A study of the conversion between the Daxigou river and groundwater

A study of the conversion between a river and groundwater is of great significance for the rational development and utilization of regional water resources. Based on the analyses of the conversion between the Daxigou River water and groundwater, this paper analyzes the groundwater dynamic field and uses hydrochemical type, dissolved total solids (TDS), chloride (Cl-) and environmental isotopes 18O, D, T and other indicators as tracers to examine the conversion relationship between the Daxigou River and groundwater and their transformation intensity. The results show that the hydrochemical types of rivers and groundwater in the study area are mainly of HCO3-Ca type, and the spatial distribution characteristics of the hydrochemical types are similar. The concentrations of TDS and Cl- increase first and then decrease, but the variation in groundwater is greater than that of the river water. The comparative analysis of hydrochemistry and environmental isotope indexes in the Daxigou river water and groundwater reveals that the supply and discharge relationship between rivers and groundwater in the study area is characterized by obvious segmentation. From river exit to downstream, conversion of the river water and groundwater occur three times. In the sloped gravel plain area in front of the mountains, the river water infiltrates into the groundwater, and the recharge accounts for 56% of the submarine runoff. In the fine soil plain area, the groundwater recharges the river water, and the recharge source is from the mixed water body in the unconfined aquifer which is a leakage recharge from the confined aquifer. The proportion from the unconfined and confined aquifers accounts for 20.4% and 58.4% of the river runoff, respectively. The river in the windy desert area supplies the groundwater until the river is zero-flow. The results of this study may provide theoretical and technical support for the establishment of the water cycle evolution model and the rational development and utilization of water resources of the study area.