Search

Search Results

• 1. [Article] Groundwater-Surface Water Interactions near Mosier, Oregon

  The town of Mosier, Oregon, is located near the east, dry end of the Columbia River Gorge, and the local area is known for cherry orchards that rely heavily on groundwater for irrigation. The CRBG groundwater ...

  Citation × Citation Citation Abstract Copy Title: Groundwater-Surface Water Interactions near Mosier, Oregon Author: Jones, Cullen Brandon Year: 2016 The town of Mosier, Oregon, is located near the east, dry end of the Columbia River Gorge, and the local area is known for cherry orchards that rely heavily on groundwater for irrigation. The CRBG groundwater system in Mosier has experienced groundwater declines of up to 60 meters due to over-pumping and or commingling. Declining groundwater levels have led to concerns over the sustainability of the resource, as it is the principle water source for irrigation and domestic use. Despite numerous previous studies of groundwater flow in CRBG aquifers here and elsewhere in the Columbia River basin, an aspect that has received relatively little attention is the interaction between groundwater and surface waters at locations where interflow zones are intersected by the surface waters. The objective of my research is to investigate how CRBG interflow zone exposures in Mosier Creek may be controlling groundwater elevations in the area. The methods used include: (1) geochemical analysis of well cuttings and detailed geologic mapping along area streams to identify interflow zones of individual CRBG flows, (2) analysis of stream discharge data and groundwater elevation data to confirm exchange of groundwater and surface waters, and (3) collection and analyses of 31 water samples from area wells, streams, and springs, to determine if waters from individual CRBG aquifers can be hydrochemically identified and to further constrain understanding of surface and groundwater interactions. My study confirms that the general elevation of the Pomona Member and Basalt of Lolo interflow zone creek exposure is coincident with the elevation where a change in slope of the decline trend in 2004 is seen in Mosier area well hydrographs. Furthermore, the results of stream discharge data indicated a close connection between drawdown from groundwater pumping during irrigation season and groundwater- surface water interaction. At the time of drawdown in the upper-most CRBG aquifer (Pomona), the stream transitions from gaining to losing water into the groundwater system. Elemental chemistry data indicates the Frenchman Springs Sentinel Gap aquifer waters are the most evolved waters in this study. Stable isotopic data reinforced this determination as the Sentinel Gap waters are the lightest, or most negative, with regard to δD and δ18O. Sentinel Gap samples were more depleted than other aquifer samples by 4.38 to 6.89 0/100 for δD and 0.39 to 0.59 0/100 for δ18O. The results of the general chemistry and isotope data reveal a more evolved chemical signature in lower watershed groundwater versus a less evolved signature for waters from wells located higher up on the Columbia Hills anticline. This was interpreted to be the result of the major structural features in the area providing for a more regional pathway of recharge in lower watershed groundwaters, versus a more local source of recharge for upper watershed groundwaters. There was also a pronounced commingled signature in the elemental ratios of lower watershed aquifer waters. The suspected mechanism of recharge to lower watershed wells is through younger Cascadian deposits upslope from the local watershed. The findings of this study reveal the importance of a detailed understanding of CRBG stratigraphy and its relation to surface waters, especially for other areas within the Yakima Fold Belt or Oregon and Washington. Studies that do not consider the influence that individual CRBG flows can have on groundwater-surface water interactions, and the groundwater system as a whole, run the risk of improperly assessing the groundwater resource for a region. Title: Groundwater-Surface Water Interactions near Mosier, Oregon Author: Jones, Cullen Brandon Year: 2016 The town of Mosier, Oregon, is located near the east, dry end of the Columbia River Gorge, and the local area is known for cherry orchards that rely heavily on groundwater for irrigation. The CRBG groundwater system in Mosier has experienced groundwater declines of up to 60 meters due to over-pumping and or commingling. Declining groundwater levels have led to concerns over the sustainability of the resource, as it is the principle water source for irrigation and domestic use. Despite numerous previous studies of groundwater flow in CRBG aquifers here and elsewhere in the Columbia River basin, an aspect that has received relatively little attention is the interaction between groundwater and surface waters at locations where interflow zones are intersected by the surface waters. The objective of my research is to investigate how CRBG interflow zone exposures in Mosier Creek may be controlling groundwater elevations in the area. The methods used include: (1) geochemical analysis of well cuttings and detailed geologic mapping along area streams to identify interflow zones of individual CRBG flows, (2) analysis of stream discharge data and groundwater elevation data to confirm exchange of groundwater and surface waters, and (3) collection and analyses of 31 water samples from area wells, streams, and springs, to determine if waters from individual CRBG aquifers can be hydrochemically identified and to further constrain understanding of surface and groundwater interactions. My study confirms that the general elevation of the Pomona Member and Basalt of Lolo interflow zone creek exposure is coincident with the elevation where a change in slope of the decline trend in 2004 is seen in Mosier area well hydrographs. Furthermore, the results of stream discharge data indicated a close connection between drawdown from groundwater pumping during irrigation season and groundwater- surface water interaction. At the time of drawdown in the upper-most CRBG aquifer (Pomona), the stream transitions from gaining to losing water into the groundwater system. Elemental chemistry data indicates the Frenchman Springs Sentinel Gap aquifer waters are the most evolved waters in this study. Stable isotopic data reinforced this determination as the Sentinel Gap waters are the lightest, or most negative, with regard to δD and δ18O. Sentinel Gap samples were more depleted than other aquifer samples by 4.38 to 6.89 0/100 for δD and 0.39 to 0.59 0/100 for δ18O. The results of the general chemistry and isotope data reveal a more evolved chemical signature in lower watershed groundwater versus a less evolved signature for waters from wells located higher up on the Columbia Hills anticline. This was interpreted to be the result of the major structural features in the area providing for a more regional pathway of recharge in lower watershed groundwaters, versus a more local source of recharge for upper watershed groundwaters. There was also a pronounced commingled signature in the elemental ratios of lower watershed aquifer waters. The suspected mechanism of recharge to lower watershed wells is through younger Cascadian deposits upslope from the local watershed. The findings of this study reveal the importance of a detailed understanding of CRBG stratigraphy and its relation to surface waters, especially for other areas within the Yakima Fold Belt or Oregon and Washington. Studies that do not consider the influence that individual CRBG flows can have on groundwater-surface water interactions, and the groundwater system as a whole, run the risk of improperly assessing the groundwater resource for a region. Close

• 2. [Article] Stable Isotope Variations (δ18O and δD) in Modern Waters Across the Andean Plateau

  Environmental parameters that influence the isotopic composition of meteoric water (δ18O and δD) are well characterized up the windward side of mountains, where orographic precipitation results in a predictable ...

  Citation × Citation Citation Abstract Copy Title: Stable Isotope Variations (δ18O and δD) in Modern Waters Across the Andean Plateau Author: Bershaw, John, Saylor, Joel E., Garzione, Carmala N., Leier, Andrew Year: 2016 Environmental parameters that influence the isotopic composition of meteoric water (δ18O and δD) are well characterized up the windward side of mountains, where orographic precipitation results in a predictable relationship between the isotopic composition of precipitation and elevation. The topographic and climatic evolution of the Andean Plateau and surrounding regions has been studied extensively by exploiting this relationship through the use of paleowater proxies. However, interpretation on the plateau itself is challenged by a poor understanding of processes that fractionate isotopes during vapor transport and rainout, and by the relative contribution of unique moisture sources. Here, we present an extensive dataset of modern surface water samples for the northern Andean Plateau and surrounding regions to elucidate patterns and causes of isotope fractionation in this continental environment. These data show a progressive increase in δ18O of stream water west of the Eastern Cordillera (∼1‰/70 km), almost identical to the rate observed across the Tibetan Plateau, attributed to a larger fraction of recycled water in precipitation and/or increased evaporative enrichment downwind. This may lead to underestimates of paleoelevation, particularly for sites deep into the rainshadow of the Eastern Cordilleran crest. That said, elevation is a primary control on the isotopic composition of surface waters across the entire Andean Plateau and its flanks when considering the most negative δ18O values, highlighting the need for sufficiently large datasets to distinguish minimally evaporated samples. There is a general increase in δ18O on the plateau from north to south, concomitant with an increase in aridity and decrease in convective moistening (amount effect). Lastly, stable isotope and seasonal precipitation patterns suggest easterlies provide the vast majority of moisture that falls as precipitation across the Andean Plateau and Western Cordillera, from Peru to northern Bolivia (−13° to −20° latitude), with Pacific-derived moisture contributing a minor amount at low elevations near the coast. Title: Stable Isotope Variations (δ18O and δD) in Modern Waters Across the Andean Plateau Author: Bershaw, John, Saylor, Joel E., Garzione, Carmala N., Leier, Andrew Year: 2016 Environmental parameters that influence the isotopic composition of meteoric water (δ18O and δD) are well characterized up the windward side of mountains, where orographic precipitation results in a predictable relationship between the isotopic composition of precipitation and elevation. The topographic and climatic evolution of the Andean Plateau and surrounding regions has been studied extensively by exploiting this relationship through the use of paleowater proxies. However, interpretation on the plateau itself is challenged by a poor understanding of processes that fractionate isotopes during vapor transport and rainout, and by the relative contribution of unique moisture sources. Here, we present an extensive dataset of modern surface water samples for the northern Andean Plateau and surrounding regions to elucidate patterns and causes of isotope fractionation in this continental environment. These data show a progressive increase in δ18O of stream water west of the Eastern Cordillera (∼1‰/70 km), almost identical to the rate observed across the Tibetan Plateau, attributed to a larger fraction of recycled water in precipitation and/or increased evaporative enrichment downwind. This may lead to underestimates of paleoelevation, particularly for sites deep into the rainshadow of the Eastern Cordilleran crest. That said, elevation is a primary control on the isotopic composition of surface waters across the entire Andean Plateau and its flanks when considering the most negative δ18O values, highlighting the need for sufficiently large datasets to distinguish minimally evaporated samples. There is a general increase in δ18O on the plateau from north to south, concomitant with an increase in aridity and decrease in convective moistening (amount effect). Lastly, stable isotope and seasonal precipitation patterns suggest easterlies provide the vast majority of moisture that falls as precipitation across the Andean Plateau and Western Cordillera, from Peru to northern Bolivia (−13° to −20° latitude), with Pacific-derived moisture contributing a minor amount at low elevations near the coast. Close

• 3. [Article] Hydrogeochemical Evaluation of the Uinta Formation and Green River Formation, Piceance Creek Basin, Northwestern Colorado, USA

  The Piceance Creek Basin in northwestern Colorado contains extensive oil shale deposits that produce natural gas and which could potentially yield ~1.5 trillion barrels of shale oil. However, much of the ...

  Citation × Citation Citation Abstract Copy Title: Hydrogeochemical Evaluation of the Uinta Formation and Green River Formation, Piceance Creek Basin, Northwestern Colorado, USA Author: Masterson, Megan E. Year: 2016 The Piceance Creek Basin in northwestern Colorado contains extensive oil shale deposits that produce natural gas and which could potentially yield ~1.5 trillion barrels of shale oil. However, much of the oil shale lies at depths too great for traditional mining practices and various innovative approaches for in situ conversion of kerogen to oil have been proposed. A firm understanding of the existing hydrogeochemistry is needed as resulting mineralogical changes or rock-fluid reactions may affect rock porosity and permeability. Using an existing database complied by the USGS, the water chemistry of 267 surface and groundwater samples in the Piceance Creek primary drainage basin have been evaluated by mapping major ion concentrations and mineral saturation indicies with respect to hydrostratigraphic units and geologic structures. Controlling processes have been further assessed using statistical correlation and factor analysis. Results indicate that shallow waters in recharge zones are dominated by mixed cations (Na, Ca, Mg) and bicarbonate anions but with increased depth, groundwater transition to nearly 100% sodium bicarbonate type water. The chemistry of lower aquifer waters are principally controlled by nahcolite dissolution, but evidence of sulfate reduction and cation exchange aid in maintaining a sodium-bicarbonate water type. Ion evolution in surface and upper aquifer waters are influenced by an increase in sulfate concentration which is necessary to evolve water to an intermediate stage with sulfate-dominant anions. The source of sulfate is speculative, but likely due in part to the oxidation of sulfide-enriched groundwater and possible dissolution of sulfate-bearing carbonates. Surface and upper aquifer water chemistry in the northern portion of the basin is the result of discharge of deeper groundwater which is controlled to some degree by preferential pathways created by faults. Lower aquifer water migrates upward and mixes with the less-concentrated near-surface water, resulting in sodium bicarbonate type water in all hydrologic units. Title: Hydrogeochemical Evaluation of the Uinta Formation and Green River Formation, Piceance Creek Basin, Northwestern Colorado, USA Author: Masterson, Megan E. Year: 2016 The Piceance Creek Basin in northwestern Colorado contains extensive oil shale deposits that produce natural gas and which could potentially yield ~1.5 trillion barrels of shale oil. However, much of the oil shale lies at depths too great for traditional mining practices and various innovative approaches for in situ conversion of kerogen to oil have been proposed. A firm understanding of the existing hydrogeochemistry is needed as resulting mineralogical changes or rock-fluid reactions may affect rock porosity and permeability. Using an existing database complied by the USGS, the water chemistry of 267 surface and groundwater samples in the Piceance Creek primary drainage basin have been evaluated by mapping major ion concentrations and mineral saturation indicies with respect to hydrostratigraphic units and geologic structures. Controlling processes have been further assessed using statistical correlation and factor analysis. Results indicate that shallow waters in recharge zones are dominated by mixed cations (Na, Ca, Mg) and bicarbonate anions but with increased depth, groundwater transition to nearly 100% sodium bicarbonate type water. The chemistry of lower aquifer waters are principally controlled by nahcolite dissolution, but evidence of sulfate reduction and cation exchange aid in maintaining a sodium-bicarbonate water type. Ion evolution in surface and upper aquifer waters are influenced by an increase in sulfate concentration which is necessary to evolve water to an intermediate stage with sulfate-dominant anions. The source of sulfate is speculative, but likely due in part to the oxidation of sulfide-enriched groundwater and possible dissolution of sulfate-bearing carbonates. Surface and upper aquifer water chemistry in the northern portion of the basin is the result of discharge of deeper groundwater which is controlled to some degree by preferential pathways created by faults. Lower aquifer water migrates upward and mixes with the less-concentrated near-surface water, resulting in sodium bicarbonate type water in all hydrologic units. Close

• 4. [Article] Hydrogeologic Investigation of a Pumice Aquifer, Fremont/Winema National Forest, Oregon

  The middle Holocene cataclysmic eruption of Mount Mazama blanketed Walker Rim, in south central Oregon, with 270 cm to 300 cm of pumice, causing capture of surface water systems by groundwater, stream ...

  Citation × Citation Citation Abstract Copy Title: Hydrogeologic Investigation of a Pumice Aquifer, Fremont/Winema National Forest, Oregon Author: Weatherford, Jonathan Michael Year: 2015 The middle Holocene cataclysmic eruption of Mount Mazama blanketed Walker Rim, in south central Oregon, with 270 cm to 300 cm of pumice, causing capture of surface water systems by groundwater, stream relocation, and the formation of biologically diverse fens and seasonal wetlands. The pumice aquifer at Round Meadow, an 8.6 km2 basin, hosts both a fen and seasonally ponded wetlands. The Round Meadow watershed lies within a closed basin between the upper Klamath and Deschutes river basins. As the highest meadow at Walker Rim, it is a relatively well-constrained system to study the effects of hydrological disruption. A water budget was calculated for the basin, hydraulic conductivity was evaluated for the three main sediment layers in the meadow, recharge sources and evaporative trends were studied using stable isotope analysis, and aquifer residence times were estimated using CFC tracer water age dating. Water year 2014 was a drought year and observation of the system under stressed conditions allowed discrimination of four independently functioning components of the hydrogeologic system. These were the meadow, which is by far the largest component in terms of water storage, the fen where iron cementation and up to 1 m of peat holds water in a berm above the meadow, three springs which are sourced from deeper groundwater hosted in the bedrock which underlies the pumice deposit, and the outflow area. In all cases, the aquifer material is pumice, but the influence of the pre-eruption landscape and post-eruption modifications of the aquifer material have resulted in partial isolation of the components. The water budget analysis indicated that the basin lost 44 cm of water storage during WY 2014. Hydraulic conductivity values of 1x10-6, 2x10-2, and 4x10-5 cm/s, were determined for the diatomaceous silt underlying the pumice, the Plinian pumice fall aquifer, and for the diatomaceous silt overlying the pumice, respectively. The pumice is characterized as a perched, weakly confined aquifer and residence times in the pumice are much longer (decades) than for water near the surface of the meadow. Water discharging at the springs is isotopically different (lighter) than either the surface water or groundwater in the pumice aquifer. The fen at Round Meadow appears dependent on seasonal precipitation to recharge water, and responds to fluctuations in annual precipitation. The wetland meadows are volumetrically the main water-storing features at Round Meadow, and these are not homogenous features, but a combination of discrete components. Title: Hydrogeologic Investigation of a Pumice Aquifer, Fremont/Winema National Forest, Oregon Author: Weatherford, Jonathan Michael Year: 2015 The middle Holocene cataclysmic eruption of Mount Mazama blanketed Walker Rim, in south central Oregon, with 270 cm to 300 cm of pumice, causing capture of surface water systems by groundwater, stream relocation, and the formation of biologically diverse fens and seasonal wetlands. The pumice aquifer at Round Meadow, an 8.6 km2 basin, hosts both a fen and seasonally ponded wetlands. The Round Meadow watershed lies within a closed basin between the upper Klamath and Deschutes river basins. As the highest meadow at Walker Rim, it is a relatively well-constrained system to study the effects of hydrological disruption. A water budget was calculated for the basin, hydraulic conductivity was evaluated for the three main sediment layers in the meadow, recharge sources and evaporative trends were studied using stable isotope analysis, and aquifer residence times were estimated using CFC tracer water age dating. Water year 2014 was a drought year and observation of the system under stressed conditions allowed discrimination of four independently functioning components of the hydrogeologic system. These were the meadow, which is by far the largest component in terms of water storage, the fen where iron cementation and up to 1 m of peat holds water in a berm above the meadow, three springs which are sourced from deeper groundwater hosted in the bedrock which underlies the pumice deposit, and the outflow area. In all cases, the aquifer material is pumice, but the influence of the pre-eruption landscape and post-eruption modifications of the aquifer material have resulted in partial isolation of the components. The water budget analysis indicated that the basin lost 44 cm of water storage during WY 2014. Hydraulic conductivity values of 1x10-6, 2x10-2, and 4x10-5 cm/s, were determined for the diatomaceous silt underlying the pumice, the Plinian pumice fall aquifer, and for the diatomaceous silt overlying the pumice, respectively. The pumice is characterized as a perched, weakly confined aquifer and residence times in the pumice are much longer (decades) than for water near the surface of the meadow. Water discharging at the springs is isotopically different (lighter) than either the surface water or groundwater in the pumice aquifer. The fen at Round Meadow appears dependent on seasonal precipitation to recharge water, and responds to fluctuations in annual precipitation. The wetland meadows are volumetrically the main water-storing features at Round Meadow, and these are not homogenous features, but a combination of discrete components. Close

• 5. [Article] Investigating the Link Between Surface Water and Groundwater in the Tule Lake Subbasin, Oregon and California

  Water allocation in the upper Klamath Basin of Oregon and California has been challenging. Irrigators have increasingly turned to groundwater to make up for surface water shortages because of shifts in ...

  Citation × Citation Citation Abstract Copy Title: Investigating the Link Between Surface Water and Groundwater in the Tule Lake Subbasin, Oregon and California Author: Pischel, Esther Maria Year: 2014 Water allocation in the upper Klamath Basin of Oregon and California has been challenging. Irrigators have increasingly turned to groundwater to make up for surface water shortages because of shifts in allocation toward in-stream flows for Endangered Species Act listed fishes. The largest increase in groundwater pumping has been in and around the Bureau of Reclamation's Klamath Irrigation Project, which includes the Tule Lake subbasin in the southern part of the upper Klamath Basin. Previous groundwater flow model simulations indicate that water level declines from pumping may result in decreased flow to agricultural drains in the Tule Lake subbasin. Agricultural drains on the Klamath Project are an important source of water for downstream irrigators and for the Tule Lake and Lower Klamath Lake National Wildlife Refuges. To better assess the impact of increased pumping on drain flow and on the water balance of the groundwater system, flow data from agricultural drains were evaluated to investigate the changes that have taken place in groundwater discharge to drains since pumping volumes increased. Additionally, a fine-grid groundwater model of the Tule Lake subbasin was developed based on the existing regional flow model. The fine-grid model has sufficient vertical and horizontal resolution to simulate vertical head gradients, takes advantage of time-series data from 38 observation wells for model calibration, and allows agricultural drains to be more explicitly represented. Results of the drain flow analysis show that the groundwater discharge to agricultural drains has decreased by approximately 4000 hectare-meters from the 1997-2000 average discharge. Most of this decrease takes place in the northern and southeastern portions of the subbasin. Results of the groundwater model show that the initial source of water to wells is groundwater storage. By 2006, approximately 56% of the water from wells is sourced from agricultural drains. Title: Investigating the Link Between Surface Water and Groundwater in the Tule Lake Subbasin, Oregon and California Author: Pischel, Esther Maria Year: 2014 Water allocation in the upper Klamath Basin of Oregon and California has been challenging. Irrigators have increasingly turned to groundwater to make up for surface water shortages because of shifts in allocation toward in-stream flows for Endangered Species Act listed fishes. The largest increase in groundwater pumping has been in and around the Bureau of Reclamation's Klamath Irrigation Project, which includes the Tule Lake subbasin in the southern part of the upper Klamath Basin. Previous groundwater flow model simulations indicate that water level declines from pumping may result in decreased flow to agricultural drains in the Tule Lake subbasin. Agricultural drains on the Klamath Project are an important source of water for downstream irrigators and for the Tule Lake and Lower Klamath Lake National Wildlife Refuges. To better assess the impact of increased pumping on drain flow and on the water balance of the groundwater system, flow data from agricultural drains were evaluated to investigate the changes that have taken place in groundwater discharge to drains since pumping volumes increased. Additionally, a fine-grid groundwater model of the Tule Lake subbasin was developed based on the existing regional flow model. The fine-grid model has sufficient vertical and horizontal resolution to simulate vertical head gradients, takes advantage of time-series data from 38 observation wells for model calibration, and allows agricultural drains to be more explicitly represented. Results of the drain flow analysis show that the groundwater discharge to agricultural drains has decreased by approximately 4000 hectare-meters from the 1997-2000 average discharge. Most of this decrease takes place in the northern and southeastern portions of the subbasin. Results of the groundwater model show that the initial source of water to wells is groundwater storage. By 2006, approximately 56% of the water from wells is sourced from agricultural drains. Close

• 6. [Article] Hydrogeology of Pumice-Hosted Fens in the Winema-Fremont National Forest, Oregon, USA

  Subaerial fallout from the Holocene eruption of Mount Mazama in the Oregon Cascade Range was deposited upon relatively low permeability volcanic and volcaniclastic bedrock and regolith. In the Walker Rim ...

  Citation × Citation Citation Abstract Copy Title: Hydrogeology of Pumice-Hosted Fens in the Winema-Fremont National Forest, Oregon, USA Author: Cummings, Michael L., Weatherford, Jonathan Michael, Mowbray, Leslie A Year: 2014 Subaerial fallout from the Holocene eruption of Mount Mazama in the Oregon Cascade Range was deposited upon relatively low permeability volcanic and volcaniclastic bedrock and regolith. In the Walker Rim study area, erosion by ephemeral streams shortly after the eruption disrupted the lateral continuity of the 270 to 300 cm-thick pumice deposit. Co-evolution of the surface- and ground-water systems in a low-relief, low-slope landscape allowed diffuse groundwater discharge from the banks of the evolving stream system. Accumulation of organic material from groundwater dependent ecosystems at these sites of discharge allowed peat deposits to form on gently sloping erosion surfaces cut into the pumice deposit. Following early stream incision, fine-grained, silt-rich deposits accumulated in valleys and contributed permeability barriers to the lateral migration of water in the pumice aquifer. Fens discharge from the pumice aquifer through gently sloping surfaces patterned after the slope of the erosion surface cut into the pumice deposit and overlain by approximately 1 m of peat on the sloping surface and alluvium or iron-cemented pumice overlain by alluvium at the toe of the slope. The predominant source of groundwater is snowmelt which infiltrates the pumice deposit during the freshet. However, shallow groundwater flow also takes place along permeable pathways in bedrock units. Locally, low volume discharge takes place along faults. The snowmelt-dependent hydrologic system that supports the fens of the Walker Rim study area occurs at elevations primarily above 1585 m. Title: Hydrogeology of Pumice-Hosted Fens in the Winema-Fremont National Forest, Oregon, USA Author: Cummings, Michael L., Weatherford, Jonathan Michael, Mowbray, Leslie A Year: 2014 Subaerial fallout from the Holocene eruption of Mount Mazama in the Oregon Cascade Range was deposited upon relatively low permeability volcanic and volcaniclastic bedrock and regolith. In the Walker Rim study area, erosion by ephemeral streams shortly after the eruption disrupted the lateral continuity of the 270 to 300 cm-thick pumice deposit. Co-evolution of the surface- and ground-water systems in a low-relief, low-slope landscape allowed diffuse groundwater discharge from the banks of the evolving stream system. Accumulation of organic material from groundwater dependent ecosystems at these sites of discharge allowed peat deposits to form on gently sloping erosion surfaces cut into the pumice deposit. Following early stream incision, fine-grained, silt-rich deposits accumulated in valleys and contributed permeability barriers to the lateral migration of water in the pumice aquifer. Fens discharge from the pumice aquifer through gently sloping surfaces patterned after the slope of the erosion surface cut into the pumice deposit and overlain by approximately 1 m of peat on the sloping surface and alluvium or iron-cemented pumice overlain by alluvium at the toe of the slope. The predominant source of groundwater is snowmelt which infiltrates the pumice deposit during the freshet. However, shallow groundwater flow also takes place along permeable pathways in bedrock units. Locally, low volume discharge takes place along faults. The snowmelt-dependent hydrologic system that supports the fens of the Walker Rim study area occurs at elevations primarily above 1585 m. Close

• 7. [Article] Hydrogeochemical Characterization of the Alvord Valley Known Geothermal Resources Area, Harney County, Oregon

  The Alvord Valley Known Geothermal Resources Area (KGRA) , located east of the Steens Mountain-Pueblo Mountains fault block in southeastern Oregon, is within the northern Basin and Range province. This ...

  Citation × Citation Citation Abstract Copy Title: Hydrogeochemical Characterization of the Alvord Valley Known Geothermal Resources Area, Harney County, Oregon Author: St. John, Anna Maria Year: 1993 The Alvord Valley Known Geothermal Resources Area (KGRA) , located east of the Steens Mountain-Pueblo Mountains fault block in southeastern Oregon, is within the northern Basin and Range province. This investigation focuses on three thermal areas in the Alvord Basin: Borax Lake and the hot springs north of Borax Lake, Alvord Hot Springs and Mickey Springs. Mickey Springs and the springs north of Borax Lake are boiling at the surface (94 and 95° C, respectively). Inflow temperatures to Borax Lake, measured at a depth of 30 m, are greater than 100° C. Surface temperatures for Alvord Hot Springs and a flowing well northeast of Borax Lake are 78 and 59° C, respectively. Thermal fluids issue from Quaternary lacustrine and alluvial deposits. While silica sinter deposits are present at all three thermal areas, sinter is not presently being deposited. Minor calcite is being deposited at the springs north of Borax Lake. The springs discharge from N to NEstriking, high-angle, basin-bounding faults along the base of Steens Mountain and Mickey Mountain and NE-striking intrabasinal faults south of Alvord Lake. The thermal waters are dilute sodium-bicarbonate waters with significant amounts of sulfate and chloride. Conservative element plots (B, F, and Li vs. Cl) indicate good correlation between Cl and the other conservative elements. These correlations could result from mixing of thermal water with a dilute cold water or fluid evolution due to increased fluid-rock interaction, evaporation, and steam loss due to boiling. The small variations in chloride concentrations of thermal fluids during the sampling period argues against mixing of thermal fluids with cold water. The geothermal system is a hot-water rather than a vapordominated system. The ỎD content of thermal fluids is similar to the ỎD content of local cold water wells, springs, basinal pore fluids at a depth of 4 to 5 m, and perennial streams. Similarities in ỎD values indicate recharge for geothermal fluids is precipitation from the Steens Mountain fault block. The Ỏ18 content of thermal fluids is shifted 2 to 3°/oo to the right of the world meteoric water line indicating fluid-rock interaction at elevated temperatures in the reservoir. Tritium contents indicate relatively long residence times and/or low-velocity circulation of meteoric water through basement rocks. Values range from 0 to 0.25 T.U. The application of two end-member models, which calculate fluid residence times, generate a minimum of 57 years and a maximum of greater than 10,000 years. Estimated reservoir temperatures based on cation and silica geothermometry are between 170 and 200°C. Oxygensulfate isotope geothermometer estimates indicate reservoir temperatures between 198 and 207' C for Borax Lake and Alvord Hot Springs. Mickey Springs and a flowing well northeast of Borax Lake yield temperature estimates of 168 and 150° C, respectively. These values indicate partial reequilibration of the isotopic system. The Ỏ13C contents of carbon dioxide and methane of gas discharges from the thermal areas are similar to geothermal fluids from other sites. The Ỏ13C of methane indicate "normal" geothermal methane for Alvord Hot Springs and Mickey Springs (-27.8 and -27.6, respectively). The Ỏ13C of CH4 for springs north of Borax Lake (-33.6) indicates a small amount of thermogenic methane may be contributed by thermal alteration of organics in basinal sediments. The Ỏ13C contents for C02 at Alvord Hot Springs and Borax Lake are within the range expected for atmospheric, fumarolic, or mantle derived C02 (-6.5 and -6.6, respectively). The Ỏ13C content of C02 from Mickey Springs is isotopically lighter than gas released from fumaroles or the mantle (-9.4). N2/Ar ratios for Mickey Springs and Borax Lake gases (39.2 and 40.8, respectively) indicate interaction with airsaturated ground water during flow through the the zone of aeration. Helium is enriched relative to Ar and N2 in gas discharges from Alvord Hot Springs, indicating longer fluid residence times and/or increased crustal interaction at high temperatures. Ratios of B/Cl indicate the fluid reservoir is hosted in volcanic rocks. The Li/Cs ratios for the Borax Lake thermal area are consistent with a reservoir located in rhyoli tic rocks. The 228Ra/226Ra content of Borax Lake thermal fluids (1.14 ± 0.13 dpm/kg) indicates interaction with volcanic rocks for Borax Lake. The 228Ra/226Ra content of thermal fluids from Alvord Hot Springs and Mickey Springs (0.38~0.02 and 0.17 ~ 0.09) are lower than those expected for volcanic rocks and may indicate local uranium accumulation in the reservoir or zones of upflow. The 87Sr / 86Sr values for thermal waters and stratigraphic uni ts indicate the fluid reservoir is located in volcanic rocks beneath Steens Basalt. Equilibration of fluids in these units argues for thermal water circulation depths of 2 to 2.5 km in the Borax Lake thermal area, greater than 3 km in the Alvord Hot Springs area and 1 to 2 km in the Mickey Springs area. Data presented in this study do not preclude a single large deep reservoir system discharging at these three thermal areas in the Alvord basin. Differences in the chemical and isotopic composition of discharge from the three thermal areas are produced during upf low from the reservoir. During upflow, thermal waters follow a complex pathway of vertical and lateral fractures which includes short residence times in shallow reservoirs before reaching the surface. Boiling, mixing with condensate, oxidation, mixing with 1-3% tritium-bearing, near-surface cold water, relative differences in flow rate and volume, and slow cooling without vigorous boiling are processes that modify fluid composition during upflow from the deep geothermal reservoir. Title: Hydrogeochemical Characterization of the Alvord Valley Known Geothermal Resources Area, Harney County, Oregon Author: St. John, Anna Maria Year: 1993 The Alvord Valley Known Geothermal Resources Area (KGRA) , located east of the Steens Mountain-Pueblo Mountains fault block in southeastern Oregon, is within the northern Basin and Range province. This investigation focuses on three thermal areas in the Alvord Basin: Borax Lake and the hot springs north of Borax Lake, Alvord Hot Springs and Mickey Springs. Mickey Springs and the springs north of Borax Lake are boiling at the surface (94 and 95° C, respectively). Inflow temperatures to Borax Lake, measured at a depth of 30 m, are greater than 100° C. Surface temperatures for Alvord Hot Springs and a flowing well northeast of Borax Lake are 78 and 59° C, respectively. Thermal fluids issue from Quaternary lacustrine and alluvial deposits. While silica sinter deposits are present at all three thermal areas, sinter is not presently being deposited. Minor calcite is being deposited at the springs north of Borax Lake. The springs discharge from N to NEstriking, high-angle, basin-bounding faults along the base of Steens Mountain and Mickey Mountain and NE-striking intrabasinal faults south of Alvord Lake. The thermal waters are dilute sodium-bicarbonate waters with significant amounts of sulfate and chloride. Conservative element plots (B, F, and Li vs. Cl) indicate good correlation between Cl and the other conservative elements. These correlations could result from mixing of thermal water with a dilute cold water or fluid evolution due to increased fluid-rock interaction, evaporation, and steam loss due to boiling. The small variations in chloride concentrations of thermal fluids during the sampling period argues against mixing of thermal fluids with cold water. The geothermal system is a hot-water rather than a vapordominated system. The ỎD content of thermal fluids is similar to the ỎD content of local cold water wells, springs, basinal pore fluids at a depth of 4 to 5 m, and perennial streams. Similarities in ỎD values indicate recharge for geothermal fluids is precipitation from the Steens Mountain fault block. The Ỏ18 content of thermal fluids is shifted 2 to 3°/oo to the right of the world meteoric water line indicating fluid-rock interaction at elevated temperatures in the reservoir. Tritium contents indicate relatively long residence times and/or low-velocity circulation of meteoric water through basement rocks. Values range from 0 to 0.25 T.U. The application of two end-member models, which calculate fluid residence times, generate a minimum of 57 years and a maximum of greater than 10,000 years. Estimated reservoir temperatures based on cation and silica geothermometry are between 170 and 200°C. Oxygensulfate isotope geothermometer estimates indicate reservoir temperatures between 198 and 207' C for Borax Lake and Alvord Hot Springs. Mickey Springs and a flowing well northeast of Borax Lake yield temperature estimates of 168 and 150° C, respectively. These values indicate partial reequilibration of the isotopic system. The Ỏ13C contents of carbon dioxide and methane of gas discharges from the thermal areas are similar to geothermal fluids from other sites. The Ỏ13C of methane indicate "normal" geothermal methane for Alvord Hot Springs and Mickey Springs (-27.8 and -27.6, respectively). The Ỏ13C of CH4 for springs north of Borax Lake (-33.6) indicates a small amount of thermogenic methane may be contributed by thermal alteration of organics in basinal sediments. The Ỏ13C contents for C02 at Alvord Hot Springs and Borax Lake are within the range expected for atmospheric, fumarolic, or mantle derived C02 (-6.5 and -6.6, respectively). The Ỏ13C content of C02 from Mickey Springs is isotopically lighter than gas released from fumaroles or the mantle (-9.4). N2/Ar ratios for Mickey Springs and Borax Lake gases (39.2 and 40.8, respectively) indicate interaction with airsaturated ground water during flow through the the zone of aeration. Helium is enriched relative to Ar and N2 in gas discharges from Alvord Hot Springs, indicating longer fluid residence times and/or increased crustal interaction at high temperatures. Ratios of B/Cl indicate the fluid reservoir is hosted in volcanic rocks. The Li/Cs ratios for the Borax Lake thermal area are consistent with a reservoir located in rhyoli tic rocks. The 228Ra/226Ra content of Borax Lake thermal fluids (1.14 ± 0.13 dpm/kg) indicates interaction with volcanic rocks for Borax Lake. The 228Ra/226Ra content of thermal fluids from Alvord Hot Springs and Mickey Springs (0.38~0.02 and 0.17 ~ 0.09) are lower than those expected for volcanic rocks and may indicate local uranium accumulation in the reservoir or zones of upflow. The 87Sr / 86Sr values for thermal waters and stratigraphic uni ts indicate the fluid reservoir is located in volcanic rocks beneath Steens Basalt. Equilibration of fluids in these units argues for thermal water circulation depths of 2 to 2.5 km in the Borax Lake thermal area, greater than 3 km in the Alvord Hot Springs area and 1 to 2 km in the Mickey Springs area. Data presented in this study do not preclude a single large deep reservoir system discharging at these three thermal areas in the Alvord basin. Differences in the chemical and isotopic composition of discharge from the three thermal areas are produced during upf low from the reservoir. During upflow, thermal waters follow a complex pathway of vertical and lateral fractures which includes short residence times in shallow reservoirs before reaching the surface. Boiling, mixing with condensate, oxidation, mixing with 1-3% tritium-bearing, near-surface cold water, relative differences in flow rate and volume, and slow cooling without vigorous boiling are processes that modify fluid composition during upflow from the deep geothermal reservoir. Close

• 8. [Article] Solidification and Morphology of Submarine Lavas: A Dependence on Extrusion Rate

  The results of recent laboratory experiments with wax extruded beneath relatively cold water may be extrapolated to predict the surface morphology of submarine lavas as a function of the extrusion rate ...

  Citation × Citation Citation Abstract Copy Title: Solidification and Morphology of Submarine Lavas: A Dependence on Extrusion Rate Author: Griffiths, Ross W., Fink, Jonathan H. Year: 1992 The results of recent laboratory experiments with wax extruded beneath relatively cold water may be extrapolated to predict the surface morphology of submarine lavas as a function of the extrusion rate and melt vIscosity. The experiments with solidifying wax indicated that the surface morphology was controlled by a single parameter, the ratio of the time taken for the surface to solidify, and a time scale for lateral flow. For submarine basalts a solution of the cooling problem (which is dominated by conduction in the lava but convective heat transfer in the water) and estimates of lava viscosities place this parameter within the empirically determined "pillowing" regime over a Wide range of extrusion rates. This result is consistent with the observation that pillow basalts are the most common products of submarine eruptions. Smoother surfaces corresponding to the various types .of submarine sheet flows are predicted for sufficiently rapid extrusions of basaltic magma. Still higher eruption rates ID regions of low topographic relief may produce submarine lava lakes. Minimum emplacement times can be calculated for submarine volocanic constructs of a single lava flow type. Title: Solidification and Morphology of Submarine Lavas: A Dependence on Extrusion Rate Author: Griffiths, Ross W., Fink, Jonathan H. Year: 1992 The results of recent laboratory experiments with wax extruded beneath relatively cold water may be extrapolated to predict the surface morphology of submarine lavas as a function of the extrusion rate and melt vIscosity. The experiments with solidifying wax indicated that the surface morphology was controlled by a single parameter, the ratio of the time taken for the surface to solidify, and a time scale for lateral flow. For submarine basalts a solution of the cooling problem (which is dominated by conduction in the lava but convective heat transfer in the water) and estimates of lava viscosities place this parameter within the empirically determined "pillowing" regime over a Wide range of extrusion rates. This result is consistent with the observation that pillow basalts are the most common products of submarine eruptions. Smoother surfaces corresponding to the various types .of submarine sheet flows are predicted for sufficiently rapid extrusions of basaltic magma. Still higher eruption rates ID regions of low topographic relief may produce submarine lava lakes. Minimum emplacement times can be calculated for submarine volocanic constructs of a single lava flow type. Close

• 9. [Article] The Morphology of Lava Flows in Planetary Environments: Predictions From Analog Experiments

  The rates of surface cooling and lateral spreading are evaluated for lava flows on the surface of Earth, Venus, Mars, the Moon, and 10. Differences between the flow morphologies expected in these environments ...

  Citation × Citation Citation Abstract Copy Title: The Morphology of Lava Flows in Planetary Environments: Predictions From Analog Experiments Author: Griffiths, Ross W., Fink, Jonathan H. Year: 1992 The rates of surface cooling and lateral spreading are evaluated for lava flows on the surface of Earth, Venus, Mars, the Moon, and 10. Differences between the flow morphologies expected in these environments are then predicted under the assumption that the results of recent laboratory simulations oflavas using wax extruded beneath cold water (Fink and Griffiths, 1990) can be carried over. These experiments involved the spreading of viscous liquid under gravity in the presence of a solidifying surface crust and revealed a set of four distinct surface morphologies. Transitions from one morphology to the next occurred in a well-defined sequence when the relative rates of surface solidification and lateral spreading were varied. In comparison with subaerial flows on Earth, the surface of lavas solidifies faster on Venus, where the dense atmosphere provides additional convective heat transfer. Lateral flow oflava is much slower under the smaller gravity of the Moon. Hence, for a given extrusion rate and viscosity, solid crust is predicted to form closer to the vent on both the Moon and Venus than on Earth. Equivalently, faster extrusion rates than those on Earth are required on the Moon, 10, and Venus in order to produce a given surface morphology. A comparison of observed structure, flow rates, and estimated viscosities for some well-documented terrestrial lava flows shows reasonable agreement with the predictions of the model. Extrapolation to extraterrestrial lavas is then illustrated by constraining the effusion rate for a Martian lava flow whose composition is assumed. Spectral information on the chemical composition of Martian flows to be sought by the thermal emission spectrometer on the Mars Observer mission, in conjunction with detailed morphologic observations from the Mars Observer camera, could allow much more accurate estimates of effusion rates for Martian lavas. Title: The Morphology of Lava Flows in Planetary Environments: Predictions From Analog Experiments Author: Griffiths, Ross W., Fink, Jonathan H. Year: 1992 The rates of surface cooling and lateral spreading are evaluated for lava flows on the surface of Earth, Venus, Mars, the Moon, and 10. Differences between the flow morphologies expected in these environments are then predicted under the assumption that the results of recent laboratory simulations oflavas using wax extruded beneath cold water (Fink and Griffiths, 1990) can be carried over. These experiments involved the spreading of viscous liquid under gravity in the presence of a solidifying surface crust and revealed a set of four distinct surface morphologies. Transitions from one morphology to the next occurred in a well-defined sequence when the relative rates of surface solidification and lateral spreading were varied. In comparison with subaerial flows on Earth, the surface of lavas solidifies faster on Venus, where the dense atmosphere provides additional convective heat transfer. Lateral flow oflava is much slower under the smaller gravity of the Moon. Hence, for a given extrusion rate and viscosity, solid crust is predicted to form closer to the vent on both the Moon and Venus than on Earth. Equivalently, faster extrusion rates than those on Earth are required on the Moon, 10, and Venus in order to produce a given surface morphology. A comparison of observed structure, flow rates, and estimated viscosities for some well-documented terrestrial lava flows shows reasonable agreement with the predictions of the model. Extrapolation to extraterrestrial lavas is then illustrated by constraining the effusion rate for a Martian lava flow whose composition is assumed. Spectral information on the chemical composition of Martian flows to be sought by the thermal emission spectrometer on the Mars Observer mission, in conjunction with detailed morphologic observations from the Mars Observer camera, could allow much more accurate estimates of effusion rates for Martian lavas. Close

• 10. [Article] Near-Surface Internal Melting: a Substantial Mass Loss on Antarctic Dry Valley Glaciers

  The McMurdo Dry Valleys, southern Victoria Land, East Antarctica, are a polar desert, and melt from glacial ice is the primary source of water to streams, lakes and associated ecosystems. Previous work ...

  Citation × Citation Citation Abstract Copy Title: Near-Surface Internal Melting: a Substantial Mass Loss on Antarctic Dry Valley Glaciers Author: Hoffman, Matthew J., Fountain, Andrew G., Liston, Glen E. Year: 2014 The McMurdo Dry Valleys, southern Victoria Land, East Antarctica, are a polar desert, and melt from glacial ice is the primary source of water to streams, lakes and associated ecosystems. Previous work found that to adequately model glacier ablation and subsurface ice temperatures with a surface energy-balance model required including the transmission of solar radiation into the ice. Here we investigate the contribution of subsurface melt to the mass balance of (and runoff from) Dry Valley glaciers by including a drainage process in the model and applying the model to three glacier sites using 13years of hourly meteorological data. Model results for the smooth glacier surfaces common to many glaciers in the Dry Valleys showed that sublimation was typically the largest component of surface lowering, with rare episodes of surface melting, consistent with anecdotal field observations. Results also showed extensive internal melting 5-15 cm below the ice surface, the drainage of which accounted for 50% of summer ablation. This is consistent with field observations of subsurface streams and formation of a weathering crust. We identify an annual cycle of weathering crust formation in summer and its removal during the 10 months of winter sublimation. Title: Near-Surface Internal Melting: a Substantial Mass Loss on Antarctic Dry Valley Glaciers Author: Hoffman, Matthew J., Fountain, Andrew G., Liston, Glen E. Year: 2014 The McMurdo Dry Valleys, southern Victoria Land, East Antarctica, are a polar desert, and melt from glacial ice is the primary source of water to streams, lakes and associated ecosystems. Previous work found that to adequately model glacier ablation and subsurface ice temperatures with a surface energy-balance model required including the transmission of solar radiation into the ice. Here we investigate the contribution of subsurface melt to the mass balance of (and runoff from) Dry Valley glaciers by including a drainage process in the model and applying the model to three glacier sites using 13years of hourly meteorological data. Model results for the smooth glacier surfaces common to many glaciers in the Dry Valleys showed that sublimation was typically the largest component of surface lowering, with rare episodes of surface melting, consistent with anecdotal field observations. Results also showed extensive internal melting 5-15 cm below the ice surface, the drainage of which accounted for 50% of summer ablation. This is consistent with field observations of subsurface streams and formation of a weathering crust. We identify an annual cycle of weathering crust formation in summer and its removal during the 10 months of winter sublimation. Close