87

Bulletin of Glaciological Research ,. (,**1) 21ῌ3.
ῌJapanese Society of Snow and Ice

Surfacewater-groundwater interaction in the Heihe River basin, Northwestern China
Tomohiro AKIYAMA+, ,, Akiko SAKAI+, Yusuke YAMAZAKI-, Genxu WANG., /,Koji FUJITA+, Masayoshi NAKAWO,, Jumpei KUBOTA, and Yuki KONAGAYA0+ Graduate School of Environmental Studies, Nagoya University, Nagoya, .0.ῌ20*+ Japan, Research Institute for Humanity and Nature, Kyoto, 0*-ῌ2*.1 Japan- Institute of Agriculture, Kyoto University, Kyoto, 0*0ῌ2/*, Japan. Cold and Arid Regions Environmental and Engineering Research Institute, Lanzhou, 1-**** China/ College of Earth and Environment Sciences, Lanzhou University, Lanzhou, 1-**** China
0 National Museum of Ethnology, Suita, /0/ῌ2/++ Japan(Received September -*, ,**0; Revised manuscript accepted November +,, ,**0)

Abstract
River discharge and groundwater level data were collected in the Heihe River basin, which is thesecond largest inland river in Northwestern China. The surfacewater-groundwater interaction,
particularly in the lower desert reaches, was analyzed with the help of isotope data of water collectedfrom the river. In the non-irrigation period, river water, which originated from the groundwater inthe middle oasis reaches, was present throughout the period in the lower desert reaches. During thisperiod, the river water recharged the groundwater not only in the riparian forest region located near
the river but also in the desert-riparian fringe region located farther away from the river. In theirrigation period, the river was usually dried up in the lower desert reaches. The river water in thelower reaches appeared just after short-term releases from the middle reaches; the groundwater levelin the riparian forest region rose rapidly, but it declined again just after the short-term releases
ﬁnished. Since the mixing ratio of the short-term released discharge to the groundwater in thedesert-riparian fringe region was smaller than that in the riparian forest region, the short-term
released discharge did not contribute to the groundwater recharge in the desert-riparian fringe region.

+.

Introduction

There are several vast inland river basins in northwestern China where people’s survival is dependent
on a very limited water resource. There is a fairamount of precipitation (more than -** mm aῌ+) in theupper mountainous reaches, while precipitation in thelower desert reaches is scanty (less than /* mm aῌ+).
The melting of glaciers and snow on those mountains
have provided water for irrigation to people living inoasis cities (Sakai et al., ,**/; Yang et al., ,**0).
However, in the Heihe River basin, the second
largest inland river in China, it is obvious that theextensive overuse of surface water for irrigation in
the middle oasis reaches has triggered a series ofsevere environmental problems such as the disappearances of the river and terminal lakes and a severe
decline of the groundwater level in the lower desert
reaches (Gong and Dong, +332; Wang and Cheng, +333;
Chen et al., ,**/; Wang et al., ,**/). Two terminal
lakes called west and east Juyan completely dried up

in +30+ and +33,, respectively (Yang et al., ,**0).
In order to obtain proper water management, it isimportant to study the impact of glacier shrinkage, asreported by Sakai et al. (,**.), on runo# characteristics and impact of human activities on the hydrological cycle, particularly surfacewater-groundwater interactions. Although many prior studies have focused on the runo# characteristics (Ujihashi et al.,+332; Fujita et al., ,**-), there has been only fragmentary information about the interactions. Wang andCheng (+333) suggested that groundwater outﬂowed
in the form of spring water to surface streams or
rivers in plain regions of the middle oasis reaches.
Akiyama et al. (,**-) suggested that the river water
recharged groundwater in the lower desert reaches,using stable isotope tracers. But river stage is di#erent with the season, and the seasonality of the ﬂow
direction between the river and groundwater should
be considered.
The objectives in this study are to analyze thegroundwater recharge mechanism in the lower desert
reaches, with consideration of their seasonality. Hy-

88Bulletin of Glaciological Researchdrological data, such as river discharge and groundwater level, were used to detect the signiﬁcance of theinteractions. The isotopic fractionation theory wasapplied to interpret the isotopic characteristics of surface water, which are necessary to discuss the groundwater recharge mechanism.

,.

Study area

Figure + shows the study area, the Heihe Riverbasin. The basin encompasses Qinhai and Gansu
Provinces and Inner Mongolia in China. The Heihe
River originates from glacial melt water and a fairamount of precipitation in the Qilian Mountains forming the northern periphery of the Tibetan Plateau (Liuet al., ,**-), ﬂowing through oasis cities and disappearing into terminal lakes. The length of the riveris about 2,+ km long. The area of the drainage basin
is about +-**** km,.
The Heihe River can be divided into three reacheswith boundaries at sites A and B: the upper mountainous, middle oasis and lower desert reaches, respectively. The upper reaches are mountainous with aglacier area of 1- km, which covers *.1ῌ of the reaches(Gao and Yang, +32/; Sakai, et al., ,**/). The middle
reaches are made up of alluvial fans with a cultivatedarea of +-+. km, in ,**, (Yamazaki, ,**0). The irrigation period in this region is from April to September(“Zhangye City Record” Compilation Committee, +33/).
The lower reaches are an alluvial and lacustrine plain
underlaid with unconsolidated sediments from the
Quaternary age. The Quaternary alluvium, consisting of ﬂuviatile sand, gravel, and silt to a depth ofseveral hundred meters, is widely distributed in thelower reaches (Ding and Li, +333; Wu et al., ,**-).
The topography of the lower reaches inclines from thesouthwest to the northeast with an average slope of+ῌ-ῌ. The lower reaches include a larger expanse ofdesert and sparse vegetation.
The annual ranges of precipitation in the upper,
middle and lower reaches are -** mm to /** mm, +**mm to -** mm, and less than +** mm, respectively(Wang and Cheng, +333). More than 3*ῌ of the precipitation in all the reaches occurs from April to September. Monthly maximum precipitation at a meteorological station in the upper reaches from ,**, to,**/ varied between 2. and +00 mm and appeared inJuly or August (Sakai et al., ,**0). Monthly mean

Fig. +. Map of study area. Landscape classiﬁcation was based on a grassland type map of Heihe River basin, China, edited by Chao and Gao(+322). Capital letters (A, B, C, D) indicate hydrological stations.

Akiyama et al.

ln῍+ῌa῎ῑ,..2..ῌ+*-ῌT,ῐ10.,.2ῌTῐ/,.0+,ῌ+*ῐ- for D.

maximum precipitation at A and B from +32* to ,***
were ., mm and +0 mm, respectively.

-.

Methods

Hydrological observations
We collected datasets of river discharges at thefour major hydrological stations, A, B, C, and D, shownin Fig. +. Elevations of sites A, B, C and D are +032 m,+,10 m, +*/0 m and 3*0 m, respectively. In addition, in
the lower reaches, we observed the groundwater levelfrom October +, ,**- to December -+, ,**. to understand its response to river discharge using level meters with a data logger (MC-++**W, STS) at a riparian
forest site + (R+) located ,* m from the river, at adesert-riparian fringe site (FG), -** m from the river,and at a Gobi desert site (DE) about +* km from theriver, as shown in Fig. +.
-.+Stable isotope tracers
Stable isotopes of oxygen and hydrogen provide
conservative tracers that are uniquely intrinsic to thewater molecule (Craig and Gordon, +30/; Kendall et al.,+33/; Neal, +331; Criss +333; Hoeg et al., ,***). We
used these isotopic contents to identify water sources
and to determine mixing ratio between waters.
The isotopic ratios of water, D/H and +2O/ +0O, areexpressed in terms of permill deviations from those ofStandard Mean Ocean Water (SMOW), which is deﬁned as-.,dῑ῍RsampleῌRsmowῐ+῎ῌ+*-ῌ

(+)

where R is the isotopic ratio D/H or O/ O.
In arid areas with high potential evaporation, thesurface water is accompanied by kinetic fractionationin association with the impact of rapid evaporation.
The kinetic fractionation e#ect, which depends on thewater surface temperature and relative humidity near
the water surface, is known as the Craig-Gordon
model (Craig and Gordon, +30/). Moreira et al. (+331)
simpliﬁed the model under the assumption that temperatures at water surface and in the atmosphere are
the same.
+2

+0

dE
ak ῑ ῍ dLda῏ΐῌ (,)῏+ῑ
῏+῏ῐhῌ῍ῌ aῌ
῎+*- ῏+ῐ῔+ῐh ῒ ῎+*- ῐ+*where dE, dL and da stand for d-values of evaporatingwater vapor, a liquid water body, and ambient air,respectively, a andak are the equilibrium and kinetic
fractionation factors, and h is the relative humidity (*῕h῕+). Majoube (+31+) expressed the equilibrium
fractionation factor as a function of water surface
temperature T (K):ln῍+ῌa῎ῑ+.+-1ῌ+*-ῌT,ῐ*..+/0ῌTῐ,.*001ῌ+*ῐ- for +2O.

(-)

89

(.)

ak ranges +.*+/ῐ+.*-+ and +.*+-ῐ+.*,0 for d +2O and dD,
respectively, with high values for di#usive boundary
layer and low values for turbulent boundary layers(Sofer and Gat, +31/; Merlivat, +312; Flanagan and Ehleringer, +33+; Wang and Yakir, ,***). The values ofdE and dL deﬁne a line in d +2O vs. dD space called theevaporation line whose slope, S, is given by:Sῑ          



. (/)



Kinetic isotope e#ects are known to occur not
only during evaporation (Craig and Gordon, +30/; Majoube, +31+; Merlivat, +312) but also during ice formation from water (Gibson and Prowse, ,**,). The
Heihe River water is frozen during winter. When
comparing the d-values with those in a di#erent season, we found it necessary to estimate d-values as theunderlying liquid of the frozen-over winter river water. The mass balance of isotopes during ice formation can be expressed in case of the absence of sublimation:
V*ῌd*ῑVwῌdw῏Viῌdi ῌ(0)where V and d are volume or depth and d-values,
respectively. Su$xes *, w, i stand for initial water,
fractionated water and frozen ice, respectively.
Water sampling and analysis
We conducted water sampling of river water andgroundwater from February ,**, to September ,**..
In the middle reaches, groundwater was collectedonce a month at a piedmont hill, an allvial-diluvial
fan, and a ﬂuvial plain covered by sand and silt; inaddition, river water was also collected at site B (Fig.
+). In the lower reaches, groundwater was collectedonce a month at a riparian forest site , (R,), a riparian
forest site - (R-) and the Gobi Desert site (DE). On
October ,**-, groundwater was collected at 0 sites
along a -**-m line transect through the riparian forestsite + (R+) to the desert-riparian fringe site (FG). On
February and June in ,**,, September and October in,**-, groundwater was collected at /0 sites in desert
and riparian vegetated areas (Fig. +). At the sametime, the river water was also collected. Because of
kinetic fractionation due to freezing in winter, wecollected both surface ice and its underlying liquidwater to estimate its original liquid d-values using Eq.
(0). All samples were ﬁltrated by *.,*-mm ﬁlters before sealing in polyethylene or glass bottles.
The stable isotopic composition was analyzed forall samples using a water equilibration system coupled to a mass spectrometer (ThermoQuest DeltaPlus)
-.-

90

Bulletin of Glaciological Research

Fig. ,. Monthly discharges at sites A, B, C and D (Fig. +)from ,**, to ,**..

maintained by the Hydrospheric Atmospheric Research Center (HyARC), Nagoya University, Japan.
Reproducibility was *.*-῍ for d +2O and *./῍ for dD(Members of Management Committee of Analytical
System for Water Isotopes at HyARC, ,**/).

..

Results

Discharge
Figure , shows monthly discharges at sites A, B, C
and D (Fig. +). Total discharges during the irrigation
period, varying from -..-ῌ+*2 m- in ,**. to 0.-+ῌ+*2 min ,**-, were released from middle reaches, while
those at the terminus of the river (site D) varied from*.,2ῌ+*2 m- in ,**- to *.-+ῌ+*2 m- in ,**.. In theirrigation periods, the river waters were released irregularly with short durations. We call such conditions short-term released discharge. The river water
was observed at site D from August +. to August -+,from October ,* to October ,2 in ,**-, and from August ,* to August ,2 and from September ,+ to November . in ,**., otherwise it was dried up in both years.
The short-term released discharge led to revival of
one of the terminal lakes. However, the river driedup again at site D in 3 to+2 days in ,**- and in +, to ./days in ,**.. On the other hand, river water waspresent at site C over the non-irrigation periods, but
did not reach the terminus (site D).
..+

Groundwater level in lower reaches
Figure -a shows daily changes in the groundwater level in the riparian forest site + (R+), the desertriparian fringe site (FG), and the Gobi Desert site (DE)with river discharge at site C from October ,**- toDecember ,**.. At the riparian forest site + (R+), in
both irrigation and non-irrigation period, groundwater levels rose rapidly after the river appeared due tothe discharge released at site C. Once that ﬂow subsided, the groundwater level gradually declined.
Therefore, groundwater recharge occurs whenever
the river water is present at around site C. In contrast, at the desert-riparian fringe site (FG), the groundwater level rose mainly in the non-irrigation period.
..,

Fig. -. (a) Daily mean groundwater levels at R+, FG
and DE (Fig. +) with daily mean river discharge at
C (Fig. +). (b) Seasonal change in d +2O of groundwater at R,, R- and DE (Fig. +).

Fig. .. Relations between distance from the river andgroundwater level, d +2O of groundwater and riverwater, and Fwinter, which is a percentage derived
from winter river water in its groundwater along a-**-m line transect through R+ to FG (Fig. +) inlower desert reaches, October ,**-. Error bars of
Fwinter were determined due to the d +2O variations ofriver water in irrigation and non-irrigation period.

Short-term released discharge in August ,**. did notcontribute to a recharge, suggesting that such transient discharge disappears before the water ﬂux reaches the desert-riparian fringe site (FG). At the Gobi
Desert site (DE), no change was found all year long,indicating that no river water is likely to recharge thegroundwater in a desert area. Akiyama et al. (,**-)
also demonstrated that the source of groundwater atAkiyama et al.

the Gobi Desert site is high-intensity precipitation.
Figure . shows a groundwater table proﬁle fromthe river to the desert in October ,**-. The surface
was based on a topographic survey. The table was
gradually inclined from the riverbed to the desert. It
was obvious that a groundwater recharge occurred.
Based on Darcian law (Darcy, +2/0), average linear
velocity V is given by
Vῑ

Kΐh
ῌ
n

(1)

where ΐhῑ(hR῏hG)/l is hydraulic gradient (hR is riverhead, hG is groundwater head, and l is distance), K is
hydraulic conductivity (m s῏+), and n is e#ective porosity. Estimation using K for *.**,, n for *., (Wu etal., ,**-), and ΐh for /.3ῐ+*῏- provided /.+ῐ+*῏/ m s῏+.
For example, it would take more than 0* days forgroundwater to ﬂow from the river bank to -** m
away.

91

tions, the degree of kinetic evaporation e#ect could beobtained. The estimated slope ranged from ..+ to ..0and from /.- to 1.- at the DE and Zhangye meteorological station, respectively. The observed slope in
Eq. (3) was similar to the estimated slope at the Gobi
Desert site (DE). Therefore, the river water in theirrigation period at site B had a trace of strong kinetic
evaporation e#ect.
A d-diagram of groundwater in the middle reaches is also shown in Figure /. The d-values of groundwater in the middle reaches, which varied little all
year long, were similar to those of the river water at B
in the non-irrigation period. d +2O of the groundwater
ranged from ῏2./+ῒ to ῏1.,+ῒ and dD ranged from῏/..+ῒ to ῏.-.2ῒ. The regression line was determined as
dDῑ1.+/d+2O῎1.21

R,ῑ*.0,῍(+*)

Stable isotopes in lower reaches
A d-diagram of river water in the lower reaches isshown in Figure /. The d-values in river water in thelower reaches varied with the period, as they did at site
B. In the irrigation period, d +2O ranged from ῏1./+ῒ to
῏..2+ῒ, and dD ranged from ῏.3.-ῒ to ῏-,.3ῒ. In
contrast, in the non-irrigation period, d +2O ranged from
῏2.-,ῒ to ῏1.20ῒ, and dD ranged from ῏/-.3ῒ to
῏/*.1ῒ. The d-values were remarkably higher in theirrigation period than in the non-irrigation period.
In non-irrigation period, since the d-values of theriver water in the lower reaches were similar to thoseof the river water at site B (Fig. /), the river waterﬂowed down to the lower reaches without being a#ected by evaporation. On the other hand, in the irrigation period, the d-values of the river water in the lower
reaches were also similar to those of the river water atsite B except when the river water was almost completely depleted. This was attributed to the fact thatthe almost completely depleted river water, which...

Stable isotopes in middle reaches
A d-diagram of river water at site B (Fig. +) isshown in Figure /. The d-values exhibited drastic
seasonal variations. In the non-irrigation period,
d +2O at site B ranged from ῏2./3ῒ to ῏0.1+ῒ and dDranged from ῏//.*ῒ to ῏-3.*ῒ. The river water
samples at site B in the period were plotted near the
Global Meteoric Water Line (GMWL). The regression
line was determined as..-

dDῑ1.*1d+2O῎0.,2R,ῑ*.21῍(2)

The results showed that the river water in the nonirrigation period had no trace of signiﬁcant kinetic
evaporation.
In the irrigation period, on the other hand, d+2O of
the river water at site B ranged from ῏0.0.ῒ to ῏,..2ῒ,and dD ranged from ῏...,ῒ to ῏,0..ῒ. They werehigher than in the non-irrigation period. The regression line was determined asdDῑ..-*d+2O῏+0.*

R,ῑ*.31῍(3)

In order to test the evaporation e#ect, we estimatedits slope using Eq. (/). Unfortunately, no meteorological data were available at site B. We used thedaily dataset measured at the Gobi Desert site (DE) inthe lower reaches (Akiyama et al., ,**-) and at the
Zhangye meteorological station in the middle reaches(Fig. +). The latter dataset was obtained from
National Climatic Data Center, National Oceanic andAtmospheric Administration, U.S. Department ofCommerce. The annual potential evaporation estimated using wind speed, air temperature and relative
humidity with no cloud cover were about -/** mmand about ,*** mm at the DE and Zhangye meteorological station, respectively, based on the method by
Kondo and Xu (+331). Comparing both slopes estimated based on such di#erent meteorological condi-

Fig. /. d-diagram of water samples collected from ,**,
to ,**. within Heihe River basin.

92

Bulletin of Glaciological Research

Table +. Result of statistical analysis of groundwater between riparian and desert areas. The analysis
was made using samples on June and February in ,**, and on September and October in ,**-.

had higher d-values, did not reach the lower reaches(Fig. ,).
A d-diagram of groundwater in the lower reaches
is also shown in Figure /. The d-values of groundwater were higher in the riparian than in the desert
areas. The t-test results in Table + demonstrated thatd-values of groundwater in the riparian area weresigniﬁcantly di#erent from those in the desert area,
indicating that the sources of the groundwater must
be di#erent.
The d-values of the groundwater in the riparianarea were plotted within the river water in both theirrigation and non-irrigation periods (Fig. /), suggesting that groundwater in the riparian area would becomposed of the river water in both periods.
Figure -b shows seasonal change of d +2O in groundwater at the riparian forest site , (R,), riparian forestsite - (R-) and the Gobi Desert rsite (DE). The valuesof d +2O ranged from ῌ1.-0῍ to ῌ0.3,῍ at R,, ῌ1..-῍to ῌ1.++῍ at R-, and from ῌ3.1*῍ to ῌ3..3῍ at DE,
respectively. There were only minor variations,which amounted to less than *...῍ for R,, *.-,῍ for R-, and *.,+῍ for DE.
Here we examines spatial variation of d +2O ingroundwater along a -**-m line transect through riparian forest site + (R+) to desert-riparian fringe site(FG). Figure . shows the d +2O proﬁle in October ,**-.
The d +2O was higher in the riparian forest region (* mto ,** m), while lower in the desert-riparian fringe
region (,/* m to -** m), averaging ῌ0.2+῍ for the
riparian forest region and ῌ1./1῍ for the desertriparian fringe region, respectively.

/.

Discussion

Formation of river water in lower reaches
In the irrigation period, most of the river water inthe middle reaches is supplied by the melt water ofglaciers together with a fair amount of precipitationfrom the upper reaches (Liu et al., ,**-). Most of thatwater is distributed to cultivated land in the reaches(Wang and Cheng, +333). A very small amount of the/.+rest is heavily a#ected by evaporation (Fig. /), andﬁnally disappears without reaching the lower reaches(Fig. ,). Only at the end of the irrigation period were
the short-term discharges released from the middle
reaches, and ﬂowed down to the terminal lakes (Fig.
,).
In the non-irrigation period, although there waslittle precipitation in the middle reaches, the discharge at site B was more than at site A (Fig. ,). Thismeans that the river water at site B is supplied bygroundwater discharge in the middle reaches. The
groundwater table inclining from piedmont hill to thelower edge of the fan (Wu et al., ,**-) also suggests thepossibility of groundwater discharge. The isotopic
compositions of groundwater in the middle reaches
were similar to those of the river water not only at site
B but also in the lower reaches (Fig. /), suggestingthat the river water derived from the groundwater inthe middle reaches ﬂowed down to the lower reaches
without being a#ected by evaporation (Fig. /).
Groundwater recharge mechanism in lower reaches
The groundwater recharge mechanism in the riparian area must be di#erent from that in the desert
area, because stable isotopic compositions were signiﬁcantly di#erent between the two areas (Fig. /).
Akiyama et al. (,**-) studied the mechanism in thedesert area, and carried out both water sampling foranalyzing isotopic composition and observations ofprecipitation, evaporation, and soil water content at
the Gobi desert site. They concluded that nothing
but high-intensity precipitation inﬁltrated rapidly
enough without being a#ected by evaporation was asource of groundwater in the Gobi Desert. Akiyama
et al. (,**-) also concluded that source of groundwaterin the riparian area was river water. Because riverwater was released from the middle reaches in di#erent manners between the irrigation and the nonirrigation periods (Fig. ,), and the amount of riverwater recharging groundwater should vary with seasons.
In the irrigation period, the river water obviously/.,Akiyama et al.

recharged at a riparian forest site + (R+) ,* m from theriver (Fig. -a). At a desert-riparian fringe site (FG)which is -** m from the river, however, the riverwater scarcely recharged the groundwater at all (Fig.
-a). Based on Darcian law (Darcy, +2/0), it would takemore than 0* days for groundwater to ﬂow from theriver bank to -** m away. However, the river driedup again at site D in less than ./ days. This is thereason why the short-term released discharge did notcontribute to recharge the groundwater in the desertriparian fringe region.
In the non-irrigation period, the river water stayed longer than in the irrigation period, and thus
recharged the groundwater even at the desertriparian fringe site (FG) (Fig. -a). This conclusion is
supported by the fact that the d-values of the groundwater in the riparian area were plotted on a regression
line within the two end members, which were theriver water in irrigation and non-irrigation periods(Fig. /).
Figure . shows that the d +2O of groundwater inthe riparian forest region (* m to ,** m) was higher
than that in the desert-riparian fringe region (,/* m to-** m). Their averages were ῌ0.2+῍ for the riparian
forest region and ῌ1./1῍ for the desert-riparianfringe region, respectively. These values were similar
to the average d-values of river water in the irrigation
period (ῌ0..,῍) and non-irrigation period (ῌ2.*.῍).
Considering that the seasonal variations in any riparian area shown in Fig. - were small, the shape of thed +2O proﬁle shown in Fig. . can be assumed to be similar throughout a year. Therefore, we suggested thatgroundwater in the riparian forest region would bederived from river water in the irrigation period,
while that in the desert-riparian fringe region would
have originated from river water in the non-irrigation
period.
Here, we estimate its mixing ratio in the samemanner as an isotopic mass balance of Eq. (0) using
d-values of the groundwater, together with the riverwater in the irrigation and non-irrigation periods.
Figure . shows the Fwinter, which is the estimatedpercentage of river water in the non-irrigation period
in the groundwater. The Fwinter in the desert-riparianfringe region was higher than that in the riparian
forest region. This is consistent with the fact thatthe groundwater level in the desert-riparian fringesite (FG), which is located -** m from the river, did not
rise due to short-term released discharge during theirrigation period (Fig. -a). Therefore, we conclude
that short-term released discharge in the irrigation
period scarcely contributes to groundwater recharge
in the desert-riparian fringe region.

0.

Conclusion
We analyzed the surfacewater-groundwater inter-93

action in the lower reaches by both hydrological analysis and tracer-based approaches with a consideration of its seasonality. The interaction was signiﬁcantly di#erent between the irrigation and nonirrigation periods. Isotopic analysis revealed thatthe river water in the non-irrigation period was mostly derived from the groundwater in the middle reaches, and recharged the groundwater in the lower
reaches throughout the period. On the other hand,short-term released discharge from the middle reaches
in the irrigation period scarcely contributed to groundwater recharge in the desert-riparian fringe region of
the lower reaches.
To protect the groundwater resources in thelower reaches, we must take steps to prevent thedisappearance of the river. Our results strongly suggest that water management of not only surface water
but also groundwater throughout the entire basin iswarranted. At the same time, further studies of thehydrological cycle in the entire basin are essential,
taking account of the glacier shrinkage and climatechange, particularly in the upper reaches as well.

Acknowledgments
The authors would like to express their appreciation for the ﬁnancial support provided by the Inoue
Field Science Research Foundation, Japanese Societyof Snow and Ice. We also wish to thank T. Hiyama(Nagoya University) and O. Abe (Nagoya University)
for their analyses of the isotopic compositions, as wellas the many local people who cooperated with us.
This research is partly funded by a contribution fromthe Oasis Project (Historical evolution of adaptability
in an oasis region to water resource changes), promoted by the Research Institute for Humanity andNature (RIHN), Japan. We also would like to express
our special gratitude to a reviewer.

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Bulletin of Glaciological Research

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