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• 1. [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

• 2. [Article] Macroinvertebrate Community Analysis on lower Hood River Before and During the Removal of Powerdale Dam: A Baseline Study

  Powerdale Dam was an 87-year-old hydroelectric complex on lower Hood River in northern Oregon which was decommissioned in 2010. Macroinvertebrate samples were collected in 2009, before the removal process ...

  Citation × Citation Citation Abstract Copy Title: Macroinvertebrate Community Analysis on lower Hood River Before and During the Removal of Powerdale Dam: A Baseline Study Author: Patterson, Howard J. Year: 2001 Powerdale Dam was an 87-year-old hydroelectric complex on lower Hood River in northern Oregon which was decommissioned in 2010. Macroinvertebrate samples were collected in 2009, before the removal process began, and in 2010, near the end of the demolition project, at one site upstream and three sites downstream of the dam. Macroinvertebrate communities were analyzed using both multi-metric (Benthic Index of Biotic Integrity [B-IBI]) and multivariate (Predictive Assessment Tool for Oregon [PREDATOR]) approaches, as well as EPT and Functional Feeding Group (FFG) analysis. All analytical approaches indicated declines in habitat quality in 2010 relative to 2009, and showed increasing impairment in the downstream sites in 2010, with sediment implicated as an impairment factor. Pollutants such as pesticides released from the impoundment might also contribute to downstream disturbance levels. The upstream, control site showed habitat quality declines in 2010 relative to 2009, indicating a possible upstream source of impairment. The demolition project did not physically impact upstream areas, and tributary turbidity does not appear to have been elevated relative to other years; however, the Hilsenhoff Biotic Index indicates an increase in upstream nutrient pollution in 2010 relative to 2009. Future research will be able to establish rate and extent of post-removal habitat recovery relative to these baseline data. Title: Macroinvertebrate Community Analysis on lower Hood River Before and During the Removal of Powerdale Dam: A Baseline Study Author: Patterson, Howard J. Year: 2001 Powerdale Dam was an 87-year-old hydroelectric complex on lower Hood River in northern Oregon which was decommissioned in 2010. Macroinvertebrate samples were collected in 2009, before the removal process began, and in 2010, near the end of the demolition project, at one site upstream and three sites downstream of the dam. Macroinvertebrate communities were analyzed using both multi-metric (Benthic Index of Biotic Integrity [B-IBI]) and multivariate (Predictive Assessment Tool for Oregon [PREDATOR]) approaches, as well as EPT and Functional Feeding Group (FFG) analysis. All analytical approaches indicated declines in habitat quality in 2010 relative to 2009, and showed increasing impairment in the downstream sites in 2010, with sediment implicated as an impairment factor. Pollutants such as pesticides released from the impoundment might also contribute to downstream disturbance levels. The upstream, control site showed habitat quality declines in 2010 relative to 2009, indicating a possible upstream source of impairment. The demolition project did not physically impact upstream areas, and tributary turbidity does not appear to have been elevated relative to other years; however, the Hilsenhoff Biotic Index indicates an increase in upstream nutrient pollution in 2010 relative to 2009. Future research will be able to establish rate and extent of post-removal habitat recovery relative to these baseline data. Close

• 3. [Article] Pend Oreille River Model: Model Scenario Simulations

  The Idaho Department of Environmental Quality is interested in developing a temperature and water quality Total Maximum Daily Load (TMDL) allocation for the Pend Oreille River between the Long Bridge near ...

  Citation × Citation Citation Abstract Copy Title: Pend Oreille River Model: Model Scenario Simulations Author: Annear, Robert Leslie, Berger, Chris, Wells, Scott A. Year: 2007 The Idaho Department of Environmental Quality is interested in developing a temperature and water quality Total Maximum Daily Load (TMDL) allocation for the Pend Oreille River between the Long Bridge near the historical Lake Pend Oreille outlet and Albeni Falls Dam (U.S. Army Corps of Engineer’s reservoir) as shown in Figure 1. This management scenario report is an update of a prior report. The management scenarios had to be rerun because of a modeling error made with the outflows rate of Albeni Falls Dam. The new calibration error statistics were compared with the old statistics in Appendix B: Model Calibration Statistics. The model error for vertical profiles was slightly improved while the error for continuous temperature data was approximately the same. Title: Pend Oreille River Model: Model Scenario Simulations Author: Annear, Robert Leslie, Berger, Chris, Wells, Scott A. Year: 2007 The Idaho Department of Environmental Quality is interested in developing a temperature and water quality Total Maximum Daily Load (TMDL) allocation for the Pend Oreille River between the Long Bridge near the historical Lake Pend Oreille outlet and Albeni Falls Dam (U.S. Army Corps of Engineer’s reservoir) as shown in Figure 1. This management scenario report is an update of a prior report. The management scenarios had to be rerun because of a modeling error made with the outflows rate of Albeni Falls Dam. The new calibration error statistics were compared with the old statistics in Appendix B: Model Calibration Statistics. The model error for vertical profiles was slightly improved while the error for continuous temperature data was approximately the same. Close

• 4. [Article] Pine Creek Conservation Area: 2013 Mapping and Monitoring Report

  Pine Creek Conservation Area (PCCA), just northeast of the John Day River in Wheeler County, Oregon, was acquired in 1999-2001 by the Confederate Tribes of Warm Springs with support from the Bonneville ...

  Citation × Citation Citation Abstract Copy Title: Pine Creek Conservation Area: 2013 Mapping and Monitoring Report Author: Nielsen, Eric M., Noone, Matthew D., Kagan, James S., Lee, Matthew T. Year: 2013 Pine Creek Conservation Area (PCCA), just northeast of the John Day River in Wheeler County, Oregon, was acquired in 1999-2001 by the Confederate Tribes of Warm Springs with support from the Bonneville Power Administration (BPA), to mitigate for wildlife losses created by the large, hydropower Columbia River Dams, particularly the Bonneville, Dalles and John Day Dams. Many thousands of acres of grassland, shrub steppe and riparian habitats were lost due to inundation, and the objectives of the acquisition included restoration of similar habitats. As part of an interagency agreement created in 2002, the Oregon Natural Heritage Information Center established a baseline monitoring program in 2002. This effort included the establishment of permanent monitoring plots to allow for a detailed assessment of vegetation change in the plant communities occurring at the site. It also included the development of an existing vegetation map, hopefully to allow for an analysis of overall vegetation change across the conservation area. The map showed the distribution of western juniper, native grasslands, big sagebrush, and weed-dominated areas at the site. In the eight years since the original map was made, a series of management actions, including juniper clearing, prescribed fires, and riparian restoration activities have significantly changed the vegetation at PCCA. In the spring and summer of 2010, the Oregon Natural Heritage Information Center, now the Oregon Biodiversity Information Center at Portland State University, visited the area to assist the land manager in developing a strategy for meeting the information needs of the Tribes and BPA in evaluating the success of the first decade of restoration. This report details that effort, which incorporated a combination of field inspection, photo-interpretation, and remote sensing-based mapping to assess change since the establishment of the conservation area, to lay a new baseline against which to measure future change, and most importantly to provide detailed information useful for land management decision making in the continuing restoration efforts. Title: Pine Creek Conservation Area: 2013 Mapping and Monitoring Report Author: Nielsen, Eric M., Noone, Matthew D., Kagan, James S., Lee, Matthew T. Year: 2013 Pine Creek Conservation Area (PCCA), just northeast of the John Day River in Wheeler County, Oregon, was acquired in 1999-2001 by the Confederate Tribes of Warm Springs with support from the Bonneville Power Administration (BPA), to mitigate for wildlife losses created by the large, hydropower Columbia River Dams, particularly the Bonneville, Dalles and John Day Dams. Many thousands of acres of grassland, shrub steppe and riparian habitats were lost due to inundation, and the objectives of the acquisition included restoration of similar habitats. As part of an interagency agreement created in 2002, the Oregon Natural Heritage Information Center established a baseline monitoring program in 2002. This effort included the establishment of permanent monitoring plots to allow for a detailed assessment of vegetation change in the plant communities occurring at the site. It also included the development of an existing vegetation map, hopefully to allow for an analysis of overall vegetation change across the conservation area. The map showed the distribution of western juniper, native grasslands, big sagebrush, and weed-dominated areas at the site. In the eight years since the original map was made, a series of management actions, including juniper clearing, prescribed fires, and riparian restoration activities have significantly changed the vegetation at PCCA. In the spring and summer of 2010, the Oregon Natural Heritage Information Center, now the Oregon Biodiversity Information Center at Portland State University, visited the area to assist the land manager in developing a strategy for meeting the information needs of the Tribes and BPA in evaluating the success of the first decade of restoration. This report details that effort, which incorporated a combination of field inspection, photo-interpretation, and remote sensing-based mapping to assess change since the establishment of the conservation area, to lay a new baseline against which to measure future change, and most importantly to provide detailed information useful for land management decision making in the continuing restoration efforts. Close

• 5. [Article] A Statistical Investigation of Lower Columbia River Water Temperature, 1915-2003

  The Columbia River is home to anadromous salmon populations that migrate upriver every year to spawn. These fish require cool water temperatures (Tw) to survive. In recent years, high summer Tw in the ...

  Citation × Citation Citation Abstract Copy Title: A Statistical Investigation of Lower Columbia River Water Temperature, 1915-2003 Author: Overman, Corina Christina Mae Year: 2017 The Columbia River is home to anadromous salmon populations that migrate upriver every year to spawn. These fish require cool water temperatures (Tw) to survive. In recent years, high summer Tw in the Columbia River has caused increased mortality of salmon. Different possible explanations for increased Tw include climate change, deforestation, and decreased summertime streamflow (Q) due to dams. In this study, robust linear regression models of Tw based on air temperature (Ta) and Q were developed to examine the change in Tw over time. The data was separated into an historical period (1938-1956) and a modern period (1977-2003). Seasonal regression models were used for May through October (summer) and November through April (winter) for each period. Comparison of these models showed that Tw has become less sensitive to recent atmospheric heating and cooling. By contrast, analysis suggested that Tw has become more sensitive to variations in Q. Of the 1.5ºC increase in maximum summertime Tw, approximately 1.3ºC was due to dams and reservoir management based on changes in regression coefficients and average Q. A smaller, 0.2ºC change was estimated to be caused by increasing Ta since the mid-20th century. While average maximum Tw has increased, both the statistical model and data suggest that the variability in Tw from its climatological average has decreased, probably due to reservoir management. Title: A Statistical Investigation of Lower Columbia River Water Temperature, 1915-2003 Author: Overman, Corina Christina Mae Year: 2017 The Columbia River is home to anadromous salmon populations that migrate upriver every year to spawn. These fish require cool water temperatures (Tw) to survive. In recent years, high summer Tw in the Columbia River has caused increased mortality of salmon. Different possible explanations for increased Tw include climate change, deforestation, and decreased summertime streamflow (Q) due to dams. In this study, robust linear regression models of Tw based on air temperature (Ta) and Q were developed to examine the change in Tw over time. The data was separated into an historical period (1938-1956) and a modern period (1977-2003). Seasonal regression models were used for May through October (summer) and November through April (winter) for each period. Comparison of these models showed that Tw has become less sensitive to recent atmospheric heating and cooling. By contrast, analysis suggested that Tw has become more sensitive to variations in Q. Of the 1.5ºC increase in maximum summertime Tw, approximately 1.3ºC was due to dams and reservoir management based on changes in regression coefficients and average Q. A smaller, 0.2ºC change was estimated to be caused by increasing Ta since the mid-20th century. While average maximum Tw has increased, both the statistical model and data suggest that the variability in Tw from its climatological average has decreased, probably due to reservoir management. Close

• 6. [Article] Willamette River and Columbia River Waste Load Allocation Model

  A hydrodynamic and water quality model of the Lower Willamette River was developed to evaluate management alternatives designed to improve water quality. The Lower Willamette River is located in Oregon ...

  Citation × Citation Citation Abstract Copy Title: Willamette River and Columbia River Waste Load Allocation Model Author: Berger, Chris, Annear, Robert Leslie, Wells, Scott A. Year: 2002 A hydrodynamic and water quality model of the Lower Willamette River was developed to evaluate management alternatives designed to improve water quality. The Lower Willamette River is located in Oregon and drains a watershed covering 11500 square miles consisting of forested, agricultural, and urban lands. Inflows include treated municipal wastes and industrial effluents along with non-point sources from agricultural, silvicultural and urbanized land. The model was designed to address temperature, dissolved oxygen, algae, pH and bacteria concerns. The Corps of Engineers two-dimensional, laterally averaged, hydrodynamic and water quality model CE-QUAL-W2, Version 3 was applied. CE-QUAL-W2 consists of directly coupled hydrodynamic and water quality transport models and simulates parameters such as temperature, algae concentration, dissolved oxygen concentration, pH, nutrient concentrations and residence time. The model domain covers a total of about 126 river miles, including the Lower Willamette River from its intersection with the Columbia River upstream to Canby Ferry (RM 35.0) and the Columbia River from Bonneville Dam (RM 144.5) to Beaver Army Terminal (River Mile 53.8). Modeling of the Columbia River was necessary to simulate tidal fluctuations and influxes of Columbia River water into the Lower Willamette. Major tributaries and major NPDES point sources were point inflows to the system model. The ability to model multiple water bodies was a feature of CE-QUAL-W2 Version 3 and allows the simulation of river, reservoir or estuary sections with varying bottom slopes separated by dams and other hydraulic structures. The model was calibrated for the summers of 1993, 1994, 1997, 1998, and 1999. Hydrodynamics were calibrated first followed by temperature and water quality. Root mean square error of model water level predictions was generally less than 0.05 m. Because of the short residence time within the model domain, the development of accurate boundary conditions was essential for good model calibration. Title: Willamette River and Columbia River Waste Load Allocation Model Author: Berger, Chris, Annear, Robert Leslie, Wells, Scott A. Year: 2002 A hydrodynamic and water quality model of the Lower Willamette River was developed to evaluate management alternatives designed to improve water quality. The Lower Willamette River is located in Oregon and drains a watershed covering 11500 square miles consisting of forested, agricultural, and urban lands. Inflows include treated municipal wastes and industrial effluents along with non-point sources from agricultural, silvicultural and urbanized land. The model was designed to address temperature, dissolved oxygen, algae, pH and bacteria concerns. The Corps of Engineers two-dimensional, laterally averaged, hydrodynamic and water quality model CE-QUAL-W2, Version 3 was applied. CE-QUAL-W2 consists of directly coupled hydrodynamic and water quality transport models and simulates parameters such as temperature, algae concentration, dissolved oxygen concentration, pH, nutrient concentrations and residence time. The model domain covers a total of about 126 river miles, including the Lower Willamette River from its intersection with the Columbia River upstream to Canby Ferry (RM 35.0) and the Columbia River from Bonneville Dam (RM 144.5) to Beaver Army Terminal (River Mile 53.8). Modeling of the Columbia River was necessary to simulate tidal fluctuations and influxes of Columbia River water into the Lower Willamette. Major tributaries and major NPDES point sources were point inflows to the system model. The ability to model multiple water bodies was a feature of CE-QUAL-W2 Version 3 and allows the simulation of river, reservoir or estuary sections with varying bottom slopes separated by dams and other hydraulic structures. The model was calibrated for the summers of 1993, 1994, 1997, 1998, and 1999. Hydrodynamics were calibrated first followed by temperature and water quality. Root mean square error of model water level predictions was generally less than 0.05 m. Because of the short residence time within the model domain, the development of accurate boundary conditions was essential for good model calibration. Close

• 7. [Article] Historical and Existing Vascular and Bryophyte Flora, Former Blue Heron Paper Mill, Willamette Falls, Oregon City, Oregon

  Willamette Falls has long been a focus of botanical interest, but industrial development at the site has limited public access for over a century. The closure of the Blue Heron paper mill on the south ...

  Citation × Citation Citation Abstract Copy Title: Historical and Existing Vascular and Bryophyte Flora, Former Blue Heron Paper Mill, Willamette Falls, Oregon City, Oregon Author: Christy, John A., Gaddis, Philip Year: 2015 Willamette Falls has long been a focus of botanical interest, but industrial development at the site has limited public access for over a century. The closure of the Blue Heron paper mill on the south bank of the river, and proposed redevelopment of the site, has given planners an opportunity to revisit this part of the falls and identify its current flora. As part of the preconstruction planning process for public access to the falls, Metro contracted John Christy to document the historical and existing vascular flora on the site, and Philip Gaddis joined us to document the bryophyte flora. For millennia, the falls has been a magnet for fishing, settlement, and more recent industrial development. Photographs by Carleton Watkins show that the south bank of the river at Willamette Falls had been modified for industrial uses as early as 1867. Infrastructure included dams and spillways to create a boat basin, and millraces to power a sawmill, gristmill, and woolen mill. Later, paper mills and electrical generating stations were built on both sides of the falls. These activities concentrated at the falls have impacted all native habitat except vertical cliff faces on basalt outcrops along the river. Significant portions of the shoreline at the Blue Heron site have been modified by fill. Remaining habitat in natural or semi-natural condition includes areas hydrated by tidal action of the Willamette River, areas of seasonal or perennial seepage below spillways and the old grinders, and basalt outcrops with varying exposures. The basalt outcrops are a relic of the Bretz or Missoula Floods (Allen et al. 1986), and exposures along this part of the Willamette River provide outlier habitat for both mesic and xeric species more common in the Columbia River Gorge (Detling 1958). Willamette Falls has a similar history to that of Niagara Falls in terms of industrial development, presence of a rock substrate supporting disjunct populations of rare plants, and botanical exploration that occurred primarily between 1885 and 1915 (Eckel 2013). Title: Historical and Existing Vascular and Bryophyte Flora, Former Blue Heron Paper Mill, Willamette Falls, Oregon City, Oregon Author: Christy, John A., Gaddis, Philip Year: 2015 Willamette Falls has long been a focus of botanical interest, but industrial development at the site has limited public access for over a century. The closure of the Blue Heron paper mill on the south bank of the river, and proposed redevelopment of the site, has given planners an opportunity to revisit this part of the falls and identify its current flora. As part of the preconstruction planning process for public access to the falls, Metro contracted John Christy to document the historical and existing vascular flora on the site, and Philip Gaddis joined us to document the bryophyte flora. For millennia, the falls has been a magnet for fishing, settlement, and more recent industrial development. Photographs by Carleton Watkins show that the south bank of the river at Willamette Falls had been modified for industrial uses as early as 1867. Infrastructure included dams and spillways to create a boat basin, and millraces to power a sawmill, gristmill, and woolen mill. Later, paper mills and electrical generating stations were built on both sides of the falls. These activities concentrated at the falls have impacted all native habitat except vertical cliff faces on basalt outcrops along the river. Significant portions of the shoreline at the Blue Heron site have been modified by fill. Remaining habitat in natural or semi-natural condition includes areas hydrated by tidal action of the Willamette River, areas of seasonal or perennial seepage below spillways and the old grinders, and basalt outcrops with varying exposures. The basalt outcrops are a relic of the Bretz or Missoula Floods (Allen et al. 1986), and exposures along this part of the Willamette River provide outlier habitat for both mesic and xeric species more common in the Columbia River Gorge (Detling 1958). Willamette Falls has a similar history to that of Niagara Falls in terms of industrial development, presence of a rock substrate supporting disjunct populations of rare plants, and botanical exploration that occurred primarily between 1885 and 1915 (Eckel 2013). Close

• 8. [Article] Siltcoos Lake Nonpoint Source Implementation Grant: Water Quality Conditions and Nutrient Sources

  Siltcoos Lake is a large (1280 hectares), shallow (mean depth 3.3 m; maximum depth 6.7 m) lake located on the Central Oregon Coast, just south of Florence and bordered by Dunes City, Oregon. The outflow ...

  Citation × Citation Citation Abstract Copy Title: Siltcoos Lake Nonpoint Source Implementation Grant: Water Quality Conditions and Nutrient Sources Author: Sytsma, Mark D., Miller, Rich Year: 2010 Siltcoos Lake is a large (1280 hectares), shallow (mean depth 3.3 m; maximum depth 6.7 m) lake located on the Central Oregon Coast, just south of Florence and bordered by Dunes City, Oregon. The outflow and water level of Siltcoos Lake is regulated by a dam on the Siltcoos River 4 km upstream from the Pacific. Several permanent streams feed the lake from its 176 square kilometer watershed including Fiddle Creek, Maple Creek, and Woahink Creek, the outflow from Woahink Lake. Much of the watershed is forested and used for timber harvest, residential development, and limited agricultural production. The lake is popular for recreational activities, particularly fishing for wild coastal Coho salmon, rainbow trout, cutthroat trout, largemouth bass, bluegill, crappie, and yellow perch (Buckman 2004). The lake is also the domestic drinking water source for approximately 125 of the 1330 residents of Dunes City and numerous residents outside the city limits within Lane and Douglas Counties (LCOG 2002). During the fall of 2007 a dense bloom of the potentially toxigenic blue-green algal species Anabaena planktonica prompted Dunes City, the South Coast Water District, the Lane County Health Department, and the Oregon Department of Human Services to issue an advisory against usage of Siltcoos Lake water for drinking and other domestic use (DHS 2007). Residents dependent upon Siltcoos Lake were forced to find alternate domestic water sources for a total of 52 days. This incident was part of a long history of water quality problems including dense algal growth and excessive growth of the non-native aquatic macrophytes Brazilian elodea (Egeria densa), parrotsfeather (Myriophyllum aquaticum), and two-leaf water milfoil (Myriophyllum heterophyllum) (Pfauth and Sytsma 2005; Johnson et al. 1985; McHugh 1979). Because of the water quality problems, the Oregon Department of Environmental Quality (DEQ) placed the lake the 303(d) list of impaired water bodies; specifically due to violations of the “aquatic weeds and algae” water quality criterion (DEQ 1998; DEQ 2006). Dunes City has acted on water quality concerns for both Siltcoos and Woahink Lakes by issuing a temporary building moratorium (Dunes City 2006a), a septic tank maintenance ordinance (Dunes City 2006b), and an ordinance limiting phosphorus use (Dunes City 2007). Preliminary assessments (Johnson, et al. 1985, LCOG 2002) indicate multiple sources of water quality problems including excess nutrient and/or sediment loading from residential development, poorly functioning on-site septic systems, private forestry and agricultural practices and introductions of non-native aquatic plant species. This report summarizes data collected by Portland State University and project partners between June 2008 and May 2009 to better define water quality conditions within the lake as well as potential nutrient sources. Physical, chemical, and biological data were collected at lake and tributary sites over the one year period. Data were evaluated across sites, depth and the season. The information collected will contribute to total maximum daily load (TMDL) development for the Midcoast Lakes and can be used to identify and prioritize restoration activities in the Siltcoos Lake watershed. Title: Siltcoos Lake Nonpoint Source Implementation Grant: Water Quality Conditions and Nutrient Sources Author: Sytsma, Mark D., Miller, Rich Year: 2010 Siltcoos Lake is a large (1280 hectares), shallow (mean depth 3.3 m; maximum depth 6.7 m) lake located on the Central Oregon Coast, just south of Florence and bordered by Dunes City, Oregon. The outflow and water level of Siltcoos Lake is regulated by a dam on the Siltcoos River 4 km upstream from the Pacific. Several permanent streams feed the lake from its 176 square kilometer watershed including Fiddle Creek, Maple Creek, and Woahink Creek, the outflow from Woahink Lake. Much of the watershed is forested and used for timber harvest, residential development, and limited agricultural production. The lake is popular for recreational activities, particularly fishing for wild coastal Coho salmon, rainbow trout, cutthroat trout, largemouth bass, bluegill, crappie, and yellow perch (Buckman 2004). The lake is also the domestic drinking water source for approximately 125 of the 1330 residents of Dunes City and numerous residents outside the city limits within Lane and Douglas Counties (LCOG 2002). During the fall of 2007 a dense bloom of the potentially toxigenic blue-green algal species Anabaena planktonica prompted Dunes City, the South Coast Water District, the Lane County Health Department, and the Oregon Department of Human Services to issue an advisory against usage of Siltcoos Lake water for drinking and other domestic use (DHS 2007). Residents dependent upon Siltcoos Lake were forced to find alternate domestic water sources for a total of 52 days. This incident was part of a long history of water quality problems including dense algal growth and excessive growth of the non-native aquatic macrophytes Brazilian elodea (Egeria densa), parrotsfeather (Myriophyllum aquaticum), and two-leaf water milfoil (Myriophyllum heterophyllum) (Pfauth and Sytsma 2005; Johnson et al. 1985; McHugh 1979). Because of the water quality problems, the Oregon Department of Environmental Quality (DEQ) placed the lake the 303(d) list of impaired water bodies; specifically due to violations of the “aquatic weeds and algae” water quality criterion (DEQ 1998; DEQ 2006). Dunes City has acted on water quality concerns for both Siltcoos and Woahink Lakes by issuing a temporary building moratorium (Dunes City 2006a), a septic tank maintenance ordinance (Dunes City 2006b), and an ordinance limiting phosphorus use (Dunes City 2007). Preliminary assessments (Johnson, et al. 1985, LCOG 2002) indicate multiple sources of water quality problems including excess nutrient and/or sediment loading from residential development, poorly functioning on-site septic systems, private forestry and agricultural practices and introductions of non-native aquatic plant species. This report summarizes data collected by Portland State University and project partners between June 2008 and May 2009 to better define water quality conditions within the lake as well as potential nutrient sources. Physical, chemical, and biological data were collected at lake and tributary sites over the one year period. Data were evaluated across sites, depth and the season. The information collected will contribute to total maximum daily load (TMDL) development for the Midcoast Lakes and can be used to identify and prioritize restoration activities in the Siltcoos Lake watershed. Close