“ICAL 1/DT X Joint International Symposium with JAALS”

沙漠研究 21-2, 75 - 79 (2011)-Refereed Article-

Journal of Arid Land Studies

Underground Irrigation Canals in the Arid Regions through theHigh-resolution Satellite Images and Field Works
Hidehiro SOHMA*1）and Hisao WUSHIKI2)
Abstract: Underground irrigation canals in the arid region are discussed through the high-resolution satellite images, Corona, which
cover whole of a single canal system and its surroundings, in addition to the terrestrial conditions. Among the karez canals in Turpan
Basin, China, the reverse “J” plan pattern at the alluvial fans is distinctive. Mother wells of this pattern were moved up-stream,
extending oblique to the slope, to manage lowering of groundwater. In Yazd area, Iran, qanat systems develop along the bottom of
the longitudinal valley reflecting the basin and range landform which can collect groundwater from the both side. This terrestrial
condition seems to have produced 300 m deep and 80 km long qanat. Some qanats are found nearly along the contour line at thelowest margin of a small pediment, like frontlet. The same type is constructed in the valley of Bamian, Afghanistan. At thenorthern piedmont alluvial fans of Qilian Mountains, China, there are underground irrigation canals with ventilation ducts dug in theupper part of the river terrace cliff and horizontal aqueduct water is flowing directly from the river channel. This system is connected
to underground irrigation canals with vertical ventilation ducts.
Key Words: Corona, Terrestrial condition, Turpan, Underground irrigation canal, Yazd

1. Introduction
Professor KOBORI Iwao promoted researches on theunderground irrigation canals, consisted of vertical shafts andnearly horizontal tunnels, called qanat, karez and so on. They
spread all over the world, especially in the arid region (Kobori,1996). It is rather difficult to catch the whole system by theground-level view. Previously, researches on qanat wererestricted within a relatively small area, mainly focused on theusages along a single or small numbers of them. However,
introduction of the high-resolution satellite images, such as
Corona and QuickBird, made possible to recognize debris
heaps of shafts of underground irrigation canals in the large
area from the great altitudes. Consequently, we could get thewhole images both of a single canal system and neighboring
ones, in addition to the terrestrial conditions, namely landform
and landscape. Based on the interpretation of Corona images,
maximum ground resolution about 3 m, following
characteristics of underground irrigation canals are identified.

2. Study area
Studies were conducted on underground irrigation canals(karez) of the Turpan Basin, China, the Yazd area (qanat), Iranand the Bamian area, Afghanistan, and the undergroundirrigation canals at the Zhangye district, Gansu, China (Fig. 1).
Except the last one in the semi-arid region, others are situatedFig. 1. Study area (Modified from Research Center for Silk Roadology, 1996).

in the arid region. Among them, the field survey wasconducted only at the Turpan Basin.

3. Results
3.1. Turpan Basin
Many karez systems distribute in the Turpan Basin,(International Conference On Karez Irrigation, 1993). Basedon the interpretation of Corona images, debris heaps of karez
systems are easily recognized as the dots. Therefore,alignments of them correspond to the karez system. Theirdistributions are classified as follows; on the alluvial fan of thegravel desert of the northern and southern piedmonts ofFlaming Mountain and on the mud desert of the lower marginof the latter, and this classification is nearly same as Yang
(1993) and a little bit different from Liu (1993).
（Received August 25th, 2011; Accepted October 13th 2011）* Corresponding Author: hsohma@cc.nara-wu.ac.jp
Kitauoya-nishimachi, Nara, Nara, 630-8506, Japan
1) Faculty of Letters, Nara Women’s University2) 4-23-16-212 Yoyogi, Shibuya-ku, Tokyo, 151-0053, Japan

Fig. 2. Distribution of karez systems at the northern piedmont of theFlaming Mountain (Lower marginal parts of the alluvial fansfrom the Tianshan Mountains).

Fig. 3. Karez repairing in theTurpan Basin.

Figure 2 shows the most typical karez systems in theTurpan Basin, namely, the shaft alignment of the parallel
pattern, development at the lower marginal part of the alluvial
fan and the length of the shaft alignment around 2 km (Sohma,2002). Generally speaking, based on the consideration of thegrain sizes of the deposits, it will be severely hard to construct
the shafts or tunnels of the karez systems at the upper or middle
reaches of the alluvial fan by the primitive methods, namely
without machine assistances.
During the research with professor Kobori in 1999, we
encountered repairing of one karez, in the gravel desert of thesouth-western part of the Flaming Mountain. The depth ofthe vertical shaft was more than 40 m (Fig. 3) and it was verydeep.
This deep aquifer level was concordant withremarkable decrease of karez systems in number at Toksun
area, western part of the Turpan (Kimoto et al., 1991).
Shaft patterns aligned in the reverse “J” shape of the upper
part of the karez systems developed at the southern piedmontsand the western parts of Flaming Mountain, but did not
develop at the mud desert areas. Figure 4 suggests, at least,

Fig. 4. Upward movements of the mother well lines (Southernpiedmont of the Flaming Mountain). Data available from
U.S.Geological Survey, EROS Data Center, Sioux Fall SD.

Fig. 5. Distribution of karez and oases along the profile in the Trupan
Basin. K: karez O: oasis

two step movements of the mother well lines, linked line of theneighboring mother wells, to the upper course against thesubsidence of the groundwater level, and the reverse “J” shapepattern was dominant at the upper most mother wells areas in
Figure 4.
Based on the above, shafts alignment of the reverse “J”
shape is considered to manage lowering of groundwater level.
Based on the Corona images taken in 1966, thedistributional relationship between the karez systems and oases
along the profile in the Turpan Basin is summarized as Figure
5. Electrically-powered pumping wells were not popular inthis basin in 1966. Figure 5 suggests distribution of oases inthis basin closely related with the karez systems
3.2. Yazd area
Yazd area is well known as one of the oldest areas where
the underground irrigation canal system, qanat, was entered inuse (for example, Kobori, 1996). In addition, there is a qanat
reached to 80 km in the length of horizontal tunnel (Yazdi,2011, personal communication), and a qanat of 300 m in depthFig. 6. Index map of the Yazd area.
Data available fromU.S.Geological Survey, EROS Data Center, Sioux Fall SD.

(Kobori, 1996).
Yazd and surrounding areas are characterized by the “basinand range” landforms of the Iranian plateau, and without
glaciers on the mountains. Annual precipitation is more than
100 mm/yr with mainly in the winter season.
Figure 6, collected of 10 sheets Corona images in themosaic style, is the index map of the Yazd area. Each Corona
images are about 18 km wide and were taken on May 25 1970.
In Figure 6, narrow nearly straight lines running in NW-SE
with shadows on the both sides are mountains and between
them are basins or valleys reflecting the “basin and range”
landforms.
3.2.1. Abarqu
Abarqu is located about 130 km southwest of Yazd.
There developed two different types of qanat; one is nearly
along the slope at the lower part of the alluvial fan from thewest, and the other is at the bottom of the valley along thesouthwestern flank of the mountain running NW to SE (Fig. 7).
Qanat systems at the marginal part of the alluvial fan havethe same terrestrial condition with those of the Turfan Basin,
and this type is most common in the underground irrigation
canals.
Qanats constructed at the valley bottom areconnecting oases and groundwater of this type come from bothside of the valley reflecting the basin and range landform.
3.2.2. Yazd
Figure 8 is the Corona image of a part of Yazd whichdeveloped at the longitudinal valley of the basin and range
landform. In Figure 8, individual debris heaps of the qanat arerecognized as each dots and their alignments show qanat
systems.
From Figure 8, followings are apparent; 1) there are clear
differences in the dot sizes showing those as the debris heap
sizes and those in the amount of debris brought from theunderground, 2) distances of the each debris heaps of a qanatare roughly classified into six groups ranging from 10 m to 15m, 25 m to 30 m, around 50 m, 60 m to 75 m and 100 m, 3)

Fig. 7. Two types of Qanat at Abarqu (Location is shown in Fig. 6)..
One is at the lower marginal part of the alluvial fan and the other
stretched along valley bottom.

Fig. 8. Qanat systems in Yazd (Location is shown in Fig. 6).

some qanat lines cross each other.
Above mentioned 2) and 3) suggest difference in the depthof the horizontal tunnels, and 3) also suggests difference indigging stages.
Based on the above, it is clear that qanat systems in Yazd
are dug at the longitudinal valleys changing in depth and inmagnitude for a long period. This terrestrial condition of thelongitudinal valleys, related with the basin and range landform,
permits to construct qanat systems such as 80 km in the lengthof horizontal tunnel and as 300 m in depth.
3.2.3. Mahyar
Mahyar is situated at about 250 km from Yazd to the WNW
and at about 45 km from Esfahan to the south. ThereFig.11 Horizontal ventilation duct type, at the northern piedmont of
the Qilian Mts. (Watanabe et al., 2006)

Fig. 9 Qanat along the frontlet of the pediment (Near Mahyar).
Qunat: white broken line.

Fig. 10. Karez of frontlet type at the southern part of Bamian,Afghanistan (Sohma, 2008).

developed a qanat system along the southeastern piedmont of
the low hill (Fig. 9). The horizontal tunnel of this qanat did not
dig in the direction of the inclination of the hill slope, but nearly
the right angle to it, intending to gather groundwater at thepiedmont part of the hill.
We call this qanat system as the frontlet type.
Figure 10 is the QuickBird image, resolution about 61 cm
and taken on Feb. 1 2003, of the southern part of Bamian,Afghanistan. There is a valley flowing to the north and small
alluvial cones from the both side develop at the bottom part ofthe valley. There are two karez systems of the frontlet type atthe lower parts of alluvial cones and distances of the debris
heaps are about 10 m (Fig. 10; Sohma, 2008): Distances ofeach shaft are around 10 m. These karez systems which arenearly impossible to recognize in the Corona taken in 1965 areconsidered to have been constructed around 2000 as a part of
the reconstruction plans for Afghanistan.

3.3. Zhangye district
There is other type of the underground irrigation canals;
horizontal ventilation ducts type (Fig. 11; Watanabe et al.,2006), at the northern piedmont alluvial fans of Qilian
Mountains, Zhangye district, Gansu, China (Fig. 1). Theirterrestrial conditions are the head parts of the large confluent
alluvial fans and climate is semi-arid.
Ordinary underground irrigation canals have verticalventilation ducts, or vertical shafts, from which debris from thehorizontal tunnel are removed outside of the systems. But theventilation ducts of the underground irrigation canals at
Zhangye district were dug at the upper part of the river terrace
to the underground aqueduct in horizontal directions.
Moreover, water flowing into underground aqueduct does not
originate from the groundwater but from river channels.
Though the ventilation ducts of this system can not berecognized in the high resolution satellite images such as theCorona image, the outlet part of it is recognized connecting todebris heaps of the underground irrigation canal of the verticalventilation ducts type. This suggests the origin of this system
is closely related with the vertical ventilation ducts type.
Anyway, this type underground irrigation canal has been
constructed under the intention of transport water for
agricultural irrigation where water is hardly available, same asunderground irrigation canal of the vertical ventilation ducts
types.

5. Concluding remarks
In this paper, based on the interpretation of high resolution
satellite images such as Corona and QucikBird, we describedunderground irrigation canals constructed in the arid regions ofAsia.
Based on the historical documents, this type undergroundirrigation canal was constructed in the Ming Dynasty(Watanabe et al., 2006).

Table 1. Comparison between Trupan and Yazd.

ClimateLandform

Distribution ofunderground irrigation
Plan pattern ofunderground irrigation

Yazd
More than 100 mm/yr(winter precipitation)
Basin and range landform
without glacier
Along the bottom of
longitudinal valley, alluvial
fan margin and frontlet ofthe pediment
Parallel,crossingwithdifferent depth and very
long, and frontlet

TrupanLess than 20 mm/yr
Tianshan mountains withglacierandFlaming
mountain at the front
Alluvial fan margin andsucceeding mud desert

Parallel, oblique, reverse ‘J’First of all, not only QuickBird images but also Corona
images are very effective to capture the whole image of a single
underground irrigation canal, in addition to the ter restrial
conditions around it.
Underground irrigation canals are well developed in Turpan
Basin and Yazd area (Table 1). Especially, in the former case,the reverse “J” plan pattern in the alluvial fans is distinctive.
By this pattern, the horizontal tunnel were extended obliqueto the slope to acquire more water within limited distances, andthe mother wells were moved up-stream to manage lowering ofgroundwater level.
In the latter case, systems were developed along the bottomof the longitudinal valley reflecting the basin and range
landform where groundwater can be collect from the both sides.
This terrestrial condition seems to have produced 300m deep
and 80km long qanat. In addition, the frontlet type qanat
extending nearly along the contour line at the lowest margin of
the small pediment is also characteristic.
At the northern piedmont alluvial fans of Qilian Mountains,
Zhangye district, Gansu, China, there exist the ventilation ductsof the underground irrigation canals dug in the upper part of theriver terrace cliff and horizontal aqueduct water is flowing
directly from the river channel. This system continues tounderground irrigation canal of the vertical ventilation ducts
types.

Acknowledgement
This work was supported by the Grant-in-Aid for Scientific
Research (A) of JSPS, No.19251009 and No.2325019.
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