Monsoon-driven Total Head and Temperature Variations at the GW-SW Interface - Implications for Biogeochemical Processes
Abstract
Extreme precipitation events associated with a monsoon-type climate can strongly influence the hydrologic dynamics of an entire watershed with implications for groundwater (GW) and surface water (SW) exchange. Often more than 60% of the annual precipitation falls within two months. The rapid basin-wide change in flow patterns controls the spatial and temporal variability of downstream GW-SW exchange. Event-based increases in SW-discharge increase the stage height relative to GW elevation and influence losing SW conditions. After the event, SW discharge decreases while adjacent GW levels potentially increase causing gaining SW conditions. The temporally variable hydraulic gradient between the SW and GW controls the associated heat and solute fluxes and can have implications on downstream water quality. In order to investigate GW-SW exchange fluxes, a piezometer transect was installed across a third-order stream in the Haean Catchment of South Korea, which is strongly influenced by monsoonal storm events. The piezometers were equipped with single-channel temperature thermistors and pressure transducers to characterize and quantify flow patterns using heat as a tracer. The data loggers recorded the quick temperature and head response at 15 min intervals. Initial results suggest that the investigated river reach exhibits primarily losing SW conditions throughout most of the year. Although, gaining SW conditions occur at specific time periods. Gaining GW conditions at the river reach are evident after monsoonal extreme precipitation events. At the transect streambed aggradation and degradation due to bedload transport was observed. Significant erosion has been reported throughout the catchment after extreme events. Results indicate that the event-based changes in streambed elevation, is an additional control on GW and SW exchange. The streambed flux reversals were found to occur in conjunction with cooler in-stream temperatures at potential GW discharge locations.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2010
- Bibcode:
- 2010AGUFM.H21B1044B
- Keywords:
-
- 1817 HYDROLOGY / Extreme events;
- 1830 HYDROLOGY / Groundwater/surface water interaction