Full text: Remote sensing for resources development and environmental management (Volume 1)

portions of the alluvial fans (Figure 4). 
On the SIR-A image, cultivated areas may be 
identified by a network of bright lines forming 
mainly rectangular (G-13), square (C-10) or 
triangular (G-10) grid patterns. These radar 
signatures result from the specific backscattering 
behavior of forested windshelter belts which often 
form so-called 'kuluns' (enclosures) to protect the 
cultivated land from wind erosion. The most common 
trees are fast growing poplars (Populus ssp.) The 
bright image tone is primarily due to the strong 
volume scattering effects of microwave energy within 
the tree canopy, independent of the orientation of 
shelter belts towards the radar (Figure 6). Other 
backscatter components include multiple reflection of 
the scattered radar signal from the trees and the 
surrounding ground surface, and scattering effects at 
the surface of the tree canopy. The linear 
arrangement of trees along cultivated land, major 
irrigation and drainage canals, roads and settlements 
eventually defines the outlines of the oases. 
In two areas windshelter belts are hardly dectable 
(H-ll, H-12)(Figure 7C), whereas the cultivated 
fields can readily be recognized by their rectangular 
shape and contrasting shades of grey tones. The high 
regularity and the relatively large size of the field 
identifies these areas as recent development schemes, 
where tree growths has not yet advanced to form 
sizeable wind shelter belts. 
The close relationship between the irrigation 
schemes of the oases and the natural drainage network 
of the Pamirs is illustrated in Figure 5. The 
discharge from the glacier-fed streams during the 
meltwater season contributes largely to the water 
supply of the Kashgar region. The catchment of the 
Gez River (D-19) is most important in terms of its 
large annual water discharge. It drains the entire 
Kingata Range, the northern and western flank of 
Mount Kongur and defines the eastern divide of the 
Sarikol Mountains. At the edge of the mountain zone 
the rivers are regulated in part by the headworks of 
the irrigation systems. The meltwater is diverted 
into distributary canals across the alluvial fans 
(E-14, G-17) and then fed into the respective 
irrigation and drainage systems. 
The irrigation schemes may be identified by 
following the outlines of the windshelter belts, 
since the course of the canals and the rows of 
protecting trees are closely associated (Figure 7). 
Irrigation canals of cultivated land along the foot 
of an alluvial fan (G-13) tap the local ground water 
horizon by a series of parallel canals. These vary 
in length between 3 km and 10 km. Irrigation within 
the alluvial plain relies on a distributary network 
of canals, providing water either directly by the 
diversion of meltwater streams or through various 
water retention basins (F-ll). The entire canal 
system extends more than 100 km and consists of 
numerous bifurcations. A high density of shelter 
belts and a high bifurcation rate of the canal system 
characterize the well developed and traditional 
cultivated areas (H-8). An elongated, low density 
network defines more recent land reclamation areas 
(F-l/2) towards the edge of the alluvial plain. 
These consist of only one or two main arteries formed 
by the irrigation canal, road, settlements and wind 
shelter belts (Plate 2). 
The surface geometry of built-up areas generally 
represent dihedral corner reflectors to incident 
radar beams, thus providing strong return signals and 
bright image tone. Market towns such as Yengisar 
(C-10) and Akto (G-13) are located in the centre of 
the traditional agricultural areas. In the more 
recent land reclamation areas smaller settlements may 
be identified (C-6, D-7, F-3 and Plate 2). 
In the western literature, there are only few remote 
sensing studies which focus on regional-geographic 
Plate 2. Oblique aerial view of windshelter belts in 
recent land reclamation areas of western Xinjiang, as 
depicted in Figure 7D. (Photo: D. Werle, Oct. 1984) 
Figure 6. Schematic profile of different tracing 
configurations and backscattering behavior of 
incident microwave beams within or at the tree canopy 
(1 = multiple scattering effects, 2 = volume scatter 
effects within the tree canopy, 3 = backscatter 
effects at the tree canopy). 
Figure 7. Four SIR-A subscenes within the study area 
representing different patterns of irrigation schemes 
as outlined by strong radar backscattering behaviour 
of windshelter belts along the canal and road 
network. (A = traditional cultivation areas along 
the foot of an alluvial fan, B = irrigation scheme 
with well developed windshelter belts and harvested 
fields, C = recent land reclamation area with less 
well developed windshelter belts and partly 
cultivated fields, D = linear development of recent 
land reclamation areas within the alluvial plain).

Note to user

Dear user,

In response to current developments in the web technology used by the Goobi viewer, the software no longer supports your browser.

Please use one of the following browsers to display this page correctly.

Thank you.