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• 1. [Article] Where Is the Rain-on-Snow Zone in the West-Central Washington Cascades?: Monte Carlo Simulation of Large Storms in the Northwest

  Rain-on-snow (ROS) occurs when warm, wet air moves into latitudes and/or elevations having vulnerable snowpacks, where it can alter water inputs to infiltration, runoff and erosion. The Pacific Northwest ...

  Citation × Citation Citation Abstract Copy Title: Where Is the Rain-on-Snow Zone in the West-Central Washington Cascades?: Monte Carlo Simulation of Large Storms in the Northwest Author: Brunengo, Matthew John Year: 2012 Rain-on-snow (ROS) occurs when warm, wet air moves into latitudes and/or elevations having vulnerable snowpacks, where it can alter water inputs to infiltration, runoff and erosion. The Pacific Northwest is particularly susceptible: winter storms off the Pacific cause locally heavy rain plus snowmelt almost annually, and disastrous flooding and landsliding intermittently. In maritime mountainous terrain, the effects seem more likely and hydrologically important where warm rains and seasonal snowpacks are liable to coincide, in middle elevations. Several questions arise: (1) In the PNW, does ROS affect the long-term frequency and magnitude of water delivery to the ground, versus total precipitation (liquid and solid), during big storms? Where and how much? (2) If so, can we determine which elevations experience maximum hydrologic effects, the peak ROS zone? Probabilistic characteristics of ROS are difficult to establish because of geographic variability and sporadic occurrence: scattered stations and short observational records make quantitative frequency analysis difficult. These problems dictate a modeling approach, combining semi-random selection of storm properties with physical rules governing snow and water behavior during events. I created a simple computer program to perform Monte Carlo simulation of large storms over 1000 "years", generating realizations of snowpack and storm-weather conditions; in each event precipitation falls, snow accumulates and/or melts, and water moves to the ground. Frequency distributions are based on data from the Washington Cascades, and the model can be applied to specific sites or generalized elevations. Many of the data sets were based on observations at Stampede Pass, where high-quality measurements of weather and snow at the Cascade crest have been made since the 1940s. These data were used to inform the model, and to test its reliability with respect to the governing data distributions. In addition, data from ROS events at Stampede, and at research sites in southwest Oregon, were used to confirm that the model's deterministic calculations of snow accumulation, snowmelt, and percolation (yielding water available for runoff) adequately simulate conditions observed in the field. The Monte Carlo model was run for elevations ranging from 200 to 1500 m, each over a hypothetical millennium. Results indicate that the presence of snow in some storms reduces the amount of water reaching the ground. This occurred more often in highlands but also at middle and lower elevations, affecting the long-term frequency-magnitude relations across the landscape. In these conditions, the rain-gauges overestimate the amount of liquid water actually reaching the ground. For many storms, however, ROS enhances water reaching the ground, most significantly at elevations between ~500-1100 m. At lower and higher elevations, the water available for runoff exceeds precipitation in ~2% of events, but this proportion rises to ~20-30% at ~800 m. Other metrics (e.g., series statistics, exponential regression coefficients, frequency-magnitude factors) also indicate that this middle-elevation band (around ~800 m) experiences ROS most often and with greatest water available for runoff. Of the west-central Washington Cascades study region, about one-third to one-half the landscape is susceptible to significant ROS influence. These results indicate areas where ROS currently has the greatest hydrologic consequence on ecosystems and human works, and possibly the greatest sensitivity to changes in land-use and climate. Title: Where Is the Rain-on-Snow Zone in the West-Central Washington Cascades?: Monte Carlo Simulation of Large Storms in the Northwest Author: Brunengo, Matthew John Year: 2012 Rain-on-snow (ROS) occurs when warm, wet air moves into latitudes and/or elevations having vulnerable snowpacks, where it can alter water inputs to infiltration, runoff and erosion. The Pacific Northwest is particularly susceptible: winter storms off the Pacific cause locally heavy rain plus snowmelt almost annually, and disastrous flooding and landsliding intermittently. In maritime mountainous terrain, the effects seem more likely and hydrologically important where warm rains and seasonal snowpacks are liable to coincide, in middle elevations. Several questions arise: (1) In the PNW, does ROS affect the long-term frequency and magnitude of water delivery to the ground, versus total precipitation (liquid and solid), during big storms? Where and how much? (2) If so, can we determine which elevations experience maximum hydrologic effects, the peak ROS zone? Probabilistic characteristics of ROS are difficult to establish because of geographic variability and sporadic occurrence: scattered stations and short observational records make quantitative frequency analysis difficult. These problems dictate a modeling approach, combining semi-random selection of storm properties with physical rules governing snow and water behavior during events. I created a simple computer program to perform Monte Carlo simulation of large storms over 1000 "years", generating realizations of snowpack and storm-weather conditions; in each event precipitation falls, snow accumulates and/or melts, and water moves to the ground. Frequency distributions are based on data from the Washington Cascades, and the model can be applied to specific sites or generalized elevations. Many of the data sets were based on observations at Stampede Pass, where high-quality measurements of weather and snow at the Cascade crest have been made since the 1940s. These data were used to inform the model, and to test its reliability with respect to the governing data distributions. In addition, data from ROS events at Stampede, and at research sites in southwest Oregon, were used to confirm that the model's deterministic calculations of snow accumulation, snowmelt, and percolation (yielding water available for runoff) adequately simulate conditions observed in the field. The Monte Carlo model was run for elevations ranging from 200 to 1500 m, each over a hypothetical millennium. Results indicate that the presence of snow in some storms reduces the amount of water reaching the ground. This occurred more often in highlands but also at middle and lower elevations, affecting the long-term frequency-magnitude relations across the landscape. In these conditions, the rain-gauges overestimate the amount of liquid water actually reaching the ground. For many storms, however, ROS enhances water reaching the ground, most significantly at elevations between ~500-1100 m. At lower and higher elevations, the water available for runoff exceeds precipitation in ~2% of events, but this proportion rises to ~20-30% at ~800 m. Other metrics (e.g., series statistics, exponential regression coefficients, frequency-magnitude factors) also indicate that this middle-elevation band (around ~800 m) experiences ROS most often and with greatest water available for runoff. Of the west-central Washington Cascades study region, about one-third to one-half the landscape is susceptible to significant ROS influence. These results indicate areas where ROS currently has the greatest hydrologic consequence on ecosystems and human works, and possibly the greatest sensitivity to changes in land-use and climate. Close

• 2. [Article] Water Supply, Demand, and Quality Indicators for Assessing the Spatial Distribution of Water Resource Vulnerability in the Columbia River Basin

  We investigated water resource vulnerability in the US portion of the Columbia River basin (CRB) using multiple indicators representing water supply, water demand, and water quality. Based on the US county ...

  Citation × Citation Citation Abstract Copy Title: Water Supply, Demand, and Quality Indicators for Assessing the Spatial Distribution of Water Resource Vulnerability in the Columbia River Basin Author: Chang, Heejun, Jung, Il-Won, Strecker, Angela L., Wise, Daniel, Lafrenz, Martin, Shandas, Vivek, Moradkhani, Hamid, Yeakley, J. Alan, Pan, Yangdong, Bean, Robert Allen, Johnson, Gunnar, Psaris, Mike Year: 2013 We investigated water resource vulnerability in the US portion of the Columbia River basin (CRB) using multiple indicators representing water supply, water demand, and water quality. Based on the US county scale, spatial analysis was conducted using various biophysical and socio-economic indicators that control water vulnerability. Water supply vulnerability and water demand vulnerability exhibited a similar spatial clustering of hotspots in areas where agricultural lands and variability of precipitation were high but dam storage capacity was low. The hotspots of water quality vulnerability were clustered around the main stem of the Columbia River where major population and agricultural centres are located. This multiple equal weight indicator approach confirmed that different drivers were associated with different vulnerability maps in the sub-basins of the CRB. Water quality variables are more important than water supply and water demand variables in the Willamette River basin, whereas water supply and demand variables are more important than water quality variables in the Upper Snake and Upper Columbia River basins. This result suggests that current water resources management and practices drive much of the vulnerability within the study area. The analysis suggests the need for increased coordination of water management across multiple levels of water governance to reduce water resource vulnerability in the CRB and a potentially different weighting scheme that explicitly takes into account the input of various water stakeholders. Title: Water Supply, Demand, and Quality Indicators for Assessing the Spatial Distribution of Water Resource Vulnerability in the Columbia River Basin Author: Chang, Heejun, Jung, Il-Won, Strecker, Angela L., Wise, Daniel, Lafrenz, Martin, Shandas, Vivek, Moradkhani, Hamid, Yeakley, J. Alan, Pan, Yangdong, Bean, Robert Allen, Johnson, Gunnar, Psaris, Mike Year: 2013 We investigated water resource vulnerability in the US portion of the Columbia River basin (CRB) using multiple indicators representing water supply, water demand, and water quality. Based on the US county scale, spatial analysis was conducted using various biophysical and socio-economic indicators that control water vulnerability. Water supply vulnerability and water demand vulnerability exhibited a similar spatial clustering of hotspots in areas where agricultural lands and variability of precipitation were high but dam storage capacity was low. The hotspots of water quality vulnerability were clustered around the main stem of the Columbia River where major population and agricultural centres are located. This multiple equal weight indicator approach confirmed that different drivers were associated with different vulnerability maps in the sub-basins of the CRB. Water quality variables are more important than water supply and water demand variables in the Willamette River basin, whereas water supply and demand variables are more important than water quality variables in the Upper Snake and Upper Columbia River basins. This result suggests that current water resources management and practices drive much of the vulnerability within the study area. The analysis suggests the need for increased coordination of water management across multiple levels of water governance to reduce water resource vulnerability in the CRB and a potentially different weighting scheme that explicitly takes into account the input of various water stakeholders. Close

• 3. [Article] Rock Glacier Surface Motion in Beacon Valley, Antarctica, from Synthetic-Aperture Radar Interferometry

  We present radar interferograms of rock glaciers in the Beacon Valley sector of the McMurdo Dry Valleys, in East Antarctica, as part of a comprehensive study of surface processes in the area. Due to the ...

  Citation × Citation Citation Abstract Copy Title: Rock Glacier Surface Motion in Beacon Valley, Antarctica, from Synthetic-Aperture Radar Interferometry Author: Fountain, Andrew G., Rignot, Eric, Hallet, Bernard Year: 2002 We present radar interferograms of rock glaciers in the Beacon Valley sector of the McMurdo Dry Valleys, in East Antarctica, as part of a comprehensive study of surface processes in the area. Due to the relative absence of net precipitation (snow) in this region and the stability of the surface, the rock glaciers maintain excellent coherence of the radar returns over several years. As a result, we obtain a spatially continuous surface velocity field with a precision of fractions of a millimeter per year. On distinct rock glaciers entering Beacon Valley, we find coherent velocity patterns, with peak velocities approaching 40 mm per year. The ice supply from these rock glaciers nourishes the central portion of Beacon Valley, where velocities are found to be vanishingly small, and partly compensates for mass losses induced by sublimation. This analysis is consistent with the tantalizing notion that Beacon Valley ice is the oldest on Earth. Title: Rock Glacier Surface Motion in Beacon Valley, Antarctica, from Synthetic-Aperture Radar Interferometry Author: Fountain, Andrew G., Rignot, Eric, Hallet, Bernard Year: 2002 We present radar interferograms of rock glaciers in the Beacon Valley sector of the McMurdo Dry Valleys, in East Antarctica, as part of a comprehensive study of surface processes in the area. Due to the relative absence of net precipitation (snow) in this region and the stability of the surface, the rock glaciers maintain excellent coherence of the radar returns over several years. As a result, we obtain a spatially continuous surface velocity field with a precision of fractions of a millimeter per year. On distinct rock glaciers entering Beacon Valley, we find coherent velocity patterns, with peak velocities approaching 40 mm per year. The ice supply from these rock glaciers nourishes the central portion of Beacon Valley, where velocities are found to be vanishingly small, and partly compensates for mass losses induced by sublimation. This analysis is consistent with the tantalizing notion that Beacon Valley ice is the oldest on Earth. Close

• 4. [Article] Soil Moisture Gradients and Controls on a Southern Appalachian Hillslope from Drought Through Recharge

  Soil moisture gradients along hillslopes in humid watersheds, although indicated by vegetation gradients and by studies using models, have been difficult to confirm empirically. While soil properties and ...

  Citation × Citation Citation Abstract Copy Title: Soil Moisture Gradients and Controls on a Southern Appalachian Hillslope from Drought Through Recharge Author: Yeakley, J. Alan, Swank, W. T., Swift, L. W., Hornberger, G. M., Shugart, H. H. Year: 1998 Soil moisture gradients along hillslopes in humid watersheds, although indicated by vegetation gradients and by studies using models, have been difficult to confirm empirically. While soil properties and topographic features are the two general physio-graphic factors controlling soil moisture on hillslopes, studies have shown conflicting results regarding which factor is more important. The relative importance of topographic and soil property controls was examined in an upland forested watershed at the Coweeta Hydrologic Laboratory in the southern Appalachian mountains. Soil moisture was measured along a hillslope transect with a mesic-to-xeric forest vegetation gradient over a period spanning precipitation extremes. The hillslope was transect instrumented with a time domain reflectometry (TDR) network at two depths. Soil moisture was measured during a severe autumn drought and subsequent winter precipitation recharge. In the upper soil depth (0-30 cm), moisture gradients persisted throughout the measurement period, and topography exerted dominant control. For the entire root zone (0-90 cm), soil moisture gradients were found only during drought. Control on soil moisture was due to both topography and storage before drought. During and after recharge, variations in soil texture and horizon distribution exerted dominant control on soil moisture content in the root zone (0-90 cm). These results indicate that topographic factors assert more control over hillslope soil moisture during drier periods as drainage progresses, while variations in soil water storage properties are more important during wetter periods. Hillslope soil moisture gradients in southern Appalachian watersheds appear to be restricted to upper soil layers, with deeper hillslope soil moisture gradients occurring only with sufficient drought. Title: Soil Moisture Gradients and Controls on a Southern Appalachian Hillslope from Drought Through Recharge Author: Yeakley, J. Alan, Swank, W. T., Swift, L. W., Hornberger, G. M., Shugart, H. H. Year: 1998 Soil moisture gradients along hillslopes in humid watersheds, although indicated by vegetation gradients and by studies using models, have been difficult to confirm empirically. While soil properties and topographic features are the two general physio-graphic factors controlling soil moisture on hillslopes, studies have shown conflicting results regarding which factor is more important. The relative importance of topographic and soil property controls was examined in an upland forested watershed at the Coweeta Hydrologic Laboratory in the southern Appalachian mountains. Soil moisture was measured along a hillslope transect with a mesic-to-xeric forest vegetation gradient over a period spanning precipitation extremes. The hillslope was transect instrumented with a time domain reflectometry (TDR) network at two depths. Soil moisture was measured during a severe autumn drought and subsequent winter precipitation recharge. In the upper soil depth (0-30 cm), moisture gradients persisted throughout the measurement period, and topography exerted dominant control. For the entire root zone (0-90 cm), soil moisture gradients were found only during drought. Control on soil moisture was due to both topography and storage before drought. During and after recharge, variations in soil texture and horizon distribution exerted dominant control on soil moisture content in the root zone (0-90 cm). These results indicate that topographic factors assert more control over hillslope soil moisture during drier periods as drainage progresses, while variations in soil water storage properties are more important during wetter periods. Hillslope soil moisture gradients in southern Appalachian watersheds appear to be restricted to upper soil layers, with deeper hillslope soil moisture gradients occurring only with sufficient drought. Close

• 5. [Article] Climate change impacts on maritime mountain snowpack in the Oregon Cascades

  This is the publisher’s final pdf. The published article is copyrighted by Copernicus Publications and can be found at: http://publications.copernicus.org/.

  Citation × Citation Citation Abstract Copy Title: Climate change impacts on maritime mountain snowpack in the Oregon Cascades Author: Sproles, E. A., Nolin, A.W., Rittger, K., Painter, T. H. This is the publisher’s final pdf. The published article is copyrighted by Copernicus Publications and can be found at: http://publications.copernicus.org/. Title: Climate change impacts on maritime mountain snowpack in the Oregon Cascades Author: Sproles, E. A., Nolin, A.W., Rittger, K., Painter, T. H. This is the publisher’s final pdf. The published article is copyrighted by Copernicus Publications and can be found at: http://publications.copernicus.org/. Close

• 6. [Article] A Multivariate Modeling Approach for Generating Ensemble Climatology Forcing for Hydrologic Applications

  Reliability and accuracy of the forcing data plays a vital role in the Hydrological Streamflow Prediction. Reliability of the forcing data leads to accurate predictions and ultimately reduction of uncertainty. ...

  Citation × Citation Citation Abstract Copy Title: A Multivariate Modeling Approach for Generating Ensemble Climatology Forcing for Hydrologic Applications Author: Khajehei, Sepideh Year: 2015 Reliability and accuracy of the forcing data plays a vital role in the Hydrological Streamflow Prediction. Reliability of the forcing data leads to accurate predictions and ultimately reduction of uncertainty. Currently, Numerical Weather Prediction (NWP) models are developing ensemble forecasts for various temporal and spatial scales. However, it is proven that the raw products of the NWP models may be biased at the basin scale; unlike model grid scale, depending on the size of the catchment. Due to the large space-time variability of precipitation, bias-correcting the ensemble forecasts has proven to be a challenging task. In recent years, Ensemble Pre-Processing (EPP), a statistical approach, has proven to be helpful in reduction of bias and generation of reliable forecast. The procedure is based on the bivariate probability distribution between observation and single-value precipitation forecasts. In the current work, we have applied and evaluated a Bayesian approach, based on the Copula density functions, to develop an ensemble precipitation forecasts from the conditional distribution of the single-value precipitation. Copula functions are the multivariate joint distribution of univariate marginal distributions and are capable of modeling the joint distribution of two variables with any level of correlation and dependency. The advantage of using Copulas, amongst others, includes its capability of modeling the joint distribution independent of the type of marginal distribution. In the present study, we have evaluated the capability of copula-based functions in EPP and comparison is made against an existing and commonly used procedure for same i.e. meta-Gaussian distribution. Monthly precipitation forecast from Climate Forecast System (CFS) and gridded observation from Parameter-elevation Relationships on Independent Slopes Model (PRISM) have been utilized to create ensemble pre-processed precipitation over three sub-basins in the western USA at 0.5-degree spatial resolution. The comparison has been made using both deterministic and probabilistic frameworks of evaluation. Across all the sub-basins and evaluation techniques, copula-based technique shows more reliability and robustness as compared to the meta-Gaussian approach. Title: A Multivariate Modeling Approach for Generating Ensemble Climatology Forcing for Hydrologic Applications Author: Khajehei, Sepideh Year: 2015 Reliability and accuracy of the forcing data plays a vital role in the Hydrological Streamflow Prediction. Reliability of the forcing data leads to accurate predictions and ultimately reduction of uncertainty. Currently, Numerical Weather Prediction (NWP) models are developing ensemble forecasts for various temporal and spatial scales. However, it is proven that the raw products of the NWP models may be biased at the basin scale; unlike model grid scale, depending on the size of the catchment. Due to the large space-time variability of precipitation, bias-correcting the ensemble forecasts has proven to be a challenging task. In recent years, Ensemble Pre-Processing (EPP), a statistical approach, has proven to be helpful in reduction of bias and generation of reliable forecast. The procedure is based on the bivariate probability distribution between observation and single-value precipitation forecasts. In the current work, we have applied and evaluated a Bayesian approach, based on the Copula density functions, to develop an ensemble precipitation forecasts from the conditional distribution of the single-value precipitation. Copula functions are the multivariate joint distribution of univariate marginal distributions and are capable of modeling the joint distribution of two variables with any level of correlation and dependency. The advantage of using Copulas, amongst others, includes its capability of modeling the joint distribution independent of the type of marginal distribution. In the present study, we have evaluated the capability of copula-based functions in EPP and comparison is made against an existing and commonly used procedure for same i.e. meta-Gaussian distribution. Monthly precipitation forecast from Climate Forecast System (CFS) and gridded observation from Parameter-elevation Relationships on Independent Slopes Model (PRISM) have been utilized to create ensemble pre-processed precipitation over three sub-basins in the western USA at 0.5-degree spatial resolution. The comparison has been made using both deterministic and probabilistic frameworks of evaluation. Across all the sub-basins and evaluation techniques, copula-based technique shows more reliability and robustness as compared to the meta-Gaussian approach. Close

• 7. [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

• 8. [Article] Streamflow Modeling of Johnson Creek Subwatersheds Using the Precipitation Runoff Modeling System

  Johnson Creek, in the Portland, Oregon metropolitan region, has several pollutants on the U.S. Environmental Protection Agency’s (EPA) 303(d) list including excess heat, low dissolved oxygen, and harmful ...

  Citation × Citation Citation Abstract Copy Title: Streamflow Modeling of Johnson Creek Subwatersheds Using the Precipitation Runoff Modeling System Author: Malone, Theophilus M Year: 2014 Johnson Creek, in the Portland, Oregon metropolitan region, has several pollutants on the U.S. Environmental Protection Agency’s (EPA) 303(d) list including excess heat, low dissolved oxygen, and harmful bacteria. Understanding streamflow response to precipitation events is an important component to evaluating water quality trends and calculating the Total Maximum Daily Load (TMDL) for pollutants of concern. Investigating the streamflow-precipitation relationship on the subwatershed scale can give insight to the hydrologic response of a given watershed. However, developing rating curves for several subwatersheds can be cost and time prohibitive. The objective of this project was to develop a hydrologic model using the Precipitation Runoff Modeling System (PRMS), developed by the United States Geological Survey (USGS) to validate streamflow estimates for subwatersheds lacking a significant period of record. ESRI’s ArcMap, a geographic information system (GIS), was used to characterize the target drainage basins and extract basin-specific parameters for upper watersheds of Johnson Creek. The Johnson Creek Upper Watershed (JCUW) model was calibrated to an existing streamflow gage at Regner Road, in Gresham, Oregon. Calibrated parameters were substituted into a second PRMS model characterizing the Sunshine Creek Subwatershed, which lies within the JCUW. The Sunshine Creek model was used to validate a flow time-series derived from a pressure transducer and a rating curve. Title: Streamflow Modeling of Johnson Creek Subwatersheds Using the Precipitation Runoff Modeling System Author: Malone, Theophilus M Year: 2014 Johnson Creek, in the Portland, Oregon metropolitan region, has several pollutants on the U.S. Environmental Protection Agency’s (EPA) 303(d) list including excess heat, low dissolved oxygen, and harmful bacteria. Understanding streamflow response to precipitation events is an important component to evaluating water quality trends and calculating the Total Maximum Daily Load (TMDL) for pollutants of concern. Investigating the streamflow-precipitation relationship on the subwatershed scale can give insight to the hydrologic response of a given watershed. However, developing rating curves for several subwatersheds can be cost and time prohibitive. The objective of this project was to develop a hydrologic model using the Precipitation Runoff Modeling System (PRMS), developed by the United States Geological Survey (USGS) to validate streamflow estimates for subwatersheds lacking a significant period of record. ESRI’s ArcMap, a geographic information system (GIS), was used to characterize the target drainage basins and extract basin-specific parameters for upper watersheds of Johnson Creek. The Johnson Creek Upper Watershed (JCUW) model was calibrated to an existing streamflow gage at Regner Road, in Gresham, Oregon. Calibrated parameters were substituted into a second PRMS model characterizing the Sunshine Creek Subwatershed, which lies within the JCUW. The Sunshine Creek model was used to validate a flow time-series derived from a pressure transducer and a rating curve. Close

• 9. [Article] Subsurface flow of a forested riparian area in the Oregon coast range

  This study was undertaken to gain further understanding of the subsurface hydrology for a stream-adjacent riparian area in Western Oregon's Coast Range. Spatial and temporal fluctuations of the free water surface ...

  Citation × Citation Citation Abstract Copy Title: Subsurface flow of a forested riparian area in the Oregon coast range Author: Reiter, Maryanne This study was undertaken to gain further understanding of the subsurface hydrology for a stream-adjacent riparian area in Western Oregon's Coast Range. Spatial and temporal fluctuations of the free water surface of a toeslope, adjacent riparian area, and stream channel in a forested terrace reach were monitored over a period of one year. A total of 27 piezometers were installed (nine in each of three transects established perpendicular to the stream) in a stream-adjacent terrace and hillslope. These piezometers were monitored from September 26, 1989 to July 25, 1990. Results indicate that the direction of flow within a forested terrace can vary throughout the year. During the drier months of September and October, flow direction was generally towards the stream. However, by November the direction of flow for those areas closest to the stream had begun to change. In some cases the direction of flow changed up to 180° from the September direction. The location of influent/effluent zones along the stream (i.e., zones along the stream where the terrace has a lower or higher hydraulic head than the stream, respectively) also varied throughout the year. During October, 1989 the furthest upvalley stream-adjacent piezometer had hydraulic heads greater than the stream for the entire month, while two other stream adjacent piezometers did not. During normal precipitation in January, 1990 both furthest upvalley and the middle stream-adjacent piezometers had hydraulic heads greater than the stream for the entire month. By July, 1990 only the middle stream-adjacent piezometer had a hydraulic head greater than the stream for the entire month, while the furthest upvalley piezometer had a higher head for 33% of the month and the hydraulic head of furthest downvalley piezometer never exceeded that of the stream. For the Deer Creek study site, subsurface velocities were estimated to be in the range of 10-8 to 10-11 m/s resulting in a 3.8 year minimum travel time for storm water to reach the stream. Thus, soil matrix velocities using the Darcy equation were not sufficient to generate stormflow. However, no overland flow was observed during storm events, indicating that alternative subsurface flow pathways, such as macrochannels, are being utilized. Previous research has suggested that the release of water from terrace storage in small headwater streams is no.t sufficient to maintain baseflow. The results of the Deer Creek study support this conclusion. Furthermore, the results of this study indicate that forested riparian areas are hydrologically complex with respect to both space and time and that oversimplification of these systems may lead to misinterpretation of other processes associated with subsurface water dynamics. Title: Subsurface flow of a forested riparian area in the Oregon coast range Author: Reiter, Maryanne This study was undertaken to gain further understanding of the subsurface hydrology for a stream-adjacent riparian area in Western Oregon's Coast Range. Spatial and temporal fluctuations of the free water surface of a toeslope, adjacent riparian area, and stream channel in a forested terrace reach were monitored over a period of one year. A total of 27 piezometers were installed (nine in each of three transects established perpendicular to the stream) in a stream-adjacent terrace and hillslope. These piezometers were monitored from September 26, 1989 to July 25, 1990. Results indicate that the direction of flow within a forested terrace can vary throughout the year. During the drier months of September and October, flow direction was generally towards the stream. However, by November the direction of flow for those areas closest to the stream had begun to change. In some cases the direction of flow changed up to 180° from the September direction. The location of influent/effluent zones along the stream (i.e., zones along the stream where the terrace has a lower or higher hydraulic head than the stream, respectively) also varied throughout the year. During October, 1989 the furthest upvalley stream-adjacent piezometer had hydraulic heads greater than the stream for the entire month, while two other stream adjacent piezometers did not. During normal precipitation in January, 1990 both furthest upvalley and the middle stream-adjacent piezometers had hydraulic heads greater than the stream for the entire month. By July, 1990 only the middle stream-adjacent piezometer had a hydraulic head greater than the stream for the entire month, while the furthest upvalley piezometer had a higher head for 33% of the month and the hydraulic head of furthest downvalley piezometer never exceeded that of the stream. For the Deer Creek study site, subsurface velocities were estimated to be in the range of 10-8 to 10-11 m/s resulting in a 3.8 year minimum travel time for storm water to reach the stream. Thus, soil matrix velocities using the Darcy equation were not sufficient to generate stormflow. However, no overland flow was observed during storm events, indicating that alternative subsurface flow pathways, such as macrochannels, are being utilized. Previous research has suggested that the release of water from terrace storage in small headwater streams is no.t sufficient to maintain baseflow. The results of the Deer Creek study support this conclusion. Furthermore, the results of this study indicate that forested riparian areas are hydrologically complex with respect to both space and time and that oversimplification of these systems may lead to misinterpretation of other processes associated with subsurface water dynamics. Close

• 10. [Article] Characterization of hydrologic parameters and processes in shrink-swell clay soils

  Vertisols and other vertic-intergrade soils are found all over the globe, including many agricultural and urban areas. These soils are characterized by their cyclical shrinking and swelling behaviors, ...

  Citation × Citation Citation Abstract Copy Title: Characterization of hydrologic parameters and processes in shrink-swell clay soils Author: Stewart, Ryan D. Vertisols and other vertic-intergrade soils are found all over the globe, including many agricultural and urban areas. These soils are characterized by their cyclical shrinking and swelling behaviors, where bulk density and porosity distribution both vary as functions of time and/or soil moisture. In turn, alterations in physical soil parameters become manifest as crack networks, which open during the shrinkage phase and re-seal as the soil swells. As a consequence, when present these soils can significantly impact agriculture and infrastructure, and can act as a dominant control on the local hydrology. Therefore, understanding how water moves through and interacts with these soils is of utmost importance to ensure their proper utilization and management. This study had three objectives: 1) to identify the role of initial soil moisture on infiltration in a rigid (non-swelling) soil; 2) to quantify variation in the soil's hydraulic properties, using single-ring infiltration measurements taken in a vertic soil over a 1.5 year period; and 3) to build on these concepts to examine data from a set of instrumented field plots in a vertic soil located in the Secano Interior region of Chile. Significant findings of the study include 1) the development of a new formulation to describe a soil's wetting front potential (a measure of capillary pull) in terms of initial degree of saturation; 2) the creation of a simple correction to approximate the decrease of wetting front potential in wetter soils, thereby improving the accuracy of the traditional Green and Ampt sorptivity model in such conditions; 3) an equation to accurately estimate hydraulic parameters from short-duration infiltration tests, when steady-state conditions have not been realized; 4) a new theoretical model to estimate crack porosity as a function of soil moisture, which was developed based on the soil shrinkage curve; and 5) modification of the traditional two-term Philip infiltration model for use in vertic soils. The field study also showed that crack networks cause highly complex and non-linear wetting of the soil profile, with water simultaneously infiltrating from the soil surface and from the soil-crack interfaces; that cracks can seal at the surface while remaining open and hydraulically active below the surface, which indicates that surface-based monitoring alone may not be sufficient to predict water movement and soil response in vertic soils; and that the transition between infiltration and runoff may be strongly correlated with the cumulative amount of net precipitation that had reached the soil surface, so that cumulative amount of precipitation has the potential to be a simple yet accurate metric to predict runoff in vertic soils. These findings offer improved understanding of soil-water interactions in vertic soils, and reveal that very simple concepts underlie seemingly complex systems. As a result, the concepts and formulations developed in this study should allow for straightforward integration into other studies and models. Title: Characterization of hydrologic parameters and processes in shrink-swell clay soils Author: Stewart, Ryan D. Vertisols and other vertic-intergrade soils are found all over the globe, including many agricultural and urban areas. These soils are characterized by their cyclical shrinking and swelling behaviors, where bulk density and porosity distribution both vary as functions of time and/or soil moisture. In turn, alterations in physical soil parameters become manifest as crack networks, which open during the shrinkage phase and re-seal as the soil swells. As a consequence, when present these soils can significantly impact agriculture and infrastructure, and can act as a dominant control on the local hydrology. Therefore, understanding how water moves through and interacts with these soils is of utmost importance to ensure their proper utilization and management. This study had three objectives: 1) to identify the role of initial soil moisture on infiltration in a rigid (non-swelling) soil; 2) to quantify variation in the soil's hydraulic properties, using single-ring infiltration measurements taken in a vertic soil over a 1.5 year period; and 3) to build on these concepts to examine data from a set of instrumented field plots in a vertic soil located in the Secano Interior region of Chile. Significant findings of the study include 1) the development of a new formulation to describe a soil's wetting front potential (a measure of capillary pull) in terms of initial degree of saturation; 2) the creation of a simple correction to approximate the decrease of wetting front potential in wetter soils, thereby improving the accuracy of the traditional Green and Ampt sorptivity model in such conditions; 3) an equation to accurately estimate hydraulic parameters from short-duration infiltration tests, when steady-state conditions have not been realized; 4) a new theoretical model to estimate crack porosity as a function of soil moisture, which was developed based on the soil shrinkage curve; and 5) modification of the traditional two-term Philip infiltration model for use in vertic soils. The field study also showed that crack networks cause highly complex and non-linear wetting of the soil profile, with water simultaneously infiltrating from the soil surface and from the soil-crack interfaces; that cracks can seal at the surface while remaining open and hydraulically active below the surface, which indicates that surface-based monitoring alone may not be sufficient to predict water movement and soil response in vertic soils; and that the transition between infiltration and runoff may be strongly correlated with the cumulative amount of net precipitation that had reached the soil surface, so that cumulative amount of precipitation has the potential to be a simple yet accurate metric to predict runoff in vertic soils. These findings offer improved understanding of soil-water interactions in vertic soils, and reveal that very simple concepts underlie seemingly complex systems. As a result, the concepts and formulations developed in this study should allow for straightforward integration into other studies and models. Close