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.

为解决石羊河流域土地沙漠化和水资源短缺等问题,发挥地下水对地表生态的支撑作用,通过采集流域泉水、地表水和地下水样品,研究其水化学和硫酸盐硫氧同位素的组成和来源,揭示流域地下水演化规律,支撑地下水的合理开发利用.结果表明,石羊河流域各类水体δ34 SSO4与δ18 OSO4整体偏低,大部分分布在大气降水和硫化物区域,离蒸发岩溶解端元较远,指示出武威盆地和民勤盆地地下水主要受到大气降水和硫化物氧化溶解控制,SO42-主要来源于二者,蒸发岩的溶解对下水影响较小,为判识SO42-的来源、迁移和转化提供线索,为分析地下水循环规律提供有力帮助.

石羊河流域地下水成为制约区域生态安全和经济发展的重要因素,通过采集流域泉水、地表水和地下水样品,研究其水化学、同位素和地球化学过程,可揭示流域地下水演化规律,支撑地下水合理开发利用.结果表明,石羊河流域地下水形成了"上咸下淡"的规律,尤其是民勤盆地浅层地下水TDS远大深层地下水,浅层地下水在水-岩作用的基础上,有向蒸发-浓缩型演化的趋势.氢氧同位素说明石羊河流域所有水体均落在全球大气降水线和当地大气降水线附近,表明石羊河流域地下水来源于大气降水,流域深层井水的δD、δ18O值比地表水、泉水和浅层井水贫化.

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 1.8684×108 m3/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°C, 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.© 2021 China Geology Editorial Office.

以上案村为例,通过典型剖面监测、元数据统计分析和数值模拟等研究方法,开展植被生态与地下水关系研究,模拟了典型植被的根系吸水速率分布规律.结果表明:地表植被结构越多,土壤水分交换越频繁,包气带同时受到大气降水入渗和毛细水的支持,整个包气带含水量较高;利用Hydrus-1D模型分析,发现典型植被在7—8月植被生长成熟期间,由于气温升高,蒸发量较大,植物需水量增加,根系吸水速率增强;9月植被进入衰退期,植被吸水能力逐渐减弱;当地下水埋深<3.0 m时,包气带中土壤水分能达到植被生长所需要的水平,植被根系吸水速率在10～40 cm内达到最大.

了解沙漠降水稳定同位素特征,有助于研究干旱区水循环过程.根据2015-2016年取自巴丹吉林沙漠4个站点的降水样品,分析了δ~2H、δ 18 O的时空分布特征及影响因素;借助后向气团轨迹模型分析了降水水汽来源;采用氘盈余模型计算了水汽再循环比.结果显示,降水δ~2H、δ 18 O均表现出季节效应,夏高冬低;沙漠腹地较外围山区δ~2H、δ 18 O偏正,d-excess偏负,反映出腹地降水的蒸发程度更高.年内降水主要来自西风水汽,夏季部分受东南季风影响.沙漠湖泊区再循环比为10.3%～10.9%,略大于山区的8.5%;再循环水汽在总蒸发量中占比11.1%,反映出沙漠强烈的蒸发对本地降水的贡献较为有限.

为研究巴丹吉林沙漠南缘水源地的地下水补给机制,分析了采自浅井、深井及湖泊的35个水样的Cl-浓度、TDS含量和氢氧同位素特征.根据巴丹吉林水源地及周边水化学水平分布特征,结合研究区气象和水文条件、水文地质结构、地下水流场发现,戈壁区地下水对沙漠区地下水无明显补给作用,但是沙漠区、戈壁区及山区地下水稳定同位素关系表明,沙漠区地下水来源于南部山区及戈壁区的地下水或降水.通过野外调查发现,沙漠边缘分布大量洪积黏土,认为沙漠外围山区、山前戈壁带降水在季节性河道形成的脉冲式洪流是沙漠区地下水的重要补给来源之一,这一认识不仅解释了采用水化学和同位素技术进行分析而获得不同结论的原因,而且有利于地下水资源评价.

[目的]确定黑河流域不同地区浅层地下水的防污性能状况,对不同区位的地下水污染设防情况给出建议.[方法]采用DRAS-TIC模型,选择地下水位埋深、包气带综合岩性、含水层岩性、地下水净补给量、水力传导系数和地形梯度6个评价因子,构建区域浅层地下水防污性能评价指标体系,进行黑河流域平原区浅层地下水系统防污性能评价.[结果]浅层地下水防污性能差和较差区占平原区面积的52.2％,主要分布在山前倾斜平原和沿河道地带;防污性能好和较好区占平原区面积的17.4％,主要分布在各盆地的中部区域;防污性能中等区占平原区面积的30.4％,分布在评价区的剩余地区.[结论]黑河流域的整体防污性能较差,尤其南部山前平原和河道带.

为了研究巴丹吉林沙漠车日格勒的湖底地形结构、温度分层特征及成因,于2016年6月1日对车日格勒5条剖面上66个测点进行水深、水温和电导率测量.结果表明:(1)车日格勒整体呈浅碟状,最大水深8.20m,湖底中部存在东西向隆起,将湖盆分为南北两个平坦的小湖盆;近岸水域存在不同规模的钙华陡坎.(2)湖水垂直变化的分层特征明显:混合层由湖面到水下3m,水温、电导率相对均匀;水深3～4m为相对高温区;4m以下为温跃层,平均梯度值达3.5℃/m,湖底水温仅10.5℃,电导率随水深增加而变大,平均梯度值8.264(mS/cm)/m.对比8月9日测量结果,混合层厚度增至6m,水体温度升高5～6℃.湖泊分层主要受太阳辐射、气温、风力、湖水电导率差异影响,淡水补给作用、湖盆结构次之.两期数据显示车日格勒为半混合湖泊,确定其混合类型仍需对水温、电导率、水位等参数进行常年全剖面观测.

This paper discusses the cause of the tufa in Badain Jaran Desert,throughout investigating the distribution of the tufa and analyzing the hydrochemical characteristics of water samples.Results indicates that the lake water is the type of C1-Na,along with low concentration of Ca2+ and high concentration of CO32-+HCO3-and groundwater are the types of Cl-SO4-Na and Cl-CO3-Na,with low concentration of CO32-+HCO3-and high concentration of Ca2+.Saturation index of calcite and aragonite in some lake water is more than 0.Based on the simulation of PHREEQC,the mixing between lake water and groundwater results in SI (saturation index) increasing.Evaporation concentration effect in the lake and the mixing effect between fresh water and salt water are the main cause of calcium carbonate and tufa precipitation.The mixing ratio companied the maximum saturation index is mainly determined by the composition of end member mixing water,while the contribution of temperature is small compared with mixing effect.