2022
Hahm, WJ; Dralle, DN; Sanders, M; Bryk, AB; Fauria, KE; Huang, MH; Hudson-Rasmussen, B; Nelson, MD; Pedrazas, MA; and, L Schmidt
Bedrock vadose zone storage dynamics under extreme drought: consequences for plant water availability, recharge, and runoff Journal Article
In: Water Resources Research, vol. 58, iss. 4, 2022.
Links | BibTeX | Tags: bedrock, Drought, ERCZO, water storage
@article{Hahm2022,
title = {Bedrock vadose zone storage dynamics under extreme drought: consequences for plant water availability, recharge, and runoff},
author = {WJ Hahm and DN Dralle and M Sanders and AB Bryk and KE Fauria and MH Huang and B Hudson-Rasmussen and MD Nelson and MA Pedrazas and L Schmidt and},
url = {https://angelo.berkeley.edu/hahm_bedrock_vadose_storage/},
doi = {https://doi.org/10.1029/2021WR031781},
year = {2022},
date = {2022-04-08},
urldate = {2022-04-08},
journal = {Water Resources Research},
volume = {58},
issue = {4},
keywords = {bedrock, Drought, ERCZO, water storage},
pubstate = {published},
tppubtype = {article}
}
2021
Dralle, D. N.; Hahm, W. J.; Chadwick, K. D.; McCormick, E.; Rempe, D. M.
Technical note: Accounting for snow in the estimation of root zone water storage capacity from precipitation and evapotranspiration fluxes Journal Article
In: Hydrology and Earth System Sciences, vol. 25, no. 5, pp. 2861–2867, 2021.
Abstract | Links | BibTeX | Tags: ERCZO, evapotranspiration, hydrologic modeling, root zone, snow melt, water storage
@article{Dralle2021,
title = {Technical note: Accounting for snow in the estimation of root zone water storage capacity from precipitation and evapotranspiration fluxes},
author = {D. N. Dralle and W. J. Hahm and K. D. Chadwick and E. McCormick and D. M. Rempe},
doi = {10.5194/hess-25-2861-2021},
year = {2021},
date = {2021-05-27},
journal = {Hydrology and Earth System Sciences},
volume = {25},
number = {5},
pages = {2861–2867},
abstract = {A common parameter in hydrological modeling frameworks is root zone water storage capacity (SR[L]), which mediates plant water availability during dry periods as well as the partitioning of rainfall between runoff and evapotranspiration. Recently, a simple flux-tracking-based approach was introduced to estimate the value of SR (Wang-Erlandsson et al., 2016). Here, we build upon this original method, which we argue may overestimate SR in snow-dominated catchments due to snow melt and evaporation processes. We propose a simple extension to the method presented by Wang-Erlandsson et al. (2016) and show that the approach provides a lower estimate of SR in snow-dominated watersheds. This SR dataset is available at a 1 km resolution for the continental USA, along with the full analysis code, on the Google Colab and Earth Engine platforms. We highlight differences between the original and new methods across the rain–snow transition in the Southern Sierra Nevada, California, USA. As climate warms and precipitation increasingly arrives as rain instead of snow, the subsurface may be an increasingly important reservoir for storing plant-available water between wet and dry seasons; therefore, improved estimates of SR will better clarify the future role of the subsurface as a storage reservoir that can sustain forests during seasonal dry periods and episodic drought.},
keywords = {ERCZO, evapotranspiration, hydrologic modeling, root zone, snow melt, water storage},
pubstate = {published},
tppubtype = {article}
}
A common parameter in hydrological modeling frameworks is root zone water storage capacity (SR[L]), which mediates plant water availability during dry periods as well as the partitioning of rainfall between runoff and evapotranspiration. Recently, a simple flux-tracking-based approach was introduced to estimate the value of SR (Wang-Erlandsson et al., 2016). Here, we build upon this original method, which we argue may overestimate SR in snow-dominated catchments due to snow melt and evaporation processes. We propose a simple extension to the method presented by Wang-Erlandsson et al. (2016) and show that the approach provides a lower estimate of SR in snow-dominated watersheds. This SR dataset is available at a 1 km resolution for the continental USA, along with the full analysis code, on the Google Colab and Earth Engine platforms. We highlight differences between the original and new methods across the rain–snow transition in the Southern Sierra Nevada, California, USA. As climate warms and precipitation increasingly arrives as rain instead of snow, the subsurface may be an increasingly important reservoir for storing plant-available water between wet and dry seasons; therefore, improved estimates of SR will better clarify the future role of the subsurface as a storage reservoir that can sustain forests during seasonal dry periods and episodic drought.
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.
2020
Schmidt, Logan; Rempe, Daniella M.
Quantifying Dynamic Water Storage in Unsaturated Bedrock with Borehole Nuclear Magnetic Resonance Journal Article
In: Geophysical Research Letters, vol. 47, no. 22, pp. e2020GL089600, 2020.
Abstract | Links | BibTeX | Tags: Critical Zone, ERCZO, hydrogeophysics, neutron moderation nuclear magnetic resonance, vadose zone, water storage
@article{Schmidt2020,
title = {Quantifying Dynamic Water Storage in Unsaturated Bedrock with Borehole Nuclear Magnetic Resonance},
author = {Logan Schmidt and Daniella M. Rempe},
doi = {10.1029/2020GL089600},
year = {2020},
date = {2020-11-02},
journal = {Geophysical Research Letters},
volume = {47},
number = {22},
pages = {e2020GL089600},
abstract = {Quantifying the volume of water that is stored in the subsurface is critical to studies of water availability to ecosystems, slope stability, and water‐rock interactions. In a variety of settings, water is stored in fractured and weathered bedrock as rock moisture. However, few techniques are available to measure rock moisture in unsaturated rock, making direct estimates of water storage dynamics difficult to obtain. Here, we use borehole nuclear magnetic resonance (NMR) at two sites in seasonally dry California to quantify dynamic rock moisture storage. We show strong agreement between NMR estimates of dynamic storage and estimates derived from neutron logging and mass balance techniques. The depths of dynamic storage are up to 9 m and likely reflect the depth extent of root water uptake. To our knowledge, these data are the first to quantify the volume and depths of dynamic water storage in the bedrock vadose zone via borehole NMR.},
keywords = {Critical Zone, ERCZO, hydrogeophysics, neutron moderation nuclear magnetic resonance, vadose zone, water storage},
pubstate = {published},
tppubtype = {article}
}
Quantifying the volume of water that is stored in the subsurface is critical to studies of water availability to ecosystems, slope stability, and water‐rock interactions. In a variety of settings, water is stored in fractured and weathered bedrock as rock moisture. However, few techniques are available to measure rock moisture in unsaturated rock, making direct estimates of water storage dynamics difficult to obtain. Here, we use borehole nuclear magnetic resonance (NMR) at two sites in seasonally dry California to quantify dynamic rock moisture storage. We show strong agreement between NMR estimates of dynamic storage and estimates derived from neutron logging and mass balance techniques. The depths of dynamic storage are up to 9 m and likely reflect the depth extent of root water uptake. To our knowledge, these data are the first to quantify the volume and depths of dynamic water storage in the bedrock vadose zone via borehole NMR.