Hydrochemical characteristics and controlling factors of karst groundwater in middle and upper reaches of Dawen River basin

Abstract

To determine the hydrochemical characteristics and ion sources of karst groundwater in the middle and upper reaches of the Dawen River basin, based on karst groundwater samples collected in dry and wet periods in 2018, hydrochemical data were analyzed by means of mathematical statistics, correlation analysis, Piper diagram, Gibbs diagram and ion ratios. The results showed that the average pH values of karst groundwater in dry and wet periods in the middle and upper reaches of the Dawen River basin were 7.6 and 7.5, respectively, showing weak alkaline conditions as a whole. Ca2+ was the dominant cation in karst groundwater, and HCO3- and SO42- were the main anions. The average contents of TDS in karst groundwater during the dry and wet periods were 645.4 mg/L and 648.4 mg/L, respectively. According to TDS, the karst groundwater in the upper and middle reaches of the Dawen River basin belonged to freshwater or brackish water; hydrochemical types of karst groundwater in dry and wet periods were mainly HCO3·SO4-Ca. Rock weathering was the main controlling factor affecting the hydrochemical characteristics of karst groundwater in the area. The dissolution of carbonate and silicate minerals was an important source of groundwater ions. At the same time, the karst groundwater in the upper and middle reaches of the Dawen River basin was also affected obviously by human activities, and NO3- in groundwater mainly came from agricultural production activities.

Keywords

• karst groundwater
• hydrochemical characteristics
• controlling factors
• dawen river basin