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.
2017
Grant, Gordon E.; Dietrich, William E.
The frontier beneath our feet Journal Article
In: Water Resources Research, vol. 53, no. 4, pp. 2605-2609, 2017.
Abstract | Links | BibTeX | Tags: Critical Zone, environmental problems, ERCZO, field studies, groundwater, landscape development, water
@article{Grant2017,
title = {The frontier beneath our feet},
author = {Gordon E. Grant and William E. Dietrich},
doi = {https://doi.org/10.1002/2017WR020835},
year = {2017},
date = {2017-04-20},
journal = {Water Resources Research},
volume = {53},
number = {4},
pages = {2605-2609},
abstract = {Following the simple question as to where water goes when it rains leads to one of the most exciting frontiers in earth science: the critical zone—Earth's dynamic skin. The critical zone extends from the top of the vegetation canopy through the soil and down to fresh bedrock and the bottom of the groundwater. Only recently recognized as a distinct zone, it is challenging to study because it is hard to observe directly, and varies widely across biogeoclimatic regions. Yet new ideas, instruments, and observations are revealing surprising and sometimes paradoxical insights, underscoring the value of field campaigns and long‐term observatories. These insights bear directly on some of the most pressing societal problems today: maintaining healthy forests, sustaining streamflow during droughts, and restoring productive terrestrial and aquatic ecosystems. The critical zone is critical because it supports all terrestrial life; it is the nexus where water and carbon is cycled, vegetation (hence food) grows, soil develops, landscapes evolve, and we live. No other frontier is so close to home.},
keywords = {Critical Zone, environmental problems, ERCZO, field studies, groundwater, landscape development, water},
pubstate = {published},
tppubtype = {article}
}
Following the simple question as to where water goes when it rains leads to one of the most exciting frontiers in earth science: the critical zone—Earth’s dynamic skin. The critical zone extends from the top of the vegetation canopy through the soil and down to fresh bedrock and the bottom of the groundwater. Only recently recognized as a distinct zone, it is challenging to study because it is hard to observe directly, and varies widely across biogeoclimatic regions. Yet new ideas, instruments, and observations are revealing surprising and sometimes paradoxical insights, underscoring the value of field campaigns and long‐term observatories. These insights bear directly on some of the most pressing societal problems today: maintaining healthy forests, sustaining streamflow during droughts, and restoring productive terrestrial and aquatic ecosystems. The critical zone is critical because it supports all terrestrial life; it is the nexus where water and carbon is cycled, vegetation (hence food) grows, soil develops, landscapes evolve, and we live. No other frontier is so close to home.
2012
Salve, Rohit; Rempe, Daniella M.; Dietrich, William E.
Rain, rock moisture dynamics, and the rapid response of perched groundwater in weathered, fractured argillite underlying a steep hillslope Journal Article
In: Water Resources Research, vol. 48, no. 11, 2012.
Abstract | Links | BibTeX | Tags: fractured argillite, groundwater, rain, rock moisture
@article{Salve2012,
title = {Rain, rock moisture dynamics, and the rapid response of perched groundwater in weathered, fractured argillite underlying a steep hillslope},
author = {Rohit Salve and Daniella M. Rempe and William E. Dietrich},
url = {https://angelo.berkeley.edu/wp-content/uploads/sites/59/Salve_2012_WatResoRese.pdf},
doi = {10.1029/2012WR012583},
year = {2012},
date = {2012-11-28},
journal = {Water Resources Research},
volume = {48},
number = {11},
abstract = {Various field studies have concluded that shallow groundwater in weathered bedrock underlying hillslopes can contribute to both base and stormflow and thus dominate runoff. The processes associated with recharge from the ground surface, through this unsaturated zone, have received little study, yet they influence runoff dynamics, the chemical evolution of water, and moisture availability. Here we use five measurement systems to document soil and rock moisture dynamics within a 4000 m2zero-order basin in which all runoff occurs through weathered argillite. At this site, the weathered bedrock zone (in which the groundwater fluctuates by 8 m seasonally) varies in depth from ∼4 m at the base of the hillslope to nearly 19 m near the hill top. An aggregate-rich, porous, 0.5 m thick soil overlies the weathered bedrock. We find that during the first rains of the wet season, water rapidly travels meters into the weathered bedrock zone. Consistently, however, groundwater at some places responds quickly to the first major storm, well before the wetting front has been detected much beyond about 1 m. Furthermore, throughout the wet season, the lower portion of the unsaturated weathered bedrock shows little or no moisture change. These observations suggest a fracture-dominated flow path, leading to a highly variably groundwater response across the hillslope for a given storm. Seasonal changes in rock moisture content are greatest in the first 5 to 10 m depth and may exceed the magnitude of moisture changes in the soil, suggesting that it could constitute a significant unmapped moisture reservoir.},
keywords = {fractured argillite, groundwater, rain, rock moisture},
pubstate = {published},
tppubtype = {article}
}
Various field studies have concluded that shallow groundwater in weathered bedrock underlying hillslopes can contribute to both base and stormflow and thus dominate runoff. The processes associated with recharge from the ground surface, through this unsaturated zone, have received little study, yet they influence runoff dynamics, the chemical evolution of water, and moisture availability. Here we use five measurement systems to document soil and rock moisture dynamics within a 4000 m2zero-order basin in which all runoff occurs through weathered argillite. At this site, the weathered bedrock zone (in which the groundwater fluctuates by 8 m seasonally) varies in depth from ∼4 m at the base of the hillslope to nearly 19 m near the hill top. An aggregate-rich, porous, 0.5 m thick soil overlies the weathered bedrock. We find that during the first rains of the wet season, water rapidly travels meters into the weathered bedrock zone. Consistently, however, groundwater at some places responds quickly to the first major storm, well before the wetting front has been detected much beyond about 1 m. Furthermore, throughout the wet season, the lower portion of the unsaturated weathered bedrock shows little or no moisture change. These observations suggest a fracture-dominated flow path, leading to a highly variably groundwater response across the hillslope for a given storm. Seasonal changes in rock moisture content are greatest in the first 5 to 10 m depth and may exceed the magnitude of moisture changes in the soil, suggesting that it could constitute a significant unmapped moisture reservoir.