of 15
Journal of Hydrology: Regional Studies 40 (2022) 101002
Available online 18 January 2022
2214-5818/© 2022 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license
(
http://creativecommons.org/licenses/by-nc-nd/4.0/
).
The lake-level
changes
of Lop Nur over the past 2000
years
and its
linkage
to the decline
of the ancient
Loulan
Kingdom
Yun Shao
a
,
b
,
h
, Huaze
Gong
a
,
b
, Charles
Elachi
c
, Brian
Brisco
d
, Jiaqi
Liu
e
,
Xuncheng
Xia
f
, Huadong
Guo
a
, Yuyang
Geng
a
,
b
,
h
, Shugang
Kang
g
, Chang-an
Liu
a
,
h
,
Zhi Yang
a
,
h
, Tingting
Zhang
a
,
b
,
*
a
Aerospace
Information
Research
Institute,
Chinese
Academy
of Sciences,
Beijing
100094,
China
b
Laboratory
of Target
Microwave
Properties,
Deqing
Academy
of Satellite
Applications,
Zhejiang
313202,
China
c
California
Institute
of Technology,
1200
East
California
Boulevard,
Pasadena,
CA 91125,
USA
d
Canada
Centre
for Remote
Sensing,
Natural
Resources
Canada,
560
Rochester
Street,
Ottawa,
Ontario
K1A
0E4,
Canada
e
Institute
of Geology
and Geophysics,
Chinese
Academy
of Sciences,
Beijing
100029,
China
f
Xinjiang
Institute
of Ecology
and Geography,
Chinese
Academy
of Sciences,
Xinjiang
830011,
China
g
State
Key Laboratory
of Loess
and Quaternary
Geology,
Institute
of Earth
Environment,
Chinese
Academy
of Sciences,
Xi
an 710061,
China
h
University
of Chinese
Academy
of Sciences,
Beijing
100049,
China
ARTICLE
INFO
Keywords:
Lop Nur
Loulan
Kingdom
SAR remote
sensing
OSL dating
ABSTRACT
Study
region:
Lop Nur,
Xinjiang
Province,
China
Study
focus:
Lop Nur has been
a vast playa
which
was a historic
lake
in eastern
Tarim
Basin,
northwest
China.
The lake
s catchment
played
a significant
role in the development
of oasis
states
in the early
Common
Era, such
as the ancient
Loulan
Kingdom.
However,
the history
of lake
dynamics
remains
unclear,
and its potential
linkage
to the decline
of Loulan
Kingdom
has been
not well-examined.
This paper
aims
to reconstruct
the lake-level
changes
in Lop Nur over
the last
2000
years
using
synthetic
aperture
radar
(SAR)
data,
optically
stimulated
luminescence
(OSL)
dating
of lacustrine
and aeolian
sediments,
and radiocarbon
(
14
C) dating
of ancient
bio-remains.
Furthermore,
the relationships
between
Lop Nur
fluctuation
and the decline
of ancient
Loulan
Kingdom
were
discussed
New
hydrological
insights
for the region:
The results
suggest
that Lop Nur once
covered
an area more
than
11, 602 km
2
and that lake-level
reduced
gradually
during
360
470 C.E. Subsequently,
the
lake
experienced
a few stages
of lake-level
fluctuation
which
never
reached
the upper-most
shorelines.
Also,
the historical
changes
in the lake
level
were
temporal
coincided
with
the
ancient
Loulan
Kingdom
s collapse,
showing
that
the dynamics
of hydrological
conditions
in
catchment
may
have
a direct
influence
on the fall of human
settlement
in drylands.
1. Introduction
Lop Nur,
located
at the east end of the Tarim
Basin,
received
most
of the drainage
from
the Tianshan
and Kunlun
Mountains
until
the 1970s,
when
Lop Nur eventually
desiccated
(Mischke
et al., 2017
; Zhang
et al., 2014,
2021
). During
the Han Dynasty
(206
B.C.
E.
220C.E.),
Lop Nur was a large
lake located
on the eastern
side of the Loulan
Kingdom
(89
55
22
′′
E
40
29
55
′′
N) (Li et al., 2019;
* Corresponding
author
at: Aerospace
Information
Research
Institute,
Chinese
Academy
of Sciences,
Beijing
100094,
China
E-mail
address:
zhangtt201832@aircas.ac.cn
(T. Zhang).
Contents
lists available
at ScienceDirect
Journal
of Hydrology:
Regional
Studies
journal
homep
age:
www.el
sevier.com/l
ocate/ejrh
https://doi.org/10.1016/j.ejrh.2022.101002
Received
27 July
2021;
Received
in revised
form
13 January
2022;
Accepted
15 January
2022
Journal of Hydrology: Regional Studies 40 (2022) 101002
2
Yang
et al., 2006a;
Yu, 2014
). The Loulan
Kingdom
existed
as early
as 176 B.C.E.
(Chen,
2014;
Xia et al., 2007
). Historical
records
and
ruins
discovered
in the territory
show
that the region
was once
the political,
military,
economic,
and cultural
center
of western
China.
It was positioned
along
the Central
Route
of the ancient
Silk Road
that connected
China
to Europe
and Central
Asia between
77 B.C.E.
and 500 C.E. (Li et al., 2021a
). However,
the Loulan
Kingdom
vanished
abruptly
around
1500
years
ago (Qin et al., 2011
; Xu et al.,
2017
).
The factors
leading
to the demise
of the Loulan
Kingdom
have
not been
fully
identified
and its disappearance
has resulted
in a
considerable
and ongoing
debate.
Proposed
causes
of its demise
have
included
climate
change
(aridification),
a change
in the river
course
of the Tarim
River,
abandonment
of this route
of the ancient
Silk Road,
and various
human
activities
such as war and feuds
over
water
for irrigation
and domestic
purposes
(Chen,
2014;
Mischke
et al., 2019;
Xia et al., 2007,
2021;
Xu et al., 2017
). However,
climate
change
is likely
to be the most
important
influencing
factor
(Xie et al., 2021
).
The multi-proxy
records
of Lop Nur show
that humid
conditions
between
400 B.C.E.
and 200 C.E. supported
the ancient
Loulan
Kingdom
until
aridification
began
and Lop Nur gradually
shrank
at 200 C.E. (Liu et al., 2016a,
2016b;
Yang
et al., 2006a,
2016b
).
Previous
studies
have
demonstrated
that the once-prosperous
Loulan
Kingdom
completely
disappeared
by about
500 C.E. (Xu et al.,
2017
). It became
a barren
landform,
even
a no man
s land,
due to a lack of water
and intensive
wind
erosion
(Liu et al., 2016a,
2016b;
Yang
et al., 2006a,
2016b
). Evidence
demonstrates
that irrigated
agriculture
was widely
practiced
in the ancient
Loulan
Kingdom
on
the west
bank
of Lop Nur (Qin et al., 2011
). Water
supply
is critical
to the survival
of all ecosystems
on the earth.
An extreme
climate
event,
especially
an aridification
event,
may lead to the collapse
of a civilization
or a kingdom
because
of its effects
on agricultural
and
pastoral
productivity
(Blom
et al., 1984;
Buckley
et al., 2010;
Büntgen
et al., 2011;
Chu et al., 2002;
Cook
et al., 2004;
Demenocal,
2001;
Elachi
et al., 1984;
Farr et al., 1986;
Hodell
et al., 1995;
Li et al., 2021b;
McCauley
et al., 1983;
Skonieczny
et al., 2015;
Turner,
1974;
Yancheva
et al., 2007
). The abandonment
of cities
in the Tarim
Basin
and the drying
of Lop Nur are attributed
to a possible
climatic
change
toward
drier
conditions
around
500 C.E. (Li et al., 2021;
Liu et al., 2016a,
2016b;
Yang
et al., 2006a,
2016b;
Zhang
et al., 2012,
2013
).
Penetration
capability
is an important
advantage
of synthetic
aperture
radar
(SAR)
remote
sensing
technology
in arid regions.
As
demonstrated
in 1981,
the Shuttle
Imaging
Radar
A (SIR-A)
mission
acquired
L-band
(25 cm wavelength)
HH polarization
SAR images
worldwide,
including
images
from
the Eastern
Sahara
Desert
(Shao
et al., 2012
). Using
the SIR-A
images,
McCauley
et al. (1983)
discovered
the buried
channels
of abandoned
rivers
and other
geoarchaeological
features
in the Eastern
Sahara.
Their
results
showed
that wave
penetration
on the order
of tens of centimeters
in desert
soils was common
for L-band
radar
(Shao
et al., 2012
). Lasne
et al.
(2009)
and Shao
et al. (2003)
focused
on the influence
of soil salinity
as a function
of soil moisture
on the dielectric
constant
of soils
and then
on the backscattering
coefficients.
Their
study
showed
that a material
with
a high-saline
moisture
content
will have
both
a
high
real (
ε
) and an imaginary
(
ε
) dielectric
constant
and that the material
will act as a strong
reflector
to microwaves.
Thus,
SAR is
highly
likely
to detect
buried,
permeable
sediments
that contain
groundwater,
such as abandoned
river
channels
and/or
lake beds.
The
echo
energy
from
the strong
reflector
under
the upper
low-loss
dielectric
layer
will be strengthened
because
of the refraction
effect
of
the upper
layer
(Liu et al., 2016a,
2016b
). Polarimetric
SAR data contains
a tremendous
amount
of information
about
its targets
(Shao
et al., 2012
). Previous
studies
have
attempted
to develop
classic
polarimetric
algorithms
and generate
polarimetric
parameters
that
could
better
describe
the targets
characteristics
and aid in our understanding
of the interaction
between
microwaves
and targets
(Touzi,
2004
).
Fig. 1.
Location
Map of Lop Nur, ruins
of cities
that existed
before
the 6th century
and adjacent
regions,
adapted
from
Zhang
et al. (2021)
. The ruins
of Loulan
City
are 20 km west
of Lop Nur;
LK City
is 60 km south
of Loulan
City.
The abandoned
Central
Route
of the ancient
Silk Road
is
demonstrated
by the dashed
red line (Frankopan,
2015
). (
©
http://srtm.csi.cgiar.orgwww.dsac.cn
).
(For interpretation
of the references
to colour
in this figure,
the reader
is referred
to the web version
of this article.).
Y. Shao
et al.