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• 1. [Image] A conservation strategy for the northern spotted owl

  	ill., maps; Shipping list no.: 90-263-P; "May 1990."; Includes bibliographical references
  	Citation × Citation Citation Abstract Copy Title: A conservation strategy for the northern spotted owl Author: Thomas, Jack Ward Year: 1990, 2010 ill., maps; Shipping list no.: 90-263-P; "May 1990."; Includes bibliographical references Title: A conservation strategy for the northern spotted owl Author: Thomas, Jack Ward Year: 1990, 2010 ill., maps; Shipping list no.: 90-263-P; "May 1990."; Includes bibliographical references Close

• 2. [Image] Evaluation and Targeting of Geothermal Energy Resources in the Southeastern United States. Progress Report, May 1, 1976--October 31, 1976

  	Progress is reported in the development of procedures for the evaluation of low-temperature radiogenically-derived geothermal resources in the eastern United States utilizing geological geochemical, and ...
  	Citation × Citation Citation Abstract Copy Title: Evaluation and Targeting of Geothermal Energy Resources in the Southeastern United States. Progress Report, May 1, 1976--October 31, 1976 Author: Costain, J.K. Year: 1976 Progress is reported in the development of procedures for the evaluation of low-temperature radiogenically-derived geothermal resources in the eastern United States utilizing geological geochemical, and geophysical data. An optimum site for geothermal development in the tectonically stable eastern United States will probably be associated with crustal igneous rocks containing relatively high concentrations of radiogenic heat-producing elements buried beneath an insulating blanket of sediments of low thermal conductivity. Evaluation of plutonic rocks exposed in the Piedmont will aid in the interpretation of gravity and magnetic data for the Atlantic Coastal Plain. Initial results of determination of heat generation from surface samples in South Caroline are encouraging, especially if granitic igneous rocks of similar heat generation can be found beneath sedimentary insulation. Continues logging of existing wells in Coastal Plain sediments supports earlier conclusion that these sediments do behave as efficient sedimentary insulators. Higher temperatures appear to be reached at shallower depths for wells drilled in Coastal Plain sediments in the vicinity of the Georgetown, South Carolina gravity law. Detailed structural mapping in the vicinity of the warm springs in northwestern Virginia has confirmed structural control of the warm springs, and has revealed the existence of kink bands. The kink bands could be related to the development of zones of vertical permeability which serve as conduits in sedimentary rocks for ascending hot water. Title: Evaluation and Targeting of Geothermal Energy Resources in the Southeastern United States. Progress Report, May 1, 1976--October 31, 1976 Author: Costain, J.K. Year: 1976 Progress is reported in the development of procedures for the evaluation of low-temperature radiogenically-derived geothermal resources in the eastern United States utilizing geological geochemical, and geophysical data. An optimum site for geothermal development in the tectonically stable eastern United States will probably be associated with crustal igneous rocks containing relatively high concentrations of radiogenic heat-producing elements buried beneath an insulating blanket of sediments of low thermal conductivity. Evaluation of plutonic rocks exposed in the Piedmont will aid in the interpretation of gravity and magnetic data for the Atlantic Coastal Plain. Initial results of determination of heat generation from surface samples in South Caroline are encouraging, especially if granitic igneous rocks of similar heat generation can be found beneath sedimentary insulation. Continues logging of existing wells in Coastal Plain sediments supports earlier conclusion that these sediments do behave as efficient sedimentary insulators. Higher temperatures appear to be reached at shallower depths for wells drilled in Coastal Plain sediments in the vicinity of the Georgetown, South Carolina gravity law. Detailed structural mapping in the vicinity of the warm springs in northwestern Virginia has confirmed structural control of the warm springs, and has revealed the existence of kink bands. The kink bands could be related to the development of zones of vertical permeability which serve as conduits in sedimentary rocks for ascending hot water. Close

• 3. [Image] Geothermal exploration assessment and interpretation, Klamath Basin, Oregon: Swan Lake and Klamath Hills area

  	A synthesis and preliminary interpretation of predominantly geophysical information relating to the Klamath Basin geothermal resource is presented. The Swan Lake Valley area, northeast of Klamath Falls, ...
  	Citation × Citation Citation Abstract Copy Title: Geothermal exploration assessment and interpretation, Klamath Basin, Oregon: Swan Lake and Klamath Hills area Author: Stark, M. Year: 1979 A synthesis and preliminary interpretation of predominantly geophysical information relating to the Klamath Basin geothermal resource is presented. The Swan Lake Valley area, northeast of Klamath Falls, and the Klamath Hills area, south of Klamath Falls, are discussed in detail. Available geophysical data, including gravity, magnetic, electrical resistivity, microearthquake, roving dipole resistivity, audio-magnetotelluric (AMT) and magnetotelluric (MT) data sets, are examined and reinterpreted for these areas. One- and two-dimensional modeling techniques are applied, and general agreement among overlapping data sets is achieved. The MT method appears well suited to this type of exploration, although interpretation is difficult in the complex geology. Roving dipole and AMT are useful in reconnaissance, while gravity and magnetics help in defining structure. For the Swan Lake Valley the data suggest buried electrically conductive zones beneath Meadow Lake Valley and Swan Lake, connected by a conductive layer at 1 kilometer depth. In the Klamath Hills area, the data suggest a conductive zone centered near the northwestern tip of Stukel Mountain, associated with a concealed northeast-trending cross-fault. Another conductive zone appears near some producing hot wells at the southwestern edge of the Klamath Hills. These conductive zones may represent geothermal reservoirs. Follow-up work is recommended for each target area; LBL-8186 Title: Geothermal exploration assessment and interpretation, Klamath Basin, Oregon: Swan Lake and Klamath Hills area Author: Stark, M. Year: 1979 A synthesis and preliminary interpretation of predominantly geophysical information relating to the Klamath Basin geothermal resource is presented. The Swan Lake Valley area, northeast of Klamath Falls, and the Klamath Hills area, south of Klamath Falls, are discussed in detail. Available geophysical data, including gravity, magnetic, electrical resistivity, microearthquake, roving dipole resistivity, audio-magnetotelluric (AMT) and magnetotelluric (MT) data sets, are examined and reinterpreted for these areas. One- and two-dimensional modeling techniques are applied, and general agreement among overlapping data sets is achieved. The MT method appears well suited to this type of exploration, although interpretation is difficult in the complex geology. Roving dipole and AMT are useful in reconnaissance, while gravity and magnetics help in defining structure. For the Swan Lake Valley the data suggest buried electrically conductive zones beneath Meadow Lake Valley and Swan Lake, connected by a conductive layer at 1 kilometer depth. In the Klamath Hills area, the data suggest a conductive zone centered near the northwestern tip of Stukel Mountain, associated with a concealed northeast-trending cross-fault. Another conductive zone appears near some producing hot wells at the southwestern edge of the Klamath Hills. These conductive zones may represent geothermal reservoirs. Follow-up work is recommended for each target area; LBL-8186 Close

• 4. [Image] Geology of the Cove Fort-Sulphurdale KGRA

  	The Cove Fort-Sulphurdale Known Geothermal Resource Area (KGRA) is located on the northwestern margin of the Marysvale volcanic field in southwestern Utah. The geology of the KGRA is dominated by lava ...
  	Citation × Citation Citation Abstract Copy Title: Geology of the Cove Fort-Sulphurdale KGRA Author: Moore, J.N. Year: 1979 The Cove Fort-Sulphurdale Known Geothermal Resource Area (KGRA) is located on the northwestern margin of the Marysvale volcanic field in southwestern Utah. The geology of the KGRA is dominated by lava flows and ash-flow tuffs of late Oligocene to mid-Miocene age that were deposited on faulted sedimentary rocks of Paleozoic to Mesozoic age. The geothermal system of the Cove Fort-Sulphurdale KGRA is structurally controlled by normal faults. High-angle faults control fluid flow within the geothermal reservoir, while the gravitational glide blocks provide an impermeable cap for the geothermal system in the central part of the field. Surficial activity occurring to the north and south of the glide blocks is characterized by the evolution of hydrogen sulfide and deposition of native sulphur. Intense acid alteration of the aluvium, resulting from downward migration of sulphuric acid, has left porous siliceous residues that retain many of the original sedimentary structures. Detailed logs of Union Oil Company drill holes Forminco No. 1, Utah State 42-7, and Utah State 31-33 are included Title: Geology of the Cove Fort-Sulphurdale KGRA Author: Moore, J.N. Year: 1979 The Cove Fort-Sulphurdale Known Geothermal Resource Area (KGRA) is located on the northwestern margin of the Marysvale volcanic field in southwestern Utah. The geology of the KGRA is dominated by lava flows and ash-flow tuffs of late Oligocene to mid-Miocene age that were deposited on faulted sedimentary rocks of Paleozoic to Mesozoic age. The geothermal system of the Cove Fort-Sulphurdale KGRA is structurally controlled by normal faults. High-angle faults control fluid flow within the geothermal reservoir, while the gravitational glide blocks provide an impermeable cap for the geothermal system in the central part of the field. Surficial activity occurring to the north and south of the glide blocks is characterized by the evolution of hydrogen sulfide and deposition of native sulphur. Intense acid alteration of the aluvium, resulting from downward migration of sulphuric acid, has left porous siliceous residues that retain many of the original sedimentary structures. Detailed logs of Union Oil Company drill holes Forminco No. 1, Utah State 42-7, and Utah State 31-33 are included Close

• 5. [Image] Bull trout restoration and brook trout eradication at Crater Lake National Park, Oregon

  	ill., 1 map (sketched) ; Report title; "Drought conditions are continuing in 1994, at the writing of this report in March of 1994, Crater Lake National Park had received approximately 50% of the annual ...
  	Citation × Citation Citation Abstract Copy Title: Bull trout restoration and brook trout eradication at Crater Lake National Park, Oregon Author: Buktenica, Mark. Year: 1994, 2008, 2009 ill., 1 map (sketched) ; Report title; "Drought conditions are continuing in 1994, at the writing of this report in March of 1994, Crater Lake National Park had received approximately 50% of the annual average accumulated precipatation to date." - P. 17.; Title: Bull trout restoration and brook trout eradication at Crater Lake National Park, Oregon Author: Buktenica, Mark. Year: 1994, 2008, 2009 ill., 1 map (sketched) ; Report title; "Drought conditions are continuing in 1994, at the writing of this report in March of 1994, Crater Lake National Park had received approximately 50% of the annual average accumulated precipatation to date." - P. 17.; Close

• 6. [Image] A review of the taxonomic status of pines including true firs within the pinus ponderosa forest in the southern portion of Crater Lake National Park, Oregon

  	ill.; Report title; "A report to the Superintendent, Crater Lake National Park, March 1982." - T.p.; Includes bibliographical references (p. 11-16)
  	Citation × Citation Citation Abstract Copy Title: A review of the taxonomic status of pines including true firs within the pinus ponderosa forest in the southern portion of Crater Lake National Park, Oregon Author: Mastrogiuseppe, R. J. Year: 1982, 2009 ill.; Report title; "A report to the Superintendent, Crater Lake National Park, March 1982." - T.p.; Includes bibliographical references (p. 11-16) Title: A review of the taxonomic status of pines including true firs within the pinus ponderosa forest in the southern portion of Crater Lake National Park, Oregon Author: Mastrogiuseppe, R. J. Year: 1982, 2009 ill.; Report title; "A report to the Superintendent, Crater Lake National Park, March 1982." - T.p.; Includes bibliographical references (p. 11-16) Close

• 7. [Image] Seeking refuge: making space for migratory waterfowl and wetlands along the Pacific Flyway

  	Abstract "Seeking Refuge" examines the history of migratory waterfowl management along the Pacific Flyway, the westernmost of four main migration routes in North America. Drawing on approaches from historical ...
  	Citation × Citation Citation Abstract Copy Title: Seeking refuge: making space for migratory waterfowl and wetlands along the Pacific Flyway Author: Wilson, Robert Michael Year: 2003, 2005, 2004 Abstract "Seeking Refuge" examines the history of migratory waterfowl management along the Pacific Flyway, the westernmost of four main migration routes in North America. Drawing on approaches from historical geography and environmental history, this study shows how wildlife officials developed migratory bird refuges in Oregon and California, where over 60 percent of Pacific Flyway waterfowl winter. During the early-twentieth century, reclamation and river diking eliminated most of the wetlands in the birds' wintering range. Bird enthusiasts such as bird watchers and duck hunters successfully lobbied for the creation of wildlife refuges in a few areas along the flyway. These early refuges failed to protect waterfowl habitat and they were severely degraded by reclamation. In the 1930s and 1940s, the U.S. Fish and Wildlife Service (FWS) and its predecessor, the Bureau of Biological Survey, undertook an ambitious program to resurrect these sanctuaries and to create new ones. Many farmers opposed these refuges out of fear that waterfowl would damage crops. To respond to these concerns and to ensure an adequate food supply for the birds, the FWS raised rice, barley, and other grains. The agency adopted many of the technologies of modern, industrial agriculture including synthetic herbicides and insecticides such as 2, 4-D and DDT. By the 1960s, the refuges had become largely mirrors of the surrounding irrigated farmlands, the main difference being that the FWS raised grain for waterfowl rather than for market. Refuges could not escape the agricultural settings in which they were embedded. As units within the irrigated countryside, Pacific Flyway refuges were often at the mercy of nearby farmers and federal reclamation agencies. Poor water quality and insufficient supplies of water often hampered FWS efforts to manage refuges. In the late-twentieth century, reduced water supply due to diversions to California municipalities and to sustain endangered fish species affected the amount of water reaching refuges. This dissertation has other goals. First, it critiques the anthropocentrism of most historical geography by focusing on how political, cultural, and ecological factors affected wildlife. Second, it contributes to the literature on the state's role in environmental protection by investigating the overlapping, and often contradictory, spaces within which wildlife managers implemented environmental regulations. Title: Seeking refuge: making space for migratory waterfowl and wetlands along the Pacific Flyway Author: Wilson, Robert Michael Year: 2003, 2005, 2004 Abstract "Seeking Refuge" examines the history of migratory waterfowl management along the Pacific Flyway, the westernmost of four main migration routes in North America. Drawing on approaches from historical geography and environmental history, this study shows how wildlife officials developed migratory bird refuges in Oregon and California, where over 60 percent of Pacific Flyway waterfowl winter. During the early-twentieth century, reclamation and river diking eliminated most of the wetlands in the birds' wintering range. Bird enthusiasts such as bird watchers and duck hunters successfully lobbied for the creation of wildlife refuges in a few areas along the flyway. These early refuges failed to protect waterfowl habitat and they were severely degraded by reclamation. In the 1930s and 1940s, the U.S. Fish and Wildlife Service (FWS) and its predecessor, the Bureau of Biological Survey, undertook an ambitious program to resurrect these sanctuaries and to create new ones. Many farmers opposed these refuges out of fear that waterfowl would damage crops. To respond to these concerns and to ensure an adequate food supply for the birds, the FWS raised rice, barley, and other grains. The agency adopted many of the technologies of modern, industrial agriculture including synthetic herbicides and insecticides such as 2, 4-D and DDT. By the 1960s, the refuges had become largely mirrors of the surrounding irrigated farmlands, the main difference being that the FWS raised grain for waterfowl rather than for market. Refuges could not escape the agricultural settings in which they were embedded. As units within the irrigated countryside, Pacific Flyway refuges were often at the mercy of nearby farmers and federal reclamation agencies. Poor water quality and insufficient supplies of water often hampered FWS efforts to manage refuges. In the late-twentieth century, reduced water supply due to diversions to California municipalities and to sustain endangered fish species affected the amount of water reaching refuges. This dissertation has other goals. First, it critiques the anthropocentrism of most historical geography by focusing on how political, cultural, and ecological factors affected wildlife. Second, it contributes to the literature on the state's role in environmental protection by investigating the overlapping, and often contradictory, spaces within which wildlife managers implemented environmental regulations. Close

• 8. [Image] The Endangered Species Act and its impact on agricultural producers: hearing before the Subcommittee on Conservation, Credit, Rural Development, and Research of the Committee on Agriculture, House of representatives, One Hundred Eighth Congress, second session, July 26, 2004, Greely, CO.

  	CONTENTS Lucas, Hon. Frank, a Representative in Congress from the State of Oklahoma, opening statement .................................................................................... 1 Musgrave, ...
  	Citation × Citation Citation Abstract Copy Title: The Endangered Species Act and its impact on agricultural producers: hearing before the Subcommittee on Conservation, Credit, Rural Development, and Research of the Committee on Agriculture, House of representatives, One Hundred Eighth Congress, second session, July 26, 2004, Greely, CO. Author: United States. Congress. House. Committee on Agriculture. Subcommittee on Conservation, Credit, Rural Development, and Research. Year: 2004, 2005 CONTENTS Lucas, Hon. Frank, a Representative in Congress from the State of Oklahoma, opening statement .................................................................................... 1 Musgrave, Hon. Marilyn N., a Representative in Congress from the State of Colorado, opening statement........................................................................... 2 Witnesses Foutz, Alan, president, Colorado Farm Bureau, Centennial, CO ........................ 10 Prepared statement .......................................................................................... 38 George, Russell, executive director, Colorado Department of Natural Resources, Denver, CO............................................................................................. 4 Prepared statement .......................................................................................... 29 Palmer, William, executive director, Rocky Mountain Bird Observatory, Brighton, CO ........................................................................................................ 16 Prepared statement.......................................................................................... 60 Sims, James T., executive director, Western Business Roundtable, Golden, CO.......................................................................................................................... 13 Prepared statement .......................................................................................... 43 Stetson, Jean, co-chairman, Endangered Species Committee, Colorado Cattlemen, Craig, CO..................................................................................................... 7 Prepared statement .......................................................................................... 36 Submitted Material Weege, Merle, secretary, Ginseng Board of Wisconsin, statement...................... 65 Title: The Endangered Species Act and its impact on agricultural producers: hearing before the Subcommittee on Conservation, Credit, Rural Development, and Research of the Committee on Agriculture, House of representatives, One Hundred Eighth Congress, second session, July 26, 2004, Greely, CO. Author: United States. Congress. House. Committee on Agriculture. Subcommittee on Conservation, Credit, Rural Development, and Research. Year: 2004, 2005 CONTENTS Lucas, Hon. Frank, a Representative in Congress from the State of Oklahoma, opening statement .................................................................................... 1 Musgrave, Hon. Marilyn N., a Representative in Congress from the State of Colorado, opening statement........................................................................... 2 Witnesses Foutz, Alan, president, Colorado Farm Bureau, Centennial, CO ........................ 10 Prepared statement .......................................................................................... 38 George, Russell, executive director, Colorado Department of Natural Resources, Denver, CO............................................................................................. 4 Prepared statement .......................................................................................... 29 Palmer, William, executive director, Rocky Mountain Bird Observatory, Brighton, CO ........................................................................................................ 16 Prepared statement.......................................................................................... 60 Sims, James T., executive director, Western Business Roundtable, Golden, CO.......................................................................................................................... 13 Prepared statement .......................................................................................... 43 Stetson, Jean, co-chairman, Endangered Species Committee, Colorado Cattlemen, Craig, CO..................................................................................................... 7 Prepared statement .......................................................................................... 36 Submitted Material Weege, Merle, secretary, Ginseng Board of Wisconsin, statement...................... 65 Close

• 9. [Image] Effect of water-column pH on sediment-phosphorus release rates in Upper Klamath Lake, Oregon, 2001

  	Abstract Sediment-phosphorus release rates as a function of pH were determined in laboratory experiments for sediment and water samples collected from Shoalwater Bay in Upper Klamath Lake, Oregon, in 2001. ...
  	Citation × Citation Citation Abstract Copy Title: Effect of water-column pH on sediment-phosphorus release rates in Upper Klamath Lake, Oregon, 2001 Author: Fisher, Lawrence H. Year: 2004, 2005 Abstract Sediment-phosphorus release rates as a function of pH were determined in laboratory experiments for sediment and water samples collected from Shoalwater Bay in Upper Klamath Lake, Oregon, in 2001. Areal release rates for a stable sediment/water interface that is representative of the sediment surface area to water column volume ratio (1:3) observed in the lake and volumetric release rates for resuspended sediment events were determined at three different pH values (8.1, 9.2, 10.2). Ambient water column pH (8.1) was maintained by sparging study columns with atmospheric air. Elevation of the water column pH to 9.2 was achieved through the removal of dissolved carbon dioxide by sparging with carbon dioxide-reduced air, partially simulating water chemistry changes that occur during algal photosynthesis. Further elevation of the pH to 10.2 was achieved by the addition of sodium hydroxide, which doubled average alkalinities in the study columns from about 1 to 2 milliequivalents per liter. Upper Klamath Lake sediments collected from the lake bottom and then placed in contact with lake water, either at a stable sediment/water interface or by resus-pension, exhibited an initial capacity to take up soluble reactive phosphorus (SRP) from the water column rather than release phosphorus to the water column. At a higher pH this initial uptake of phosphorus was slowed, but not stopped. This initial phase was followed by a reversal in which the sediments began to release SRP back into the water column. The release rate of phosphorus 30 to 40 days after suspension of sediments in the columns was 0.5 |ig/L/day (micrograms per liter per day) at pH 8, and 0.9 |ug/L/day at pH 10, indicating that the higher pH increased the rate of phosphorus release by a factor of about two. The highest determined rate of release was approximately 10% (percent) of the rate required to explain the annual internal loading to Upper Klamath Lake from the sediments as calculated from a lake-wide mass balance and observed in total phosphorus data collected at individual locations. Title: Effect of water-column pH on sediment-phosphorus release rates in Upper Klamath Lake, Oregon, 2001 Author: Fisher, Lawrence H. Year: 2004, 2005 Abstract Sediment-phosphorus release rates as a function of pH were determined in laboratory experiments for sediment and water samples collected from Shoalwater Bay in Upper Klamath Lake, Oregon, in 2001. Areal release rates for a stable sediment/water interface that is representative of the sediment surface area to water column volume ratio (1:3) observed in the lake and volumetric release rates for resuspended sediment events were determined at three different pH values (8.1, 9.2, 10.2). Ambient water column pH (8.1) was maintained by sparging study columns with atmospheric air. Elevation of the water column pH to 9.2 was achieved through the removal of dissolved carbon dioxide by sparging with carbon dioxide-reduced air, partially simulating water chemistry changes that occur during algal photosynthesis. Further elevation of the pH to 10.2 was achieved by the addition of sodium hydroxide, which doubled average alkalinities in the study columns from about 1 to 2 milliequivalents per liter. Upper Klamath Lake sediments collected from the lake bottom and then placed in contact with lake water, either at a stable sediment/water interface or by resus-pension, exhibited an initial capacity to take up soluble reactive phosphorus (SRP) from the water column rather than release phosphorus to the water column. At a higher pH this initial uptake of phosphorus was slowed, but not stopped. This initial phase was followed by a reversal in which the sediments began to release SRP back into the water column. The release rate of phosphorus 30 to 40 days after suspension of sediments in the columns was 0.5 |ig/L/day (micrograms per liter per day) at pH 8, and 0.9 |ug/L/day at pH 10, indicating that the higher pH increased the rate of phosphorus release by a factor of about two. The highest determined rate of release was approximately 10% (percent) of the rate required to explain the annual internal loading to Upper Klamath Lake from the sediments as calculated from a lake-wide mass balance and observed in total phosphorus data collected at individual locations. Close

• 10. [Image] Klamath River fish die-off, September 2002 : causative factors of mortality

  	Executive Summary This report provides information describing the biological, hydrological, meteorological, and water quality conditions associated with the die-off of an estimated 34,056 fish in the Klamath ...
  	Citation × Citation Citation Abstract Copy Title: Klamath River fish die-off, September 2002 : causative factors of mortality Author: Guillen, George Year: 2003, 2005, 2004 Executive Summary This report provides information describing the biological, hydrological, meteorological, and water quality conditions associated with the die-off of an estimated 34,056 fish in the Klamath River, California in September 2002. The proximate cause of death was heavy infections of two fish pathogens, Ich and columnaris. However, given that these ubiquitous pathogens are normally found in the Klamath River, additional factors must have played a role for them to have become lethal. It is our conclusion based on multiple lines of evidence that the fish die-off in the lower Klamath River in 2002 was a result of a combination of factors that began with an early peak in the return of a large run of fall Chinook salmon. Low river discharges apparently did not provide suitable attraction flows for migrating adult salmon, resulting in large numbers of fish congregating in the warm waters of the lower River. The high density offish, low discharges, warm water temperatures, and possible extended residence time of salmon created optimal conditions for parasite proliferation and precipitated an epizootic of Ich and columnaris. Based on a review of available literature and historical records, this was the largest known pre-spawning adult salmonid die-off recorded for the Klamath River and possibly the Pacific coast. Title: Klamath River fish die-off, September 2002 : causative factors of mortality Author: Guillen, George Year: 2003, 2005, 2004 Executive Summary This report provides information describing the biological, hydrological, meteorological, and water quality conditions associated with the die-off of an estimated 34,056 fish in the Klamath River, California in September 2002. The proximate cause of death was heavy infections of two fish pathogens, Ich and columnaris. However, given that these ubiquitous pathogens are normally found in the Klamath River, additional factors must have played a role for them to have become lethal. It is our conclusion based on multiple lines of evidence that the fish die-off in the lower Klamath River in 2002 was a result of a combination of factors that began with an early peak in the return of a large run of fall Chinook salmon. Low river discharges apparently did not provide suitable attraction flows for migrating adult salmon, resulting in large numbers of fish congregating in the warm waters of the lower River. The high density offish, low discharges, warm water temperatures, and possible extended residence time of salmon created optimal conditions for parasite proliferation and precipitated an epizootic of Ich and columnaris. Based on a review of available literature and historical records, this was the largest known pre-spawning adult salmonid die-off recorded for the Klamath River and possibly the Pacific coast. Close