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• 1. [Article] Assessing Hydrologic and Water Quality Sensitivities to Precipitation Changes, Urban Growth and Land Management Using SWAT

  Precipitation changes and urban growth are two factors altering the state of water quality. Changes in precipitation will alter the amount and timing of flows, and the corresponding sediment and nutrient ...

  Citation × Citation Citation Abstract Copy Title: Assessing Hydrologic and Water Quality Sensitivities to Precipitation Changes, Urban Growth and Land Management Using SWAT Author: Psaris, Alexander Michael Year: 2014 Precipitation changes and urban growth are two factors altering the state of water quality. Changes in precipitation will alter the amount and timing of flows, and the corresponding sediment and nutrient dynamics. Meanwhile, densification associated with urban growth will create more impervious surfaces which will alter sediment and nutrient loadings. Land and water managers often rely on models to develop possible future scenarios and devise management responses to these projected changes. We use the Soil and Water Assessment Tool (SWAT) to assess the sensitivities of stream flow, sediment, and nutrient loads in two urbanizing watersheds in Northwest Oregon, USA to various climate and urbanization scenarios. We evaluate the spatial patterns climate change and urban growth will have on water, sediment and nutrient yields. We also identify critical source areas (CSAs) and investigate how implementation of vegetative filter strips (VFS) could ameliorate the effects of these changes. Our findings suggest that: 1) Water yield is tightly coupled to precipitation. 2) Large increases in winter and spring precipitation provide enough sub-surface storage to increase summertime water yields despite a moderate decrease in summer precipitation. 3) Expansion of urban areas increases surface runoff and has mixed effects on sediment and nutrients. 4) Implementation of VFS reduces pollutant loads helping overall watershed health. This research demonstrates the usefulness of SWAT in facilitating informed land and water management decisions. Title: Assessing Hydrologic and Water Quality Sensitivities to Precipitation Changes, Urban Growth and Land Management Using SWAT Author: Psaris, Alexander Michael Year: 2014 Precipitation changes and urban growth are two factors altering the state of water quality. Changes in precipitation will alter the amount and timing of flows, and the corresponding sediment and nutrient dynamics. Meanwhile, densification associated with urban growth will create more impervious surfaces which will alter sediment and nutrient loadings. Land and water managers often rely on models to develop possible future scenarios and devise management responses to these projected changes. We use the Soil and Water Assessment Tool (SWAT) to assess the sensitivities of stream flow, sediment, and nutrient loads in two urbanizing watersheds in Northwest Oregon, USA to various climate and urbanization scenarios. We evaluate the spatial patterns climate change and urban growth will have on water, sediment and nutrient yields. We also identify critical source areas (CSAs) and investigate how implementation of vegetative filter strips (VFS) could ameliorate the effects of these changes. Our findings suggest that: 1) Water yield is tightly coupled to precipitation. 2) Large increases in winter and spring precipitation provide enough sub-surface storage to increase summertime water yields despite a moderate decrease in summer precipitation. 3) Expansion of urban areas increases surface runoff and has mixed effects on sediment and nutrients. 4) Implementation of VFS reduces pollutant loads helping overall watershed health. This research demonstrates the usefulness of SWAT in facilitating informed land and water management decisions. Close

• 2. [Article] Effects of Runoff Sensitivity and Catchment Characteristics on Regional Actual Evapotranspiration Trends in the Conterminous US

  An understanding of the role of hydro-climatic and geographic regimes on regional actual evapotranspiration (AET) change is essential to improving our knowledge on predicting water availability in a changing ...

  Citation × Citation Citation Abstract Copy Title: Effects of Runoff Sensitivity and Catchment Characteristics on Regional Actual Evapotranspiration Trends in the Conterminous US Author: Jung, Il-Won, Chang, Heejun, Risley, John Year: 2013 An understanding of the role of hydro-climatic and geographic regimes on regional actual evapotranspiration (AET) change is essential to improving our knowledge on predicting water availability in a changing climate. This study investigates the relationship between AET change for a 60 year period (1951–2010) and the runoff sensitivity in 255 undisturbed catchments over the US. The runoff sensitivity to climate change is simply defined as the relative magnitude between runoff and precipitation changes with time. Runoff sensitivity can readily explain the conflicting directions of AET changes under similar precipitation change. Under increasing precipitation, AET decreases when runoff is increasing more rapidly than precipitation based on the water balance. Conversely, AET increases when runoff is decreasing more rapidly than precipitation. This result indicates that runoff sensitivity to climate change is a key factor for understanding regional water availability change at the catchment scale. In addition, a stepwise multiple regression analysis and a geographically weighted regression analysis show that the portion of evergreen forest and the mean elevation of a catchment may play a secondary role in the spatial pattern of the AET change, and the relative importance of such explanatory variables may change over space. Title: Effects of Runoff Sensitivity and Catchment Characteristics on Regional Actual Evapotranspiration Trends in the Conterminous US Author: Jung, Il-Won, Chang, Heejun, Risley, John Year: 2013 An understanding of the role of hydro-climatic and geographic regimes on regional actual evapotranspiration (AET) change is essential to improving our knowledge on predicting water availability in a changing climate. This study investigates the relationship between AET change for a 60 year period (1951–2010) and the runoff sensitivity in 255 undisturbed catchments over the US. The runoff sensitivity to climate change is simply defined as the relative magnitude between runoff and precipitation changes with time. Runoff sensitivity can readily explain the conflicting directions of AET changes under similar precipitation change. Under increasing precipitation, AET decreases when runoff is increasing more rapidly than precipitation based on the water balance. Conversely, AET increases when runoff is decreasing more rapidly than precipitation. This result indicates that runoff sensitivity to climate change is a key factor for understanding regional water availability change at the catchment scale. In addition, a stepwise multiple regression analysis and a geographically weighted regression analysis show that the portion of evergreen forest and the mean elevation of a catchment may play a secondary role in the spatial pattern of the AET change, and the relative importance of such explanatory variables may change over space. Close

• 3. [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

• 4. [Article] Watershed Response to Climate Change and Fire-Burns in the Upper Umatilla River Basin Using the Precipitation Runoff Modeling System

  This study provides an analysis of watershed response to climate change and forest fire impacts, to better understand the hydrologic budget and inform water management decisions for present and future ...

  Citation × Citation Citation Abstract Copy Title: Watershed Response to Climate Change and Fire-Burns in the Upper Umatilla River Basin Using the Precipitation Runoff Modeling System Author: Yazzie, Kimberly Crystal Year: 2016 This study provides an analysis of watershed response to climate change and forest fire impacts, to better understand the hydrologic budget and inform water management decisions for present and future needs. The study site is 2,365 km2, located in the upper Umatilla River Basin (URB) in northeastern Oregon. The Precipitation Runoff Modeling System, a distributed-parameter, physical-process watershed model, was used in this study. Model calibration yielded a Nash Sutcliffe Model Efficiency of 0.73 for both calibration (1995-2010) and validation (2010-2014) of daily streamflow. Ten Global Climate Models using Coupled Model Intercomparison Project Phase 5 experiments with Representative Concentration Pathways 4.5 and 8.5 (RCP), were used to observe hydrologic regime shifts in the 2020s, 2050s, and 2080s. Mean center timing of flow occurs earlier in the year in both pre- and post-fire conditions, where there are increased winter flows and decreased summer flows throughout the 21st century. Change in temperature and percent change in precipitation is more variable in the summer than winter increasing over time, with a slight decrease in winter precipitation in the 2080s in RCP 8.5. Temperature increases 1.6°C in RCP 4.5 and 3.3°C in RCP 8.5 by the end of the 21st century. The ratio of Snow Water Equivalent to Precipitation decreases 96% in the 2080s in RCP 8.5 before forest cover reduction, and decreases 90-99% after forest cover reduction. Potential basin recharge and the base-flow index are both sustained throughout the 21st century with slight declines before forest cover reduction, with an increase in basin recharge and increase in base-flows in the 2080s after fire-burns. However, the simulated sustained base-flows and area-weighted basin recharge in this study, do not take into account the complex geologic structure of the Columbia River Basalt Group (CRBG). A more robust characterization and simulation of URB aquifer recharge would involve coupling the PRMS model with a groundwater model in a future study. Although groundwater recharge in the CRBG in the URB is not well understood, the long-term decline of groundwater storage presents a serious environmental challenge for the Confederated Tribes of the Umatilla Indian Reservation and communities in the URB. Title: Watershed Response to Climate Change and Fire-Burns in the Upper Umatilla River Basin Using the Precipitation Runoff Modeling System Author: Yazzie, Kimberly Crystal Year: 2016 This study provides an analysis of watershed response to climate change and forest fire impacts, to better understand the hydrologic budget and inform water management decisions for present and future needs. The study site is 2,365 km2, located in the upper Umatilla River Basin (URB) in northeastern Oregon. The Precipitation Runoff Modeling System, a distributed-parameter, physical-process watershed model, was used in this study. Model calibration yielded a Nash Sutcliffe Model Efficiency of 0.73 for both calibration (1995-2010) and validation (2010-2014) of daily streamflow. Ten Global Climate Models using Coupled Model Intercomparison Project Phase 5 experiments with Representative Concentration Pathways 4.5 and 8.5 (RCP), were used to observe hydrologic regime shifts in the 2020s, 2050s, and 2080s. Mean center timing of flow occurs earlier in the year in both pre- and post-fire conditions, where there are increased winter flows and decreased summer flows throughout the 21st century. Change in temperature and percent change in precipitation is more variable in the summer than winter increasing over time, with a slight decrease in winter precipitation in the 2080s in RCP 8.5. Temperature increases 1.6°C in RCP 4.5 and 3.3°C in RCP 8.5 by the end of the 21st century. The ratio of Snow Water Equivalent to Precipitation decreases 96% in the 2080s in RCP 8.5 before forest cover reduction, and decreases 90-99% after forest cover reduction. Potential basin recharge and the base-flow index are both sustained throughout the 21st century with slight declines before forest cover reduction, with an increase in basin recharge and increase in base-flows in the 2080s after fire-burns. However, the simulated sustained base-flows and area-weighted basin recharge in this study, do not take into account the complex geologic structure of the Columbia River Basalt Group (CRBG). A more robust characterization and simulation of URB aquifer recharge would involve coupling the PRMS model with a groundwater model in a future study. Although groundwater recharge in the CRBG in the URB is not well understood, the long-term decline of groundwater storage presents a serious environmental challenge for the Confederated Tribes of the Umatilla Indian Reservation and communities in the URB. Close

• 5. [Article] Climate Change Effects and Water Vulnerability in the Molalla Pudding River Basin, Oregon, USA

  Water management plans are typically developed using historical data records and historical return periods for extreme events, such as floods or droughts. Since these analyses of return periods typically ...

  Citation × Citation Citation Abstract Copy Title: Climate Change Effects and Water Vulnerability in the Molalla Pudding River Basin, Oregon, USA Author: Wherry, Susan Amelia Year: 2012 Water management plans are typically developed using historical data records and historical return periods for extreme events, such as floods or droughts. Since these analyses of return periods typically assume a certain degree of stationarity (constant mean, standard deviation, distribution) in hydrologic variables, the potential future impacts of climate change are excluded. In developing water management plans, predicted changes to climate variables should be considered to evaluate the degree of non-stationarity that may exist in the future. In this way, regions most sensitive to climate change can be identified and managed appropriately. This study performed such a task by using predicted climate data that were downscaled from general circulation models (GCM) by regional climate models (RCM) to compare climate variables in the historical period of 1971-1998 to the future period of 2041-2068. The study evaluated the precipitation and minimum/maximum temperature data from five different GCM/RCM combinations: 1) CCSM/CRCM; 2) CCSM/WRFG; 3) CGCM3/CRCM; 4) CGCM3/WRFG; and 5) HadCM3/HRM3. The five datasets were then used to calculate drought indices and drive a calibrated PRMS model of the Molalla Pudding river basin in order to evaluate changes in droughts and streamflow. The predicted changes in droughts and streamflow were then evaluated with social/economic factors for twelve cities in the Molalla Pudding river basin by two different water vulnerability indices. The index values were used to determine a rank for each city that indicated its relative vulnerability to water scarcity as compared to the other cities. In this study, three out of the five datasets predicted increased precipitation (+97-115 mm/year) over the Molalla Pudding basin and the two datasets using the CCSM GCM data predicted either no change or slightly decreased precipitation (-60 mm/year) over the Molalla Pudding basin in 2041-2068. All datasets predicted increased minimum and maximum average temperature of +1.5°C and +1.4°C respectively, and all datasets displayed increasing trends in temperature. The drought indices predicted fewer drought events (-2.4 events) over 2041-2068 with no change in duration, and no change to the number of serious drought events over 2041-2068 but with increased durations (+1.9 months). Results from the hydrologic modeling predicted increased streamflow (+4-249 cfs) in four out of the five future datasets. Using the predicted changes in hydrologic variables and social/economic census data from 2000, two types of water vulnerability indices were calculated for the twelve cities of interest. The results suggested that cities in the western portion of the basin would be more susceptible to current and future water vulnerability due to high irrigation demands for water and high social vulnerability as determined by minority populations and higher poverty, while the small cities with less dependence on agriculture would be less vulnerable. Title: Climate Change Effects and Water Vulnerability in the Molalla Pudding River Basin, Oregon, USA Author: Wherry, Susan Amelia Year: 2012 Water management plans are typically developed using historical data records and historical return periods for extreme events, such as floods or droughts. Since these analyses of return periods typically assume a certain degree of stationarity (constant mean, standard deviation, distribution) in hydrologic variables, the potential future impacts of climate change are excluded. In developing water management plans, predicted changes to climate variables should be considered to evaluate the degree of non-stationarity that may exist in the future. In this way, regions most sensitive to climate change can be identified and managed appropriately. This study performed such a task by using predicted climate data that were downscaled from general circulation models (GCM) by regional climate models (RCM) to compare climate variables in the historical period of 1971-1998 to the future period of 2041-2068. The study evaluated the precipitation and minimum/maximum temperature data from five different GCM/RCM combinations: 1) CCSM/CRCM; 2) CCSM/WRFG; 3) CGCM3/CRCM; 4) CGCM3/WRFG; and 5) HadCM3/HRM3. The five datasets were then used to calculate drought indices and drive a calibrated PRMS model of the Molalla Pudding river basin in order to evaluate changes in droughts and streamflow. The predicted changes in droughts and streamflow were then evaluated with social/economic factors for twelve cities in the Molalla Pudding river basin by two different water vulnerability indices. The index values were used to determine a rank for each city that indicated its relative vulnerability to water scarcity as compared to the other cities. In this study, three out of the five datasets predicted increased precipitation (+97-115 mm/year) over the Molalla Pudding basin and the two datasets using the CCSM GCM data predicted either no change or slightly decreased precipitation (-60 mm/year) over the Molalla Pudding basin in 2041-2068. All datasets predicted increased minimum and maximum average temperature of +1.5°C and +1.4°C respectively, and all datasets displayed increasing trends in temperature. The drought indices predicted fewer drought events (-2.4 events) over 2041-2068 with no change in duration, and no change to the number of serious drought events over 2041-2068 but with increased durations (+1.9 months). Results from the hydrologic modeling predicted increased streamflow (+4-249 cfs) in four out of the five future datasets. Using the predicted changes in hydrologic variables and social/economic census data from 2000, two types of water vulnerability indices were calculated for the twelve cities of interest. The results suggested that cities in the western portion of the basin would be more susceptible to current and future water vulnerability due to high irrigation demands for water and high social vulnerability as determined by minority populations and higher poverty, while the small cities with less dependence on agriculture would be less vulnerable. Close

• 6. [Article] Effects of HRU Size on PRMS Performance in 30 Western U.S. Basins

  Semi-distributed hydrological models are often used for streamflow forecasting, hydrological climate change impact assessments, and other applications. In such models, basins are broken up into hydrologic ...

  Citation × Citation Citation Abstract Copy Title: Effects of HRU Size on PRMS Performance in 30 Western U.S. Basins Author: Steele, Madeline Olena Year: 2013 Semi-distributed hydrological models are often used for streamflow forecasting, hydrological climate change impact assessments, and other applications. In such models, basins are broken up into hydrologic response units (HRUs), which are assumed to have a relatively homogenous response to precipitation. HRUs are delineated in a variety of ways, and the procedure used may impact model performance. HRU delineation procedures have been researched, but it is still not clear how important these subdivision schemes are or which delineation methods are most effective. To start addressing this knowledge gap, this project investigated whether or not HRU size has a significant effect on streamflow simulation at the mouth of a watershed. To test this, 30 gaged, relatively unimpaired western U.S. basins were each modeled with 6 HRU sets of different sizes using the Precipitation Runoff Modeling System (PRMS). To isolate size as a variable, HRUs were delineated using stream catchments. For each basin, streams were defined with 6 different threshold levels, producing HRUs of differing sizes. Nineteen model parameters were derived for each HRU using nationally consistent GIS datasets, and all other model parameters were left at default values. Climate inputs were derived from a national 4-km2 gridded daily climate dataset. After calibration, 4 goodness-of-fit metrics were calculated for daily streamflow for each HRU set. Uncalibrated model performance was generally poor for a variety of reasons, but comparison of the models was still informative. Results for the 30 basins across the 6 HRU size classes showed that HRU size did not significantly impact model performance across all basins. However, in basins that had less total precipitation and higher elevation, sensitivity of model performance to HRU subdivision levels was slightly greater, though not significantly so. Findings indicate that, in most basins, little subdivision may be required for good model performance, allowing for desirable simplicity and fewer degrees of freedom without sacrificing runoff simulation accuracy. Title: Effects of HRU Size on PRMS Performance in 30 Western U.S. Basins Author: Steele, Madeline Olena Year: 2013 Semi-distributed hydrological models are often used for streamflow forecasting, hydrological climate change impact assessments, and other applications. In such models, basins are broken up into hydrologic response units (HRUs), which are assumed to have a relatively homogenous response to precipitation. HRUs are delineated in a variety of ways, and the procedure used may impact model performance. HRU delineation procedures have been researched, but it is still not clear how important these subdivision schemes are or which delineation methods are most effective. To start addressing this knowledge gap, this project investigated whether or not HRU size has a significant effect on streamflow simulation at the mouth of a watershed. To test this, 30 gaged, relatively unimpaired western U.S. basins were each modeled with 6 HRU sets of different sizes using the Precipitation Runoff Modeling System (PRMS). To isolate size as a variable, HRUs were delineated using stream catchments. For each basin, streams were defined with 6 different threshold levels, producing HRUs of differing sizes. Nineteen model parameters were derived for each HRU using nationally consistent GIS datasets, and all other model parameters were left at default values. Climate inputs were derived from a national 4-km2 gridded daily climate dataset. After calibration, 4 goodness-of-fit metrics were calculated for daily streamflow for each HRU set. Uncalibrated model performance was generally poor for a variety of reasons, but comparison of the models was still informative. Results for the 30 basins across the 6 HRU size classes showed that HRU size did not significantly impact model performance across all basins. However, in basins that had less total precipitation and higher elevation, sensitivity of model performance to HRU subdivision levels was slightly greater, though not significantly so. Findings indicate that, in most basins, little subdivision may be required for good model performance, allowing for desirable simplicity and fewer degrees of freedom without sacrificing runoff simulation accuracy. Close

• 7. [Article] Watershed Response to Climate Change and Fire-Burns in the Upper Umatilla River Basin, USA

  This study analyzed watershed response to climate change and forest fire impacts in the upper Umatilla River Basin (URB), Oregon, using the precipitation runoff modeling system. Ten global climate models ...

  Citation × Citation Citation Abstract Copy Title: Watershed Response to Climate Change and Fire-Burns in the Upper Umatilla River Basin, USA Author: Yazzie, Kimberly Crystal, Chang, Heejun Year: 2017 This study analyzed watershed response to climate change and forest fire impacts in the upper Umatilla River Basin (URB), Oregon, using the precipitation runoff modeling system. Ten global climate models using Coupled Intercomparison Project Phase 5 experiments with Representative Concentration Pathways (RCP) 4.5 and 8.5 were used to simulate the effects of climate and fire-burns on runoff behavior throughout the 21st century. We observed the center timing (CT) of flow, seasonal flows, snow water equivalent (SWE) and basin recharge. In the upper URB, hydrologic regime shifts from a snow-rain-dominated to rain-dominated basin. Ensemble mean CT occurs 27 days earlier in RCP 4.5 and 33 days earlier in RCP 8.5, in comparison to historic conditions (1980s) by the end of the 21st century. After forest cover reduction in the 2080s, CT occurs 35 days earlier in RCP 4.5 and 29 days earlier in RCP 8.5. The difference in mean CT after fire-burns may be due to projected changes in the individual climate model. Winter flow is projected to decline after forest cover reduction in the 2080s by 85% and 72% in RCP 4.5 and RCP 8.5, in comparison to 98% change in ensemble mean winter flows in the 2080s before forest cover reduction. The ratio of ensemble mean snow water equivalent to precipitation substantially decreases by 81% and 91% in the 2050s and 2080s before forest cover reduction and a decrease of 90% in RCP 4.5 and 99% in RCP 8.5 in the 2080s after fire-burns. Mean basin recharge is 10% and 14% lower in the 2080s before fire-burns and after fire-burns, and it decreases by 13% in RCP 4.5 and decreases 22% in RCP 8.5 in the 2080s in comparison to historical conditions. Mixed results for recharge after forest cover reduction suggest that an increase may be due to the size of burned areas, decreased canopy interception and less evaporation occurring at the watershed surface, increasing the potential for infiltration. The effects of fire on the watershed system are strongly indicated by a significant increase in winter seasonal flows and a slight reduction in summer flows. Findings from this study may improve adaptive management of water resources, flood control and the effects of fire on a watershed system. Title: Watershed Response to Climate Change and Fire-Burns in the Upper Umatilla River Basin, USA Author: Yazzie, Kimberly Crystal, Chang, Heejun Year: 2017 This study analyzed watershed response to climate change and forest fire impacts in the upper Umatilla River Basin (URB), Oregon, using the precipitation runoff modeling system. Ten global climate models using Coupled Intercomparison Project Phase 5 experiments with Representative Concentration Pathways (RCP) 4.5 and 8.5 were used to simulate the effects of climate and fire-burns on runoff behavior throughout the 21st century. We observed the center timing (CT) of flow, seasonal flows, snow water equivalent (SWE) and basin recharge. In the upper URB, hydrologic regime shifts from a snow-rain-dominated to rain-dominated basin. Ensemble mean CT occurs 27 days earlier in RCP 4.5 and 33 days earlier in RCP 8.5, in comparison to historic conditions (1980s) by the end of the 21st century. After forest cover reduction in the 2080s, CT occurs 35 days earlier in RCP 4.5 and 29 days earlier in RCP 8.5. The difference in mean CT after fire-burns may be due to projected changes in the individual climate model. Winter flow is projected to decline after forest cover reduction in the 2080s by 85% and 72% in RCP 4.5 and RCP 8.5, in comparison to 98% change in ensemble mean winter flows in the 2080s before forest cover reduction. The ratio of ensemble mean snow water equivalent to precipitation substantially decreases by 81% and 91% in the 2050s and 2080s before forest cover reduction and a decrease of 90% in RCP 4.5 and 99% in RCP 8.5 in the 2080s after fire-burns. Mean basin recharge is 10% and 14% lower in the 2080s before fire-burns and after fire-burns, and it decreases by 13% in RCP 4.5 and decreases 22% in RCP 8.5 in the 2080s in comparison to historical conditions. Mixed results for recharge after forest cover reduction suggest that an increase may be due to the size of burned areas, decreased canopy interception and less evaporation occurring at the watershed surface, increasing the potential for infiltration. The effects of fire on the watershed system are strongly indicated by a significant increase in winter seasonal flows and a slight reduction in summer flows. Findings from this study may improve adaptive management of water resources, flood control and the effects of fire on a watershed system. Close

• 8. [Article] Map-based Probabilistic Infinite Slope Analysis of the Stephens Creek Watershed, Portland, Oregon

  The Stephens Creek Watershed in southwest Portland, Oregon was chosen by the city as a pilot project for urban stream restoration efforts, and the infiltration of stormwater was identified as a potential ...

  Citation × Citation Citation Abstract Copy Title: Map-based Probabilistic Infinite Slope Analysis of the Stephens Creek Watershed, Portland, Oregon Author: Cole, Ryan Andrew Year: 2013 The Stephens Creek Watershed in southwest Portland, Oregon was chosen by the city as a pilot project for urban stream restoration efforts, and the infiltration of stormwater was identified as a potential restoration strategy. The Stephens Creek Watershed has historically been known to be unstable during high precipitation events (Burns, 1996), and the need to address the response of slope stability to anthropogenically-driven changing groundwater conditions is the focus of this study. Airborne light detection and ranging (LiDAR) and geotechnical data from the City of Portland were employed to create a high resolution (0.84 m2) physics-based probabilistic slope stability model for this watershed, using the map-based probabilistic infinite slope analysis program PISA-m (Haneberg, 2007). Best and worst case models were run using fully dry and fully saturated soil conditions, respectively. Model results indicate that 96.3% of the watershed area had a probability [less than or equal to] 0.25 that the slope factor of safety (FOS) was [less than or equal to] 1 for fully dry conditions, compared to 76.4% for fully saturated conditions. Areas that had a probability [greater than or equal to] 0.25 that the slope factor of safety (FOS) was [less than or equal to] 1 were found to occur mainly along cut/fill slopes as well as within the deeply incised canyons of Stephens Creek and its tributaries. An infiltration avoidance map was derived to define areas that appear to be unsuitable for infiltration. Based on these results, it is recommended that stormwater continues to be directed to existing sewer infrastructure and that the "storm water disconnect" restoration approach not be used by the city. Title: Map-based Probabilistic Infinite Slope Analysis of the Stephens Creek Watershed, Portland, Oregon Author: Cole, Ryan Andrew Year: 2013 The Stephens Creek Watershed in southwest Portland, Oregon was chosen by the city as a pilot project for urban stream restoration efforts, and the infiltration of stormwater was identified as a potential restoration strategy. The Stephens Creek Watershed has historically been known to be unstable during high precipitation events (Burns, 1996), and the need to address the response of slope stability to anthropogenically-driven changing groundwater conditions is the focus of this study. Airborne light detection and ranging (LiDAR) and geotechnical data from the City of Portland were employed to create a high resolution (0.84 m2) physics-based probabilistic slope stability model for this watershed, using the map-based probabilistic infinite slope analysis program PISA-m (Haneberg, 2007). Best and worst case models were run using fully dry and fully saturated soil conditions, respectively. Model results indicate that 96.3% of the watershed area had a probability [less than or equal to] 0.25 that the slope factor of safety (FOS) was [less than or equal to] 1 for fully dry conditions, compared to 76.4% for fully saturated conditions. Areas that had a probability [greater than or equal to] 0.25 that the slope factor of safety (FOS) was [less than or equal to] 1 were found to occur mainly along cut/fill slopes as well as within the deeply incised canyons of Stephens Creek and its tributaries. An infiltration avoidance map was derived to define areas that appear to be unsuitable for infiltration. Based on these results, it is recommended that stormwater continues to be directed to existing sewer infrastructure and that the "storm water disconnect" restoration approach not be used by the city. Close

• 9. [Article] Effects of Beaver Dams on Surface Water Flow During Storm Events in an Urban Landscape

  Urban land-use generally alters the hydrologic cycle, leading to changes in the natural flow regime of local streams. Runoff from impervious surfaces and routing of stormwater to streams causes urban streams ...

  Citation × Citation Citation Abstract Copy Title: Effects of Beaver Dams on Surface Water Flow During Storm Events in an Urban Landscape Author: Poor, Erin Year: 2017 Urban land-use generally alters the hydrologic cycle, leading to changes in the natural flow regime of local streams. Runoff from impervious surfaces and routing of stormwater to streams causes urban streams to respond quickly and more intensely to storm events-more so than then would be observed in a less urbanized landscape. The rapid pulse of water that is routed to streams during precipitation events can degrade the physical structure of the channel and alter water quality and habitat availability. To manage these common urban stream issues, agencies have been seeking alternative ways of restoring and enhancing resilience in urban stream networks within the constraints of existing infrastructure. One potential strategy may be to support beaver recolonization of urban streams. This is because beaver dam building activity has been found to attenuate streamflow in areas that have experienced minimal human impact. Currently, however, no studies have been published that examine how beaver dams affect stream flow in altered urban systems. This study seeks to determine if the presence of beaver dams and ponds in urban stream reaches in the Tualatin River basin, Oregon, modifies the stream’s response to storm events. Continuous surface water levels are being collected upstream and downstream of two beaver affected reaches in order to determine how the presence of dams and ponds affect the flow regime, and whether this more closely resembles a less degraded state. Title: Effects of Beaver Dams on Surface Water Flow During Storm Events in an Urban Landscape Author: Poor, Erin Year: 2017 Urban land-use generally alters the hydrologic cycle, leading to changes in the natural flow regime of local streams. Runoff from impervious surfaces and routing of stormwater to streams causes urban streams to respond quickly and more intensely to storm events-more so than then would be observed in a less urbanized landscape. The rapid pulse of water that is routed to streams during precipitation events can degrade the physical structure of the channel and alter water quality and habitat availability. To manage these common urban stream issues, agencies have been seeking alternative ways of restoring and enhancing resilience in urban stream networks within the constraints of existing infrastructure. One potential strategy may be to support beaver recolonization of urban streams. This is because beaver dam building activity has been found to attenuate streamflow in areas that have experienced minimal human impact. Currently, however, no studies have been published that examine how beaver dams affect stream flow in altered urban systems. This study seeks to determine if the presence of beaver dams and ponds in urban stream reaches in the Tualatin River basin, Oregon, modifies the stream’s response to storm events. Continuous surface water levels are being collected upstream and downstream of two beaver affected reaches in order to determine how the presence of dams and ponds affect the flow regime, and whether this more closely resembles a less degraded state. Close

• 10. [Article] Statistical Analysis of Stormwater Device Testing Protocols in Portland, Oregon

  Stormwater treatment is commonly performed with a combination of approaches including the utilization of natural systems and engineered devices. Before using a proprietary treatment instrument it is required ...

  Citation × Citation Citation Abstract Copy Title: Statistical Analysis of Stormwater Device Testing Protocols in Portland, Oregon Author: Kavianpour Isfahani, Zahra Year: 2013 Stormwater treatment is commonly performed with a combination of approaches including the utilization of natural systems and engineered devices. Before using a proprietary treatment instrument it is required to verify its performance and efficiency in reducing different pollution components including the TSS. Different states have developed strategies and regulations for accepting new instruments. In this thesis the stormwater management plan of the City of Portland, Oregon(2008), is analyzed in order to improve the current regulations. These rules apply to new technologies which are proposed by vendors to be used in Portland's stormwater treatment plans. Each requirement which should be met by the applying vendors is thoroughly analyzed followed by a comparison with the Stormwater management plan(2008)regulations of the state of Washington the so called Technology Assessment Plan-Ecology TAPE (Howie, 2011). Because of the similarities in the climate and land use between these two testing frameworks in order to evaluate the potential applicability of data submitted by vendors who had devices approved by Washington, to be utilized by Portland. The treatment of total suspended solids (TSS) is the focus of this thesis since it is central to the testing process and since most of the other pollutions are attached to TSS and will get treated if TSS is treated. The overall analysis shows that Portland adopts more restrictive requirements on the characterization of stormwater event samples to be treated by a technological instrument while Washington's restriction are more stringent on the efficiency of total suspended solid removal, in which it demands higher standards on the treatment of TSS compared to Portland's efficiency requirements. In order to study practical context in which regulations are administrated by Portland, rainfall data from 66 gauges covering the period of 1980-2011 was studied and the impacts of seasonality, land use, land form, periods of no rain before and after an event and Portland's Modified Performance line on the number of accepted rain events were analyzed. The results which were accepted by state of Washington were also compared with the results accepted by the city of Portland on Portland's Standard Performance line. Our seasonality study suggests that Portland's requirements are unnecessarily restrictive which results in the disqualification of many otherwise useful stormwater events, sometimes allowing no natural events to be available for testing in dry years. The analysis of land use showed that land use has no statistically significant impact on the concentration levels of TSS, thereby indicating that land use restrictions in the testing rules could be usefully relaxed. Decreasing the interevent no-rain period significantly increases the total number of events providing sufficient data to assess the performance of treatment facilities. We also showed that many more events become suitable for performance testing if events separated by one hours or less are considered a single, longer event. Finally we identified a statistical relationship between number of forecasted accepted stormwater events and the total average daily precipitation in a given year. Title: Statistical Analysis of Stormwater Device Testing Protocols in Portland, Oregon Author: Kavianpour Isfahani, Zahra Year: 2013 Stormwater treatment is commonly performed with a combination of approaches including the utilization of natural systems and engineered devices. Before using a proprietary treatment instrument it is required to verify its performance and efficiency in reducing different pollution components including the TSS. Different states have developed strategies and regulations for accepting new instruments. In this thesis the stormwater management plan of the City of Portland, Oregon(2008), is analyzed in order to improve the current regulations. These rules apply to new technologies which are proposed by vendors to be used in Portland's stormwater treatment plans. Each requirement which should be met by the applying vendors is thoroughly analyzed followed by a comparison with the Stormwater management plan(2008)regulations of the state of Washington the so called Technology Assessment Plan-Ecology TAPE (Howie, 2011). Because of the similarities in the climate and land use between these two testing frameworks in order to evaluate the potential applicability of data submitted by vendors who had devices approved by Washington, to be utilized by Portland. The treatment of total suspended solids (TSS) is the focus of this thesis since it is central to the testing process and since most of the other pollutions are attached to TSS and will get treated if TSS is treated. The overall analysis shows that Portland adopts more restrictive requirements on the characterization of stormwater event samples to be treated by a technological instrument while Washington's restriction are more stringent on the efficiency of total suspended solid removal, in which it demands higher standards on the treatment of TSS compared to Portland's efficiency requirements. In order to study practical context in which regulations are administrated by Portland, rainfall data from 66 gauges covering the period of 1980-2011 was studied and the impacts of seasonality, land use, land form, periods of no rain before and after an event and Portland's Modified Performance line on the number of accepted rain events were analyzed. The results which were accepted by state of Washington were also compared with the results accepted by the city of Portland on Portland's Standard Performance line. Our seasonality study suggests that Portland's requirements are unnecessarily restrictive which results in the disqualification of many otherwise useful stormwater events, sometimes allowing no natural events to be available for testing in dry years. The analysis of land use showed that land use has no statistically significant impact on the concentration levels of TSS, thereby indicating that land use restrictions in the testing rules could be usefully relaxed. Decreasing the interevent no-rain period significantly increases the total number of events providing sufficient data to assess the performance of treatment facilities. We also showed that many more events become suitable for performance testing if events separated by one hours or less are considered a single, longer event. Finally we identified a statistical relationship between number of forecasted accepted stormwater events and the total average daily precipitation in a given year. Close