdown, showing analyses for all separate areas contributing to the totals shown in Table 1, is included in the auxiliary material.
Codes for methods correspond to ordered listing in Methods discussion (1 = water‐level change; 2 = gravity; 3 = flow model; 4 = confining unit
analysis; 5. water budget; 6 = pumpage data; 7 = partial record extrapolation; 8 = subsidence).
c
Negative values indicate an increase in the volume of groundwater in storage and an equivalent drop in sea level.
d
Conversion based on an ocean surface area of 3.61 × 108 km2 [Duxbury et al., 2000].
b

3 of 5

 L17401

L17401

KONIKOW: GROUNDWATER DEPLETION

Table 2. Estimated Average Volumetric Rates of Groundwater Depletion for Selected Time Periodsa
Average Volumetric Rate of Groundwater Depletion (km3/yr)
1900–2000 1900–2008 1900–1950 1951–1960 1961–1970 1971–1980 1981–1990 1991–2000 2001–2008
Atlantic Coastal Plain
Gulf Coastal Plain
High Plains (Ogallala) Aquifer
Central Valley, California
Western USA Alluvial Basins
Western Volcanic Systems
Deep Confined Bedrock Aquifers
Agricultural and Land Drainage
TOTAL (all USA systems)
TOTAL Non‐USA Aquifer Systems
TOTAL (all evaluated systems)
TOTAL GLOBAL ESTIMATE

0.144
1.985
2.586
1.134
1.751
−0.479
0.330
0.540
7.992
15.59
23.58
33.71

0.159
2.463
3.271
1.340
1.643
−0.417
0.329
0.500
9.289
20.07
29.40
41.98

0.078
0.620
0.311
0.522
0.692
−0.902
0.371
0.824
2.515
0.939
3.454
4.940

0.261
1.242
6.100
2.900
4.408
−0.592
0.258
0.421
15.00
8.225
23.22
33.21

0.282
1.577
6.192
0.998
4.598
−0.307
0.429
0.383
14.15
14.63
28.78
41.16

0.136
2.894
6.192
2.361
4.248
−0.045
0.529
0.355
16.67
24.77
41.44
59.26

0.333
4.838
2.003
2.870
0.427
0.307
0.105
0.111
10.99
42.76
53.76
76.87

0.038
6.202
3.823
−0.398
0.373
0.356
0.123
0.009
10.53
60.77
71.30
102.0

0.349
8.430
11.830
3.919
0.292
0.355
0.323
0.000
25.50
76.14
101.6
145.3

a

A more detailed breakdown, showing analyses for all separate areas contributing to the totals shown in Table 2, is included in the auxiliary material.

by depletion are used to estimate global depletion in the rest
of the world. Global depletion is estimated from USA values
using correlation‐based extrapolations, similar to the
approach of Gornitz [2001]. This results in an estimate of
total global groundwater depletion of ∼3,400 km3 during
the 20th century, and 4,500 km3 from 1900–2008, equivalent to a sea‐level rise of 9.3 and 12.6 mm, respectively
(Tables 1 and S1). This is equivalent to volumetric rates
of depletion of 34 km3/yr during the 20th century and
42 km3/yr for 1900–2008 (Tables 2 and S2), and rates of
equivalent SLR of 0.093 mm/yr and 0.12 mm/yr for those
same two time periods (Table 3). These average rates are
substantially lower than the rate given by Wada et al. [2010].
As an identifiable, separate, semi‐independent hydrologic
process, the volume and rate of estimated long‐term global
groundwater depletion can explain 6 to 7 percent of the
observed SLR since 1900.
[25] An estimate of the uncertainty associated with each
method for computing the depletion in each particular system is discussed in the auxiliary material, and ranges from
about ±20 percent to ±40 percent, depending on the method
and data availability for each system. These uncertainty
estimates were integrated over all systems to yield an
approximate error band of ±27 percent for the total global
depletion values (Figure 2).
[26] The multi‐year average rates of groundwater depletion
varied considerably with time, but in general were relatively
low prior to 1950 and clearly highest during 2001–2008
(Tables 2, 3, and S2). However, in some USA systems, peak
depletion rates occurred during the 1950s and 1960s, and
subsequently slowed due to self‐limiting controls (such as
reduced withdrawals due to higher pump lifts and energy
costs), improved water management practices and regulations, and artificial recharge programs. The 2001–08 rate of
groundwater depletion (145 km3/yr, or 0.40 mm/yr of
equivalent SLR) can account for 22 percent of the long‐term

average SLR rate of 1.8 mm/yr and 13 percent of the more
recent (1993–2003) and higher rate of SLR of 3.1 mm/yr.

6. Conclusions
[27] This study improves and constrains the quantification
of estimates of global groundwater depletion. The cumulative global groundwater depletion from 1900–2008 totaled
∼4,500 km3 from 1900–2008, equivalent to a sea‐level rise
of 12.6 mm. As an identifiable, separate, semi‐independent
hydrologic process, the volume and rate of estimated long‐
term global groundwater depletion balances 6 to 7 percent of
the observed SLR since 1900.
[28] Even though increases in storage of large volumes of
surface water in reservoirs have the opposite effect on sea
level than does groundwater depletion, so that the net effect
of terrestrial changes in liquid water storage are smaller than
from the individual components, it is still important to
understand the contribution of each process. During the 21st
century, their relative magnitudes may shift, so the net effect
of changes in terrestrial water storage may be different than
during the 20th century. Surface water storage will probably
stabilize because of reservoir sedimentation and slowing of
construction of new large dams [Huntington, 2008]. On the
other hand, data from this study indicate that the rate of
groundwater depletion is still accelerating (though ultimately it tends to be self‐limiting).
[29] This better understanding and quantification of the
contribution of groundwater depletion to sea‐level rise
should facilitate an improved understanding of 20th century
sea‐level rise and more confidence in predictions of 21st
century sea‐level changes. The comprehensive census of
depletion in the USA is based primarily on direct calculations of volumetric changes in groundwater storage. Global
estimates for the rest of the world are less reliable. Additional assessments are needed for systems around the world

Table 3. Estimated Rates of Sea‐Level Rise From Groundwater Depletion for Selected Time Periods
Average Rate of Sea‐Level Rise From Groundwater Depletion (mm/yr)
1900–2000 1900–2008 1900–1950 1951–1960 1961–1970 1971–1980 1981–1990 1991–2000 2001–2008
TOTAL
TOTAL
TOTAL
TOTAL

(all USA systems)
(Non‐USA Aquifer Systems)
(all evaluated systems)
GLOBAL ESTIMATE

0.022
0.043
0.065
0.093

0.026
0.056
0.081
0.116

0.007
0.003
0.010
0.014

4 of 5

0.042
0.023
0.064
0.092

0.039
0.041
0.080
0.114

0.046
0.069
0.115
0.164

0.030
0.118
0.149
0.213

0.029
0.168
0.197
0.282

0.071
0.211
0.282
0.403

 L17401

KONIKOW: GROUNDWATER DEPLETION

with substantial known depletion to more accurately quantify these estimates and to complete a global census of
groundwater depletion. Nevertheless, the data clearly indicate that groundwater depletion, as a distinct hydrologic
factor, is a small but nontrivial and increasing contributor
to SLR.
[30] Acknowledgments. I greatly appreciate the assistance of E. A.
Achey, S. M. Feeney, D. P. McGinnis, and J. Donovan, who assisted with
analyses and calculations for some of the aquifer systems. Helpful review
comments from USGS colleagues J. R. Bartolino and T. G. Huntington are
also greatly appreciated.
[31] The Editor thanks Tom Gleeson and an anonymous reviewer for
their assistance in evaluating this paper.

References
Alley, W. M., T. E. Reilly, and O. L. Franke (1999), Sustainability of
ground‐water resources, U.S. Geol. Surv. Circ., 1186, 79 pp.
Alley, W. M., R. W. Healy, J. W. LaBaugh, and T. E. Reilly (2002), Flow
and storage in groundwater systems, Science, 296, 1985–1990,
doi:10.1126/science.1067123.
Bartolino, J. R., and W. L. Cunningham (2003), Ground‐water depletion
across the Nation, U.S. Geol. Surv. Fact Sheet, 103‐03, 4 pp.
Bindoff, N. L., et al. (2007), Observations: Oceanic climate change and sea
level, in Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, edited by S. Solomon et al.,
pp. 385–432, Cambridge Univ. Press, Cambridge, U. K.
CEDARE (2001), Regional strategy for the Utilisation of the Nubian Sandstone Aquifer System, Volume III: Ground Water Model, Cent. for Environ.
and Dev. for the Arab Reg. and Eur., Cairo.
Church, J. A., and N. J. White (2006), A 20th century acceleration in global sea‐
level rise, Geophys. Res. Lett., 33, L01602, doi:10.1029/2005GL024826.
Döll, P., and K. Fiedler (2008), Global‐scale modeling of groundwater
recharge, Hydrol. Earth Syst. Sci., 12, 863–885, doi:10.5194/hess-12863-2008.
Duxbury, A. C., A. B. Duxbury, and K. A. Sverdrup (2000), An Introduction to the World’s Oceans, 6th ed., McGraw‐Hill, Boston, Mass.
Famiglietti, J. S., et al. (2011), Satellites measure recent rates of groundwater depletion in California’s Central Valley, Geophys. Res. Lett., 38,
L03403, doi:10.1029/2010GL046442.
Faunt, C. C., et al. (2009), Numerical model of the hydrologic landscape
and groundwater flow in California’s Central Valley, in Groundwater
Availability of the Central Valley Aquifer, California, edited by C. C.
Faunt, U.S. Geol. Surv. Prof. Pap., 1766, 121–212.
Gornitz, V. (2001), Impoundments, groundwater mining, and other hydrologic
transformation: Impacts on global sea level rise, in Sea Level Rise: History
and Consequences, Int. Geophys., vol. 75, edited by B. C. Douglas, M. S.
Kearney, and S. P. Leatherman, chap. 5, pp. 97–119, Academic, San Diego,
Calif., doi:10.1016/S0074-6142(01)80008-5.
Gornitz, V., C. Rosenzweig, and D. Hillel (1997), Effects of anthropogenic
intervention in the land hydrologic cycle on global sea level rise, Global
Planet. Change, 14, 147–161, doi:10.1016/S0921-8181(96)00008-2.
Healy, R. W., T. C. Winter, J. W. LaBaugh, and O. L. Franke (2007),
Water budgets: Foundations for effective water‐resources and environmental management, U.S. Geol. Surv. Circ., 1308, 90 pp.

L17401

Huntington, T. G. (2008), Can we dismiss the effect of changes in land‐based
water storage on sea‐level rise?, Hydrol. Processes, 22, 717–723,
doi:10.1002/hyp.7001.
Kjelstrom, L. C. (1995), Streamflow gains and losses in the Snake River
and ground‐water budgets for the Snake River Plain, Idaho and eastern
Oregon, U.S. Geol. Surv. Prof. Pap., 1408‐C, 47 pp.
Konikow, L. F., and E. Kendy (2005), Groundwater depletion: A global
problem, Hydrogeol. J., 13(1), 317–320, doi:10.1007/s10040-0040411-8.
Konikow, L. F., and C. E. Neuzil (2007), A method to estimate groundwater depletion from confining layers, Water Resour. Res., 43, W07417,
doi:10.1029/2006WR005597.
Lettenmaier, D., and P. C. D. Milly (2009), Land waters and sea level, Nat.
Geosci., 2, 452–454, doi:10.1038/ngeo567.
Margat, J., S. Foster, and A. Droubi (2006), Concept and importance of
non‐renewable resources, in Non‐renewable Groundwater Resources:
A Guidebook on Socially‐Sustainable Management for Water‐Policy
Makers, IHP‐VI Ser. Groundwater, vol. 10, edited by S. Foster, and
D. P. Loucks, pp. 13–24, UNESCO, Paris.
McGuire, V. L., et al. (2003), Water in storage and approaches to ground‐
water management, High Plains Aquifer, 2000, U.S. Geol. Surv. Circ.,
1243, 51 pp.
Milly, P. C. D., A. Cazenave, and M. C. Gennero (2003), Contribution of
climate‐driven change in continental water storage to recent sea‐level
rise, Proc. Natl. Acad. Sci. U. S. A., 100, 13,158–13,161, doi:10.1073/
pnas.2134014100.
Milly, P. C. D., et al. (2010), Terrestrial water‐storage contributions to sea‐
level rise and variability, in Understanding Sea‐Level Rise and Variability, edited by J. A. Church et al., chap. 8, pp. 226–255, Wiley‐Blackwell,
Oxford, U. K., doi:10.1002/9781444323276.ch8.
Milne, G. A., W. R. Gehrels, C. W. Hughes, and M. E. Tamisiea (2009),
Identifying the causes of sea‐level change, Nat. Geosci., 2, 471–478,
doi:10.1038/ngeo544.
Munk, W. (2002), Twentieth century sea level: An enigma, Proc. Natl.
Acad. Sci. U. S. A., 99, 6550–6555, doi:10.1073/pnas.092704599.
Oki, T., and S. Kanae (2006), Global hydrological cycles and world water
resources, Science, 313, 1068–1072, doi:10.1126/science.1128845.
Rodell, M., I. Velicogna, and J. S. Famiglietti (2009), Satellite‐based estimates of groundwater depletion in India, Nature, 460, 999–1002,
doi:10.1038/nature08238.
Sahagian, D. L. (2000), Global physical effects of anthropogenic hydrological alterations: Sea level and water redistribution, Global Planet.
Change, 25, 39–48, doi:10.1016/S0921-8181(00)00020-5.
Sahagian, D. L., F. W. Schwartz, and D. K. Jacobs (1994), Direct anthropogenic contributions to sea level rise in the twentieth century, Nature,
367, 54–57, doi:10.1038/367054a0.
Schwartz, F. W., and M. Ibaraki (2011), Groundwater: A resource in
decline, Elements, 7, 175–179, doi:10.2113/gselements.7.3.175.
Theis, C. V. (1940), The source of water derived from wells, Civ. Eng., 10,
277–280.
Tiwari, V. M., J. Wahr, and S. Swenson (2009), Dwindling groundwater
resources in northern India, from satellite gravity observations, Geophys.
Res. Lett., 36, L18401, doi:10.1029/2009GL039401.
U.S. Geological Survey (2002), Concepts for national assessment of water
availability and use, U.S. Geol. Surv. Circ., 1223, 34 pp.
Wada, Y., L. P. H. van Beek, C. M. van Kempen, J. W. T. M. Reckman,
S. Vasak, and M. F. P. Bierkens (2010), Global depletion of groundwater
resources, Geophys. Res. Lett., 37, L20402, doi:10.1029/2010GL044571.
L. F. Konikow, U.S. Geological Survey, 431 National Cent., Reston, VA
20192, USA. (lkonikow@usgs.gov)

5 of 5