Monitoring Changes to Small-Sized Lakes Using Medium Spatial and Temporal Satellite Imagery in the Badain Jaran Desert from 2015 to 2020

There are many viewpoints about the sources of groundwater in the Badain Jaran Desert (BJD), such as precipitation and snowmelt from the Qilian Mountains (the upper reaches [UR] of the Heihe River Basin [HRB]) and precipitation from the BJD and the Yabulai Mountains. To understand the source of the groundwater of the BJD and their possible associations with nearby bodies of water, we analyzed variations of stable isotope ratios (δD and δ(18) O) and the deuterium excess (d-excess) of groundwater and precipitation in the BJD, of groundwater, precipitation, river and spring water in the UR, and of groundwater and river water in the middle and lower reaches (MR and LR) of the HRB. In addition, the climatic condition under which the groundwater was formed in the BJD was also discussed. We found obvious differences in δD, δ(18) O, and d-excess among groundwater in the BJD, nearby water bodies and the HRB. The groundwater δD-δ(18) O equation for the BJD was δD = 4.509δ(18) O-30.620, with a slope and intercept similar to that of nearby areas (4.856 and -29.574), indicating a strong evaporation effect in the BJD and its surrounding areas. The equation's slope of the BJD was significantly lower than those of HRB groundwater (6.634), HRB river water (6.202), precipitation in the BJD and Youqi (7.841), and the UR of the HRB (7.839). The d-excess (-17.5‰) of the BJD was significantly lower than those of nearby groundwater (-7.4‰), HRB groundwater (12.1‰), precipitation in the BJD (5.7‰) and in the UR of the HRB (15.2‰), and HRB river water (14.4‰). The spatial patterns of δ(18) O and d-excess values in the BJD suggest mixing and exchange of groundwater between the BJD and neighboring regions, but no hydraulic relationship between the BJD groundwater and water from more distant regions except Outer Mongolia, which is north of the BJD. Moreover, we conclude that there is little precipitation recharge to groundwater because of the obvious d-excess difference between groundwater and local precipitation, low precipitation, and high evaporation rates. The abnormally negative d-excess values in groundwater of the BJD indicate that this water was formed in the past under higher relative humidity and lower temperatures than modern values.

Geochemical and geomorphological evidence for the provenance of aeolian deposits in the Badain Jaran Desert, northwestern China

Groundwater characteristics and climate and ecological evolution in the Badain Jaran Desert in the southwest Mongolian Plateau

Geochemical evidence of the sources of aeolian sands and their transport pathways in the Minqin Oasis, northwestern China

The Badain Jaran Desert (BJD) and surrounding deserts are the main sources of sand and dust storms in Asia. However, for complex factors, the descriptions of the sand dune dynamics in the BJD and investigations on the contribution of the BJD to the formation of the Tengger Desert (TD) and the Ulan Buh Desert (UBD) are lacking. We evaluated the performance of the discrete Fourier transform method in achieving subpixel precision when measuring the displacements of sand dunes in the BJD and surrounding deserts. This method was applied to Landsat 5/8 and 7 scan-line-corrector (SLC)-off/8 image pairs, respectively. The results show that it is a robust method in desert conditions without ground control points. Nineteen scenes of Landsat 5/8 were tested for estimating the movements of the BJD and surrounding areas. We found that the sand dunes moved eastward during 2004–2016. However, the dunes’ movements showed different patterns in different parts of the desert. In the western BJD, the dunes moved at an average speed of 1–3 myr−1, while in the southern and middle parts of the BJD, the dunes’ speed was about 0.1–1 myr−1. The fastest displacements of dunes were located in the northeastern BJD, and the mean speed was about 12 myr−1. The sand fluxes in the two corridors between the BJD and the TD and UBD were estimated. The annual total amount of sand transported from the BJD to the TD through the main corridor was about 0.95 million tonnes, while that from the BJD to the UBD was about 2.24 million tonnes. The estimations of dune displacements and sand transport based on Landsat images in this study are important for understanding the dynamics of the BJD and surrounding areas.

Sand wedge is a product of permafrost in cold climate, and it is of great significance to restore paleoclimate and paleoenvironment. Since the early 20th century, periglacial landforms such as sand, ice, and soil wedges and glacial mud have been intensively studied in North America, Europe, and Russia. Nevertheless, the distribution of desert areas in the permafrost regions after the last glacial period is still debated in academia. Particularly, in China, it has been argued that desert areas were not the parts of ancient permafrost regions. Moreover, the studies of ancient sand wedges are mostly limited to the last glacial period. In recent years, several groups of ancient sand wedges and glacial mud have been recognized in the Badain Jaran Desert. This filled the gap in the Chinese literature regarding ancient permafrost and proved that desert region belonged to the scope of permafrost regions during the last glacial period. The newly discovered sand wedges in the southeast Badain Jaran Desert comprise sand and gravel layers. Optically stimulated luminescence dating of the filler in the sand wedges suggests that they formed during the last glacial period and the late glacial maximum, in particular. The annual average temperatures in the Badain Jaran Desert during the last glacial period were approximately −3–−6°C, and it is 12–15°C cooler than present. The filler in sand wedges was mainly poorly sorted fine sand that was not transported from afar but from nearby sand dunes. According to the sand wedge groups of the last glacial period in the desert and seasonal frozen soil, we can infer that the Badain Jaran Desert was a part of the permafrost that may have been continuous and widespread. The extent and distribution of the Badain Jaran Desert in the last glacial period was probably different than today, reflecting the dynamic nature of sand dunes. According to the law of sand dunes’ movement in the Badain Jaran Desert, combining with the characteristics of aeolian sand of the desert’s ancient permafrost wedge can indirectly infer that three large desert areas of the Alxa Plateau were connected more than ten thousand years ago when the entire Alxa Plateau was part of the permafrost; furthermore, the desert hinterland and the surrounding sand dunes would have been frozen and the movement and development of the sand dunes would have been suppressed. Surface landscape and the kinetics of the sand and landform need to be studied further. While the Badain Jaran Desert was likely a part of the cryosphere climate zone during the last glacial period, whether the Chinese northern desert belonged to the frozen earth region is still questionable.

Geochemical characteristics of surface aeolian sand in the Badain Jaran Desert, northwestern China: Implications for weathering, sedimentary processes and provenance

Optical dating of Yardang sediments and its implications for past flood events on the border of the Badain Jaran Desert, Northern China

<p>Transversal dunes are widespread in many deserts, but the application of these un-stabilized dunes in the palaeoclimate region is limited. Because transversal dunes normally migrate too fast, which means this kind of dune has a low possibility to record long period paleoclimate information. Nevertheless, both model simulations and field observation demonstrate that larger (higher) dunes containing a greater mass of sand have longer turn-over times. If so, there may be particular giant transversal dunes, in which long periods of climate changes are actually preserved and could be used as geoproxy to reconstruct paleoenvironment changes.</p><p>The Badain Jaran desert, situated in north-western China, features the tallest dunes (about 480 m) on the earth. More than 50% of the sand sea is covered by transversal dunes with an average height of 200 to 300 m. Here, we investigated two representative mega-dunes in the center of the desert and took 22 OSL samples systematically to try to reconstruct the deposition history of these two mega-dunes. Our result demonstrates that one of the dunes is formed since ~62 ka, with two phases of superposed dunes dated to 26~32 ka and modern time. Another mage-dune started to deposited from 29 ka and climbed by early to middle Holocene superposed-dunes and modern ones. Furthermore, while other active sand seas preserve scarcely aeolian sand deposited during the LGM period (Last Glacial Maximum: 26.5-19.0 ka BP), 11 of our 22 OSL dating results fall into the LGM period, which indicates that mega-dunes in the Badain Jaran desert continue aggradation during LGM. In that case，we speculate there are at least three factors facilitating the mega-dunes in Badain Jaran desert different from other transversal dunes that can preserve LGM sediments. (1) Badain Jaran desert, situated in a relatively subsiding basin, has a favor deposition condition; (2) The desert is close to the aeolian sand provenance area, an alluvial fan stored abundant silt-sand material derived from the southeast Tibet; (3) the shallow buried wet sand in Badain Jaran desert may promote the formation of the mega-dunes and reduce their migration speed, so that extend the turn-over times of the mega-dunes.</p>

Badain Jaran Desert, the coexistence of dunes and lakes, and the presence of the world’s tallest dunes, has attracted worldwide attention among hydrologists. Freshwater, brackish, and saline lakes coexistence in the Badain Jaran Desert under extremely arid environmental conditions. This raises the question of why diverse lake water types exist under the same climatic conditions. Answering this question requires the characterization of lake hydrochemistry and the main controlling factors. The purpose of the presented research was to systematically analyzed samples from 80 lakes using statistical analysis, correlation analysis and hydrogeochemical methods to investigate the hydrochemical status and evolution of lakes in the Badain Jaran Desert. The results showed that the lake water in Badain Jaran Desert is generally alkaline, with the average pH and TDS were 9.31 and 165.12 g L−1, respectively. The main cations to be Na+ and K+, whereas the main anions are Cl− and SO42−. HCO3− and CO32− decreased and SO42− and Cl− increased from southeast to northwest, whereas lake hydrochemistry changed from the SO42−-Cl−-HCO3− type to the SO42−-Cl− type and lakes transitioned from freshwater to saline. The freshwater and slightly brackish lakes are mainly distributed in the piedmont area at a high altitude near the Yabulai Moutains, whereas saline lakes are mainly distributed in the desert hinterland at a low altitude, and there is a roughly increasing trend of ions from the Yabulai Mountains. The evaporation-crystallization reactions are the dominant in the study region. Moreover, some saline mineral deposits, are extensive in these regions caused by intense evaporation-crystallization.

The Badain Jaran Desert (BJD) in China is a desert with impressive sand dunes and a groundwater situation that has attracted numerous researchers. This paper gives an overview of the mysteries of groundwater in the BJD that are exhibited as five key problems identified in previous studies. These problems relate to the origin of the groundwater, the hydrological connection between the BJD and the Heihe River Basin (HRB), the infiltration recharge, the lake–groundwater interactions, and the features of stable isotope analyses. The existing controversial analyses and hypotheses have caused debate and have hindered effective water resources management in the region. In recent years, these problems have been partly addressed by additional surveys. It has been revealed that the Quaternary sandy sediments and Neogene-Cretaceous sandstones form a thick aquifer system in the BJD. Groundwater flow at the regional scale is dominated by a significant difference in water levels between the surrounding mountains and lowlands at the western and northern edges. Discharge of groundwater from the BJD to the downstream HRB occurs according to the regional flow. Seasonal fluctuations of the water level in lakes are less than 0.5 m due to the quasi-steady groundwater discharge. The magnitude of infiltration recharge is still highly uncertain because significant limitations existed in previous studies. The evaporation effect may be the key to interpreting the anomalous negative deuterium-excess in the BJD groundwater. Further investigations are expected to reveal the hydrogeological conditions in more detail.

Desert landscapes are widely distributed in the arid northern China. The Badain Jaran Desert (BJD) is located north-west of the Tengger Desert (TD) and Ulan Buh Desert (UBD), with the Yabrai and Bayan Ulan Mountains separating the BJD from the TD and UBD. Many sand belts with an orientation of NW-SE, which is similar to that of the prevailing sand-transporting winds, connect the BJD with the TD and UBD, forming the sand transportation routes from the BJD to the TD and UBD. Thus, these sand belts are sensitive to the expansion or shrinkage of the BJD, whose chronologies could be critical for understanding the evolution of the BJD. However, age data are still very limited. In this study, field investigation and optically stimulated luminescence (OSL) dating have been conducted in 14 profiles, and 24 OSL ages are obtained. The OSL ages range from approximately 15 ka to modern. Our results and previous chronological data revealed that the BJD’s expansion initiated at 20 ka, and the present-day landscape formed within the latest 2 ka with periodic expansions at 19–15, 11–9, 7.3 and 6–5 ka. We propose that these expansions of the BJD before ~5 ka and during the 0.9–0.8 ka interval were responses to regionally low effective moisture conditions in north-western China, while the expansions at ~2 ka and within the latest 200 years were likely triggered by intensified human activity.

Landscape evolution and palaeoclimate in the deserts of northwestern China, with a special reference to Badain Jaran and Taklamakan

The Badain Jaran Desert, located in the Alxa Plateau, Northwest China, features mega-dunes and a unique dune-lake alternation landscape. This paper presented the aeolian sediment structures of three representative dunes in the Badain Jaran Desert using ground-penetrating radar (GPR). We processed and analyzed the GPR data and investigated the feasibility of using integrated GPR and sedimentological data to reconstruct dunes structure, sedimentary environment and geomorphological evolution. The results show that the internal structures of star dune and transverse dune represent various stages of mega-dune evolution: the main deposition processes of mega-dune are similar to those of transverse dunes but have a more complicated mechanism of sand transport and deposition because of the superimposition of dunes; the upper section of the mega-dune has a structure similar to that of star dune, with vertical aggradations on top. Diffraction hyperbolae in the GPR profile indicates that the presence of ancient dunes characterized by calcareous cementation layers is involved in the maintenance of mega-dunes, and water levels, shown by continuous, sub-horizontal GPR reflections, are supposed to be closely related to mega-dunes and the interdune lakes. Outcrop of wet sand and horizontal stratifications on the GPR image indicate moisture potentials with different levels inside mega-dunes. The multiplex geomorphology in the Badain Jaran Desert is the result of global climatic undulation, the unique geographical location, the geological structural features, etc.

Quantitative reconstruction of regional paleotemperature is the key to understanding temperature change and its driving mechanisms. In this study, 133 phytolith samples were collected as proxy indicators from lacustrine sediments of the Zhunzhahanjilin (ZZH) profile in the hinterland of the Badain Jaran Desert, China. The phytolith samples were then analyzed to quantitatively reconstruct the Holocene paleotemperature at the millennial scale. Based on accelerator mass spectrometry (AMS), 14C dates and an ordered clustering method were used to divide the phytoliths into five assemblage zones with environmental significance. The quantitative reconstruction results indicated that the paleotemperature in the Badain Jaran Desert was relatively high during the early Holocene (11,040–8,200 cal a BP), and the average paleotemperature was approximately 9.5°C. This may have led to increased melt water near the surrounding area and recharged the lakes in the Badain Jaran Desert, resulting in the expansion of the lakes during the early Holocene. The average paleotemperature during the middle Holocene (8,200–3,100 cal a BP) was approximately 7.9°C. This period was warm and the environment was humid, with extensive precipitation from summer monsoons and low evaporation leading to higher water levels in the lakes. The paleotemperature decreased during the late Holocene (3,100 cal a BP to the present), and lakes retreated or dried up because of the decreased summer monsoon rains. The Holocene paleotemperature in the Badain Jaran Desert may have been related to July insolation in the Northern Hemisphere and had a range of impacts on the hydrological cycle in this arid region.