Geologic and Geomorphic Controls on the Occurrence of Fens in the Oregon Cascades and Implications for Vulnerability and Conservation

Aldous, Allison; Gannett, Marshall W.; Keith, Mackenzie K.; O’Connor, Jim E.

doi:10.1007/s13157-015-0667-x

Cited by 15 publications

(15 citation statements)

References 37 publications

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“…At the CCPWS, springflow records for the period 2004-2017 show springflow ranged from 0-190 L min −1 [14], and shallow-aquifer recharge estimates (2014-2017) range from 0.6-1.5 m year −1 [32]. These conditions allow for the presence of groundwater-related ecosystems, as seen in other studies within the Pacific Northwest [13], and drive many land-management decisions in the region such as those in ranching and farming. During the many field visits to the study area, we observed the presence of multiple wildlife species (e.g., deer, antelope, and various avian species) directly associated with surface and subsurface water flow response to seasonal precipitation inputs.…”

Section: Discussionmentioning

confidence: 73%

“…Local flow systems are typically shallow systems often characterized by the presence of small springs not far from areas of recharge [12]. A study by Aldous et al [13] investigated the linkages between the hydrogeologic setting and the presence of groundwater-dependent ecosystems in the montane setting of the Deschutes Basin of central Oregon. They found some of these systems to be associated with areas of low-permeability strata and local recharge systems [13].…”

Section: Introductionmentioning

confidence: 99%

“…A study by Aldous et al [13] investigated the linkages between the hydrogeologic setting and the presence of groundwater-dependent ecosystems in the montane setting of the Deschutes Basin of central Oregon. They found some of these systems to be associated with areas of low-permeability strata and local recharge systems [13]. This seems to be the case at our Camp Creek Paired Watershed Study (CCPWS) site in central Oregon, where we have conducted extensive research on the hydrologic response to vegetative management practices such as western juniper (Juniperus occidentalis) removal.…”

Section: Introductionmentioning

confidence: 99%

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A Hydrogeologic Framework for Understanding Local Groundwater Flow Dynamics in the Southeast Deschutes Basin, Oregon, USA

et al. 2019

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Understanding local hydrogeology is important for the management of groundwater resources and the ecosystems that depend on them. The main objective of this study conducted in central Oregon, USA was to characterize the hydrogeologic framework of a part of the semiarid Upper Deschutes Basin. Information on local geology and hydrology was synthesized to construct a hydrogeologic framework and a conceptual model of groundwater movement in shallow and previously unmapped deeper aquifers. Study results show that local geology drives many of the surface water and groundwater connections that sustain groundwater-related ecosystems and ranching-related activities in the geographical area of interest. Also, the findings of this study suggest that ecohydrological investigations can be used to mitigate concerns regarding groundwater development. Likewise, newly-developed conceptual models of the hydrogeology of previously unstudied areas within a groundwater basin undergoing regulation offer opportunities to not only address concerns regarding integrated surface water–groundwater interactions but also provide supplemental sources of water for nearby areas undergoing groundwater depletion through proposed bulk water transfers.

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Section: Discussionmentioning

confidence: 73%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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A Hydrogeologic Framework for Understanding Local Groundwater Flow Dynamics in the Southeast Deschutes Basin, Oregon, USA

et al. 2019

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“…The Round Meadow watershed ( Figure 1) has flow paths and interactions between the ground-and surface-water systems that are similar to those observed elsewhere in the pumice-blanketed landscapes of south central Oregon [1]- [3]. The perched pumice aquifer provides near-surface groundwater storage that maintains biologically diverse wetland environments in the rain shadow of the Cascade Range.…”

Section: Introductionmentioning

confidence: 74%

Ground- and Surface-Water Interactions of a Pumice Aquifer in a Headwaters Watershed: Round Meadow, Fremont-Winema National Forest, Oregon, USA

Weatherford¹,

Cummings²

2016

JWARP

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Plinian pumice fall from the Holocene eruption of Mount Mazama in the Cascade volcanic arc is an unconfined, perched aquifer in south-central Oregon. The pumice aquifer provides near-surface groundwater storage that maintains biologically diverse wetland environments. Wetland environments reflect post-eruption disruption of the once uniform pumice blanket by fluvial and lacustrine processes operating within the template of the pre-eruption landscape. In the 8.6 km 2 Round Meadow watershed the pumice aquifer interacts with a seasonally flooded meadow, fen, springs, and perennial stream. The laterally uniform, isotropic pumice aquifer is disrupted by flat-bottomed ephemeral stream valleys that drain to the seasonally flooded meadow. Surface water levels in the seasonally flooded meadow are controlled by a knickpoint developed on bedrock. The underlying aquifer is confined by a layer of glass-rich diatomaceous silt grading upward to organic-rich silt. Here, the aquifer is comprised of remnants of the pumice deposit, lag sand, and reworked pumice. The water level in the confined aquifer is maintained by recharge from the unconfined pumice aquifer following flow pathways beneath ephemeral stream valleys. The fen is developed on a down-thrown block of welded tuff and pre-eruption diatomaceous silt. Water levels in the fen are sensitive to inter-annual variations in precipitation. Low discharge, low temperature (5.0˚C to 6.5˚C), and low conductivity (30 to 50 μS/cm) springs appear to be fracture controlled and rising through welded tuff. Spring discharge and seepage through pumice from the welded tuff support perennial flow in the creek that also carries discharge from the seasonally flooded meadow when water levels are high enough to cross the knickpoint.

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“…The relationship between geology and spring discharge has important implications for the springs' relative vulnerabilities to various hydrologic stressors. Low-discharge springs with local, shallow flow paths and smaller aquifer volumes are more likely to be rapidly affected by groundwater extraction and climate stresses such as drought and higher air temperatures, in contrast to longer flow-path regional springs (Aldous, Gannett, Keith, & O'Connor, 2015;Manga, 1999;Waibel et al, 2013).…”

Section: Many Of the Springs Visited During The Inventory In The Crookedmentioning

confidence: 99%

Landscape controls on the distribution and ecohydrology of central Oregon springs

2019

Self Cite

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Small springs in semiarid landscapes are essential for maintaining aquatic biodiversity and supporting livestock grazing operations. However, little is known about controls on the distribution and physical characteristics of small springs, the aquatic species they support, or their sensitivity to disturbance. We address this information gap in the Crooked River subbasin, a tributary of the Deschutes River in Oregon. We conducted spatial analyses on 2,519 mapped springs to investigate the influence of landscape controls (precipitation and bedrock permeability) on spring density in the Crooked River subbasin and the adjacent Upper Deschutes subbasin. Spring density was highest in areas of low bedrock permeability (P < 0.0001) and high annual precipitation (P < 0.0001). We suggest that the high density of small springs on low‐permeability bedrock indicates that these springs generally have short, shallow flow paths and thus may be susceptible to forecasted climate changes. A survey of 137 springs in the Crooked River subbasin revealed the hydrogeologic setting affects spring discharge type (P = 0.017), temperature (P = 0.011), and pH (P = 0.026). We found a high frequency of anthropogenic impacts on springs: 95% of diffuse‐discharge springs and 79% of discrete‐discharge springs were disturbed by livestock grazing. Species inventories at 10 of the most intact surveyed springs confirm that small springs are biologically diverse, with 151 total species of plants and 135 total taxa of macroinvertebrates. Springs in the Crooked River subbasin are ecologically important habitats but require careful management to protect against livestock disturbance and development.

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Geologic and Geomorphic Controls on the Occurrence of Fens in the Oregon Cascades and Implications for Vulnerability and Conservation

Cited by 15 publications

References 37 publications

A Hydrogeologic Framework for Understanding Local Groundwater Flow Dynamics in the Southeast Deschutes Basin, Oregon, USA

A Hydrogeologic Framework for Understanding Local Groundwater Flow Dynamics in the Southeast Deschutes Basin, Oregon, USA

Ground- and Surface-Water Interactions of a Pumice Aquifer in a Headwaters Watershed: Round Meadow, Fremont-Winema National Forest, Oregon, USA

Landscape controls on the distribution and ecohydrology of central Oregon springs

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