Determination of soil-groundwater systems recharge mechanism in the middle Inner Mongolia Plateau by isotopic tracers
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ORIGINAL ARTICLE
Determination of soil‑groundwater systems recharge mechanism in the middle Inner Mongolia Plateau by isotopic tracers Yanfei Zhang1 · Yongfu Wei1 · Zilong Liao1 · Xiaomin Xu1 · Zhenhua Han1 · Wentao Liang1 · Yinhui Long1 · Jianying Guo1 Received: 24 December 2019 / Accepted: 23 September 2020 / Published online: 6 October 2020 © Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract 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. Keywords Soil water · Groundwater · Stable isotopes of hydrogen and oxygen · Recharge · Steppe
Introduction The Inner Mongolia plateau (IMP) is located in the west side of Daxingan Mountains and north side of Yin Mountains at an average altitude of over 1000 m above sea level. The climate in this region is dominated by the continental and arid-semiarid monsoon, with uneven seasonal precipitation and large seasonal temperature difference. The annual precipitation from the northeast to the southwest of the IMP has decreased from 368 mm (Hailaer station) to 205 mm (Bayanhaote station) in recent 10 years, but potential evaporation is about several times higher than the precipitation. Evaporation and water consumption by local people are the main causes of water loss. In most areas, grass vegetation are * Yanfei Zhang [email protected] 1
Institute of Water Resource for Pastoral Area, Ministry of Water Resources of the People’s Republic of China, Hohhot, China
groundwater-dependent ecosystems. Even small water deficiency causes heavy drought stress on the fragile grassland ecosystem. F
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