Geologic map of the Gothic quadrangle, Gunnison County, Colorado

Gaskill, David L.

doi:10.3133/gq1689

“…Descriptions of individual geologic units are provided in Table 1. (Gaskill et al, 1991) with geologic units described in Table 1. Original hydrological modeling of Copper Creek for years 1987-2018 captures a wide range of snow accumulation and snowmelt scenarios and estimates annual precipitation equal to 1.39 ± 0.27 m/year, of which 78 ± 7% is snow (mean ± sd; see section 3.2 for a description of method) (Carroll et al, 2019). Annually, the basin is simulated as energy limited (potential ET < precipitation) with average ET losses equal to 36% of annual precipitation.…”

Section: Site Descriptionmentioning

confidence: 99%

“…Descriptions of individual geologic units are provided in Table 1. (Gaskill et al, 1991) with geologic units described in Table 1.…”

Section: Site Descriptionmentioning

confidence: 99%

“…This younger, intrusive rock has upturned Paleozoic and Mesozoic sedimentary strata into steeply dipping hydrostratigraphic units that underlay the lower portion of Copper Creek (Figure 1b). Talus, rock glaciers, and alluvial fans dominate surficial deposits within Copper Creek's glacially sculpted valleys (Gaskill et al, 1991). Descriptions of individual geologic units are provided in Table 1.…”

Section: Site Descriptionmentioning

confidence: 99%

“…Inset shows location of the site in the context of the western United States and the Upper Colorado River Basin. (b) Geologic cross-section A-A′ modified from(Gaskill et al, 1991) with geologic units described in Table1.…”

mentioning

confidence: 99%

See 2 more Smart Citations

Baseflow Age Distributions and Depth of Active Groundwater Flow in a Snow‐Dominated Mountain Headwater Basin

Carroll

¹

,

Manning

²

,

Niswonger

³

et al. 2020

Water Resources Research

View full text Add to dashboard Cite

Deeper flows through bedrock in mountain watersheds could be important, but lack of data to characterize bedrock properties limits understanding. To address data scarcity, we combine a previously published integrated hydrologic model of a snow-dominated, headwater basin of the Colorado River with a new method for dating baseflow age using dissolved gas tracers SF 6 , CFC-113, N 2 , and Ar. The original flow model predicts the majority of groundwater flow through shallow alluvium (<8 m) sitting on top of less permeable bedrock. The water moves too quickly and is unable to reproduce observed SF 6 concentrations. To match gas data, bedrock permeability is increased to allow a larger fraction of deeper and older groundwater flow (median 112 m). The updated hydrologic model indicates interannual variability in baseflow age (3-12 years) is controlled by the volume of seasonal interflow and tightly coupled to snow accumulation and monsoon rain. Deeper groundwater flow remains stable (11.7 ± 0.7 years) as a function mean historical recharge to bedrock hydraulic conductivity (R/K). A sensitivity analysis suggests that increasing bedrock K effectively moves this alpine basin away from its original conceptualization of hyperlocalized groundwater flow (high R/K) with groundwater age insensitive to changes in water inputs. Instead, this basin is situated close to the precipitation threshold defining recharge controlled groundwater flow conditions (low R/K) in which groundwater age increases with small reductions in precipitation. Work stresses the need to explore alternative methods characterizing bedrock properties in mountain basins to better quantify deeper groundwater flow and predict their hydrologic response to change. Plain Language Summary Snow in mountain systems is an important water source but little is understood how snow processes dictate groundwater flow paths, the age of stream water, and its sensitivity to climate or land use change. We use a recently developed stream water gas tracer experiment in a steep mountain stream in a Colorado River headwater basin. A hydrologic model cannot match gas tracer data if groundwater flow is shallow, moving through the unconsolidated material near land surface, because groundwater moves too quickly. Instead, groundwater must follow deeper, longer flow paths through the fractured granitic bedrock. A sensitivity analysis shows that this snow-dominated headwater basin is functioning near a precipitation threshold. With wetter conditions, little change occurs to groundwater flow paths and ages are insensitive to changes in climate or forest removal. However, with small decreases in snowpack accumulation, groundwater flow paths become increasingly deeper and older. Collecting stream water gas data helped identify groundwater flow path sensitivity to climate and land use change.

show abstract

“…Epoch Name Description (modified Gaskill et al, 1991) K0 ( before and extending through the gas sampling period. Local barometric pressure was obtained from a Rocky Mountain Biological Laboratory weather station located 1.9 km from CC03 ( Figure 1) and adjusted for the elevational difference of 70 m. Water samples for N 2 , Ar, SF 6 , and CFC-113 were collected in duplicate every hour from 8:30 a.m. to 8:30 p.m. (supporting information Tables S1 and S2), to capture minimum and maximum diurnal stream fluctuation.…”

Section: Unitmentioning

confidence: 99%

Baseflow Age Distributions and Depth of Active Groundwater Flow in a Snow-Dominated Mountain Headwater Basin

Carroll

¹

,

Manning

²

,

Niswonger

³

et al. 2020

Preprint

View full text Add to dashboard Cite

Deeper flows through bedrock in mountain watersheds could be important, but lack of data to characterize bedrock properties limits understanding. To address data scarcity, we combine a previously published integrated hydrologic model of a snow-dominated, headwater basin of the Colorado River with a new method for dating baseflow age using dissolved gas tracers SF 6 , CFC-113, N 2 , and Ar. The original flow model predicts the majority of groundwater flow through shallow alluvium (<8 m) sitting on top of less permeable bedrock. The water moves too quickly and is unable to reproduce observed SF 6 concentrations. To match gas data, bedrock permeability is increased to allow a larger fraction of deeper and older groundwater flow (median 112 m). The updated hydrologic model indicates interannual variability in baseflow age (3-12 years) is controlled by the volume of seasonal interflow and tightly coupled to snow accumulation and monsoon rain. Deeper groundwater flow remains stable (11.7 ± 0.7 years) as a function mean historical recharge to bedrock hydraulic conductivity (R/K). A sensitivity analysis suggests that increasing bedrock K effectively moves this alpine basin away from its original conceptualization of hyperlocalized groundwater flow (high R/K) with groundwater age insensitive to changes in water inputs. Instead, this basin is situated close to the precipitation threshold defining recharge controlled groundwater flow conditions (low R/K) in which groundwater age increases with small reductions in precipitation. Work stresses the need to explore alternative methods characterizing bedrock properties in mountain basins to better quantify deeper groundwater flow and predict their hydrologic response to change. Plain Language Summary Snow in mountain systems is an important water source but little is understood how snow processes dictate groundwater flow paths, the age of stream water, and its sensitivity to climate or land use change. We use a recently developed stream water gas tracer experiment in a steep mountain stream in a Colorado River headwater basin. A hydrologic model cannot match gas tracer data if groundwater flow is shallow, moving through the unconsolidated material near land surface, because groundwater moves too quickly. Instead, groundwater must follow deeper, longer flow paths through the fractured granitic bedrock. A sensitivity analysis shows that this snow-dominated headwater basin is functioning near a precipitation threshold. With wetter conditions, little change occurs to groundwater flow paths and ages are insensitive to changes in climate or forest removal. However, with small decreases in snowpack accumulation, groundwater flow paths become increasingly deeper and older. Collecting stream water gas data helped identify groundwater flow path sensitivity to climate and land use change.

show abstract

The Colorado East River Community Observatory Data Collection

Kakalia

¹

,

Varadharajan

²

,

Alper

³

et al. 2021

Hydrological Processes

View full text Add to dashboard Cite

The U.S. Department of Energy's (DOE) Colorado East River Community Observatory (ER) in the Upper Colorado River Basin was established in 2015 as a representative mountainous, snow‐dominated watershed to study hydrobiogeochemical responses to hydrological perturbations in headwater systems. The ER is characterized by steep elevation, geologic, hydrologic and vegetation gradients along floodplain, montane, subalpine, and alpine life zones, which makes it an ideal location for researchers to understand how different mountain subsystems contribute to overall watershed behaviour. The ER has both long‐term and spatially‐extensive observations and experimental campaigns carried out by the Watershed Function Scientific Focus Area (SFA), led by Lawrence Berkeley National Laboratory, and researchers from over 30 organizations who conduct cross‐disciplinary process‐based investigations and modelling of watershed behaviour. The heterogeneous data generated at the ER include hydrological, genomic, biogeochemical, climate, vegetation, geological, and remote sensing data, which combined with model inputs and outputs comprise a collection of datasets and value‐added products within a mountainous watershed that span multiple spatiotemporal scales, compartments, and life zones. Within 5 years of collection, these datasets have revealed insights into numerous aspects of watershed function such as factors influencing snow accumulation and melt timing, water balance partitioning, and impacts of floodplain biogeochemistry and hillslope ecohydrology on riverine geochemical exports. Data generated by the SFA are managed and curated through its Data Management Framework. The SFA has an open data policy, and over 70 ER datasets are publicly available through relevant data repositories. A public interactive map of data collection sites run by the SFA is available to inform the broader community about SFA field activities. Here, we describe the ER and the SFA measurement network, present the public data collection generated by the SFA and partner institutions, and highlight the value of collecting multidisciplinary multiscale measurements in representative catchment observatories.

show abstract

Geologic map of the Gothic quadrangle, Gunnison County, Colorado

Cited by 13 publications

References 16 publications

Baseflow Age Distributions and Depth of Active Groundwater Flow in a Snow‐Dominated Mountain Headwater Basin

Baseflow Age Distributions and Depth of Active Groundwater Flow in a Snow‐Dominated Mountain Headwater Basin

Baseflow Age Distributions and Depth of Active Groundwater Flow in a Snow-Dominated Mountain Headwater Basin

The Colorado East River Community Observatory Data Collection

Contact Info

Product

Resources

About