Study On Groundwater Circulation Patterns And Renewability In The Western Plain Of Ili River Valley,Xinjiang

Ili Kazak Autonomous Prefecture is located in the western part of Xinjiang Uygur Autonomous Region.As an important hub of the Silk Road Economic Belt in China's"One Belt,One Road"strategy,it has a very important strategic position.Groundwater resources are abundant in the plain area of the western Ili River Valley,but the regional geological and hydrogeological conditions are complicated,and the regional groundwater circulation patterns are very complicated.It is significant to carry out the research on groundwater circulation patterns and groundwater renewability in this area,to evaluate groundwater resources scientifically and to exploit and utilize groundwater moderately.This paper takes the western plain area of the Ili River Valley as the research area.Based on the investigation and analysis of regional geological and hydrogeological conditions and the analysis of previous achievements,combined with multiple environmental isotope tracers,hydrochemical analysis,CFCs,thermal tracers and other methods,the groundwater circulation patterns of different levels in the region were established,and the renewable capacity of groundwater was evaluated.The main results of the study are as follows:1.The results of hydrochemical analysis and hydrogen-oxygen stable isotope tracing show that there are multiple conversion relations between groundwater and river water in the study area.There are multiple groundwater-river water transformations in the alluvial fine soil plain with gravel and the alluvial-proluvial fine soil plain on both sides of the Ili River.The results of thermal tracer calculation show that during the monitoring period,the permeation fluxes of the river at Daxigou and downstream of Shuimogo are1296.0L/?m²·d?and 112.3L/?m²·d?,respectively.The discharge fluxes of groundwater at Heishuigou and upstream of Shuimogou and are 86.4L/?m²·d?and 33.5L/?m²·d?,respectively.2.Controlled by the topography,geomorphology and hydrogeological conditions of the north and south sides of Ili River Valley,the regional groundwater flow exhibits multi-level circulation characteristics.The local-scale groundwater circulation is greatly affected by topography,the runoff path is short,the circulation depth is shallow,and the circulation speed is fast;the middle-scale groundwater circulation is developed from the gravel plain to the alluvial plain,with slow runoff,strong lixiviation,and a long circulation path;the regional-scale groundwater circulation develops in front of the mountain and flows to the center of the Ili River Valley.The groundwater runoff speed is extremely slow and the circulation depth is deep.3.The age and renewability of the shallow and deep groundwater in the study area are quite different.From the front of the mountain to the center of the valley,the model age of shallow groundwater³H and CFCs increased from 20 to 60 years.The renewal rate of shallow groundwater in the south bank of Ili River is basically greater than 10%/a,while the renewal rate of shallow groundwater in the north bank of Ili river is mainly between 1¹0%/a.The renewal rate of the alluvial-proluvial fine soil plain in the central part of Ili River Valley is less than 1%/a.From the front of the mountain to the center of the valley,the age of the ¹⁴C model of the deep groundwater increased from 2000 to more than 10000 years ago.The renewal rate of the deep groundwater in most areas on both sides of the Ili River was 0.01⁰.03%/a,and the renewal rate of some locations in the alluvial fine soil plain with gravel were greater than 0.03%/a.