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• 1. [Article] Changes in hyporheic exchange flow following experimental wood removal in a small, low-gradient stream

  This is the publisher’s final pdf. The published article is copyrighted by the American Geophysical Union and can be found at: http://www.agu.org/journals/wr/.

  Citation × Citation Citation Abstract Copy Title: Changes in hyporheic exchange flow following experimental wood removal in a small, low-gradient stream Author: Haggerty, Roy, Edwards, Richard T., LaNier, Justin, Wondzell, Steven M., Woodsmith, Richard D. This is the publisher’s final pdf. The published article is copyrighted by the American Geophysical Union and can be found at: http://www.agu.org/journals/wr/. Title: Changes in hyporheic exchange flow following experimental wood removal in a small, low-gradient stream Author: Haggerty, Roy, Edwards, Richard T., LaNier, Justin, Wondzell, Steven M., Woodsmith, Richard D. This is the publisher’s final pdf. The published article is copyrighted by the American Geophysical Union and can be found at: http://www.agu.org/journals/wr/. Close

• 2. [Article] Determining in-channel (dead zone) transient storage by comparing solute transport in a bedrock channel–alluvial channel sequence, Oregon

  This is the publisher’s final pdf. The published article is copyrighted by the American Geophysical Union and can be found at: http://www.agu.org/journals/wr/.

  Citation × Citation Citation Abstract Copy Title: Determining in-channel (dead zone) transient storage by comparing solute transport in a bedrock channel–alluvial channel sequence, Oregon Author: Haggerty, Roy, Gooseff, Michael N., LaNier, Justin, Kokkeler, Kenneth This is the publisher’s final pdf. The published article is copyrighted by the American Geophysical Union and can be found at: http://www.agu.org/journals/wr/. Title: Determining in-channel (dead zone) transient storage by comparing solute transport in a bedrock channel–alluvial channel sequence, Oregon Author: Haggerty, Roy, Gooseff, Michael N., LaNier, Justin, Kokkeler, Kenneth This is the publisher’s final pdf. The published article is copyrighted by the American Geophysical Union and can be found at: http://www.agu.org/journals/wr/. Close

• 3. [Article] A fluid-mechanics based classification scheme for surface transient storage in riverine environments: quantitatively separating surface from hyporheic transient storage

  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: A fluid-mechanics based classification scheme for surface transient storage in riverine environments: quantitatively separating surface from hyporheic transient storage Author: Jackson, T. R., Haggerty, R., Apte, Sourabh V. 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: A fluid-mechanics based classification scheme for surface transient storage in riverine environments: quantitatively separating surface from hyporheic transient storage Author: Jackson, T. R., Haggerty, R., Apte, Sourabh V. 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

• 4. [Article] Spatial and Temporal Variability of Macroinvertebrates in Spawning and Non-Spawning Habitats during a Salmon Run in Southeast Alaska

  This is the publisher’s final pdf. The published article is copyrighted by PLoS ONE and can be found at: http://www.plosone.org/home.action.

  Citation × Citation Citation Abstract Copy Title: Spatial and Temporal Variability of Macroinvertebrates in Spawning and Non-Spawning Habitats during a Salmon Run in Southeast Alaska Author: Merritt, Richard W., Campbell, Emily Y., Benbow, M. Eric, Cummins, Kenneth W. This is the publisher’s final pdf. The published article is copyrighted by PLoS ONE and can be found at: http://www.plosone.org/home.action. Title: Spatial and Temporal Variability of Macroinvertebrates in Spawning and Non-Spawning Habitats during a Salmon Run in Southeast Alaska Author: Merritt, Richard W., Campbell, Emily Y., Benbow, M. Eric, Cummins, Kenneth W. This is the publisher’s final pdf. The published article is copyrighted by PLoS ONE and can be found at: http://www.plosone.org/home.action. Close

• 5. [Article] Geomorphic controls on hyporheic exchange flow in mountain streams

  Simulations of stream-subsurface water exchange (hyporheic exchange) using a three-dimensional steady state groundwater flow model and a particle tracking model in unconstrained and constrained reaches ...

  Citation × Citation Citation Abstract Copy Title: Geomorphic controls on hyporheic exchange flow in mountain streams Author: Kasahara, Tamao Simulations of stream-subsurface water exchange (hyporheic exchange) using a three-dimensional steady state groundwater flow model and a particle tracking model in unconstrained and constrained reaches of small (2nd-order) and intermediate (5th-order) mountain streams were conducted to estimate the effects of geomorphic features on the extent, volume and residence time of hyporheic exchange flow. Study sites were located in the Lookout Creek drainage in the western Cascades of Oregon. Stream water and water table elevations and saturated hydraulic conductivity were collected from four field sites. Steps were the dominant geomorphic features creating vertical complexity in 2nd-order streams and dominating hyporheic exchange flow. The removal of steps from the simulation models of 2nd-order stream reduced the total volume of hyporheic exchange by 54 %. Furthermore, hyporheic exchange flows resulting from steps had relatively short residence times. Horizontal complexity, resulting from secondary channels and channel splits, had strong effects on hyporheic exchange, as did vertically extensive features, such as riffles, in 5th-order streams. Removal of secondary channels, channel splits and riffles from the simulation models reduced hyporheic exchange flow by 25 %, 30 % and 40 %, respectively. Secondary channels contributed to hyporheic exchange with relatively long residence time, where as channel splits and riffles contributed to hyporheic exchange with short residence time. Thus, multiple features strongly contributed to the creation of hyporheic exchange flow and drove various types of the exchange flows. Also, the simulation results and stream survey showed that the interactions between multiple features, for example secondary channels and riffles, enhanced hyporheic exchange. Because horizontally extensive features were important in driving hyporheic exchange flow in the studied unconstrained reaches, the width of the valley floor strongly controlled hyporheic exchange flow in 5th-order streams. Geomorphic controls on hyporheic exchange flow differed between the two stream sizes sampled. Second-order streams had a single key geomorphic feature (i.e. steps) influencing the hyporheic exchange flow, whereas multiple geomorphic features (i.e. riffles, secondary channels and channel splits) were important in 5 b-order streams. As a result, residence time distribution of hyporheic exchange flow was narrow in 2nd- order stream and wide in 5th-order stream. Title: Geomorphic controls on hyporheic exchange flow in mountain streams Author: Kasahara, Tamao Simulations of stream-subsurface water exchange (hyporheic exchange) using a three-dimensional steady state groundwater flow model and a particle tracking model in unconstrained and constrained reaches of small (2nd-order) and intermediate (5th-order) mountain streams were conducted to estimate the effects of geomorphic features on the extent, volume and residence time of hyporheic exchange flow. Study sites were located in the Lookout Creek drainage in the western Cascades of Oregon. Stream water and water table elevations and saturated hydraulic conductivity were collected from four field sites. Steps were the dominant geomorphic features creating vertical complexity in 2nd-order streams and dominating hyporheic exchange flow. The removal of steps from the simulation models of 2nd-order stream reduced the total volume of hyporheic exchange by 54 %. Furthermore, hyporheic exchange flows resulting from steps had relatively short residence times. Horizontal complexity, resulting from secondary channels and channel splits, had strong effects on hyporheic exchange, as did vertically extensive features, such as riffles, in 5th-order streams. Removal of secondary channels, channel splits and riffles from the simulation models reduced hyporheic exchange flow by 25 %, 30 % and 40 %, respectively. Secondary channels contributed to hyporheic exchange with relatively long residence time, where as channel splits and riffles contributed to hyporheic exchange with short residence time. Thus, multiple features strongly contributed to the creation of hyporheic exchange flow and drove various types of the exchange flows. Also, the simulation results and stream survey showed that the interactions between multiple features, for example secondary channels and riffles, enhanced hyporheic exchange. Because horizontally extensive features were important in driving hyporheic exchange flow in the studied unconstrained reaches, the width of the valley floor strongly controlled hyporheic exchange flow in 5th-order streams. Geomorphic controls on hyporheic exchange flow differed between the two stream sizes sampled. Second-order streams had a single key geomorphic feature (i.e. steps) influencing the hyporheic exchange flow, whereas multiple geomorphic features (i.e. riffles, secondary channels and channel splits) were important in 5 b-order streams. As a result, residence time distribution of hyporheic exchange flow was narrow in 2nd- order stream and wide in 5th-order stream. Close

• 6. [Article] Patterns in stream geomorphology and implications for hyporheic exchange flow

  Longitudinal water surface profiles from high-gradient mountain streams provide useful indicators of the relative potential for hyporheic exchange flow in stream reaches with varying morphology. The spacing ...

  Citation × Citation Citation Abstract Copy Title: Patterns in stream geomorphology and implications for hyporheic exchange flow Author: Anderson, Justin K. Longitudinal water surface profiles from high-gradient mountain streams provide useful indicators of the relative potential for hyporheic exchange flow in stream reaches with varying morphology. The spacing between slope breaks in step-pool and pool-riffle streams provides a geomorphic scaling metric that indicates how the length of average hyporheic flow paths change throughout the river continuum. Twelve stream reaches were randomly selected and surveyed in the Lookout Creek basin at the H.J. Andrews Experimental Forest in the western Cascades Mountains of Oregon. Stream reach morphology was examined for patterns that are expressed over a continuum ranging from headwater to mid-order streams that can be predicted from easily measured drainage basin characteristics. Simple and multiple linear regression models were used to predict changes in lateral complexity in stream reaches, and to predict how the general shape of the water surface profile changes as drainage basin area increases from 0.6 km² to 62.3 km². Patterns in the lateral complexity of stream reaches were associated with the degree of channel confinement in valley segments, and longitudinal patterns in bed configuration were strongly associated with the position of a stream reach within the river continuum. Stream reach longitudinal profiles were evaluated to determine how patterns in slope breaks change throughout the portion of the river continuum represented by the study area. Channel units were defined according to slope categories for flat water, steep water, and step units (FLATs, STEEPs and STEPs). A set of regression models was used to predict how slope break spacing and the general shape of the water surface profile change as drainage basin area increases from 0.6 km² to 62.3 km². Output from these regression equations was tested against independent field data to evaluate model performance. The models generally performed well. Longitudinal transects of piezometers were installed along the thalweg of a second order, and a third order stream reach. Longitudinal profiles in the piezometer transects were surveyed, and piezometers were used to measure hydraulic head in stream beds. Data were used to test a theoretical model that predicts downwelling where stream profiles are convex, and upwelling where stream profiles are concave. Overall, the shape of the water surface profile explained 38% of the variation in the distribution of hydraulic pressure head in the streambed. Results demonstrated the usefulness of quantifying the magnitude of concavities and convexities in stream profiles. A metric for expressing the average water surface concavity (AWSC) is proposed. I demonstrated that this metric could be useful for comparing the potential for hyporheic exchange in stream reaches with varying degrees of stream profile roughness. Results showed a decreasing trend in AWSC as drainage basin area increased. Upwelling and downwelling zones were identified in piezometer transects, and their longitudinal lengths were measured. The lengths of downwelling zones were compared to the spacing between slope breaks in the water surface profile. Average lengths of downwelling zones and FLAT channel slope units increased with increasing basin area at a similar rate, indicating that slope break spacing was a useful indicator for average downwelling zone length. My results demonstrate that patterns in stream morphology are useful for predicting patterns in hyporheic exchange flow throughout the river continuum. I suggest that the potential for gravity driven exchange flow decreases along the river continuum as AWSC decreases. I also suggest that the frequency of hydrologic exchange between the stream and the hyporheic zone decreases, and that the average length of hyporheic flow paths increase, across the river continuum. Title: Patterns in stream geomorphology and implications for hyporheic exchange flow Author: Anderson, Justin K. Longitudinal water surface profiles from high-gradient mountain streams provide useful indicators of the relative potential for hyporheic exchange flow in stream reaches with varying morphology. The spacing between slope breaks in step-pool and pool-riffle streams provides a geomorphic scaling metric that indicates how the length of average hyporheic flow paths change throughout the river continuum. Twelve stream reaches were randomly selected and surveyed in the Lookout Creek basin at the H.J. Andrews Experimental Forest in the western Cascades Mountains of Oregon. Stream reach morphology was examined for patterns that are expressed over a continuum ranging from headwater to mid-order streams that can be predicted from easily measured drainage basin characteristics. Simple and multiple linear regression models were used to predict changes in lateral complexity in stream reaches, and to predict how the general shape of the water surface profile changes as drainage basin area increases from 0.6 km² to 62.3 km². Patterns in the lateral complexity of stream reaches were associated with the degree of channel confinement in valley segments, and longitudinal patterns in bed configuration were strongly associated with the position of a stream reach within the river continuum. Stream reach longitudinal profiles were evaluated to determine how patterns in slope breaks change throughout the portion of the river continuum represented by the study area. Channel units were defined according to slope categories for flat water, steep water, and step units (FLATs, STEEPs and STEPs). A set of regression models was used to predict how slope break spacing and the general shape of the water surface profile change as drainage basin area increases from 0.6 km² to 62.3 km². Output from these regression equations was tested against independent field data to evaluate model performance. The models generally performed well. Longitudinal transects of piezometers were installed along the thalweg of a second order, and a third order stream reach. Longitudinal profiles in the piezometer transects were surveyed, and piezometers were used to measure hydraulic head in stream beds. Data were used to test a theoretical model that predicts downwelling where stream profiles are convex, and upwelling where stream profiles are concave. Overall, the shape of the water surface profile explained 38% of the variation in the distribution of hydraulic pressure head in the streambed. Results demonstrated the usefulness of quantifying the magnitude of concavities and convexities in stream profiles. A metric for expressing the average water surface concavity (AWSC) is proposed. I demonstrated that this metric could be useful for comparing the potential for hyporheic exchange in stream reaches with varying degrees of stream profile roughness. Results showed a decreasing trend in AWSC as drainage basin area increased. Upwelling and downwelling zones were identified in piezometer transects, and their longitudinal lengths were measured. The lengths of downwelling zones were compared to the spacing between slope breaks in the water surface profile. Average lengths of downwelling zones and FLAT channel slope units increased with increasing basin area at a similar rate, indicating that slope break spacing was a useful indicator for average downwelling zone length. My results demonstrate that patterns in stream morphology are useful for predicting patterns in hyporheic exchange flow throughout the river continuum. I suggest that the potential for gravity driven exchange flow decreases along the river continuum as AWSC decreases. I also suggest that the frequency of hydrologic exchange between the stream and the hyporheic zone decreases, and that the average length of hyporheic flow paths increase, across the river continuum. Close

• 7. [Article] Economic analysis of restoration practices to improve water quality and fish habitat of a large river floodplain : a case study of the Willamette River, Oregon

  In- stream water temperature is one of the most important environmental factors associated with the decline in salmonid populations and their habitats in the Pacific Northwest. Most ecological restoration ...

  Citation × Citation Citation Abstract Copy Title: Economic analysis of restoration practices to improve water quality and fish habitat of a large river floodplain : a case study of the Willamette River, Oregon Author: Seedang, Saichon In- stream water temperature is one of the most important environmental factors associated with the decline in salmonid populations and their habitats in the Pacific Northwest. Most ecological restoration practices that attempt to reduce instream temperatures center on replanting or reestablishing riparian vegetation and increasing flows. However, in a large floodplain river like the Willamette, restoring hyporheic flow may also play an important role in reducing water temperature. The objective of this dissertation is to examine restoration practices that focus on the reduction of water temperatures in the upper mainstem Willamette River, Oregon, for the benefit of salmonid species. Economic information is developed to determine the cost-effectiveness of water temperature reduction strategies. The CEQUAL- W2 water temperature model is used to simulate the effects of upstream combinations of riparian shading and flow increments on downstream water temperatures. Costs associated with these strategies are estimated. These costs consist of the opportunity costs of losing agricultural production, and losing recreation due to flow releases from up-stream reservoirs. The effectiveness of each strategy in reducing water temperature and the associated costs are used to construct a cost-effectiveness frontier. The results indicate that the cumulative effects of shading and flows have little impact on temperature reduction downstream. Even when maximum available resources are allocated to investments in shade and flow increases they cannot lower summer water temperatures sufficiently to meet the state water temperature standard. However, the restoration practices selected from the cost-effectiveness frontiers method do provide ranges of achievable temperature reductions at minimum costs. These results are thus useful management tools when selecting policies to pursue water temperature goals. Hyporheic temperature reduction is also examined. Restoration practices associated with this type of cooling are done through removal/reconnection of the obstacles that are necessary to allow the process of re-creating dynamic channel complexity. The observed significant reduction of summer water temperatures associated with channel complexity indicates that this approach is more flexible in reducing temperature than approaches that rely on flow increments or/and shade. Although the costs associated with the hyporheic approach are substantial, the effects of such a long-term ecological improvement of floodplain habitat may substantially benefit salmonid populations. Title: Economic analysis of restoration practices to improve water quality and fish habitat of a large river floodplain : a case study of the Willamette River, Oregon Author: Seedang, Saichon In- stream water temperature is one of the most important environmental factors associated with the decline in salmonid populations and their habitats in the Pacific Northwest. Most ecological restoration practices that attempt to reduce instream temperatures center on replanting or reestablishing riparian vegetation and increasing flows. However, in a large floodplain river like the Willamette, restoring hyporheic flow may also play an important role in reducing water temperature. The objective of this dissertation is to examine restoration practices that focus on the reduction of water temperatures in the upper mainstem Willamette River, Oregon, for the benefit of salmonid species. Economic information is developed to determine the cost-effectiveness of water temperature reduction strategies. The CEQUAL- W2 water temperature model is used to simulate the effects of upstream combinations of riparian shading and flow increments on downstream water temperatures. Costs associated with these strategies are estimated. These costs consist of the opportunity costs of losing agricultural production, and losing recreation due to flow releases from up-stream reservoirs. The effectiveness of each strategy in reducing water temperature and the associated costs are used to construct a cost-effectiveness frontier. The results indicate that the cumulative effects of shading and flows have little impact on temperature reduction downstream. Even when maximum available resources are allocated to investments in shade and flow increases they cannot lower summer water temperatures sufficiently to meet the state water temperature standard. However, the restoration practices selected from the cost-effectiveness frontiers method do provide ranges of achievable temperature reductions at minimum costs. These results are thus useful management tools when selecting policies to pursue water temperature goals. Hyporheic temperature reduction is also examined. Restoration practices associated with this type of cooling are done through removal/reconnection of the obstacles that are necessary to allow the process of re-creating dynamic channel complexity. The observed significant reduction of summer water temperatures associated with channel complexity indicates that this approach is more flexible in reducing temperature than approaches that rely on flow increments or/and shade. Although the costs associated with the hyporheic approach are substantial, the effects of such a long-term ecological improvement of floodplain habitat may substantially benefit salmonid populations. Close

• 8. [Article] Quantifying spatial differences in metabolism in headwater streams

  This is an author's peer-reviewed final manuscript, as accepted by the publisher. The published article is copyrighted by The Society for Freshwater Science and published by The University of Chicago Press. ...

  Citation × Citation Citation Abstract Copy Title: Quantifying spatial differences in metabolism in headwater streams Author: Haggerty, Roy, Argerich, Alba, Gonzalez-Pinzon, Ricardo This is an author's peer-reviewed final manuscript, as accepted by the publisher. The published article is copyrighted by The Society for Freshwater Science and published by The University of Chicago Press. It can be found at: https://www.freshwater-science.org/Journal/Access-FWS.aspx Title: Quantifying spatial differences in metabolism in headwater streams Author: Haggerty, Roy, Argerich, Alba, Gonzalez-Pinzon, Ricardo This is an author's peer-reviewed final manuscript, as accepted by the publisher. The published article is copyrighted by The Society for Freshwater Science and published by The University of Chicago Press. It can be found at: https://www.freshwater-science.org/Journal/Access-FWS.aspx Close

• 9. [Article] Influence of hyporheic flow and geomorphology on temperature of a large, gravel-bed river, Clackamas River, Oregon, USA

  The hyporheic zone influences the thermal regime of rivers, buffering temperature by storing and releasing heat over a range of timescales. We examined the relationship between hyporheic exchange and temperature ...

  Citation × Citation Citation Abstract Copy Title: Influence of hyporheic flow and geomorphology on temperature of a large, gravel-bed river, Clackamas River, Oregon, USA Author: Burkholder, Barbara K. The hyporheic zone influences the thermal regime of rivers, buffering temperature by storing and releasing heat over a range of timescales. We examined the relationship between hyporheic exchange and temperature along a 24-km reach of the lower Clackamas River, a large gravel-bed river in northwestern Oregon (median discharge = 75.7 m³/s; minimum mean monthly discharge = 22.7 m³/s in August 2006). With a simple mixing model, we estimated how much hyporheic exchange cools the river during hot summer months. Hyporheic exchange was primarily identified by temperature anomalies, which are patches of water that demonstrate at least a 1 °C temperature difference from the main channel. Forty hyporheic temperature anomalies were identified through field investigations and TIR (Thermal-Infrared-Radiometry) in summer 2006. The location of anomalies was associated with specific geomorphic features, primarily bar channels and bar heads that act as preferential pathways for hyporheic flow. Detailed field characterization and groundwater modeling on three Clackamas gravel bars indicate residence times of hyporheic water can vary from hours to weeks and months. This was largely determined by hydraulic conductivity, which is affected by how recently the gravel bar formed or was reworked. Upscaling of modeled discharges and hydrologic parameters from these bars to the other anomalies on the Clackamas network shows that hyporheic discharge from anomalies comprises a small fraction (<< 1 %) of mainstem discharge, resulting in small river cooling effects (0.012 °C). However, the presence of cooler patches of water within rivers can act as thermal refugia for fish and other aquatic organisms, making the creation or enhancement of hyporheic exchange an attractive method in restoring the thermal regime of rivers. Title: Influence of hyporheic flow and geomorphology on temperature of a large, gravel-bed river, Clackamas River, Oregon, USA Author: Burkholder, Barbara K. The hyporheic zone influences the thermal regime of rivers, buffering temperature by storing and releasing heat over a range of timescales. We examined the relationship between hyporheic exchange and temperature along a 24-km reach of the lower Clackamas River, a large gravel-bed river in northwestern Oregon (median discharge = 75.7 m³/s; minimum mean monthly discharge = 22.7 m³/s in August 2006). With a simple mixing model, we estimated how much hyporheic exchange cools the river during hot summer months. Hyporheic exchange was primarily identified by temperature anomalies, which are patches of water that demonstrate at least a 1 °C temperature difference from the main channel. Forty hyporheic temperature anomalies were identified through field investigations and TIR (Thermal-Infrared-Radiometry) in summer 2006. The location of anomalies was associated with specific geomorphic features, primarily bar channels and bar heads that act as preferential pathways for hyporheic flow. Detailed field characterization and groundwater modeling on three Clackamas gravel bars indicate residence times of hyporheic water can vary from hours to weeks and months. This was largely determined by hydraulic conductivity, which is affected by how recently the gravel bar formed or was reworked. Upscaling of modeled discharges and hydrologic parameters from these bars to the other anomalies on the Clackamas network shows that hyporheic discharge from anomalies comprises a small fraction (<< 1 %) of mainstem discharge, resulting in small river cooling effects (0.012 °C). However, the presence of cooler patches of water within rivers can act as thermal refugia for fish and other aquatic organisms, making the creation or enhancement of hyporheic exchange an attractive method in restoring the thermal regime of rivers. Close

• 10. [Article] Redd site selection and spawning habitat use by fall chinook salmon

  The spawning habitat associated with fall chinook salmon (Oncorhynchus tshawytscha) redd clusters was investigated in the Hanford Reach of the Columbia River. A conceptual spawning habitat model is proposed ...

  Citation × Citation Citation Abstract Copy Title: Redd site selection and spawning habitat use by fall chinook salmon Author: Geist, David R. The spawning habitat associated with fall chinook salmon (Oncorhynchus tshawytscha) redd clusters was investigated in the Hanford Reach of the Columbia River. A conceptual spawning habitat model is proposed that describes how geomorphic features of river channels create hydraulic processes, including hyporheic flows, that influence where salmon spawn in unconstrained reaches of large mainstem alluvial rivers. Spatial point pattern analysis of redds showed that redd clusters averaged approximately 10 hectares in area and their locations were consistent from year to year. The tendency to spawn in clusters suggests fall chinook salmon's use of spawning habitat is highly selective. Hydraulic characteristics of the redd clusters were significantly different than the habitat surrounding them. Velocity and lateral slope of the river bottom were the most important habitat variables in predicting redd site selection. While these variables explained a large proportion of the variance in redd site selection (86 to 96%), some unmeasured factors still accounted for a small percentage of actual spawning site selection. Further investigation showed that the magnitude and chemical characteristics of hyporheic discharge were different between and within two spawning areas. Apparently, fall chinook salmon used chemical and physical cues from the discharge to locate spawning areas. Traditional spawning habitat models could be improved if they: used spawning area-specific, rather than river-specific; spawning characteristics; incorporated hyporheic discharge measurements; and gave further consideration to the geomorphic features that are present in the unconstrained segments of large alluvial rivers. Ultimately the recovery of endangered fall chinook salmon will depend on how well we are able to recreate the characteristics once common in alluvial floodplains of large rivers. The results from this research can be used to better define the relationship between these physical habitat characteristics and fall chinook salmon spawning site selection, and provide more efficient use of limited recovery resources. Title: Redd site selection and spawning habitat use by fall chinook salmon Author: Geist, David R. The spawning habitat associated with fall chinook salmon (Oncorhynchus tshawytscha) redd clusters was investigated in the Hanford Reach of the Columbia River. A conceptual spawning habitat model is proposed that describes how geomorphic features of river channels create hydraulic processes, including hyporheic flows, that influence where salmon spawn in unconstrained reaches of large mainstem alluvial rivers. Spatial point pattern analysis of redds showed that redd clusters averaged approximately 10 hectares in area and their locations were consistent from year to year. The tendency to spawn in clusters suggests fall chinook salmon's use of spawning habitat is highly selective. Hydraulic characteristics of the redd clusters were significantly different than the habitat surrounding them. Velocity and lateral slope of the river bottom were the most important habitat variables in predicting redd site selection. While these variables explained a large proportion of the variance in redd site selection (86 to 96%), some unmeasured factors still accounted for a small percentage of actual spawning site selection. Further investigation showed that the magnitude and chemical characteristics of hyporheic discharge were different between and within two spawning areas. Apparently, fall chinook salmon used chemical and physical cues from the discharge to locate spawning areas. Traditional spawning habitat models could be improved if they: used spawning area-specific, rather than river-specific; spawning characteristics; incorporated hyporheic discharge measurements; and gave further consideration to the geomorphic features that are present in the unconstrained segments of large alluvial rivers. Ultimately the recovery of endangered fall chinook salmon will depend on how well we are able to recreate the characteristics once common in alluvial floodplains of large rivers. The results from this research can be used to better define the relationship between these physical habitat characteristics and fall chinook salmon spawning site selection, and provide more efficient use of limited recovery resources. Close