陕北淤地坝土壤水氢氧稳定同位素特征及其补给规律

Characteristics and recharge mechanisms of hydrogen and oxygen stable isotopes in soil water of check dam in northern Shaanxi

摘要

为系统揭示黄土高原淤地坝区土壤水分运移规律及其补给机制，选取陕北神木六道沟流域一处典型淤地坝为研究对象，于2018−2020年定期采集降水、不同深度土壤水和地下水样品，运用氢氧稳定同位素[δ(²H)和δ(¹⁸O)]技术开展分析研究。结果表明：浅层（0～40 cm）土壤水δ(²H)和δ(¹⁸O)同位素显著富集，明显高于深层（100～800 cm）土壤水、降水及地下水，表明浅层土壤水经历了较强的蒸发分馏作用；土壤水蒸发线（soil water line，SWL）和地下水线（ground water line，GWL）的斜率与截距均低于当地大气水线（local meteoric water line，LMWL：δ(²H)=7.54×δ(¹⁸O)+5.41），表明水分入渗过程中发生了显著的同位素分馏；地下水δ(²H)和δ(¹⁸O)的变异系数（4%～8%）显著低于降水的变异系数（39%～57%）和土壤水的变异系数（9%～33%），且土壤水同位素变异系数在剖面中随深度增加呈递减趋势，进一步表明地下水受外界干扰最小、稳定性最高；相关性分析显示，淤地坝400 cm深度处土壤水δ(¹⁸O)与地下水δ(¹⁸O)同位素呈显著相关，地下水向上补给的土层深度范围逐年变化，分别为416～568 cm（2018年）、462～528 cm（2019年）和530～578 cm（2020年）。研究明晰了淤地坝区土壤-地下水系统的水分运移路径与补给动态，可为黄土高原淤地坝区水土资源评价与可持续管理提供数据支撑和理论依据。

Abstract

Check dams on the Loess Plateau play a pivotal role in soil and water conservation, as well as regulating water resource. The success of ecological restoration and the long-term sustainability of water resource use are significantly influenced by the dynamics of soil water movement and groundwater recharge within these systems. Prior research has mostly concentrated on vegetation-soil interactions, sediment retention, and erosion control. However, there is still a lack of systematic characterization of the coupling mechanisms between groundwater and soil water in check dam areas, particularly the recharge pathways from various sources and the stable isotope fractionation characteristics that go along with them. The hydrogen and oxygen stable isotope technique provides an effective means to trace water movement and mixing processes, and it has been widely applied in arid and semi-arid regions. Nonetheless, due to the distinct topographic and hydrological configuration of check dam systems, the mechanisms controlling soil water recharge and their spatiotemporal variability are poorly constrained. To address this knowledge gap, this study was conducted in a typical check dam of northern Shaanxi. We aim to systematically reveal the sources, transport pathways, and temporal dynamics of soil water recharge in the dam land by integrating multi-depth soil water, groundwater, and precipitation sampling with δ(²H) and δ(¹⁸O) analyses. The findings provide robust scientific support for optimizing water resource management and guiding ecological restoration across the Loess Plateau. A typical check dam in the Liudaogou watershed in Shenmu City, northern Shaanxi Province, was chosen as the study's research location. Field sampling and laboratory analyses were carried out over a three-year period, from 2018 to 2020. During the study period, precipitation, soil water (0 to 800 cm), and groundwater samples were collected on a regular basis throughout the study area. The hydrogen and oxygen stable isotope compositions [δ(²H) and δ(¹⁸O)] of all water samples were measured and analyzed. Concurrently, soil water content was measured at various depths. The relationships within the "precipitation-soil water-groundwater" system were clarified by correlation analysis to examine soil water transport patterns, groundwater recharge characteristics, and isotope fractionation mechanisms. The results indicated that hydrogen and oxygen stable isotopes in shallow soil water (0 to 40 cm) exhibited significant enrichment, with δ(²H) and δ(¹⁸O) values markedly higher than those in deep soil water (100 to 800 cm), precipitation, and groundwater. This pattern suggests that near-surface soil water movement is strongly influenced by evaporation-driven fractionation. Both the slope and intercept of the soil water line (SWL) and the groundwater line (GWL) were lower than those of the local meteoric water line (LMWL: δ(²H) = 7.54 × δ(¹⁸O) + 5.41). This reflects the significant isotopic fractionation that various water bodies undergo prior to infiltration and subsequent recharge of groundwater or deep soil water. The coefficients of variation for δ(²H) and δ(¹⁸O) in groundwater ranged from 4% to 8%, significantly lower than those of precipitation (39% to 57%) and soil water (9% to 33%). Furthermore, throughout the soil profile, the coefficient of variation for stable isotopes exhibited a gradual decline with increasing depth. This indicates that groundwater represented the most stable water body in the system and was least affected by short-term climatic fluctuations or surface disturbances. Soil water content (SWC) displayed a vertical distribution pattern of an initial decrease followed by an increase with depth, accompanied by clear interannual variability. The highest mean SWC was recorded in 2018 [(0.150 ± 0.057) g·g⁻¹], followed by 2019 [(0.149 ± 0.079) g·g⁻¹], and the lowest in 2020 [(0.111 ± 0.086) g·g⁻¹]. Correlation analysis revealed a statistically significant positive relationship between δ(¹⁸O) values in soil water at 400 cm depth and those in groundwater, indicating a strong hydraulic connection between soil water at this depth and the aquifer. The upward recharge zone of groundwater into the overlying soil profile showed marked interannual variation, with recharge depths of 416 to 568 cm in 2018, 462 to 528 cm in 2019, and 530 to 578 cm in 2020. These interannual variations in recharge depth were closely related to changes in soil water content and groundwater table depth. This study identified the patterns of hydrogen and oxygen stable isotope fractionation in various water bodies in the northern Shaanxi check dam region using integrated field sampling and laboratory analysis. It elucidated the coupled mechanisms and vertically stratified recharge dynamics within the "precipitation-soil water-groundwater" system, characterized the distinctive vertical soil water distribution pattern ("decreasing first and then increasing") and its interannual fluctuations, and quantified the dynamic range of upward groundwater recharge into the soil profile. The dominant processes controlling soil water dynamics and recharge mechanisms in check dam systems are clarified by the integrated dataset of soil water, isotopic signatures, and groundwater recharge estimates. These findings provide data support and a theoretical foundation for the rational development, efficient utilization, and long-term management of soil and groundwater resources in such areas, as well as actionable insights for regional ecological restoration and adaptive water resource management.

关键词

淤地坝 / 土壤水 / 地下水 / 氢氧稳定同位素 / 黄土高原

Key words

check dam / soil water / groundwater / hydrogen and oxygen stable isotope / Loess Plateau

参考文献

[1] 林珂, 崔俊芳, 李若萱, 等. 西南干热河谷土壤水分对降雨入渗的响应机制[J]. 南水北调与水利科技（中英文）, 2024, 22(4): 736-746. DOI: 10.13476/j.cnki.nsbdqk.2024.0075.

[2] Dymond S F, Wagenbrenner J W, Keppeler E T, et al. Dynamic hillslope soil moisture in a Mediterranean Montane watershed[J]. Water Resources Research, 2021, 57(11): e2020WR029170. DOI: 10.1029/2020WR029170.

[3] Xie Yiran, Wang Xu, Qian Yatong, et al. Ecosystem evolution and drivers across the Tibetan Plateau and surrounding regions[J]. Journal of Environmental Management, 2025, 380： 124885. DOI: 10.1016/j.jenvman.2025.124885.

[4] 戴前坤, 杨海青, 郭子钰, 等. 嘉陵江流域植被NPP时空演变及驱动因素探究[J]. 水利水电技术（中英文）, 2025, 56(1): 61-77. DOI: 10.13928/j.cnki.wrahe.2025.08.005.

[5] Dong Jingnuo, Ochsner T E. Soil texture often exerts a stronger influence than precipitation on mesoscale soil moisture patterns[J]. Water Resources Research, 2018, 54(3): 2199-2211. DOI: 10.1002/2017WR021692.

[6] 李培月, 李佳慧, 吴健华, 等. 黄土-古土壤互层对土壤水分运移及土体微结构的影响[J]. 水文地质工程地质, 2024, 51(3): 1-11. DOI: 10.16030/j.cnki.issn.1000-3665.202403039.

[7] Zhang Dinghai, Zhao Youyi, Qi Haidi, et al. Effects of micro-topography and vegetation on soil moisture on fixed sand dunes in Tengger Desert, China[J]. Plants (Basel), 2024, 13(11): 1571. DOI: 10.3390/plants13111571.

[8] 张建国, 李晶晶, 余红兵. 黄河流域黄土高原地区水土流失动态变化及分布特征[J]. 水土保持研究, 2025, 32(4): 110-116. DOI: 10.13869/j.cnki.rswc.2025.04.043.

[9] Shi Hui, Shao Mingan. Soil and water loss from the Loess Plateau in China[J]. Journal of Arid Environments, 2000, 45(1): 9-20. DOI: 10.1006/jare.1999.0618.

[10] Bai Xiao, Fang Junjie, Liu Chenggong, et al. Assessing the cooling effects of vegetation greening on surface temperature under climate warming in China's Loess Plateau[J]. Ecological Engineering, 2025, 221： 107787. DOI: 10.1016/j.ecoleng.2025.107787.

[11] Zeng Yi, Jing Tongge, Xu Baodong, et al. Vectorized dataset of silted land formed by check dams on the Chinese Loess Plateau[J]. Scientific Data, 2024, 11(1): 348. DOI: 10.1038/S41597-024-03198-Z.

[12] Feng Xiaoming, Fu Bojie, Piao Shilong, et al. Revegetation in China's Loess Plateau is approaching sustainable water resource limits[J]. Nature Climate Change, 2016, 6(11): 1019-1022. DOI: 10.1038/nclimate3092.

[13] Wei Wei, Pan Daili, Yang Yong. Effects of terracing measures on water retention of pinus Tabulaeformis forest in the dryland loess hilly region of China[J]. Agricultural and Forest Meteorology, 2021, 308： 108544. DOI: 10.1016/j.agrformet.2021.108544.

[14] Huang Jinbai, Hinokidani O, Yasuda H S, et al. Effects of the check dam system on water redistribution in the Chinese Loess Plateau[J]. Journal of Hydrologic Engineering, 2013, 18(8): 929-940. DOI: 10.1061/(ASCE)HE.1943-5584.0000689.

[15] Tang Honglei, Pan Hailong, Ran Qihua. Impacts of filled check dams with different deployment strategies on the flood and sediment transport processes in a Loess Plateau catchment[J]. Water, 2020, 12(5): 1319. DOI: 10.3390/w12051319.

[16] Cucchiaro S, Cavalli M, Vericat D, et al. Geomorphic effectiveness of check dams in a debris-flow catchment using multi-temporal topographic surveys[J]. Catena, 2019, 174： 73-83. DOI: 10.1016/j.catena.2018.11.004.

[17] Zema D A, Bombino G, Denisi P, et al. Evaluating the effects of check dams on channel geometry, bed sediment size and riparian vegetation in Mediterranean mountain torrents[J]. Science of the Total Environment, 2018, 642： 327-340. DOI: 10.1016/j.scitotenv.2018.06.035.

[18] Sun Yi, Zhang Yi, Liu Xiaojun, et al. The construction of check dams on the Loess Plateau has prolonged water transmission times and altered recharge relationships[J]. Water, 2025, 17(22): 3320. DOI: 10.3390/w17223320.

[19] Chen Zuyu, Chen Shujing, Yin Penghai, et al. Check dams on China's Loess Plateau: An overview[J]. River, 2025, 4： 1-20. DOI: 10.1002/rvr2.118.

[20] 甄自强. 黄土高原北部淤地坝区域土壤水分模拟及水分有效性分析[D]. 扬州: 扬州大学, 2017.

[21] 盖佳敏, 樊军, 王胜. 黄土高原粗质地土壤剖面水分运动与浅层地下水补给可能性模拟[J]. 中国生态农业学报, 2018, 26(2): 253-262. DOI: 10.13930/j.cnki.cjea.170495.

[22] 金沐. 黄土高原淤地坝内浅层地下水动态及补给规律[D]. 杨凌: 西北农林科技大学, 2020.

[23] 袁鸿猷. 水蚀风蚀交错区淤地坝水循环关键过程研究[D]. 杨凌: 西北农林科技大学, 2021.

[24] 徐忠宝, 杨丽萍, 翁白莎, 等. 青藏高原不同水体氢氧稳定同位素特征[J]. 南水北调与水利科技（中英文）, 2024, 22(3): 521-533. DOI: 10.13476/j.cnki.nsbdqk.2024.0054.

[25] 张小娟, 宋维峰, 吴锦奎, 等. 元阳梯田水源区土壤水氢氧同位素特征[J]. 环境科学, 2015, 36(6): 2102-2108. DOI: 10.13227/j.hjkx.2015.06.025.

[26] 徐英德, 汪景宽, 高晓丹, 等. 氢氧稳定同位素技术在土壤水研究上的应用进展[J]. 水土保持学报, 2018, 32(3): 1-9. DOI: 10.13870/j.cnki.stbcxb.2018.03.001.

[27] Dansgaard W. The abundance of¹⁸O in atmospheric water and water vapor[J]. Tellus, 1953, 5(4): 461-469. DOI: 10.3402/tellusa.v5i4.8697.

[28] 姬王佳, 黄亚楠, 李冰冰, 等. 陕北黄土区深剖面不同土地利用方式下土壤水氢氧稳定同位素特征[J]. 应用生态学报, 2019, 30(12): 4143-4149. DOI: 10.13287/j.1001-9332.201912.020.

[29] 裴艳武, 黄来明, 邵明安, 等. 毛乌素沙地不同地下水位埋深下土壤水补给特征及影响因素[J]. 农业工程学报, 2021, 37(12): 108-116. DOI: 10.11975/j.issn.1002-6819.2021.12.013.

[30] 杨凡, 马玉学, 杨丽虎, 等. 宁南黄土高原退耕还林（草）区深厚包气带土壤水氢氧同位素特征及其补给规律[J]. 地理研究, 2024, 43(12): 3385-3396. DOI: 10.11821/dlyj020240187.

[31] Jia Xiaoxu Bai Xiao, Liu Chenggong, et al. Differences in plant water use between check-dam land and slope land on the Loess Plateau: Significance for vegetation restoration[J]. Agriculture, Ecosystems & Environment, 2024, 362: 108849. DOI: 10.1016/j.agee.2023.108849.

[32] Luo Zhanbin, Yong Chenxu, Fan Jun, et al. Precipitation recharges the shallow groundwater of check dams in the loessial hilly and gully region of China[J]. Science of the Total Environment, 2020, 742： 140625. DOI: 10.1016/j.scitotenv.2020.140625.

[33] Wang Jian, Fu Bojie, Lu Nan, et al. Water use characteristics of native and exotic shrub species in the semi-arid Loess Plateau using an isotope technique[J]. Agriculture, Ecosystems & Environment, 2019, 276: 55-63. DOI: 10.1016/j.agee.2019.02.015.

[34] 邵明安, 王全九, 黄明斌. 土壤物理学[M]. 北京: 高等教育出版社, 2006.

[35] Craig H. Isotopic variations in meteoric waters[J]. Science, 1961, 133(3465): 1702-1703. DOI: 10.1126/science.133.3465.1702.

[36] Wang Wanzhou, Sun Jineng, Xia Yun, et al. Identifying hydraulic connectivity among the vadose zone, unconfined and confined aquifers in the thick loess deposits using multiple tracers[J]. Journal of Hydrology, 2023, 626： 130339. DOI: 10.1016/j.jhydrol.2023.130339.

[37] Bowen G J, Cai Zhongyin, Fiorella R P, et al. Isotopes in the water cycle: Regional-to global-scale patterns and applications[J]. Annual Review of Earth and Planetary Sciences, 2019, 47： 453-479. DOI: 10.1146/annurev-earth-053018-060220.

[38] 朱宝文, 郑有飞, 陈晓光. 高寒针茅草原植物生长季土壤水分动态变化规律[J]. 干旱地区农业研究, 2009, 27(3): 96-100.

[39] Liu Shaozhen, Van Meerveld I, Zhao Yali, et al. Seasonal dynamics and spatial patterns of soil moisture in a loess catchment[J]. Hydrology and Earth System Sciences, 2024, 28： 205-216. DOI: 10.5194/hess-28-205-2024.

[40] Ma Yuanyuan, Zhou Xiaoping, Shen Yan, et al. Long-term alfalfa planting mediates the coupling of soil water and organic carbon storage in a semi-arid area of the Loess Plateau, China[J]. Peer J, 2024, 12： e18373. DOI: 10.7717/PEERJ.18373.

[41] 白晓, 贾小旭, 邵明安, 等. 黄土高原北部土地利用变化对长期土壤水分平衡影响模拟[J]. 水科学进展, 2021, 32(1): 109-119. DOI: 10.14042/j.cnki.32.1309.2021.01.011.

[42] Wang Yunqiang, Shao Mingan, Liu Zhipeng. Vertical distribution and influencing factors of soil water content within 21 m profile on the Chinese Loess Plateau[J]. Geoderma, 2013, 193-194: 300-310. DOI: 10.1016/j.geoderma.2012.10.011.

[43] 于晓燕. 黄土丘陵区深层土壤干化背景下降雨对初植苜蓿地土壤水分的影响[D]. 银川: 宁夏大学, 2023.

[44] Guan Ning, Bi Huaxing, Zhao Danyang, et al. Soil water response to rainfall in Loess Plateau forests: Insights from water transport and recharge processes[J]. Hydrological Processes, 2025, 39(8): e70249. DOI: 10.1002/hyp.70249.

[45] Rao Wenbo, Chen Xi, Meredith K T, et al. Water uptake of riparian plants in the lower Lhasa River basin, south Tibetan Plateau using stable water isotopes[J]. Hydrological Processes, 2020, 34(16): 3492-3505. DOI: 10.1002/hyp.13831.

[46] Gamie R, De Smedt F. Experimental and statistical study of saturated hydraulic conductivity and relations with other soil properties of a desert soil[J]. European Journal of Soil Science, 2018, 69(2): 256-264. DOI: 10.1111/ejss.12519.

[47] 刘伟佳, 吴军虎, 裴青宝, 等. 不同地下水埋深条件下均质土壤毛管上升水运动特性试验研究[J]. 水资源与水工程学报, 2010, 21(1): 67-70.

[48] 刘丙霞, 任健, 邵明安, 等. 黄土高原北部人工灌草植被土壤干燥化过程研究[J]. 生态学报, 2020, 40(11): 3795-3803. DOI: 10.5846/stxb201905311151.

[49] Mata-González R, Mclendon T, Martin D W, et al. Vegetation as affected by groundwater depth and microtopography in a shallow aquifer area of the Great basin[J]. Ecohydrology, 2012, 5(1): 54-63. DOI: 10.1002/eco.196.

基金资助

国家自然科学基金项目(42307407)

陕西省教育厅科学研究计划项目(23JK0540)