2023
Dralle, DN; Hahm, WJ; Rempe, DM
Inferring hillslope groundwater recharge ratios from the storage-discharge relation Journal Article
In: Geophysical Research Letters, 2023.
Abstract | Links | BibTeX | Tags: ERCZO, groundwater, hillslope
@article{Dralle2023b,
title = {Inferring hillslope groundwater recharge ratios from the storage-discharge relation},
author = {DN Dralle and WJ Hahm and DM Rempe},
doi = {https://doi.org/10.1029/2023GL104255},
year = {2023},
date = {2023-07-25},
urldate = {2023-07-25},
journal = {Geophysical Research Letters},
abstract = {Accurate observation of hillslope groundwater storage and instantaneous recharge remains difficult due to limited monitoring and the complexity of mountainous landscapes. We introduce a novel storage-discharge method to estimate hillslope recharge and the recharge ratio—the fraction of precipitation that recharges groundwater. The method, which relies on streamflow data, is corroborated by independent measurements of water storage dynamics inside the Rivendell experimental hillslope at the Eel River Critical Zone Observatory, California USA. We find that along-hillslope patterns in bedrock weathering and plant-driven storage dynamics govern the seasonal evolution of recharge ratios. Thinner weathering profiles and smaller root-zone storage deficits near-channel are replenished before larger ridge-top deficits. Consequently, precipitation progressively activates groundwater from channel to divide, with an attendant increase in recharge ratios throughout the wet season. Our novel approach and process observations offer valuable insights into controls on groundwater recharge, enhancing our understanding of a critical flux in the hydrologic cycle.},
keywords = {ERCZO, groundwater, hillslope},
pubstate = {published},
tppubtype = {article}
}
Accurate observation of hillslope groundwater storage and instantaneous recharge remains difficult due to limited monitoring and the complexity of mountainous landscapes. We introduce a novel storage-discharge method to estimate hillslope recharge and the recharge ratio—the fraction of precipitation that recharges groundwater. The method, which relies on streamflow data, is corroborated by independent measurements of water storage dynamics inside the Rivendell experimental hillslope at the Eel River Critical Zone Observatory, California USA. We find that along-hillslope patterns in bedrock weathering and plant-driven storage dynamics govern the seasonal evolution of recharge ratios. Thinner weathering profiles and smaller root-zone storage deficits near-channel are replenished before larger ridge-top deficits. Consequently, precipitation progressively activates groundwater from channel to divide, with an attendant increase in recharge ratios throughout the wet season. Our novel approach and process observations offer valuable insights into controls on groundwater recharge, enhancing our understanding of a critical flux in the hydrologic cycle.
2021
Pedrazas, Michelle A.; Hahm, W. Jesse; Huang, Mong-Han; Dralle, David; Nelson, Mariel D.; Breunig, Rachel E.; Fauria, Kristen E.; Bryk, Alexander B.; Dietrich, William E.; Rempe, Daniella M.
The Relationship Between Topography, Bedrock Weathering, and Water Storage Across a Sequence of Ridges and Valleys Journal Article
In: JGR Earth Surface, vol. 126, no. 4, 2021.
Abstract | Links | BibTeX | Tags: bedrock weathering, Critical Zone, ERCZO, hillslope, unsaturated zone, water storage, Weathering
@article{Pedrazas2021,
title = {The Relationship Between Topography, Bedrock Weathering, and Water Storage Across a Sequence of Ridges and Valleys},
author = {Michelle A. Pedrazas and W. Jesse Hahm and Mong-Han Huang and David Dralle and Mariel D. Nelson and Rachel E. Breunig and Kristen E. Fauria and Alexander B. Bryk and William E. Dietrich and Daniella M. Rempe},
url = {https://angelo.berkeley.edu/jgr-earth-surface-2021-pedrazas-the-relationship-between-topography-bedrock-weathering-and-water-storage-across-a-1/},
doi = {10.1029/2020JF005848},
year = {2021},
date = {2021-03-23},
urldate = {2021-03-23},
journal = {JGR Earth Surface},
volume = {126},
number = {4},
abstract = {Bedrock weathering regulates nutrient mobilization, water storage, and soil production. Relative to the mobile soil layer, little is known about the relationship between topography and bedrock weathering. Here, we identify a common pattern of weathering and water storage across a sequence of three ridges and valleys in the sedimentary Great Valley Sequence in Northern California that share a tectonic and climate history. Deep drilling, downhole logging, and characterization of chemistry and porosity reveal two weathering fronts. The shallower front is ∼7 m deep at the ridge of all three hillslopes, and marks the extent of pervasive fracturing and oxidation of pyrite and organic carbon. A deeper weathering front marks the extent of open fractures and discoloration. This front is 11 m deep under two ridges of similar ridge-valley spacing, but 17.5 m deep under a ridge with nearly twice the ridge-valley spacing. Hence, at ridge tops, the fraction of the hillslope relief that is weathered scales with hillslope length. In all three hillslopes, below this second weathering front, closed fractures and unweathered bedrock extend about one-half the hilltop elevation above the adjacent channels. Neutron probe surveys reveal that seasonally dynamic moisture is stored to approximately the same depth as the shallow weathering front. Under the channels that bound our study hillslopes, the two weathering fronts coincide and occur within centimeters of the ground surface. Our findings provide evidence for feedbacks between erosion and weathering in mountainous landscapes that result in systematic subsurface structuring and water routing.},
keywords = {bedrock weathering, Critical Zone, ERCZO, hillslope, unsaturated zone, water storage, Weathering},
pubstate = {published},
tppubtype = {article}
}
Bedrock weathering regulates nutrient mobilization, water storage, and soil production. Relative to the mobile soil layer, little is known about the relationship between topography and bedrock weathering. Here, we identify a common pattern of weathering and water storage across a sequence of three ridges and valleys in the sedimentary Great Valley Sequence in Northern California that share a tectonic and climate history. Deep drilling, downhole logging, and characterization of chemistry and porosity reveal two weathering fronts. The shallower front is ∼7 m deep at the ridge of all three hillslopes, and marks the extent of pervasive fracturing and oxidation of pyrite and organic carbon. A deeper weathering front marks the extent of open fractures and discoloration. This front is 11 m deep under two ridges of similar ridge-valley spacing, but 17.5 m deep under a ridge with nearly twice the ridge-valley spacing. Hence, at ridge tops, the fraction of the hillslope relief that is weathered scales with hillslope length. In all three hillslopes, below this second weathering front, closed fractures and unweathered bedrock extend about one-half the hilltop elevation above the adjacent channels. Neutron probe surveys reveal that seasonally dynamic moisture is stored to approximately the same depth as the shallow weathering front. Under the channels that bound our study hillslopes, the two weathering fronts coincide and occur within centimeters of the ground surface. Our findings provide evidence for feedbacks between erosion and weathering in mountainous landscapes that result in systematic subsurface structuring and water routing.