TY - JOUR
T1 - Preferential flow through shallow fractured bedrock and a 3D fill-and-spill model of hillslope subsurface hydrology
AU - Guo, Li
AU - Lin, Henry
AU - Fan, Bihang
AU - Nyquist, Jonathan
AU - Toran, Laura
AU - Mount, Gregory J.
N1 - Funding Information:
This study has been supported by United States National Science Foundation Hydrologic Sciences Program Grant EAR-1416881 (PI: H. Lin). The NSF Critical Zone Observatory Program is acknowledged for its support to the Susquehanna Shale Hills Critical Zone Observatory. Logistical support and/or data were provided by the NSF-supported Susquehanna Shale Hills Critical Zone Observatory. This research was conducted in Penn State's Stone Valley Forest, which is funded by the Penn State College of Agriculture Sciences, Department of Ecosystem Science and Management and managed by the staff of the Forestlands Management Office.
Funding Information:
This study has been supported by United States National Science Foundation Hydrologic Sciences Program Grant EAR-1416881 (PI: H. Lin). The NSF Critical Zone Observatory Program is acknowledged for its support to the Susquehanna Shale Hills Critical Zone Observatory. Logistical support and/or data were provided by the NSF-supported Susquehanna Shale Hills Critical Zone Observatory. This research was conducted in Penn State's Stone Valley Forest, which is funded by the Penn State College of Agriculture Sciences , Department of Ecosystem Science and Management and managed by the staff of the Forestlands Management Office.
PY - 2019/9
Y1 - 2019/9
N2 - The role of preferential flow through unsaturated saprock (fractured bedrock with weathering restricted to fracture margins) in hillslope hydrology remains inadequately described. To address this issue, ground-penetrating radar (GPR), controlled infiltration, and high-frequency subsurface moisture monitoring were integrated to characterize saprock preferential flow (SPF) in the Susquehanna Shale Hills Critical Zone Observatory in Pennsylvania, U.S.A. In a planar hillslope with shallow fractured shale bedrock (starting at 0.1–0.3 m below ground), two pulses of water (79.5 L in total) were released followed by time-lapse GPR surveys. Differentiating GPR images collected before and after infiltration revealed lateral SPF in the direction of bedding plane fractures near the infiltration trench but with limited development of SPF down gradient along the hillslope. This was confirmed by soil and saprock moisture monitoring at a soil pit (0.2 m downslope of the GPR grid) where only one out of fifteen probes responded to the controlled infiltration. Lateral SPF frequently occurred at the GPR grid during a 24-day period with ten rainfall events, especially under the wet initial conditions. Additional infiltration experiments in a convex hillslope and a nearby bare slope with exposed saprock demonstrated the impact of fracture patterns on the routing of SPF. Three types of SPF in hillslope hydrology were identified, including (1) vertical percolation, (2) exfiltration from saprock to soil, and (3) stormwater transported downslope from planar and convex hillslopes to concave hillslopes. A 3D fill-and-spill model is proposed for the study site and similar areas that recognizes the importance of subsurface flow networks, with shallow saprock and concave hillslopes as essential controls of hillslope subsurface flow.
AB - The role of preferential flow through unsaturated saprock (fractured bedrock with weathering restricted to fracture margins) in hillslope hydrology remains inadequately described. To address this issue, ground-penetrating radar (GPR), controlled infiltration, and high-frequency subsurface moisture monitoring were integrated to characterize saprock preferential flow (SPF) in the Susquehanna Shale Hills Critical Zone Observatory in Pennsylvania, U.S.A. In a planar hillslope with shallow fractured shale bedrock (starting at 0.1–0.3 m below ground), two pulses of water (79.5 L in total) were released followed by time-lapse GPR surveys. Differentiating GPR images collected before and after infiltration revealed lateral SPF in the direction of bedding plane fractures near the infiltration trench but with limited development of SPF down gradient along the hillslope. This was confirmed by soil and saprock moisture monitoring at a soil pit (0.2 m downslope of the GPR grid) where only one out of fifteen probes responded to the controlled infiltration. Lateral SPF frequently occurred at the GPR grid during a 24-day period with ten rainfall events, especially under the wet initial conditions. Additional infiltration experiments in a convex hillslope and a nearby bare slope with exposed saprock demonstrated the impact of fracture patterns on the routing of SPF. Three types of SPF in hillslope hydrology were identified, including (1) vertical percolation, (2) exfiltration from saprock to soil, and (3) stormwater transported downslope from planar and convex hillslopes to concave hillslopes. A 3D fill-and-spill model is proposed for the study site and similar areas that recognizes the importance of subsurface flow networks, with shallow saprock and concave hillslopes as essential controls of hillslope subsurface flow.
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U2 - 10.1016/j.jhydrol.2019.06.070
DO - 10.1016/j.jhydrol.2019.06.070
M3 - Article
AN - SCOPUS:85067839445
SN - 0022-1694
VL - 576
SP - 430
EP - 442
JO - Journal of Hydrology
JF - Journal of Hydrology
ER -