We thank the following individuals for their assistance. Paul Thorne provided geology information... more We thank the following individuals for their assistance. Paul Thorne provided geology information from the EarthVision database; Mark Rockhold provided water level data and material property values and reviewed the manuscript; John P. McDonald provided additional water level data and helpful comments on their quality; and Duane Ward provided Figure 1.1. This study was supported by the U.S. Department of Energy under Contract DE-AC05-76RLO1830. This report is available in Portable Document Format (PDF) from the PNNL publications (a) external website. The electronic version contains hyperlinks to facilitate navigation between all cross-referenced material, including section headings, figures, tables, and references.
Runoff (streamflow) from Cold and Dry Creeks was studied as part of a larger effort to evaluate n... more Runoff (streamflow) from Cold and Dry Creeks was studied as part of a larger effort to evaluate natural recharge to the Hanford Site. Natural recharge to the Site can take the form of direct infiltration of precipitation, lateral inflow of groundwater, and infiltration of streamflow. This report is concerned with the streamflow pathway and considers both historical runoff events and probabilistic extreme events. The observed runoff events were used to fit models of runoff generation, hydrograph shape, and channel infiltration. The models were then used to estimate the magnitude and location of potential recharge from several design storm events based on previous studies of maximum precipitation probability. The Cold and Dry Creek watersheds were divided into upper, middle, and lower basins, based on the U.S. Geological Survey stream gauge locations described by Dinicola (1997). The upper basins are the primary areas of runoff generation, while the middle and lower basins are areas of infiltration. Hourly weather data and 15-minute streamflow data from January 1995, a period of significant runoff, were used to evaluate the meteorological conditions of the relatively rare runoff generation and to fit and calibrate the models. Frozen ground and melting snow appeared to play important roles in the runoff generation. Hydrographs of Cold and Dry Creeks indicated rapid cresting of streamflows and subsequent rapid recession, with 8 distinct events in Cold Creek. For each runoff event, the duration, volume, and volume of the causative precipitation were tabulated. Curve numbers were computed using the Soil Conservation Service method. A linear relationship between precipitation duration and streamflow duration was also derived. The curve numbers and duration relationship were subsequently used to estimate runoff and hydrograph shape from the design storms of maximum precipitation. A firstorder decay model was fit to the observed streamflows at the upper and lower Cold Creek gauges and used to estimate the spatial pattern of infiltration of streamflow (recharge) resulting from the design storms. The double-triangle hydrograph model was also fit to the data and used to complete the characterization of runoff from the design storms. Four hypothetical rainfall events (design storms) were used to drive the runoff and infiltration models: 1) 4.6 inches over 6 hours, 2) 1.61 inches over 24 hours, 3) 2.16 inches over 3 days, and 4) 2.71 inches over 7 days. The first value is the "probable maximum precipitation" from Skaggs and Walters (1981), and the latter three values from Wigmosta and Guensch (2005) correspond to a return period of 100 years. For comparison, the largest rainfall event during January 1995 was 1.02 inches over approximately 3 days. Combined Cold and Dry Creek recharge volumes for the 100-year rainfall events were 7,700 ac-ft, 11,700 ac-ft, and 15,900 ac-ft, respectively. These recharge volumes are 7 to 14 times the average annual recharge rate for surface runoff estimated by Dinicola (1997), and fall between two estimates of direct recharge from infiltrating rainfall and snowmelt for the entire Hanford Site: 6,680 ac-ft/y (Fayer and Walters 1995) and 14,467 ac-ft/y (Jacobsen and Freshley 1990). In Cold Creek, simulated streamflow and recharge volumes were largest just above the lower gage. In Dry Creek, simulated runoff volumes were largest at the upper gage, and recharge volumes are greatest in the ponding area downstream from the lower gage.
I’ve been waiting a long time to write this story and I’m sure that all of you floodies have want... more I’ve been waiting a long time to write this story and I’m sure that all of you floodies have wanted to read this for an equally long time. After a congressional roller coaster ride during late winter and early spring, it finally happened. On March 25th Congress passed H.R. 146: The Omnibus Public Land Management Act of 2009, and on March 30th President Obama signed the bill into law. There will be an Ice Age Floods National Geologic Trail as a unit of the National Park System! The actual process of passing this major piece of legislation still makes my head swim. In a nutshell, over 160 bills, including our Floods Trail bill, that had been bottled up at various points in the legislative process, were packaged together in the Senate and eventually added as an amendment to another bill that had already been considered by the House of Representatives. Congressional procedures are such that this process avoided the possibility of further delay and the House approved the Senate’s amendme...
Columbia River water elevations and flows in the Hanford Reach affect the environment and facilit... more Columbia River water elevations and flows in the Hanford Reach affect the environment and facilities along the shoreline, including movement of contaminants in groundwater, fish habitat, and infrastructure subject to flooding. This report describes the hydraulic simulation of hypothetical flood flows using the best available topographic and bathymetric data for the Hanford Reach and the Modular Aquatic Simulation System in 1 Dimension (MASS1) hydrodynamic model. The MASS1 model of the Hanford Reach was previously calibrated to field measurements of water surface elevations. The current model setup can be used for other studies of flow, water levels, and temperature in the Reach. The existing MASS1 channel geometry and roughness and other model configuration inputs for the Hanford Reach were used for this study, and previous calibration and validation results for the model are reprinted here for reference. The flood flows for this study were simulated by setting constant flow rates obtained from the U.S. Army Corps of Engineers (USACE) for the Columbia, Snake, and Yakima Rivers, and a constant water level at McNary Dam, and then running the model to steady state. The discharge levels simulated were all low-probability events; for example, a 100-year flood is one that would occur on average every 100 years, or put another way, in any given year there is a 1% chance that a discharge of that level or higher will occur. The simulated floods and their corresponding Columbia River discharges were 100-year (445,000 cfs), 500-year (520,000 cfs), and the USACE-defined Standard Project Flood (960,000 cfs). The resulting water levels from the steady-state floods can be viewed as "worst case" outcomes for the respective discharge levels. The MASS1 output for water surface elevations was converted to the North American Vertical Datum of 1988 and projected across the channel and land surface to enable mapping of the floodplain for each scenario. Floodplain maps show that for the 100-year and 500-year discharge levels, flooding is mainly confined to the topographic trench that is the river channel. The flooded area for the Standard Project Flood extends out of the channel area in some places, particularly in the 100-F Area. All of the output from the simulations have been archived and are available for future investigations in the Hanford Reach.
Three-dimensional variably saturated flow and multicomponent biogeochemical reactive transport mo... more Three-dimensional variably saturated flow and multicomponent biogeochemical reactive transport modeling, based on published and newly generated data, is used to better understand the interplay of hydrology, geochemistry, and biology controlling the cycling of carbon, nitrogen, oxygen, iron, sulfur, and uranium in a shallow floodplain. In this system, aerobic respiration generally maintains anoxic groundwater below an oxic vadose zone until seasonal snowmelt-driven water table peaking transports dissolved oxygen (DO) and nitrate from the vadose zone into the alluvial aquifer. The response to this perturbation is localized due to distinct physico-biogeochemical environments and relatively long time scales for transport through the floodplain aquifer and vadose zone. Naturally reduced zones (NRZs) containing sediments higher in organic matter, iron sulfides, and non-crystalline U(IV) rapidly consume DO and nitrate to maintain anoxic conditions, yielding Fe(II) from FeS oxidative dissol...
Field-scale biostimulation and desorption tracer experiments conducted in a uranium (U) contamina... more Field-scale biostimulation and desorption tracer experiments conducted in a uranium (U) contaminated, shallow alluvial aquifer have provided insight into the coupling of microbiology, biogeochemistry, and hydrogeology that control U mobility in the subsurface. Initial experiments successfully tested the concept that Fe-reducing bacteria such as Geobacter sp. could enzymatically reduce soluble U(VI) to insoluble U(IV) during in situ electron donor amendment (Anderson et al., 2003; Williams et al., 2011). In parallel, in situ desorption tracer tests using bicarbonate amendment demonstrated rate-limited U(VI) desorption (Fox et al., 2012). These results and prior laboratory studies underscored the importance of enzymatic U(VI)-reduction and suggested the ability to combine desorption and bioreduction of U(VI). Here we report the results of a new field experiment in which bicarbonate-promoted uranium desorption and acetate amendment were combined and compared to an acetate amendment-only experiment in the same experimental plot. Results confirm that bicarbonate amendment to alluvial aquifer sediments desorbs U(VI) and increases the abundance of Ca-uranyl-carbonato complexes. At the same time, the rate of acetate-promoted enzymatic U(VI) reduction was greater in the presence of added bicarbonate in spite of the increased dominance of Ca-uranyl-carbonato aqueous complexes. A model-simulated peak rate of U(VI) reduction was ~3.8 times higher during acetate-bicarbonate treatment than under acetate-only conditions. Lack of consistent differences in microbial community structure between acetate-bicarbonate and acetate-only treatments suggest that a significantly higher rate of U(VI) reduction in the bicarbonate-impacted sediment may be due to a higher intrinsic rate of microbial reduction induced by elevated concentrations of the bicarbonate oxyanion. The findings indicate that bicarbonate amendment may be useful in improving the engineered bioremediation of uranium in aquifers.
advised the author on PNNL document requirements. Bill Perkins/Hydrology provided the first draft... more advised the author on PNNL document requirements. Bill Perkins/Hydrology provided the first draft of the document class file as well as many helpful examples and valuable L A T E X expertise.
Sea-level rise is one of the most critical challenges facing coastal ecosystems under climate cha... more Sea-level rise is one of the most critical challenges facing coastal ecosystems under climate change. Observations of elevated tree mortality in global coastal forests are increasing, but important knowledge gaps persist concerning the mechanism of salinity stress-induced nonhalophytic tree mortality. We monitored progressive mortality and associated gas exchange and hydraulic shifts in Sitka-spruce (Picea sitchensis) trees located within a salinity gradient under an ecosystem-scale change of seawater exposure in Washington State, USA. Percentage of live foliated crown (PLFC) decreased and tree mortality increased with increasing soil salinity during the study period. A strong reduction in gas exchange and xylem hydraulic conductivity (Ks) occurred during tree death, with an increase in the percentage loss of conductivity (PLC) and turgor loss point (πtlp). Hydraulic and osmotic shifts reflected that hydraulic function declined from seawater exposure, and dying trees were unable to ...
Increasing seawater exposure is causing mortality of coastal forests, yet the physiological respo... more Increasing seawater exposure is causing mortality of coastal forests, yet the physiological response associated with seawater-induced tree mortality, particularly in non-halophytes, is poorly understood. We investigated the shifts in carbon and nitrogen (N) metabolism of mature Sitka-spruce trees that were dying after an ecosystem-scale manipulation of tidal seawater exposure. Soil porewater salinity and foliar ion concentrations increased after seawater exposure and were strongly correlated with the percentage of live foliated crown (PLFC; e.g., crown ‘greenness’, a measure of progression to death). Co-occurring with decreasing PLFC was decreasing photosynthetic capacity, N-investment into photosynthesis, N-resorption efficiency and non-structural carbohydrate (soluble sugars and starch) concentrations, with the starch reserves depleted to near zero when PLFC dropped below 5%. Combined with declining PLFC, these changes subsequently decreased total carbon gain and thus exacerbated ...
Increasing sea levels associated with climate change threaten the survival of coastal forests, ye... more Increasing sea levels associated with climate change threaten the survival of coastal forests, yet the mechanisms by which seawater exposure causes tree death remain poorly understood. Despite the potentially crucial role of nonstructural carbohydrate (NSC) reserves in tree survival, their dynamics in the process of death under seawater exposure are unknown. Here we monitored progressive tree mortality and associated NSC storage in Sitka-spruce (Picea sitchensis) trees dying under ecosystem-scale increases in seawater exposure in western Washington, USA. All trees exposed to seawater, because of monthly tidal intrusion, experienced declining crown foliage during the sampling period, and individuals with a lower percentage of live foliated crown (PLFC) died faster. Tree PLFC was strongly correlated with subsurface salinity and needle ion contents. Total NSC concentrations in trees declined remarkably with crown decline, and reached extremely low levels at tree death (2.4% and 1.6% in...
Columbia River water elevations and flows in the Hanford Reach affect the environment and facilit... more Columbia River water elevations and flows in the Hanford Reach affect the environment and facilities along the shoreline, including movement of contaminants in groundwater, fish habitat, and infrastructure subject to flooding. This report describes the hydraulic simulation of hypothetical flood flows using the best available topographic and bathymetric data for the Hanford Reach and the Modular Aquatic Simulation System in 1 Dimension (MASS1) hydrodynamic model. The MASS1 model of the Hanford Reach was previously calibrated to field measurements of water surface elevations. The current model setup can be used for other studies of flow, water levels, and temperature in the Reach. The existing MASS1 channel geometry and roughness and other model configuration inputs for the Hanford Reach were used for this study, and previous calibration and validation results for the model are reprinted here for reference. The flood flows for this study were simulated by setting constant flow rates obtained from the U.S. Army Corps of Engineers (USACE) for the Columbia, Snake, and Yakima Rivers, and a constant water level at McNary Dam, and then running the model to steady state. The discharge levels simulated were all low-probability events; for example, a 100-year flood is one that would occur on average every 100 years, or put another way, in any given year there is a 1% chance that a discharge of that level or higher will occur. The simulated floods and their corresponding Columbia River discharges were 100-year (445,000 cfs), 500-year (520,000 cfs), and the USACE-defined Standard Project Flood (960,000 cfs). The resulting water levels from the steady-state floods can be viewed as "worst case" outcomes for the respective discharge levels. The MASS1 output for water surface elevations was converted to the North American Vertical Datum of 1988 and projected across the channel and land surface to enable mapping of the floodplain for each scenario. Floodplain maps show that for the 100-year and 500-year discharge levels, flooding is mainly confined to the topographic trench that is the river channel. The flooded area for the Standard Project Flood extends out of the channel area in some places, particularly in the 100-F Area. All of the output from the simulations have been archived and are available for future investigations in the Hanford Reach.
Recent experiments have shown that atmospheric radioxenon passing over a sampling site can be tra... more Recent experiments have shown that atmospheric radioxenon passing over a sampling site can be transported into the shallow subsurface by barometric pressure changes. The STOMP simulator is used to examine the impact of seven hydrologic/geologic parameters and water infiltration on the imprinting of radioxenon from a transient plume during two pressure scenarios. The maximum concentration of Xe at a depth of two meters and the time of maximum concentration at that depth were calculated for each parameter set and the most impactful parameters were identified.
We thank the following individuals for their assistance. Paul Thorne provided geology information... more We thank the following individuals for their assistance. Paul Thorne provided geology information from the EarthVision database; Mark Rockhold provided water level data and material property values and reviewed the manuscript; John P. McDonald provided additional water level data and helpful comments on their quality; and Duane Ward provided Figure 1.1. This study was supported by the U.S. Department of Energy under Contract DE-AC05-76RLO1830. This report is available in Portable Document Format (PDF) from the PNNL publications (a) external website. The electronic version contains hyperlinks to facilitate navigation between all cross-referenced material, including section headings, figures, tables, and references.
Runoff (streamflow) from Cold and Dry Creeks was studied as part of a larger effort to evaluate n... more Runoff (streamflow) from Cold and Dry Creeks was studied as part of a larger effort to evaluate natural recharge to the Hanford Site. Natural recharge to the Site can take the form of direct infiltration of precipitation, lateral inflow of groundwater, and infiltration of streamflow. This report is concerned with the streamflow pathway and considers both historical runoff events and probabilistic extreme events. The observed runoff events were used to fit models of runoff generation, hydrograph shape, and channel infiltration. The models were then used to estimate the magnitude and location of potential recharge from several design storm events based on previous studies of maximum precipitation probability. The Cold and Dry Creek watersheds were divided into upper, middle, and lower basins, based on the U.S. Geological Survey stream gauge locations described by Dinicola (1997). The upper basins are the primary areas of runoff generation, while the middle and lower basins are areas of infiltration. Hourly weather data and 15-minute streamflow data from January 1995, a period of significant runoff, were used to evaluate the meteorological conditions of the relatively rare runoff generation and to fit and calibrate the models. Frozen ground and melting snow appeared to play important roles in the runoff generation. Hydrographs of Cold and Dry Creeks indicated rapid cresting of streamflows and subsequent rapid recession, with 8 distinct events in Cold Creek. For each runoff event, the duration, volume, and volume of the causative precipitation were tabulated. Curve numbers were computed using the Soil Conservation Service method. A linear relationship between precipitation duration and streamflow duration was also derived. The curve numbers and duration relationship were subsequently used to estimate runoff and hydrograph shape from the design storms of maximum precipitation. A firstorder decay model was fit to the observed streamflows at the upper and lower Cold Creek gauges and used to estimate the spatial pattern of infiltration of streamflow (recharge) resulting from the design storms. The double-triangle hydrograph model was also fit to the data and used to complete the characterization of runoff from the design storms. Four hypothetical rainfall events (design storms) were used to drive the runoff and infiltration models: 1) 4.6 inches over 6 hours, 2) 1.61 inches over 24 hours, 3) 2.16 inches over 3 days, and 4) 2.71 inches over 7 days. The first value is the "probable maximum precipitation" from Skaggs and Walters (1981), and the latter three values from Wigmosta and Guensch (2005) correspond to a return period of 100 years. For comparison, the largest rainfall event during January 1995 was 1.02 inches over approximately 3 days. Combined Cold and Dry Creek recharge volumes for the 100-year rainfall events were 7,700 ac-ft, 11,700 ac-ft, and 15,900 ac-ft, respectively. These recharge volumes are 7 to 14 times the average annual recharge rate for surface runoff estimated by Dinicola (1997), and fall between two estimates of direct recharge from infiltrating rainfall and snowmelt for the entire Hanford Site: 6,680 ac-ft/y (Fayer and Walters 1995) and 14,467 ac-ft/y (Jacobsen and Freshley 1990). In Cold Creek, simulated streamflow and recharge volumes were largest just above the lower gage. In Dry Creek, simulated runoff volumes were largest at the upper gage, and recharge volumes are greatest in the ponding area downstream from the lower gage.
I’ve been waiting a long time to write this story and I’m sure that all of you floodies have want... more I’ve been waiting a long time to write this story and I’m sure that all of you floodies have wanted to read this for an equally long time. After a congressional roller coaster ride during late winter and early spring, it finally happened. On March 25th Congress passed H.R. 146: The Omnibus Public Land Management Act of 2009, and on March 30th President Obama signed the bill into law. There will be an Ice Age Floods National Geologic Trail as a unit of the National Park System! The actual process of passing this major piece of legislation still makes my head swim. In a nutshell, over 160 bills, including our Floods Trail bill, that had been bottled up at various points in the legislative process, were packaged together in the Senate and eventually added as an amendment to another bill that had already been considered by the House of Representatives. Congressional procedures are such that this process avoided the possibility of further delay and the House approved the Senate’s amendme...
Columbia River water elevations and flows in the Hanford Reach affect the environment and facilit... more Columbia River water elevations and flows in the Hanford Reach affect the environment and facilities along the shoreline, including movement of contaminants in groundwater, fish habitat, and infrastructure subject to flooding. This report describes the hydraulic simulation of hypothetical flood flows using the best available topographic and bathymetric data for the Hanford Reach and the Modular Aquatic Simulation System in 1 Dimension (MASS1) hydrodynamic model. The MASS1 model of the Hanford Reach was previously calibrated to field measurements of water surface elevations. The current model setup can be used for other studies of flow, water levels, and temperature in the Reach. The existing MASS1 channel geometry and roughness and other model configuration inputs for the Hanford Reach were used for this study, and previous calibration and validation results for the model are reprinted here for reference. The flood flows for this study were simulated by setting constant flow rates obtained from the U.S. Army Corps of Engineers (USACE) for the Columbia, Snake, and Yakima Rivers, and a constant water level at McNary Dam, and then running the model to steady state. The discharge levels simulated were all low-probability events; for example, a 100-year flood is one that would occur on average every 100 years, or put another way, in any given year there is a 1% chance that a discharge of that level or higher will occur. The simulated floods and their corresponding Columbia River discharges were 100-year (445,000 cfs), 500-year (520,000 cfs), and the USACE-defined Standard Project Flood (960,000 cfs). The resulting water levels from the steady-state floods can be viewed as "worst case" outcomes for the respective discharge levels. The MASS1 output for water surface elevations was converted to the North American Vertical Datum of 1988 and projected across the channel and land surface to enable mapping of the floodplain for each scenario. Floodplain maps show that for the 100-year and 500-year discharge levels, flooding is mainly confined to the topographic trench that is the river channel. The flooded area for the Standard Project Flood extends out of the channel area in some places, particularly in the 100-F Area. All of the output from the simulations have been archived and are available for future investigations in the Hanford Reach.
Three-dimensional variably saturated flow and multicomponent biogeochemical reactive transport mo... more Three-dimensional variably saturated flow and multicomponent biogeochemical reactive transport modeling, based on published and newly generated data, is used to better understand the interplay of hydrology, geochemistry, and biology controlling the cycling of carbon, nitrogen, oxygen, iron, sulfur, and uranium in a shallow floodplain. In this system, aerobic respiration generally maintains anoxic groundwater below an oxic vadose zone until seasonal snowmelt-driven water table peaking transports dissolved oxygen (DO) and nitrate from the vadose zone into the alluvial aquifer. The response to this perturbation is localized due to distinct physico-biogeochemical environments and relatively long time scales for transport through the floodplain aquifer and vadose zone. Naturally reduced zones (NRZs) containing sediments higher in organic matter, iron sulfides, and non-crystalline U(IV) rapidly consume DO and nitrate to maintain anoxic conditions, yielding Fe(II) from FeS oxidative dissol...
Field-scale biostimulation and desorption tracer experiments conducted in a uranium (U) contamina... more Field-scale biostimulation and desorption tracer experiments conducted in a uranium (U) contaminated, shallow alluvial aquifer have provided insight into the coupling of microbiology, biogeochemistry, and hydrogeology that control U mobility in the subsurface. Initial experiments successfully tested the concept that Fe-reducing bacteria such as Geobacter sp. could enzymatically reduce soluble U(VI) to insoluble U(IV) during in situ electron donor amendment (Anderson et al., 2003; Williams et al., 2011). In parallel, in situ desorption tracer tests using bicarbonate amendment demonstrated rate-limited U(VI) desorption (Fox et al., 2012). These results and prior laboratory studies underscored the importance of enzymatic U(VI)-reduction and suggested the ability to combine desorption and bioreduction of U(VI). Here we report the results of a new field experiment in which bicarbonate-promoted uranium desorption and acetate amendment were combined and compared to an acetate amendment-only experiment in the same experimental plot. Results confirm that bicarbonate amendment to alluvial aquifer sediments desorbs U(VI) and increases the abundance of Ca-uranyl-carbonato complexes. At the same time, the rate of acetate-promoted enzymatic U(VI) reduction was greater in the presence of added bicarbonate in spite of the increased dominance of Ca-uranyl-carbonato aqueous complexes. A model-simulated peak rate of U(VI) reduction was ~3.8 times higher during acetate-bicarbonate treatment than under acetate-only conditions. Lack of consistent differences in microbial community structure between acetate-bicarbonate and acetate-only treatments suggest that a significantly higher rate of U(VI) reduction in the bicarbonate-impacted sediment may be due to a higher intrinsic rate of microbial reduction induced by elevated concentrations of the bicarbonate oxyanion. The findings indicate that bicarbonate amendment may be useful in improving the engineered bioremediation of uranium in aquifers.
advised the author on PNNL document requirements. Bill Perkins/Hydrology provided the first draft... more advised the author on PNNL document requirements. Bill Perkins/Hydrology provided the first draft of the document class file as well as many helpful examples and valuable L A T E X expertise.
Sea-level rise is one of the most critical challenges facing coastal ecosystems under climate cha... more Sea-level rise is one of the most critical challenges facing coastal ecosystems under climate change. Observations of elevated tree mortality in global coastal forests are increasing, but important knowledge gaps persist concerning the mechanism of salinity stress-induced nonhalophytic tree mortality. We monitored progressive mortality and associated gas exchange and hydraulic shifts in Sitka-spruce (Picea sitchensis) trees located within a salinity gradient under an ecosystem-scale change of seawater exposure in Washington State, USA. Percentage of live foliated crown (PLFC) decreased and tree mortality increased with increasing soil salinity during the study period. A strong reduction in gas exchange and xylem hydraulic conductivity (Ks) occurred during tree death, with an increase in the percentage loss of conductivity (PLC) and turgor loss point (πtlp). Hydraulic and osmotic shifts reflected that hydraulic function declined from seawater exposure, and dying trees were unable to ...
Increasing seawater exposure is causing mortality of coastal forests, yet the physiological respo... more Increasing seawater exposure is causing mortality of coastal forests, yet the physiological response associated with seawater-induced tree mortality, particularly in non-halophytes, is poorly understood. We investigated the shifts in carbon and nitrogen (N) metabolism of mature Sitka-spruce trees that were dying after an ecosystem-scale manipulation of tidal seawater exposure. Soil porewater salinity and foliar ion concentrations increased after seawater exposure and were strongly correlated with the percentage of live foliated crown (PLFC; e.g., crown ‘greenness’, a measure of progression to death). Co-occurring with decreasing PLFC was decreasing photosynthetic capacity, N-investment into photosynthesis, N-resorption efficiency and non-structural carbohydrate (soluble sugars and starch) concentrations, with the starch reserves depleted to near zero when PLFC dropped below 5%. Combined with declining PLFC, these changes subsequently decreased total carbon gain and thus exacerbated ...
Increasing sea levels associated with climate change threaten the survival of coastal forests, ye... more Increasing sea levels associated with climate change threaten the survival of coastal forests, yet the mechanisms by which seawater exposure causes tree death remain poorly understood. Despite the potentially crucial role of nonstructural carbohydrate (NSC) reserves in tree survival, their dynamics in the process of death under seawater exposure are unknown. Here we monitored progressive tree mortality and associated NSC storage in Sitka-spruce (Picea sitchensis) trees dying under ecosystem-scale increases in seawater exposure in western Washington, USA. All trees exposed to seawater, because of monthly tidal intrusion, experienced declining crown foliage during the sampling period, and individuals with a lower percentage of live foliated crown (PLFC) died faster. Tree PLFC was strongly correlated with subsurface salinity and needle ion contents. Total NSC concentrations in trees declined remarkably with crown decline, and reached extremely low levels at tree death (2.4% and 1.6% in...
Columbia River water elevations and flows in the Hanford Reach affect the environment and facilit... more Columbia River water elevations and flows in the Hanford Reach affect the environment and facilities along the shoreline, including movement of contaminants in groundwater, fish habitat, and infrastructure subject to flooding. This report describes the hydraulic simulation of hypothetical flood flows using the best available topographic and bathymetric data for the Hanford Reach and the Modular Aquatic Simulation System in 1 Dimension (MASS1) hydrodynamic model. The MASS1 model of the Hanford Reach was previously calibrated to field measurements of water surface elevations. The current model setup can be used for other studies of flow, water levels, and temperature in the Reach. The existing MASS1 channel geometry and roughness and other model configuration inputs for the Hanford Reach were used for this study, and previous calibration and validation results for the model are reprinted here for reference. The flood flows for this study were simulated by setting constant flow rates obtained from the U.S. Army Corps of Engineers (USACE) for the Columbia, Snake, and Yakima Rivers, and a constant water level at McNary Dam, and then running the model to steady state. The discharge levels simulated were all low-probability events; for example, a 100-year flood is one that would occur on average every 100 years, or put another way, in any given year there is a 1% chance that a discharge of that level or higher will occur. The simulated floods and their corresponding Columbia River discharges were 100-year (445,000 cfs), 500-year (520,000 cfs), and the USACE-defined Standard Project Flood (960,000 cfs). The resulting water levels from the steady-state floods can be viewed as "worst case" outcomes for the respective discharge levels. The MASS1 output for water surface elevations was converted to the North American Vertical Datum of 1988 and projected across the channel and land surface to enable mapping of the floodplain for each scenario. Floodplain maps show that for the 100-year and 500-year discharge levels, flooding is mainly confined to the topographic trench that is the river channel. The flooded area for the Standard Project Flood extends out of the channel area in some places, particularly in the 100-F Area. All of the output from the simulations have been archived and are available for future investigations in the Hanford Reach.
Recent experiments have shown that atmospheric radioxenon passing over a sampling site can be tra... more Recent experiments have shown that atmospheric radioxenon passing over a sampling site can be transported into the shallow subsurface by barometric pressure changes. The STOMP simulator is used to examine the impact of seven hydrologic/geologic parameters and water infiltration on the imprinting of radioxenon from a transient plume during two pressure scenarios. The maximum concentration of Xe at a depth of two meters and the time of maximum concentration at that depth were calculated for each parameter set and the most impactful parameters were identified.
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