Application of Stable Isotope in Hydrologic Analysis of a Rainfall-Runoff Event in the Xin’an Jiang River Basin

Thursday, 17 December 2015
Poster Hall (Moscone South)
Xuegao Chen1, Peng Yi1, LI Chen2 and Ala Aldahan3, (1)Hohai University, Nanjing, China, (2)Desert Research Institute, Las Vegas, NV, United States, (3)United Arab Emirates University, Geology, Al Ain, United Arab Emirates
Stable isotopes abundance of hydrogen (δ2H) and oxygen (δ18O) are very sensitive to environmental changes and can help understand the complex recharges between surface water and groundwater. However, details of variability in the different components of water supply to watersheds are generally missing. We present here evaluation of isotopic changes in small watershed (0.19 km2) in the upstream of Xin’an River, Anhui province, China based on daily sampling of rainfall events and runoff (river and soil water). The δ2H and δ18O of different water sources in the watershed were aimed in order explore interactions between different parts of the hydrological processes. The collected water samples were analyzed for δ2H and δ18O using Picarro L-2120i analyzer at a precision of 1.0 and 0.1 ‰, respectively. The results indicated higher abundance of 2H and 18O in precipitation than those in river. Additionally, the content of the heavy isotopes also decreases in soil water with depth, while surface soil water was enriched because of evaporation. The response of the watershed to the changes in δ2H and δ18O varied, where water in upstream gained more heavy isotopes rapidly, while in the downstream part the enrichment happened after a few days. This feature suggests a different but still strong hydraulic connection between surface water and groundwater in the small watershed tested here. Accordingly, variability of δ2H and δ18O should be carefully evaluated on a local scale before application in transport system of large rivers and exchange with groundwater.