The steppe located in the middle Inner Mongolia Plateau (IMP) has scarce water resources and fragile ecosystems and has an arid-semiarid monsoon characterized by low and uneven seasonal precipitation and high evaporation. Until now, problems relating to the hydrologic processes in the area remain poorly understood, and thus strategies for the exploitation and utilization of the area’s local water resource remain limited. This study aimed to investigate the recharge and discharge processes of soil water and the source and circulation of groundwater through geochemical methods. The local meteoric water line (LMWI) of our study area in the middle IMP was first proposed and compared with the local meteoric water line of Baotou in Inner Mongolia and Ulan Bator. The δ¹⁸O and δD values of precipitation showed an increasing trend from June to August and decreasing trend from August to late October. The H and O isotopes of soil water varied with time, location, and soil profile depth. Besides the geographical and climatic factors, the Cl concentrations of soil water can be affected remarkably by land use type and land cover change. In our monitoring period, variations in the Cl concentrations and δ¹⁸O and δD values of shallow soil water indicated that the evaporation of soil water was in the sequence August > June > October. Furthermore, the detailed evaporation proportions of soil water were estimated. The isotope compositions of groundwater plotted on the LMWI and there could be a rapid recharge mechanism of the groundwater.

草原位于内蒙古高原中部（IMP），水资源稀缺，生态系统脆弱，具有干旱半干旱季风，季节降水量少且不均匀，蒸发量高。直到现在，与该地区水文过程有关的问题仍知之甚少，因此，该地区当地水资源的开发和利用策略仍然有限。本研究旨在通过地球化学方法研究土壤水的补给和排放过程以及地下水的来源和循环。首先提出了我们研究区中部IMP的局部大气水位线（LMWI），并将其与内蒙古包头和Ulan Bator的局部大气水位线进行了比较。该δ ¹⁸降水的O和δD值从6月至8月呈上升趋势，从8月至10月下旬呈下降趋势。土壤水的氢和氧同位素随时间，位置和土壤剖面深度而变化。除地理和气候因素外，土地利用类型和土地覆被变化还会显着影响土壤水的Cl浓度。在我们的监测期，在氯浓度和δ变化^18个浅层土壤水分的O和δD值表明，土壤水分的蒸发是序列八月>六月>十月英寸 此外，估算了土壤水分的详细蒸发比例。LMWI上标绘的地下水的同位素组成可能是地下水的快速补给机制。