Transport of Solutes in Groundwater Through a Hillslope-Riparian Transition During two Rain Events at the Panola Moutain Research Watershed, Georgia
Abstract
Studies of the interaction of hydrologic transport processes with solute dynamics at hillslope-riparian transitions are needed to develop a better conceptualization of how riparian zones interact with the surrounding landscape, which may lead to the development of improved water quality models. However, few field studies have been performed that examine these dynamics, especially during rain and snowmelt events. We sampled hillslope and riparian groundwater, and stream water during two rain events in March 1996 at the Panola Mountain Research Watershed, Georgia to examine hillslope-riparian groundwater interactions. During a 96-mm event on March 6 and 7, a shallow riparian piezometer at 1.34 m depth showed dilution of Na+ and H4SiO4 concentrations near the time of peak groundwater stage. Results of an end-member model based on conservative mixing indicated the presence of about 25% hillslope groundwater at this depth at peak stage. Riparian groundwater chemistry rapidly returned to pre-event concentrations, an indication that hillslope groundwater rapidly transits to the stream with little permanent recharge of the riparian aquifer. At depths of 2.61 and 3.73 m, however, little change in pre-event water chemistry was observed, an indication of minimal penetration of hillslope groundwater to these depths. During a smaller and more typical 26 mm rain event on March 27, little change in groundwater chemistry was observed at even the shallow piezometer suggesting that hillslope groundwater contributes little to stream water during moderate rain events. These results indicate that transient hillslope groundwater enters only the shallow part of the riparian aquifer near the peak of large storms. The shallow part of the riparian aquifer is therefore, a zone in which transient groundwater mixes with pre-event groundwater, and is then rapidly delivered to the stream. Some unanswered questions remain, however, such as the ability of rapid biogeochemical reactions to attenuate solute transport through the riparian aquifer during storms.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2002
- Bibcode:
- 2002AGUFM.H51D..05B
- Keywords:
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- 1829 Groundwater hydrology;
- 1831 Groundwater quality;
- 1860 Runoff and streamflow