Material processing at Haean Basin scale: The role of hyporheic exchange and the riparian zone in NO3 and DOC export from catchments

TERRECO WP 2-12

Abstract: In landscapes where groundwater and surface waters actively interact, the high concentrations of dissolved constituents in groundwater can have significant implications for surface water quality. In the Haean Catchment in South Korea, which has a strong monsoon type climate, high nitrate concentrations of up to 39.8 mg/L in the groundwater were measured in 2009. It is hypothesized that river-aquifer exchange in the Haean Catchment can significantly affect the nutrient export from the catchment and that the export is variable in time driven by monsoonal events. The identification of nitrate sink and source areas is based on groundwater and river water sampling at sites which reflect the dominant land uses as well as different elevations. Furthermore, we investigated the dynamics of river-aquifer exchange at two sites via piezometer transects at mid and lower elevations within the catchment. Our results suggest that due to river-aquifer exchange the river reaches in the lower part of the catchment have significantly higher nitrate concentrations than reaches at mid and high elevations. Hence, river-aquifer exchange fluxes might be an important control for the nitrate export from the catchment. However, this study also suggests that more research is needed to prove the general significance of this transport pathway.

Keywords: nitrate export, river-aquifer exchange, agriculture, monsoonal storm events, subcatchment, land use

project description in detail from proceedings of 2011 TERRECO Science Conference GAP