IJERD – International Journal of Environmental and Rural Development (2012) 3-1

Research article
erdInfluences of Agricultural Irrigation on Regional Salinity
Balance in Arid Areas of Northwestern China
ABDISALAM JALALDIN*
College of Resources and Environmental Sciences, Xinjiang University, Xinjiang, China
Email: asalam188@hotmail.com

TADAO YAMAMOTO
Research Faculty of Agriculture, Hokkaido University, Hokkaido, Japan

TAKU OIKAWA
Graduate School of Agriculture, Hokkaido University, Hokkaido, JapanANWAIRE MAIMAIDI
Xayar Water Resource Agency, Xinjiang, ChinaTETUAKI NAGASAWA
Research Faculty of Agriculture, Hokkaido University, Hokkaido, Japan
Received 15 December 2011

Accepted 2 April 2012(* : Corresponding Author)

Abstract It is widely recognized that saline transfer and distribution are importantconsiderations in arid areas, where salinization is prevalent, not only for sustainableagricultural production but also for regional environmental conservation. This study
discusses the saline balance of the irrigation area in the Tarim River basin of northwestern
China. Water quality was investigated at irrigation and drainage channels from 2007 to2011. The regional water balance was calculated using the water supply and drainage
volume data owned by the Xayar Water Management Office and its branches. Comparing
the quality of irrigation and drainage water, the concentration of cations (except K+) indrainage water was found to be 15 times more than that in irrigation water. Based on theestimation of water balance, it was confirmed that only approximately 5% of the irrigationwater flowed out as drainage water. The remaining supplied water is used forevapotranspiration, and groundwater recharge was considered. In addition, the output loadof K+, Ca2+, and Mg2+ was lower than the input load. However, the output load of Na+
increased by approximately 20% of the input load. This indicates that continuous irrigation
does not necessarily promote saline transfer and that salinity is retained in groundwater orsoil in this region. Finally, because of the substantial exhaustion of Na+, it is necessary toconsider the influence of increased levels of Na+ in downstream drainage areas.
Keywords salinization, saline movement, irrigation and drainage, water balance, water
quality

INTRODUCTION
In arid areas where salinization is prevalent, an important question to consider is where the salinity
moves. If saline simply moves downstream through drainage, then water containing saline
nourishes irrigated areas and natural vegetation in the downstream areas. If saline does not move
downstream through drainage, it may accumulate in the groundwater or soil and lead to problems
in future groundwater use. Thus, it is widely recognized that saline transfer and distribution areimportant considerations in arid areas, where salinization is prevalent, not only for sustainableagricultural production but also for regional environmental conservation.
While many studies have described soil salinization and prevention of salinization in the field(Chen, 2010, Barrett-Lennard, 2002), research concerning saline movement and saline balance overⒸ ISERD108

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wide areas, particularly in arid areas such as the Tarim River basin, is lacking. In the Tarim Riverbasin, soil salinization has occurred in approximately 80% of the irrigated area (Yamamoto et al.,2006). Consequently, it is necessary to examine saline movement and saline balance not only at thefield level but also over wide areas in this region.
METHODOLOGY
The study was conducted at the Xayar County in Xinjiang, northwest China (Fig. 1). Xayar County
is located in the Ugen River basin. Ugen River is a branch on the upper stream of the Tarim River.
The county population is approximately 180,000 and its area is 31.97×103 km2. The main local
crop is cotton and other crops such as wheat and corn. The cultivated area is 0.632×103 km2,
where cotton plants cover approximately 50% of the total cultivated area. Irrigation relies mainly
on surface water from the Ugen River and ground water is used mainly in cotton and fruit fields fordrip irrigation. Annual rainfall is 47.3 mm, potential evapotranspiration is 2000.7 mm and theannual mean temperature is 10.7°C (maximum temperature, 41.6°C and minimum temperature,-28.7°C) (Xayar Government HP).

Fig. 1 Outline of Investigation Area
The regional water balance was calculated by using the 2007 - 2009 data of daily water supply
and drainage discharge owned by the Xayar Water Management Office. Each discharge wascalculated several times a day by flow measurement. Evapotranspiration data was derived from Ge
Gao et al. (2007) because it was not available for this site. Water was collected at irrigation anddrainage canals several times in 2007-2011 only during which water flowed, and then thesesamples were analyzed in the laboratory. Electric conductivity (EC) was measured by EC meter(HANNA Instruments) and sodium (Na+), calcium (Ca2+), potassium (K+) and magnesium (Mg2+)
were analyzed by ion chromatography (SHIMADZU Corp).

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RESULTS AND DISCUSSION
Discharge of irrigation and drainage and water balanceTo estimate the water balance in Xayar County, the irrigation and drainage discharge data suppliedby water management office were used. In addition, the drainage volume flowing through Xayar
and Xinhe counties was estimated by multiplying the irrigation distribution rate by the totaldrainage volume. Irrigation water from Ugen River is distributed to these counties at a constant rate
(Xayar, 32.5%; Xinhe, 28.0%; Kuqar, 39.5%) at Longkou headwork located at the upper point ofthese counties (Abdisalam Jalaldin, 2005) and the drainage discharge was assumed to depend on
the irrigation requirement as rainfall runoff has little influence. To estimate evapotranspiration in
Xayar County, we multiplied potential evapotranspiration by the constant 0.1. This constant is theratio of annual actual evapotranspiration to annual potential evapotranspiration during 1971 - 2000
(Ge Gao et al., 2007). Fig. 2 shows the monthly change in irrigation and drainage discharge and Fig.
3 shows the annual water balance in 2007 - 2009.
The largest discharge of irrigation water occurs in March and in summer season because water
demand rises during the sowing and growing periods. In addition, irrigation water is required in
November for sowing wheat in autumn. The largest discharge of drainage occurs in March andApril, decreasing in summer. Drainage discharge is believed to increase when shallow groundwater
outflows by thawing of the frozen soil layer. In contrast, drainage discharge is believed to decrease
when outflow from shallow groundwater is restricted by soil drying that is a result of increasing
evapotranspiration potential in summer.
The water balance in 2007 and 2008 showed the same tendency. However, the supplied water
volume decreased in 2009. This reduction is believed to have been caused by decreasing water
intake from the river resulting from improved water-conserving irrigation techniques, suchtechniques being introduced widely to farmers at the beginning of 2007 (T. Yamamoto et al., 2010).
Water balance data suggest that approximately 800-1000 mm y-1 of supplied water seeps into theground. Water management office data suggest that water-conserving irrigation techniques havebeen implemented in 10% - 20% of the total cultivated area. The net water requirement of cotton is
540 mm y-1 in this area. If this volume is pumped up from groundwater in the water-conserving
irrigation area, we can estimate that 5% - 13% of seepage water was utilized, which is equal to thereduction in water supplied during this period.

Fig. 2 Irrigation and drainage discharge(2007-2009)

Fig. 3 Water balance (2007-2009)

Water quality of irrigation and drainage water
Table 1 shows water quality of irrigation and drainage water on each sampling day. Changes in EC
values were small in irrigation water except for August 2007. Concentration of Na + varied
considerably, but concentrations of other cations exhibited only small changes. In particular, Na +concentrations tended to decrease during summer and increase during winter. EC values ofⒸ ISERD110

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drainage water were stably higher. Changes in cation concentrations in drainage water were lower
according to the variation coefficient, but the concentration of each cation measured was higher
than that in irrigation water. In addition, the seasonal changes in cation concentrations were notconfirmed. When the average quality of irrigation and drainage water was compared, theconcentrations of Ca2+ and Mg2+ in drainage water were found to be 15 times higher than those inirrigation water. Na+ concentration in drainage water was also 20 times higher than that inirrigation water. This indicates that the soil in this region is naturally saline or has turned saline
because of irrigation with water that became concentrated with salts before running off. In contrast,
K+ concentration in drainage water was only 4 times higher than that in irrigation water. This is
likely because the concentration of K+ was lower than that of other cations, and K+ in supplied
water is absorbed by plants more than other ions because K+ requirement for plants is higher.
Sodium adsorption rates (SAR) were measured based on the average concentrations. The SARof irrigation water was 3.6 and that of drainage water was 19.8. These levels indicate that based onthe standards of water quality for agriculture, the risk of soil salinization when irrigation waterfrom the river is used is slight to moderate, but the risk is extremely severe when drainage water isused (Soil Survey Division Staff., 1993, R.S. Ayers & D.W. Westcot, 1994). However, in the lower
basin where water shortage occurred, soil salinization might have been promoted because drainage
water was used for irrigation.
Table 1 Water quality of irrigation and drainage water
Irrigation water
Samplingdate
2007/6/6
2007/8/10
2007/11/25
2007/11/26
2008/3/29
2008/3/31
2008/12/17
2009/6/5
2009/8/9
2009/8/10
2010/3/12
2010/3/14
2010/7/21
2010/7/26
2010/11/26
2010/11/22
2011/7/27
2011/7/29
AverageSD
Variation
Coefficent

EC-1(dS m )

Draingae water-1

Concetration (mg L )++2+2+
Na
K
Mg
Ca

0.1
0.7

49.3
117.7

2.0
14.6

ND 6.3
ND 28.4

0.7

44.8

8.6

28.4

28.0

0.9

155.3

19.3

11.5

ND

0.6

19.3

7.6

33.8

5.7

0.7

25.0

17.9

33.5

18.8

0.4
0.9

14.5
35.2

ND 29.7
ND 9.2

3.6
55.9

0.6171.6

17.3

16.6

13.0

EC
Concetration (mg L-1)
-1++2+2+(dS m )
NaK
Mg
Ca
1220.1
33.1 349.3 341.0
15.4
1271.135.0 301.7 264.6
9.2
11.5

1458.5

10.0
9.5
12.4

ND
ND
ND
ND
937.2
80.2 448.2 239.5
918.2 124.1 496.6 329.1

9.2

1271.1

35.0

13.7
12.1

ND
2110.7

ND
22.1

ND
ND
ND 370.5

11.1

1860.018.1

ND2179.51576.1
528.3

76.5 369.7 459.5
48.1 386.6 322.4
37.2
71.9
70.2

0.3

0.6
0.2

70.3
61.0

12.56.5

22.7
11.0

20.4
17.3

18.0
12.3
2.6

0.4

0.9

0.5

0.5

0.8

0.2

31.0

0.8

354.4

301.7

0.2

275.0

264.6

ND

0.2

Saline movement and balance
The saline load balance in Xayar district area located in the Ugen River basin was calculated fromthe difference between input load and output load. Each load is calculated by multiplying theaverage concentration of irrigation and drainage water by monthly irrigation and drainage
discharge. The average concentration was calculated from the values of Table 1. In ourexamination, it was assumed that input derives only from supplied water for irrigation and output
was the outflow through the drainage canal.

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25
20
15
10
50
-5-10-15-20

Input

OutputBalance

Input

4.0

21.0

K+ Load (× 106 kg)

Na+ Load ( × 106 kg)

Figure 4 shows the monthly change in saline balance. Input loads increased compared withoutput loads in summer and vice versa in winter. Even when drainage discharge was low, theoutput load was high because the concentration of drainage water was higher than that of suppliedwater. The change in saline balance was divided into outflow and retention types (Table 2). Na+
was outflow type and other cations were retention type. As determined by three year averages, theoutput loads of K+, Ca2+, and Mg2+ decreased compared with the input loads; however, the output
load of Na+ increased by approximately 20% of the input load. Because the soil adsorptive propertyof Na+ is lower than that of Ca2+ or Mg2+; plants require less Na+ compared with K+; Na+ poorly
retained in this region was assumed to run off. In addition, each load balance tended to decrease.
This characteristic of decrease is because the cations retained in this region gradually flow out todrainage canals and that supplied water decreases. In addition, Ca2+ and Mg2+ loads indicate that
continuous irrigation does not necessarily promote saline transfer and that salinity is retained ingroundwater or soil in this region. Moreover, it is necessary to consider how Na+ outflow todownstream areas affects the lower basin and Tarim River at long term.
Outputbalance

3.73

3.0
2.0
1.0
0.0
-0.55

-18.1

-1.0 Jan Apr Jul Oct Jan Apr Jul Oct Jan Apr Jul Oct

Jan Apr Jul Oct Jan Apr Jul Oct Jan Apr Jul Oct

Fig. 4 Monthly change in saline load
Table 2 Saline load balance in 2007-2009
Na+
Input
20072008
2009
Average

K+

Output Balance Input

106
96
82
95

89
134
125
116

17-38
-43-21

19171417Mg 2+

Output Balance Input
344416131113343126
31

Output Balance Input

Ca2+
Output Balance

221231
181333-22827131-42425-228227244(Balance = Input - Output, Unit; x10 6 kg)

CONCLUSION
We analyzed discharge water and the quality of irrigation and drainage water and discussed waterand saline balance in the Tarim River basin in Xayar County. We found that the saline
concentration of drainage water was considerably higher than that of irrigation water. Water
balance data showed that approximately 80% of supplied water was seeped into groundwater orsoil. In addition, Na+ runoff from this area was greater than that of other cations and the exhaustionof other cations was smaller than that of Na+ because Na+ was not efficiently consumed or retained.
Considering the high exhaustion rates of Na+, it is necessary to consider the influence ondownstream areas when developing irrigation strategies in future.

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ACKNOWLEDGEMENTS
Xayar County Government, Xayar Water Management Agency and Xinjiang Uyghur AutonomousRegion Water Resource Management Bureau supported this research. This study is a part of theacademic research (No.21405031) supported by Grant-in-Aid for Scientific Research (B) from Japan
Society for the Promotion of Science (JSPS).
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