沙漠研究 24-1, 97-100 (2014)
Ἃ₍◊✲ 24-1, 97 - 100 (2014)
Journal of Arid Land Studies
Journal of Arid Land Studies－ DT11 Refereed Paper －㸫DT11 Refereed Paper㸫

Groundwater Recharge Revealed by Multi-tracers Approach and EMMAin Semi-arid Irrigated Village, Heihe River Basin, Northwest China
Yutaka ABE*1), Maki TSUJIMURA2) and Masayoshi NAKAWO3)
Abstract: A hydrological field survey using multi-tracers was performed to identify groundwater recharge sources and thosecontribution rates at the village scale in an irrigated area in a semi-arid region. Groundwater, river water and irrigation water samples
were taken in Pingchuan village which is irrigated by river water and groundwater in Heihe River basin, Northwest China in August
2010. Major inorganic solute compositions and Hydrogen and Oxygen stable isotopes were analyzed and End Member Mixing
Analysis (EMMA) was calculated using two tracers of Cl and įD, and end members of Heihe River main stream, Liyuanhe River as
branch and old groundwater outside of irrigated area. Ion compositions of groundwater in the irrigated area tended to be similar toriver water as Ca, Mg - HCO3 type and the groundwater also had similar isotope compositions to river water. Recharge contribution
calculated by EMMA showed high contribution of water from the Heihe main stream and Liyuanhe River. Thus, it is suggested thatgroundwater in this village is not only recharged by the Heihe River main stream via irrigation activities but also by branches such as
Liyuanhe River. On the other hand, a few groundwater samples had Na+, Mg2+, Cl-, SO42- dominant and high concentrated water
quality and lower isotopic compositions. The high concentrated groundwater located along the boundary between Gobi desert area
and the irrigated area tended to have relatively high contribution rates of old groundwater outside of the irrigated area which indicate
low sustainability and possibility of soil salinization for irrigation farming. Our results indicate that there are significant differences
between the irrigated area and marginal area in groundwater quality and recharge system even at the small village scale.
Key Words: Contribution rate, EMMA, Groundwater recharge, Heihe river basin in Northwest China, Multi-tracers1. Introduction
Social concerns regarding the conservation of water
resources have been growing for the last several years.
Especially in arid and semi-arid regions, groundwater tends tobe the main water resource due to lack of surface water.
There are several issues to be addressed such as rapid
depression of groundwater level caused by unrestrictedpumping without any strategies of sustainable groundwater
management based on scientific information in irrigated farmareas. Thus, it is essential to have a sustainable control ofwater resources with enough understanding of the hydrologicalcycle such as groundwater recharge and flow processes
especially in arid and semi-arid regions.
Previous researches show that geochemical approaches
such as stable isotopes, radio isotopes and inorganic soluteconcentrations are effective ways to determine groundwater
recharge and flow processes in arid regions (Scanlon et al.,2002). Many hydrological studies observed that groundwater
recharge flow processes tend to be preferential or
inhomogeneous in scale and time in arid and semi-arid regions(Onodera, 1996; Tsujimura et al., 2007).
Howevergroundwater recharge system in relation to human effects suchas in irrigation activities is not widely understood. Abe et al.
(2011) observed local characteristics of geochemical andisotopic compositions in upper, middle and lower reach in
irrigated areas in Zyangye flat plain in the center of the Heihe
River basin. They also noted complex groundwater recharge
processes in middle reach. Thus, there is a need to detailobservations in a smaller scale.
Therefore the purpose of this presentation is to identify
local characteristics of groundwater recharge resources andthose contribution rates in small scale (i.e. village scale about
20 km) in a semi-arid irrigated region in northwest China.

2. Study Area
The study area was set in the Pingchuan region which is avillage that primarily uses irrigated farmland for cultivationand is located in Heihe river middle basin, northwestern China(Fig. 1). The upper basin is comprised of mountains up to4,000m in elevation called Qilian Mountains. The annual
precipitation ranges from 300 to 500 mm a year and glaciers㸦Received, September 15th, 2013; Accepted, March 5th, 2014㸧

* Corresponding Author: abe.yutaka.hydro@gmail.com
Motoyama, Kamigamo, Kita-ku, Kyoto 603-8047, Japan
1) Research Institutes for humanities and Nature2) University of Tsukuba

3) National Institutes for the Humanities

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Fig. 2. Land use of study area and sampling sites in Pingchuan
region in middle basin. Land use data is modified by authors
after non published data of Cold and Arid Regions Environmentaland Engineering Research Institute, CAS, China. Land use inSouthern part of the map from Heihe river is unknown.
However, it was confirmed by authors that land use in thoseregions is mainly irrigated farmland.

Fig. 1. Topography of Heihe river basin and location of Pingchuan
region. Black lines show river line of Heihe river and theirbranches flowing from Qilian Mts. Study area shown by square islocated in meshed irrigated region.

are present. The middle basin where Pingchuan region islocated is in a semi-arid region with average precipitation ofless than 200 mm a year (Wang and Cheng, 1999). In thisregion, people take Heihe River water from the upper
mountainous region for irrigation through concrete canals
widely spread in farmland to produce mainly maize and wheatfrom May to September. Therefore the mountainous area
provides the main water source for the irrigated region in themiddle basin. Because of problems such as river dry-up anddecreasing groundwater levels in the lower basin caused byoveruse of irrigation water in the middle basin, regulation ofriver water for irrigation has been enforced since the beginningof 2000. This intervention caused groundwater use toincrease as the alternative water resource (Yamazaki, 2006).
In such severe condition of groundwater overexploitation, it isimportant to understand the groundwater recharge and flowsystem.
Abe (2012) suggested that the sources ofgroundwater recharge may be not only Heihe River by
irritation water but also the Branch River in the middle basin ofHeihe River.
The geological setting on alluvial fan and flat plain of theirrigated area is underlain by Quaternary deposit with the depthof approximately 100 m (Hu et al., 2007).

3. Methodology
Field work for inorganic solute concentrations andHydrogen and Oxygen stable isotopes analysis of river andgroundwater in Pingchuan village in the middle basin of HeiheRiver were performed from 9th to 13th August 2010.
Groundwater samples from 37 sites and 1 sample from Heihe
River, the source of irrigation farming, were taken in
Pingchuan village (Fig. 2). Also, irrigation canal water in
Pingchuan village and river water in Liyuanhe River which ismajor branch of Heihe River basin were sampled.
Groundwater samples were collected from basically 3
types of wells: house wells, farm wells, and observation wells.
“House wells” are in farmer’s houses for daily use with depths
ranging from 5 to 20 m. “Farm wells” are for irrigation waterand are relatively deeper than other wells with depths ranging
from 20 to 100m. “Observation wells” are owned by Coldand Arid Regions Environmental and Engineering ResearchInstitute, CAS, China. Their depth ranges from 10 to 15 m.
Because those wells were constructed for groundwater
research, they are not used daily.
Major inorganic solute concentrations (HCO3-, Cl-, NO3-,SO42-, Na+, K+, Mg2+, Ca2+, Si) and Hydrogen and Oxygen
stable isotopes (įD, į18O) were measured in water samples at
the University of Tsukuba, Japan.
End Member Mixing Analysis (EMMA) is an effective
way to identify the contribution rates on discharge of eachresource from geochemical data. Contribution rates arecalculated using tracers such as inorganic solute concentrations
and isotopes on the condition that discharge consists of only
mixing from groundwater and soil water in the catchment (e.g.
Hooper et al., 1990). Contribution rates “f” are calculated byfollowing mass balance equations.

fa  fb  fc

1

C1a f a  C1b f b  C1c f c

C1gw

C 2 a f a  C 2b f b  C 2c f c

C 2 gw(1)

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Fig. 3. Spatial distribution of water quality of groundwater and river water with hexa-diagram in Pingchuan village.

Where C1 and C2 are concentrations of tracers and a, d, c arecomponent of end members. In this study, we endeavored tocalculate which source water contributes to each groundwater.
According to previous research of groundwater recharge
resource (Abe, 2012), Heihe river main stream water andbranches which infiltrate into irrigated area from NE side of
Qilian Mountains are important sources of groundwater in theirrigation flat plain. Third End member should be identified
from an area outside of the irrigated area which does not seemto have interaction between river or irrigation water. It wasobserved that the groundwater outside of the irrigated area has
longer residence time (before 1950) than other groundwaterusing Tritium analysis. Thus, site Rm.3 as “Heihe River mainstream” which can be irrigation water, site Rb.102 as “Branchfrom NE side of Qilian Mountains” (Liyuanhe River) and site
W-ob.4 gobi as “old water outside of irrigated area” weredecided as end members. Chloride concentrations and įD
were chosen as tracers.

Those highly concentrated groundwaters were located along
the boundary between Gobi desert area and irrigated area.

4. Results and Discussion

4.2. End member mixing analysis and sustainability ofgroundwater
Figure 4 shows spatial distribution of contribution rates ofgroundwater calculated by EMMA. Contribution rates
showed high contribution of Heihe main stream and LiyuanheRiver. It is suggested that groundwater in this village recharged
by the Heihe River main stream by irrigation activities as well asbranches such as Liyuanhe River via groundwater.
On the other hand, a few groundwater sites showed
relatively high contribution of old groundwater outside ofirrigation. This groundwater is generally located on the edgeof the irrigated area and has high concentrations of ioncompositions. These results indicate low sustainability ofwater resources for irrigation farming and possibility of soil
salinization. Furthermore, there are significant differences
between the irrigated area and marginal area in groundwater
water quality and recharge system even on a kilometer scale.

4.1. Inorganic solute concentrations and isotopes

5. Conclusion

Figure 3 shows spatial distribution of inorganic soluteconcentrations in groundwater and river water withhexa-diagram in Pingchuan village. Ion compositions ofgroundwater located in the irrigated area near Heihe Rivertended to be similar to river water as Ca, Mg - HCO3 type.
On the other hand, there were a few samples having Na, Mg,
Cl, SO4 dominant and high concentration of ion compositions.

A hydrological field survey using multi-tracers wasperformed to identify groundwater recharge sources and thosecontribution rates on a village scale in an irrigated area in thesemi-arid region, Heihe River basin. Groundwater in theirrigated area was found to be recharged by the Heihe River
main stream by irrigation activity and branches such as
Liyuanhe River via groundwater. On the other hand, a few

100Fig. 4. Spatial distribution of contribution rates of groundwater calculated by EMMA in Pingchuan village.

groundwater sites in the marginal area showed significant
difference such as high contribution rates of old groundwateroutside of the irrigated area and higher concentrations of ioncompositions. Those results indicate that groundwater in themarginal areas has low sustainability for irrigation farming andpossibility of soil salinization exists at short distances from theirrigated area. We observed inhomogeneous groundwater
quality and groundwater recharge processes even at the village
scale in this semi-arid irrigated area.
Appendix
The authors would like to heartily thank Prof. Xiao HL., Dr.
Zhao LJ., Dr. Ren J. and Dr. Yang Q. (Cold and Arid Regions
Environmental and Engineering Research Institute, CAS,
China) for all the support on field survey in China. This work
was financially supported by Precipitation change in western
China during Qing Era reconstructed with the official
document data.

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