Groundwater recharge via precipitation in the Badain Jaran Desert,China

Precipitation infiltration serves as a significant source of groundwater in the Badain Jaran Desert.To investigate variations in precipitation infiltration within the desert,this study collected data on moisture content and temperature from the vadose zone through in-situ field monitoring.Utilizing these data,a numerical model is employed to explore the mechanism of groundwater recharge via precipitation.The results are as follows:(1)Moisture content and temperature in the shallow vadose zone exhibit significant seasonal variations,with moisture content diminishing with increasing depth;(2)Groundwater recharge via precipitation infiltration initially increases and then decreases with groundwater level depth(GWD).Peak groundwater recharge via precipitation occurs at a GWD of 0.75 m,decreasing to merely 0.012 cm at GWDs exceeding 2 m;(3)Groundwater is no longer susceptible to phreatic water evaporation when the GWD reaches approximately 3.7 m.Therefore,GWD plays a crucial role in governing groundwater recharge via precipitation in the Badain Jaran Desert.

Hydrochemistry of the lakes in the southern Badain Jaran Desert and its paleosalinity reconstruction

The reconstruction of paleohydrology,especially paleosalinity,is an important component of paleoenvironmental research.Researches on the modern characteristics of lake water chemistry and the relationship between lake salinity and hydrochemistry are the basis of paleoenvironment reconstruction.The modern hydrochemical characteristics and the relationship between ion composition and salinity of modern lakes are the basis of paleosalinity reconstruction.In this study,hydrochemical analysis of 21 lakes in the Badain Jaran Desert(BJD)was carried out.The relationships between the Sr/Ca and Mg/Ca ratios and total dissolved solids(TDS)were analyzed.The results show that Na^(+),K^(+),Cl-and SO_(4)^(2-)have high positive correlations with TDS,and Mg^(2+),Sr^(2+),CO_(3)_(2-)and HCO_(3)^(-)have lower correlations with TDS.The Sr/Ca and Mg/Ca ratios do not increase linearly with TDS.Hydrochemical analysis indicates that the studied lakes are in the carbonate precipitation stage and that evaporation is the main factor controlling lake evolution in the BJD.The relationships between the Mg/Ca and Sr/Ca ratios and TDS are mainly influenced by lake evolution stage and the hydrochemical types of the lakes.On the basis of comprehensive previous studies,the factors affecting lake evolution,the Mg and Sr partition coefficients and other hydrochemical parameters that change with lake evolution all affect the relationship between chemical composition and salinity.To reconstruct paleosalinity more accurately,more detailed research on the modern hydrochemical characteristics of lakes and the relationship between the element ratios of carbonates and water salinity should be carried out.

New evidence for the links between the local water cycle and the underground wet sand layer of a mega-dune in the Badain Jaran Desert, China

Scientists and the local government have great concerns about the climate change and water resources in the Badain Jaran Desert of western China. A field study for the local water cycle of a lake-desert system was conducted near the Noertu Lake in the Badain Jaran Desert from 21 June to 26 August 2008. An underground wet sand layer was observed at a depth of 20–50 cm through analysis of datasets collected during the field experiment. Measurements unveiled that the near surface air humidity increased in the nighttime. The sensible and latent heat fluxes were equivalent at a site about 50 m away from the Noertu Lake during the daytime, with mean values of 134.4 and 105.9 W/m2 respectively. The sensible heat flux was dominant at a site about 500 m away from the Noertu Lake, with a mean of 187.7 W/m2, and a mean latent heat flux of only 26.7 W/m2. There were no apparent differences for the land surface energy budget at the two sites during the night time. The latent heat flux was always negative with a mean value of –12.7 W/m2, and the sensible heat flux was either positive or negative with a mean value of 5.10 W/m2. A portion of the local precipitation was evaporated into the air and the top-layer of sand dried quickly after every rainfall event, while another portion seeped deep and was trapped by the underground wet sand layer, and supplied water for surface psammophyte growth. With an increase of air humidity and the occurrence of negative latent heat flux or water vapor condensation around the Noertu Lake during the nighttime, we postulated that the vapor was transported and condensed at the lakeward sand surface, and provided supplemental underground sand pore water. There were links between the local water cycle, underground wet sand layer, psammophyte growth and landscape evolution of the mega-dunes surrounding the lakes in the Badain Jaran Desert of western China.

Geochemical Information Indicating the Water Recharge to Lakes and Immovable Megadunes in the Badain Jaran Desert

Calc-sintersdistributed in the middle of lakes and rhizoconcretions scattered at the slopes of sand dunes were observed during three explorations to the Badain Jaran Desert in the past two years. Wet sands were also found underneath the dry surface sand layers of about 20-50 cm in thickness. The geochemical parameters were measured on minerals and water samples collected from the Badain Jaran Desert and neighboring areas. The results show that the water system in the desert may be recharged from the groundwater originating from the precipitation of the Qilian Mountains and/or the Tibetan Plateau rather than the local rainfalls.

Eddy covariance measurements of water vapor and energy flux over a lake in the Badain Jaran Desert,China

Exploring the surface energy exchange between atmosphere and water bodies is essential to gain a quantitative understanding of regional climate change, especially for the lakes in the desert. In this study, measurements of energy flux and water vapor were performed over a lake in the Badain Jaran Desert, China from March 2012 to March 2013. The studied lake had about a 2-month frozen period （December and January） and a 10-month open-water period （February-November）. Latent heat flux （LE） and sensible heat flux （Hs） acquired using the eddy covariance technique were argued by measurements of long＇wave and shortwave radiation. Both fluxes of longwave and shortwave radiation showed seasonal dynamics and daily fluctuations during the study period. The reflected solar radiation was much higher in winter than in other seasons. LE exhibited diurnal and seasonal variations. On a daily scale, LE was low in the morning and peaked in the afternoon. From spring （April） to winter （January）, the diurnal amplitude of LE decreased slowly. LE was the dominant heat flux throughout the year and consumed most of the energy from the lake. Generally speaking, LE was mostly affected by changes in the ambient wind speed, while Hs was primarily affected by the product of water-air temperature difference and wind speed. The diurnal LE and Hs were negatively correlated in the open-water period. The variations in Hs and LE over the lake were differed from those on the nearby land surface. The mean evaporation rate on the lake was about 4.0 mm/d over the entire year, and the cumulative annual evaporation rate was 1445 mm/a. The cumulative annual evaporation was 10 times larger than the cumulative annual precipitation. Furthermore, the average evaporation rates over the frozen period and open-water period were approximately 0.6 and 5.0 mm/d, respectively. These results can be used to analyze the water balance and quantify the source of lake water in the Badain Jaran Desert.

Geomorphological Evolution Revealed by Aeolian Sedimentary Structure in Badain Jaran Desert on Alxa Plateau, Northwest China

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.

Lake Area Changes and the main causes in the hinterland of Badain Jaran Desert during 1973–2010,China

Lake area information in the Badain Jaran Desert in 1973, 1990, 2000, and 2010 was obtained by visual interpretation and water index analysis of remote sensing images, based on the spatial and temporal characteristics of lake area changes during 37 years. Results indicated that the nttmber of lakes declined from 94 to 82 and the total surface area was reduced by 3.69 km2 during 1973-2010. The desert lake area reduced by different degrees in different periods, but this occurred most rapidly during 1973-1990. According to the statistics of lake area changes, lake area decreases mainly occurred in the lakes with areas less than 0.2 km2, while the areas of lakes greater than 0.9 km2 only fluctuated. The changes of lake areas were probably due to changes in the quantity of underground water supplies rather than the effects of local climate change or human factors.

The Role of Groundwater in the Salt Lakes in the Badain Jaran Desert,China

The Badain Jaran Desert is the second largest desert in China with tallest sand dunes on the earth.In contrast to the extremely dry climate,there are about 100 lakes spreading regularly over the depressions among high

Analyzing the differences of brackish-water in the Badain Lake by geophysical exploration method

BadainJ aran Desert of Inner Mongolia is arid and rainless all the year around,with much more evaporation than rainfall.But the special groundwater recharge mechanism contributes to the generation of several lakes of different sizes that have never not dried up for years,among which there are many freshwater lakes.As the research object in this paper,East Badain Lake and West Badain Lake in the southeast of the desert,which are less than 50m away from each other,show the considerable difference in mineralization.In fact,one is a freshwater lake,but the other is a brackish-water lake.Considering the underground aquifer structure of BadainJ aran Desert and the special formation structure the particularity of the stratigraphic structure around Badain Lake,the author uses AMT(audio magneto telluric)method and ultra-high density resistivity method to analyze the difference in mineralization of East Badain Lake and West Badain Lake from the perspective of geophysical prospecting methods.

Wind regimes and associated sand dune types in the hinterland of the Badain Jaran Desert,China

Wind controls the formation and development of sand dunes.Therefore,understanding the wind regimes is necessary in sand dune research.In this study,we combined the wind data from 2017 to 2019 at four meteorological stations(Cherigele and Wuertabulage stations in the lake basins,and Yikeri and Sumujilin stations on the top of sand dunes)in the hinterland of the Badain Jaran Desert in China,with high resolution Google Earth images to analyze the correlation between the wind energy environments and dune morphology.The results of data analysis indicated that both the wind direction and sand drift intensity exhibited notable spatial and temporal variations.The highest level of wind activity was observed in spring.Northwesterly and northeasterly winds were the dominant in the Badain Jaran Desert.At the Cherigele,Wuertabulage,and Yikeri stations,the drift potential(DP)was below 200.00 vector units(VU).The wind energy environments in most areas could be classified as low-energy environments.The resultant drift direction differed at different stations and in different seasons,but the overall direction was mainly the southeast.The resultant drift potential(RDP)/DP ratio was greater than 0.30 in most parts of the study area,suggesting that the wind regimes mainly exhibited unimodal or bimodal characteristics.Differences between the thermodynamic properties and the unique landscape settings of lakes and sand dunes could alter the local circulation and intensify the complexity of the wind regimes.The wind regimes were weaker in the lake basins than on the top of sand dunes.Transverse dunes were the most dominant types of sand dunes in the study area,and the wind regimes at most stations were consistent with sand dune types.Wind was thus the main dynamic factor affecting the formation of sand dunes in the Badain Jaran Desert BJD.The results of this study are important for understanding the relationship between the wind regimes and aeolian landforms of the dune field in the deserts.

Radionuclide dating(^(210)Pb,^(137)Cs) of recent inter-dune saline lake sediment cores in the Badain Jaran Desert,Inner Mongolia,Northwest China

Inter-dune lake sediment cores are ideal and unavailable materials for study climate and environmental changes of arid region.The precious dating of lake sediment cores is required for carrying out high resolution climate and environmental changes with these cores.The Badain Jaran inter-dune lake group embedding in the sand sea is the

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

The Badain Jaran Desert is the third largest desert in China,covering an area of 50000 km2.It lies in Northwest China,where the arid and rainless natural environment has a great impact on the climate,environment,and human living conditions.Based on the results of 1∶250000 regional hydrogeological surveys and previous researches,this study systematically investigates the circulation characteristics and resource properties of the groundwater as well as the evolution of the climate and ecological environment since the Quaternary in the Badain Jaran Desert by means of geophysical exploration,hydrogeological drilling,hydrogeochemistry,and isotopic tracing.The results are as follows.(1)The groundwater in the Badain Jaran Desert is mainly recharged through the infiltration of local precipitation and has poor renewability.The groundwater recharge in the desert was calculated to be 1.8684×10^(8)m^(3)/a using the water balance method.(2)The Badain Jaran Desert has experienced four humid stages since the Quaternary,namely MIS 13-15,MIS 5,MIS 3,and the Early‒Middle Holocene,but the climate in the desert has shown a trend towards aridity overall.The average annual temperature in the Badain Jaran Desert has significantly increased in the past 50 years.In detail,it has increased by about 2.5℃,with a higher rate in the south than in the north.Meanwhile,the precipitation amount has shown high spatial variability and the climate has shown a warming-drying trend in the past 50 years.(3)The lakes in the hinterland of the Badain Jaran Desert continuously shrank during 1973‒2015.However,the vegetation communities maintained a highly natural distribution during 2000‒2016,with the vegetation cover has increased overall.Accordingly,the Badain Jaran Desert did not show any notable expansion in that period.This study deepens the understanding of groundwater circulation and the climate and ecological evolution in the Badain Jaran Desert.It will provide a scientific basis for the rational exploitation of the groundwater resources and the ecological protection and restoration in the Badain Jaran Desert.

Badain Nyima:Ph.D in Education

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Landscape evolution and precipitation changes in the Badain Jaran Desert during the last 30 000 years

On the basis of field expeditions into different parts of the Badain Jaran Desert, new evidence of landscape evolution and precipitation changes during the last 30 000 years has been found from the geomorphological, sedimentological and geochronological studies of the megadune. Different cemented surfaces of palaeo-dunes have been observed in many localities, which are representatives of relatively moister environment. The chronological data show that four periods of more humid environment occurred in the past 30 000 years. The stabilization of dunes in a large scale and the existence of many palaeo-lakes and lacustrine terraces confirm the periodic fluctuations of climate. It implies that the intensity of westerlies and Eastasian monsoons varied in the region of Alashan, and the periods of higher precipitation took place even in the times close to the last glacial maximum.

Holocene high lake-levels and pan-lake period on Badain Jaran Desert

Many lakes exist in southeastern Badain Jaran Desert and its hinterland, including 110 perennial lakes and some seasonal or extinct lakes. Geomorphological, sedimentological, and bioglyph evidence obtained from field investigations on Badain Jaran Desert lake group, alongside measurements and dating performed on lake relic, prove that these lakes expanded while the climate was relatively wet during early and middle Holocene. The dating results suggest that the pan-lake period of the Badain Jaran Desert began at 10 cal kyr BP, before which the limnic peat period occurred(11–10 cal kyr BP). Many lakes reached their maximal water-level during 8.6–6.3 cal kyr BP and retreated or dried up in the late Holocene(about 3.5–0 cal kyr BP). During that period, the precipitation at Badain Jaran Desert may have reached 200 mm yr^(-1) for 7.7–5.3 cal kyr BP, inferred from both the age and precipitation rate of calcareous root tubes. The water balance calculation shows that wetter and warmer climate and the increase of underground water recharge were key factors in maintaining and developing the lake group at both centennial and millennial time scales. Furthermore, lake surface expansion and the increasing fresh water availability set the background for the prosperous prehistoric culture.

Recharge sources and chemical composition types of groundwater and lake in the Badain Jaran Desert, northwestern China

Based on the analysis of ion chemical composition of lake water and shallow groundwater in the Badain Jaran Desert, this paper discussed the characteristics of ion chemical composition, spatial variation of lake water, and possible supply sources of lake water and groundwater in the desert areas. The results show that the pH, salinity, TDS and electrical conductivity of the lake water are greater than those of groundwater. The ion contents of water samples are dominated by Na^＋ and Cl^-. Most of the higher salinity lakes are Na （K）-CI-（SO4） type, and a few of low salinity lakes belong to the Na-（Mg）-（Ca）-Cl-（SO4）-（HCO3） type. Most of the groundwater is Na-（Ca）-（Mg）-Cl-（SO4）-（HCO3） type, attributed to subsaline lake, and only a few present the Na-Cl-SO4 type, flowing under saline lake. The pH, salinity, TDS and electrical conductivity in the southeastern lakes are relatively low, and there are slightly alkaline lakes. The pH, salinity, TDS and electrical conductivity in the northern lakes are much greater than those of the southeastern lakes, and the northern lakes are moderately alkaline and saline ones. In the southeastern part of the Badain Jaran Desert, the ion chemical characteristics of the lake water from south to north show a changing trend of subsaline →saline→hypersaline. The changing trend of chemical compositions of ions in recent 9 years indicates that most of the ion contents have a shade of reduction in Boritaolegai, Badain, Nuoertu and Huhejilin lakes, which state clearly that the amount of fresh water supply is increasing in the 9-year period. The ion chemical composition of the lake water reveals that the flow direction of lake water is from southeast to northwest in the Badain Jaran Desert. The ion chemical composition, moisture content of sand layer water level height and hierarchical cluster analysis of the lake water and groundwater demonstrate that the lake water is mainly supplied by local rainfall and infiltration of precipitation in Yabulai Mountains and Heishantou Mountain, and the supply from the Qilian Mountains is almost impossible.

Climatic changes on southern fringe of the Badain Jaran Desert since the Late Pleistocene

Situated in the center of Alxa Desert, the Badain Jaran Desert(fig. 1), with an area of4.9×10~4km^2, is China’s second largest mobile sandy desert. The desert’s huge megadunes,generally 300m even over 500m in height, are seldom seen in other deserts of the world.Especially the desert’s location at the terminus of moderm East Asian summer monsoon

Groundwater net discharge rates estimated from lake level change in Badain Jaran Desert, Northwest China

Over a hundred sizable lakes,some even larger than^1 km2,are distributed across the lowlands between megadunes in the southeastern Badain Jaran Desert(BJD),northwest China.With rather limited precipitation and hardly any surface runoff,these lakes are fed mainly by groundwater.However,the source of the groundwater and the groundwater discharge rates to these lakes are poorly understood.Water level and temperature of four representative lakes in the southeastern BJD were monitored continuously between 2013 and 2017.Water surface evaporation and rainfall in this area were also measured.Combining these acquired data,groundwater discharge rates were estimated using water balance models.The results show that the four lakes have similar recharge and discharge patterns,but at different average net groundwater discharge rates ranging from 1.79 to 3.09 mm d?1.The lake level variation mainly depends on groundwater discharge and lake surface evaporation.We found that diurnal lake level variation may be controlled by earth tide and atmospheric pressure change,and is five times greater than the evaporation.The desert precipitation and deep confined groundwater with high temperature were found also recharging the desert lakes.An Empirical Mode Decomposition(EMD)method was used to identify the lake level trend.All lake levels increased over the last four years,except one decreased in 2015 and 2016.The lake levels’increasing trend is synchronously similar with the precipitation in north China.This study analyzes annual and seasonal lake level variations,and also finds the diurnal water cycle between the groundwater and lake water for the first time.

Groundwater recharge and climatic change during the last 1000 years from unsaturated zone of SE Badain Jaran Desert

The history of groundwater recharge and climatic changes during the last 1000 years has been estimated and reconstructed using environmental chloride from unsaturated zone profile in the southeast Badain Jaran Desert, NW China. By using a steady-state model for duplicate unsaturated zone chloride profiles, the long-term recharge at the site was estimated to be 1.3 mm yr-1. From one profile, which reached the water table, the climatic change events of 10—20 years duration were well preserved. There were 3 wet phases and 4 dry episodes during the recent 800 years according to the peaks and troughs of recharge rate calculated via chloride concentration and moisture content. There was a dry episode before 1290 AD. At ca. 1500—1530 AD, which is an important date, there was an abrupt change from drought to wet conditions. At the beginning of the 1800s, local climate changed from wet to dry occurred and subsequently deteriorated over the past 200 years. The unsaturated profile was compared with the Guliya ice core records. The agreement of wet and dry phases from 1200 to 1900 AD is quite good, whilst trends diverged during the last 100 years. It seems that the large-scale climate difference took place between mountain regions and the desert basin in NW China during the 20th century, which closely correspond to the water table reduction of some 1 metre.

Hydrochemical characteristics and recharge sources of Lake Nuoertu in the Badain Jaran Desert

We present a case study of physical and chemical indicators and isotope characteristics of Lake Nuoertu,one of the largest and deepest lakes of the Badain Jaran Desert.We analyze the concentrations of eight ions,total dissolved solids,and stable isotope composition of the lake and groundwater,as well as radioactive isotope tritium concentration in groundwater.The results show that annual and seasonal variations of the physical and chemical characteristics of Lake Nuoertu water are significantly greater than those of groundwater.The lake is uniformly mixed in the horizontal and vertical directions,and the hydrochemical types of the lake at different depths are consistent for Na–Cl–CO3–(SO4).Stable isotope composition of the lake and groundwater at Nuoertu is distributed along the local evaporation line(EL)slope,which is less than the slope of the global meteoric water line.The comparatively small slope shows the characteristic strong evaporation in the study area.Lake water isotopes are mostly in the upper right corner of the EL,whereas groundwater is mostly in the lower left corner.The main recharge source of Nuoertu lake water is groundwater,in combination with lake water and groundwater level change.The age of tufa springs around Nuoertu is about75–80 a,which shows that the initial recharge source of the lake is a mix between modern and 1952 or older;however,further research is required.