Abstract:

        With the application of hydrogen and oxygen isotopes (²H,³H and ¹⁸O) and carbon isotope (¹⁴C), the recharge and renewability of confined water in Yinchuan Plain have been analyzed.Forty five groups of confined water samples have been collected in the plain for isotope analysis. The analysis results show that the distribution characteristics of hydrogen and oxygen isotopes (²H,³H and ¹⁸O) and carbon (¹⁴C) possess very good consistency, revealing the regional regularities of recharge and flow,and local change features of confined water in the study area. ¹⁴C dating results indicate that the age of confined water is within the range of 3，000 to 22，290 a. Correcting ¹⁴C age has been calibrated by Tamers and Gonfiantinie models,and the results have been compared. Along the isotope hydrogeological profile, it is calculated that the flow rate of groundwater from Helan mountain piedmont in the north to the middle part of Yinchuan Plain is from 2.22 to 0.63 m/a, showing the decreasing characteristics from south to north; the flow rate of groundwater from Qingtongxia alluvial-diluvial area to middle part of Yinchuan Plain is from more than 10 to 2 m. It is concluded that the flow rate of confined groundwater in Yinchuan Plain is slow and the water exchange takes longer time. Confined water has hydraulic connection with locally phreatic water. The leakage recharge of phreatic water can amount to 45%,so that the appropriate exploitation of confined water can be conducted for renewability of confined water to a certain degree.

Key words: confined water, hydrogen and oxygen isotopes, ¹⁴C age, hydrogeology, distribution characteristics, Yinchuan Plain