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Flow directions of stream‐groundwater exchange in a headwater catchment during the hydrologic year
Author(s) -
Bonanno Enrico,
Blöschl Günter,
Klaus Julian
Publication year - 2021
Publication title -
hydrological processes
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.222
H-Index - 161
eISSN - 1099-1085
pISSN - 0885-6087
DOI - 10.1002/hyp.14310
Subject(s) - groundwater , hydrology (agriculture) , water table , bedrock , groundwater flow , groundwater discharge , streams , riparian zone , geology , streamflow , aquifer , piezometer , subsurface flow , inflow , groundwater model , environmental science , drainage basin , geomorphology , geotechnical engineering , computer network , ecology , computer science , geography , biology , oceanography , cartography , habitat
Understanding near‐stream groundwater dynamics and flow directions is important for predicting hillslope‐stream connectivity, streamflow generation, and hydrologic controls of streamwater quality. To determine the drivers of groundwater flow in the stream corridor (i.e., the stream channel and the adjacent groundwater in footslopes and riparian areas), we observed the water levels of 36 wells and 7 piezometers along a headwater stream section over a period of 18 months. Groundwater dynamics during events were controlled by the initial position of the groundwater table relative to the subsurface structure. The near‐stream groundwater table displayed a fast and pronounced response to precipitation events when lying in fractured bedrock with low storage capacity, and responded less frequently and in a less pronounced way when lying in upper layers with high storage capacity. Precipitation depth, intensity, regolith thickness above the fractured bedrock, and proximity to and elevation above the stream channel also had an effect on the groundwater dynamics, which varied with hydrologic conditions. Our high‐frequency and spatially dense measurements highlight the competing influence of groundwater inflow from upslope locations, streamwater level and bedrock properties on the spatiotemporal dynamics of flowpaths in the stream corridor. Near‐stream groundwater pointed uniformly towards the stream channel when the stream corridor was hydrologically connected to upslope groundwater. However, local interruptions of the water inflow from upslope locations caused flow reversals towards the footslopes. The direction of near‐stream groundwater followed the local fractured bedrock topography during dry hydrologic conditions on a few occasions after events. The outcomes of this research contribute to a better understanding of the drivers controlling spatiotemporal changes in near‐stream groundwater dynamics and flow directions in multiple wetness states of the stream corridor.