Analysis of the evolution and causes of groundwater chemistry after ecological water replenishment of the Jialu River, China.

Ecological water replenishment is an important measure for conserving water sources and improving the water environment. To explore the evolution and causes of groundwater chemistry after ecological water replenishment in the Jialu River, this study utilized groundwater monitoring data from 2015 to 2019 following ecological water replenishment. Various methods, including Piper's trilinear diagram, Gibbs diagram, principal component analysis, and ion ratio analysis, were employed for research purposes. The results indicate that (1) since the implementation of ecological water replenishment in the Jialu River, there has been a general downwards trend in total dissolved solids (TDS) in groundwater. The dominant cation in groundwater is Ca, whereas HCO is the dominant anion. The concentration of cations in groundwater has generally decreased, with noticeable reductions in SO and Cl concentrations in the upper reaches of the recharge river contributing to improved groundwater quality. (2) A comparison with 2015 reveals a gradual transition at sampling points from chemical types such as HCO-Ca·Mg and HCO·Cl-Ca·Mg to an ecological water replenishment chemical type (HCO-Ca).