Hydrochemical characteristics and water quality evaluation of groundwater in lower reaches of the Qiantang River

In order to explore the hydrochemical characteristics and water quality of groundwater in the lower reaches of the Qiantang River, the test data of 46 groundwater samples in this area were analyzed by mathematical statistics, Piper's three-line diagram, Gibbs diagram, single-index evaluation method, comprehensive quality evaluation method and fuzzy comprehensive evaluation method.The results showed that the phreatic water hydrochemical types were HCO3-Na·Ca·Mg and HCO3·Cl-Na respectively, which were mainly affected by dissolution of rock salt, ion exchange, and human activities.The confined water hydrochemical types were Cl-Na·Ca·Mg and Cl-Na, which were mainly affected by seawater.By comparing and analyzing the differences between the evaluation methods, the evaluation results of fuzzy comprehensive evaluation method were more objective for regional groundwater assessment.The results showed that the phreatic water quality in the study area was generally good, and some phreatic water might be polluted by the original geological environment.While the confined water was mainly affected by marine intrusion and was not suitable for drinking.The research has positive guiding significance for the development, utilization and protection of groundwater in the area.