Towards a better understanding of riparian zone water table response to precipitation: surface water infiltration, hillslope contribution or pressure wave processes?

Determining how riparian zone hydrological conditions may change in response to precipitation in various geomorphic settings is critical to determine the occurrence of hot moments of biogeochemical transformations for phosphorus, nitrogen, sulfate, mercury and greenhouse gases in these systems. The author investigate water table response to precipitation at a high temporal resolution (15?min) in a riparian zone located in a deeply incised glacial till valley (20?m) with approximately 2?m of alluvium over a confining layer, in Indiana, USA. During storms, larger water table fluctuations (approximately 100?cm) occurred near the stream than near the toe slope (1025?cm). A quick rise in water table near the stream occurred for all storms, with partial flow reversals occurring for three of seven storms. The quick rise of the water table near the stream was associated with a decrease in hillslope water contributions to the stream during storms and the development of a water table down valley gradient for most storms. Water table fluctuations, groundwater flow velocities and electrical conductivity data indicated that riparian zone water table response to precipitation was primarily regulated by pressure wave processes. Regardless of the storm, high water tables persisted for at least 2?days after the cessation of precipitation. Although this suggests that high-resolution precipitation data may be useful to quantify hot moments of biogeochemical transformation associated with high water tables in riparian zones, precipitation data alone are not sufficient to correctly estimate the magnitude of riparian water table level changes during storms. Copyright (C) 2011 John Wiley & Sons, Ltd.