Integrating hydrogeochemical and biological approaches to investigate the surface water and groundwater interactions in the hyporheic zone of the Liuxi River basin, southern China

•Integration of microbial and hydrochemical approaches revealed GW–SW interactions.•GW–SW interactions induced the mixing of chemicals and microbes in the hyporheic zone.•Hyporheic zone was identified as being within 0.5–2 m from the riverbank.•Denitrification was the main cause of the loss of NO3− in the hyporheic zone.