Identifying the distribution of groundwater discharge in a curved river

Groundwater discharge to rivers is crucial to river quality and aqueous ecosystem, and has increasingly drawn researchers’ attention. However, accurately identifying the locations of groundwater discharge in a curved river is still a challenge in hydrology and hydrogeology because the concave and convex banks cause the river-groundwater interaction complicated. This study applied spatial radon isotope ( 222 Rn) continuous-monitoring and spatial high-precision measurements of multiple parameters (temperature, pH, and dissolved oxygen) to identify the groundwater discharge location in a ∼ 10 km curved reach in the lower Ganjiang River (LGJR). The river water influenced by groundwater discharge in the LGJR contained high 222 Rn activity, low pH and high temperature. Six sections with groundwater discharge then were identified in the LGJR. Groundwater discharge is more significant on the east bank than on the west. On the concave and convex banks, the groundwater discharge generally occurs in the front neck, which is contrary to the results of most previous studies considering the hyporheic exchange. We inferred that the groundwater discharge in the LGJR is dominated by heterogeneity of regional groundwater flow . This work provides a new insight on the groundwater discharge in the curved river (a common natural morphology of rivers).