Hydrochemical characteristic and interaction process of surface and groundwater in mid-lower reach of Hanjiang River, China

Abstract

Hanjiang River, the largest tributary of Yangtze, faces environmental pressures from South-to-North Water Transfer project and anthropogenic influences. In order to reveal the chemical characteristics of river and contribution of groundwater to the river along mid-lower reaches of Hanjiang River, field works have been conducted in wet and dry seasons. The major ion compositions are characterized by the dominance of Ca2+, and HCO3 − in surface water and groundwater. As a result, calcite weathering is a dominant process for surface water and groundwater. Additionally, dolomite weathering also contributes to hydrochemical evolution in the groundwater of the basin. Stable isotopes (δ18O, δD) show that both surface and groundwater most probably originate from present-day precipitation. Isotopic of both surface water and groundwater can provide greater confidence in identifying the weathering and extent of interaction processes. It was found that river water was mainly recharged by tributaries in wet season while recharged by groundwater in dry season. Dissolved solute flux from tributaries and groundwater to the river was estimated by water balance budget model and environmental tracer mass balance approach. Tributaries and groundwater contribute to mid-lower reach of Hanjiang River in wet season and dry season, respectively. From section H1 to H9, there were 455.4 kg/s of total dissolved solute (TDS) transferred from tributaries to the main channel and 99.8 kg/s of TDS fluxed from groundwater to river water in dry season.