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• 1451. [Image] Klamath River Basin issues and activities

  	Klamath River Basin Issues and Activities: An Overview Summary The Klamath River Basin, an area on the California-Oregon border, has become a focal point for local and national discussions on water ...
  	Citation × Citation Citation Abstract Copy Title: Klamath River Basin issues and activities Author: Kyna Powers Year: 2005, 2008, 2006 Klamath River Basin Issues and Activities: An Overview Summary The Klamath River Basin, an area on the California-Oregon border, has become a focal point for local and national discussions on water management and water scarcity. Water and species management issues were brought to the forefront when severe drought in 2001 exacerbated competition for scarce water resources and generated conflict among several interests - farmers, Indian tribes, commercial and sport fishermen, other recreationists, federal wildlife refuge managers, environmental groups, and state, local, and tribal governments. The conflicts over water distribution and allocation are physically and legally complex, reflecting the varied and sometimes competing uses of limited water supplies in the Basin. For management purposes, the Basin is divided at Iron Gate Dam into the Upper and Lower Basins. As is true in many regions in the West, the federal government plays a prominent role in the Klamath Basin's water management. This role stems from three primary activities: (1) the operation and management of the Bureau of Reclamation's Klamath Water Project and Central Valley Project (e.g., Trinity River dams); (2) management of federal lands in the Basin, including five national wildlife refuges, several national forests, and public lands; and (3) implementation of federal laws, such as the Endangered Species Act (ESA), Clean Water Act (CWA), and National Environmental Policy Act (NEPA). Conflict was sparked in April of 2001 when the Bureau of Reclamation, which has supplied water to farms in the Upper Basin for nearly 100 years, announced that "no water [would] be available" for farms normally receiving water from the Upper Klamath Lake to avoid jeopardizing the existence of three fish species listed as endangered or threatened under the ESA. While some water was subsequently made available to some farmers from other sources (e.g., wells and other Bureau sources), many farmers faced serious hardships. During Reclamation's operations in September of 2002, warm water temperatures and atypically low flows in the lower Klamath contributed to the death of at least 33,000 adult salmonids. This die-off damaged fish stocks and the tribes, commercial fishermen, and recreational anglers that catch Klamath fish. There have been many studies, Biological Opinions, and operating plans over recent years, all of which have been controversial. The events of 2001 and 2002 prompted renewed efforts to resolve water conflicts in the Klamath Basin. Congress has responded to the controversy in a number of ways, including holding oversight hearings and appropriating funds for activities in the area. This report provides an overview of recent conflict in the Klamath Basin, with an emphasis on activities in the Upper Basin, and summarizes some of the activities taking place to improve water supply reliability and fish survival. This report will be updated as events warrant. Title: Klamath River Basin issues and activities Author: Kyna Powers Year: 2005, 2008, 2006 Klamath River Basin Issues and Activities: An Overview Summary The Klamath River Basin, an area on the California-Oregon border, has become a focal point for local and national discussions on water management and water scarcity. Water and species management issues were brought to the forefront when severe drought in 2001 exacerbated competition for scarce water resources and generated conflict among several interests - farmers, Indian tribes, commercial and sport fishermen, other recreationists, federal wildlife refuge managers, environmental groups, and state, local, and tribal governments. The conflicts over water distribution and allocation are physically and legally complex, reflecting the varied and sometimes competing uses of limited water supplies in the Basin. For management purposes, the Basin is divided at Iron Gate Dam into the Upper and Lower Basins. As is true in many regions in the West, the federal government plays a prominent role in the Klamath Basin's water management. This role stems from three primary activities: (1) the operation and management of the Bureau of Reclamation's Klamath Water Project and Central Valley Project (e.g., Trinity River dams); (2) management of federal lands in the Basin, including five national wildlife refuges, several national forests, and public lands; and (3) implementation of federal laws, such as the Endangered Species Act (ESA), Clean Water Act (CWA), and National Environmental Policy Act (NEPA). Conflict was sparked in April of 2001 when the Bureau of Reclamation, which has supplied water to farms in the Upper Basin for nearly 100 years, announced that "no water [would] be available" for farms normally receiving water from the Upper Klamath Lake to avoid jeopardizing the existence of three fish species listed as endangered or threatened under the ESA. While some water was subsequently made available to some farmers from other sources (e.g., wells and other Bureau sources), many farmers faced serious hardships. During Reclamation's operations in September of 2002, warm water temperatures and atypically low flows in the lower Klamath contributed to the death of at least 33,000 adult salmonids. This die-off damaged fish stocks and the tribes, commercial fishermen, and recreational anglers that catch Klamath fish. There have been many studies, Biological Opinions, and operating plans over recent years, all of which have been controversial. The events of 2001 and 2002 prompted renewed efforts to resolve water conflicts in the Klamath Basin. Congress has responded to the controversy in a number of ways, including holding oversight hearings and appropriating funds for activities in the area. This report provides an overview of recent conflict in the Klamath Basin, with an emphasis on activities in the Upper Basin, and summarizes some of the activities taking place to improve water supply reliability and fish survival. This report will be updated as events warrant. Close

• 1452. [Image] Oregon lampreys : natural history, status, and analysis of management issues

  	Executive Summary The jawless lampreys are remnants of the oldest vertebrates in the world. Oregon has somewhere between eight and a dozen species of these primitive fishes. Their taxonomy is obscure ...
  	Citation × Citation Citation Abstract Copy Title: Oregon lampreys : natural history, status, and analysis of management issues Author: Kostow, Kathryn Year: 2002, 2008, 2005 Executive Summary The jawless lampreys are remnants of the oldest vertebrates in the world. Oregon has somewhere between eight and a dozen species of these primitive fishes. Their taxonomy is obscure because different species tend to look very similar through most of their life cycle, and they have not been well-studied in Oregon. Lampreys occur in the Columbia Basin, including the lower Snake River, along the Oregon coast, in the upper Klamath Basin, and in Goose Lake Basin in southeastern Oregon. They all begin life in fresh water where juveniles burrow into silt and filter feed on algae. As some species approach adulthood they migrate to the ocean or to lakes where they briefly become ecto-parasites, feeding on other live fishes by attaching to them with sucker disc mouths. Other species remain non-parasitic. In addition to some enigmatic species identities, we generally have very little information about the detailed distributions, life histories and basic biology of lampreys. Lampreys became a conservation concern in the early 1990s when tribal co-managers and some Oregon Department of Fish and Wildlife (ODFW) staff noted that populations of Pacific Lampreys, Lampetra tridentata, were apparently declining to perilously low numbers. Pacific Lampreys were listed as an Oregon State sensitive species in 1993 and were given further legal protected status by the state in 1997 (OAR 635-044-0130). Lamprey status is difficult to assess for several reasons: 1) Most observations of lampreys in fresh water are of juveniles and it is difficult to tell the various species apart, even to the extent that the various species are currently clearly designated; 2) Data on lamprey is only collected incidental to monitoring of salmonids. The design and efficiency of the data collection effort is not always adequate for lampreys; and 3) We have very few historic data sets for lampreys. Therefore we often cannot determine how the abundances and distributions we see now compare with those in the past. The limited data that we have suggests that lampreys have declined through many parts of their ranges. The most precipitous declines appear to be in the upper Columbia and Snake basins where we have some historic data from mainstem dam counts. Pacific Lampreys have declined to only about 200 adults annually passing the Snake River dams. We also have evidence of declines of Pacific Lampreys in the lower Columbia and on the Oregon coast, although our data is quite limited. We have little to no information about any of the other species of lampreys. We are not even sure whether some of the recognized species, like the River Lamprey (L. ayresi), is still present in Oregon. This paper concludes with a Problem Analysis for Oregon lampreys. Our biggest problem is poor information, ranging from not knowing basic species identity to having inefficient or no systematic monitoring of lamprey abundance and distribution. ODFW continued an annual harvest on Pacific Lamprey in the Willamette Basin in 2001, but we lack the necessary information to assess the affects of the harvest on the population. Major habitat problems that affect lampreys include upstream passage over artificial barriers, a need for lamprey-friendly screening of water diversions, and urban and agricultural development of low-gradient flood plain habitats. Title: Oregon lampreys : natural history, status, and analysis of management issues Author: Kostow, Kathryn Year: 2002, 2008, 2005 Executive Summary The jawless lampreys are remnants of the oldest vertebrates in the world. Oregon has somewhere between eight and a dozen species of these primitive fishes. Their taxonomy is obscure because different species tend to look very similar through most of their life cycle, and they have not been well-studied in Oregon. Lampreys occur in the Columbia Basin, including the lower Snake River, along the Oregon coast, in the upper Klamath Basin, and in Goose Lake Basin in southeastern Oregon. They all begin life in fresh water where juveniles burrow into silt and filter feed on algae. As some species approach adulthood they migrate to the ocean or to lakes where they briefly become ecto-parasites, feeding on other live fishes by attaching to them with sucker disc mouths. Other species remain non-parasitic. In addition to some enigmatic species identities, we generally have very little information about the detailed distributions, life histories and basic biology of lampreys. Lampreys became a conservation concern in the early 1990s when tribal co-managers and some Oregon Department of Fish and Wildlife (ODFW) staff noted that populations of Pacific Lampreys, Lampetra tridentata, were apparently declining to perilously low numbers. Pacific Lampreys were listed as an Oregon State sensitive species in 1993 and were given further legal protected status by the state in 1997 (OAR 635-044-0130). Lamprey status is difficult to assess for several reasons: 1) Most observations of lampreys in fresh water are of juveniles and it is difficult to tell the various species apart, even to the extent that the various species are currently clearly designated; 2) Data on lamprey is only collected incidental to monitoring of salmonids. The design and efficiency of the data collection effort is not always adequate for lampreys; and 3) We have very few historic data sets for lampreys. Therefore we often cannot determine how the abundances and distributions we see now compare with those in the past. The limited data that we have suggests that lampreys have declined through many parts of their ranges. The most precipitous declines appear to be in the upper Columbia and Snake basins where we have some historic data from mainstem dam counts. Pacific Lampreys have declined to only about 200 adults annually passing the Snake River dams. We also have evidence of declines of Pacific Lampreys in the lower Columbia and on the Oregon coast, although our data is quite limited. We have little to no information about any of the other species of lampreys. We are not even sure whether some of the recognized species, like the River Lamprey (L. ayresi), is still present in Oregon. This paper concludes with a Problem Analysis for Oregon lampreys. Our biggest problem is poor information, ranging from not knowing basic species identity to having inefficient or no systematic monitoring of lamprey abundance and distribution. ODFW continued an annual harvest on Pacific Lamprey in the Willamette Basin in 2001, but we lack the necessary information to assess the affects of the harvest on the population. Major habitat problems that affect lampreys include upstream passage over artificial barriers, a need for lamprey-friendly screening of water diversions, and urban and agricultural development of low-gradient flood plain habitats. Close

• 1453. [Image] Research information needs on terrestrial vertebrate species of the interior Columbia River basin and northern portions of the Klamath and Great basins: research, development, and application database

  	"September 1997"; Includes bibliographical references (p. 24)
  	Citation × Citation Citation Abstract Copy Title: Research information needs on terrestrial vertebrate species of the interior Columbia River basin and northern portions of the Klamath and Great basins: research, development, and application database Author: Marcot, Bruce G. Year: 1997, 2005, 2004 "September 1997"; Includes bibliographical references (p. 24) Title: Research information needs on terrestrial vertebrate species of the interior Columbia River basin and northern portions of the Klamath and Great basins: research, development, and application database Author: Marcot, Bruce G. Year: 1997, 2005, 2004 "September 1997"; Includes bibliographical references (p. 24) Close

• 1454. [Image] Sediment oxygen demand in Upper Klamath and Agency Lakes, Oregon, 1999

  	SIGNIFICANT FINDINGS The distribution of SOD2q values (measured sediment oxygen demand values corrected to 20°C [degrees Celsius]) had a median value of 1.6 g/m2/day (grams per square meter per day) in ...
  	Citation × Citation Citation Abstract Copy Title: Sediment oxygen demand in Upper Klamath and Agency Lakes, Oregon, 1999 Author: Wood, Tamara M. Year: 2001, 2005, 2004 SIGNIFICANT FINDINGS The distribution of SOD2q values (measured sediment oxygen demand values corrected to 20°C [degrees Celsius]) had a median value of 1.6 g/m2/day (grams per square meter per day) in the spring and 1.7 g/m2/day in the late summer. These values were well within the range of values in the literature for sites with similar sediment characteristics: primarily silty with at least a moderate amount of organic content. Over most of the lake there appears to be relatively little variation in SOD 14the interquartile range in values was 0.4 g/m2/day in the spring and 0.7 g/m2/day in the late summer. A significant exception was apparent in Ball Bay, where SOD in the late summer was greater than 10.2 g/m2/day. In the absence of primary production, an SOD of this magnitude could deplete the water column of oxygen in a few days. This measurement provided evidence that localized areas of very high SOD occur episodically in the bays, perhaps associated with large algal mats being trapped by the lake circulation patterns. A statistical test for a spring to late summer difference in the median values of SOD confirmed that SOD in the late summer (median value 1.7 g/m2/day) was significantly higher than in the spring (median value 1.2 g/m2/day). The difference was primarily due to seasonal changes in temperature; when SOD values were corrected to 20°C, there was no seasonal difference in the median values. There was no correlation between SOD20 and the sediment characteristics measured in this study: percent fines, organic carbon, and residue lost on ignition. Title: Sediment oxygen demand in Upper Klamath and Agency Lakes, Oregon, 1999 Author: Wood, Tamara M. Year: 2001, 2005, 2004 SIGNIFICANT FINDINGS The distribution of SOD2q values (measured sediment oxygen demand values corrected to 20°C [degrees Celsius]) had a median value of 1.6 g/m2/day (grams per square meter per day) in the spring and 1.7 g/m2/day in the late summer. These values were well within the range of values in the literature for sites with similar sediment characteristics: primarily silty with at least a moderate amount of organic content. Over most of the lake there appears to be relatively little variation in SOD 14the interquartile range in values was 0.4 g/m2/day in the spring and 0.7 g/m2/day in the late summer. A significant exception was apparent in Ball Bay, where SOD in the late summer was greater than 10.2 g/m2/day. In the absence of primary production, an SOD of this magnitude could deplete the water column of oxygen in a few days. This measurement provided evidence that localized areas of very high SOD occur episodically in the bays, perhaps associated with large algal mats being trapped by the lake circulation patterns. A statistical test for a spring to late summer difference in the median values of SOD confirmed that SOD in the late summer (median value 1.7 g/m2/day) was significantly higher than in the spring (median value 1.2 g/m2/day). The difference was primarily due to seasonal changes in temperature; when SOD values were corrected to 20°C, there was no seasonal difference in the median values. There was no correlation between SOD20 and the sediment characteristics measured in this study: percent fines, organic carbon, and residue lost on ignition. Close

• 1455. [Image] Effects of water quality on growth of juvenile shortnose suckers, Chasmistes brevirostris (Catostomidae: Cypriniformes), from Upper Klamath Lake, Oregon

  	One chapter of a seven chapter annual report from 1999 examining ecological issues regarding the shortnose and Lost River sucker populations in Upper Klamath Lake and Williamson River.
  	Citation × Citation Citation Abstract Copy Title: Effects of water quality on growth of juvenile shortnose suckers, Chasmistes brevirostris (Catostomidae: Cypriniformes), from Upper Klamath Lake, Oregon Author: Oregon Cooperative Wildlife Research Unit Year: 2000, 2005 One chapter of a seven chapter annual report from 1999 examining ecological issues regarding the shortnose and Lost River sucker populations in Upper Klamath Lake and Williamson River. Title: Effects of water quality on growth of juvenile shortnose suckers, Chasmistes brevirostris (Catostomidae: Cypriniformes), from Upper Klamath Lake, Oregon Author: Oregon Cooperative Wildlife Research Unit Year: 2000, 2005 One chapter of a seven chapter annual report from 1999 examining ecological issues regarding the shortnose and Lost River sucker populations in Upper Klamath Lake and Williamson River. Close

• 1456. [Image] Recent paleolimnology of Upper Klamath Lake, Oregon

  	Recent Paleolimnology of Upper Klamath Lake Eilers et al. 2001 ABSTRACT Sediment cores were collected from Upper Klamath Lake in October, 1998 and analyzed for 210Pb, 14C, 15N, N, P, C, Ti, Al, diatoms, ...
  	Citation × Citation Citation Abstract Copy Title: Recent paleolimnology of Upper Klamath Lake, Oregon Author: United States. Bureau of Reclamation Year: 2001, 2005 Recent Paleolimnology of Upper Klamath Lake Eilers et al. 2001 ABSTRACT Sediment cores were collected from Upper Klamath Lake in October, 1998 and analyzed for 210Pb, 14C, 15N, N, P, C, Ti, Al, diatoms, Pediastrum, and cyanobacterial akinetes. These results were used to reconstruct changes in water quality in Upper Klamath Lake over the last 150 years. The results showed that there was substantial mixing of the upper 10 cm of sediment, representing the previous 20 to 30 years. However, below that, 210Pb activity declined monotonically, allowing reasonable dating for the period from about 1850 to 1970. The sediment accumulation rates (SAR) showed a substantial increase in the 20th century. The increase in SAR corresponded with increases in erosional input from the watershed as represented by the increases in sediment concentrations of Ti and Al. The upper 20 cm of sediment (representing the last 150 years) also showed increases in C, N, P, and 15N. The increases in nutrient concentrations may be affected to various degrees by diagenetic reactions within the sediments, although the changes in concentrations also were marked by changes in the N:P ratio and in a qualitative change in the source of N as reflected in increasing S15N. The diatoms showed modest changes, particularly in the upper sediments, with increases in Asterionellaformosa, Stephanodiscus hantzschii, and S. parvus. Pediastrum, a green alga, was well-preserved in the sediments and exhibited a sharp decline in relative abundance in the upper sediments. Total cyanobacteria, as represented by preserved akinetes, exhibited only minor changes in the last 1000 years. However, a taxon which was formerly not present in the lake 150 years ago, Aphanizomenon, has shown major increases in recent decades. Although the mixing in the upper sediments prevents high-resolution temporal analysis of the recent history (e.g. last 30 years) of Upper Klamath Lake, the results demonstrate that major changes in water quality likely have occurred leading to a major modification of the phytoplankton assemblage. The changes in sediment composition are consistent with land use activities during this period that include substantial deforestation, drainage of wetlands, and agricultural activities associated with livestock and irrigated cropland. Title: Recent paleolimnology of Upper Klamath Lake, Oregon Author: United States. Bureau of Reclamation Year: 2001, 2005 Recent Paleolimnology of Upper Klamath Lake Eilers et al. 2001 ABSTRACT Sediment cores were collected from Upper Klamath Lake in October, 1998 and analyzed for 210Pb, 14C, 15N, N, P, C, Ti, Al, diatoms, Pediastrum, and cyanobacterial akinetes. These results were used to reconstruct changes in water quality in Upper Klamath Lake over the last 150 years. The results showed that there was substantial mixing of the upper 10 cm of sediment, representing the previous 20 to 30 years. However, below that, 210Pb activity declined monotonically, allowing reasonable dating for the period from about 1850 to 1970. The sediment accumulation rates (SAR) showed a substantial increase in the 20th century. The increase in SAR corresponded with increases in erosional input from the watershed as represented by the increases in sediment concentrations of Ti and Al. The upper 20 cm of sediment (representing the last 150 years) also showed increases in C, N, P, and 15N. The increases in nutrient concentrations may be affected to various degrees by diagenetic reactions within the sediments, although the changes in concentrations also were marked by changes in the N:P ratio and in a qualitative change in the source of N as reflected in increasing S15N. The diatoms showed modest changes, particularly in the upper sediments, with increases in Asterionellaformosa, Stephanodiscus hantzschii, and S. parvus. Pediastrum, a green alga, was well-preserved in the sediments and exhibited a sharp decline in relative abundance in the upper sediments. Total cyanobacteria, as represented by preserved akinetes, exhibited only minor changes in the last 1000 years. However, a taxon which was formerly not present in the lake 150 years ago, Aphanizomenon, has shown major increases in recent decades. Although the mixing in the upper sediments prevents high-resolution temporal analysis of the recent history (e.g. last 30 years) of Upper Klamath Lake, the results demonstrate that major changes in water quality likely have occurred leading to a major modification of the phytoplankton assemblage. The changes in sediment composition are consistent with land use activities during this period that include substantial deforestation, drainage of wetlands, and agricultural activities associated with livestock and irrigated cropland. Close

• 1457. [Image] Pinniped and seabird predation : implications for recovery of threatened stocks of salmonids in Oregon under the Oregon Plan for Salmon and Watersheds

  	"December 22, 1998."
  	Citation × Citation Citation Abstract Copy Title: Pinniped and seabird predation : implications for recovery of threatened stocks of salmonids in Oregon under the Oregon Plan for Salmon and Watersheds Author: Independent Multidisciplinary Science Team (Or.) Year: 1998, 2005 "December 22, 1998." Title: Pinniped and seabird predation : implications for recovery of threatened stocks of salmonids in Oregon under the Oregon Plan for Salmon and Watersheds Author: Independent Multidisciplinary Science Team (Or.) Year: 1998, 2005 "December 22, 1998." Close

• 1458. [Image] Western water resource issues

  	CRS issue brief; "Updated May 19, 2005."
  	Citation × Citation Citation Abstract Copy Title: Western water resource issues Author: Cody, Betsy A.; Sheikh, Pervaze A. Year: 2005 CRS issue brief; "Updated May 19, 2005." Title: Western water resource issues Author: Cody, Betsy A.; Sheikh, Pervaze A. Year: 2005 CRS issue brief; "Updated May 19, 2005." Close

• 1459. [Image] The Klamath Project

  	"Seventh draft"; Includes bibliographical references and index
  	Citation × Citation Citation Abstract Copy Title: The Klamath Project Author: Stene, Eric A. Year: 1994, 2004 "Seventh draft"; Includes bibliographical references and index Title: The Klamath Project Author: Stene, Eric A. Year: 1994, 2004 "Seventh draft"; Includes bibliographical references and index Close

• 1460. [Image] The Chemical and biological impact of Klamath Marsh on the Williamson River, Oregon

  	A comparative study of the Williamson River (before and after passage through Klamath Marsh) and the Sprague River (which is a major tributary of the Williamson River) in South Central Oregon has provided ...
  	Citation × Citation Citation Abstract Copy Title: The Chemical and biological impact of Klamath Marsh on the Williamson River, Oregon Author: Perdue, Edward M. Year: 1981, 2005 A comparative study of the Williamson River (before and after passage through Klamath Marsh) and the Sprague River (which is a major tributary of the Williamson River) in South Central Oregon has provided substantial insight into the effects of a marsh environment on the transport of iron and aquatic humus in river water. In the Sprague River and in the pre-marsh Williamson River, iron is transported primarily as 0.80 ym suspended particulate material. In Klamath Marsh, this coarse particulate material is "weathered11, yielding iron-aquatic humus "complexes'1. Thus, most iron and aquatic humus in the post-marsh Williamson River are in the 0.025 ?m size fraction. Presumably, other trace metals would be similarly affected. Klamath Marsh serves as an important source of biologically derived solutes such as amino acids and sugars. Fractionation studies have shown that amino acids are almost exclusively humic-bound in the Will-iamson River system, while sugars may be present as either polysacchar-ides (PS) or humic-bound saccharides (HS). The PS/HS ratio may reflect the relative importance of autochthonous and allochthonous sources of sugars. Major solute composition strongly indicates that ground waters flowing into the pre-marsh Williamson River and the Sprague River are derived from a different source than are ground waters which enter the post-marsh Williamson River from Big Springs, Spring Creek, and from unidentified springs below Klamath Marsh. Nutrient concentrations (H4SiO4, NO3, PO43) are significantly higher in spring waters than elsewhere in the system. While nitrate levels (3-11 ?m) were somewhat low, phosphate levels (1-3 ?m) were quite high throughout the Williamson River system. There was some evidence for nitrogen limitation of algal growth in the pre-marsh Williamson River. While Fragilaria construens was dominant throughout the Williamson River system, several Navicula spp. were restricted to the pre-marsh Williamson River and several Fragilaria spp. and Nitzschia, spp. were found only in the post-marsh Williamson River. In Upper Klamath Lake, Stephanodiscus astrea minuta, Fragilaria construens, and Aphanizomenon flos-aquae appeared in succession, with nuisance blooms of the latter organism occurring July-November. The cessation of flow of humic-rich water from Klamath Marsh during the summer months drastically decreased the flux of aquatic humus, iron, amino acids, and other marsh-derived solutes in the post-marsh Williamson River. At the time of cessation of flow from Klamath Marsh, nuisance blooms of Aphanizomenon flos-aquae appeared in Upper Klamath Lake. Furthermore, when flow from the marsh was re-established with the first major winter rains in November or December, Aphanizomenon flos-aquae abruptly ceased to grow in Upper Klamath Lake. Further studies are planned to determine whether this correlation is causal or coincidental. Title: The Chemical and biological impact of Klamath Marsh on the Williamson River, Oregon Author: Perdue, Edward M. Year: 1981, 2005 A comparative study of the Williamson River (before and after passage through Klamath Marsh) and the Sprague River (which is a major tributary of the Williamson River) in South Central Oregon has provided substantial insight into the effects of a marsh environment on the transport of iron and aquatic humus in river water. In the Sprague River and in the pre-marsh Williamson River, iron is transported primarily as 0.80 ym suspended particulate material. In Klamath Marsh, this coarse particulate material is "weathered11, yielding iron-aquatic humus "complexes'1. Thus, most iron and aquatic humus in the post-marsh Williamson River are in the 0.025 ?m size fraction. Presumably, other trace metals would be similarly affected. Klamath Marsh serves as an important source of biologically derived solutes such as amino acids and sugars. Fractionation studies have shown that amino acids are almost exclusively humic-bound in the Will-iamson River system, while sugars may be present as either polysacchar-ides (PS) or humic-bound saccharides (HS). The PS/HS ratio may reflect the relative importance of autochthonous and allochthonous sources of sugars. Major solute composition strongly indicates that ground waters flowing into the pre-marsh Williamson River and the Sprague River are derived from a different source than are ground waters which enter the post-marsh Williamson River from Big Springs, Spring Creek, and from unidentified springs below Klamath Marsh. Nutrient concentrations (H4SiO4, NO3, PO43) are significantly higher in spring waters than elsewhere in the system. While nitrate levels (3-11 ?m) were somewhat low, phosphate levels (1-3 ?m) were quite high throughout the Williamson River system. There was some evidence for nitrogen limitation of algal growth in the pre-marsh Williamson River. While Fragilaria construens was dominant throughout the Williamson River system, several Navicula spp. were restricted to the pre-marsh Williamson River and several Fragilaria spp. and Nitzschia, spp. were found only in the post-marsh Williamson River. In Upper Klamath Lake, Stephanodiscus astrea minuta, Fragilaria construens, and Aphanizomenon flos-aquae appeared in succession, with nuisance blooms of the latter organism occurring July-November. The cessation of flow of humic-rich water from Klamath Marsh during the summer months drastically decreased the flux of aquatic humus, iron, amino acids, and other marsh-derived solutes in the post-marsh Williamson River. At the time of cessation of flow from Klamath Marsh, nuisance blooms of Aphanizomenon flos-aquae appeared in Upper Klamath Lake. Furthermore, when flow from the marsh was re-established with the first major winter rains in November or December, Aphanizomenon flos-aquae abruptly ceased to grow in Upper Klamath Lake. Further studies are planned to determine whether this correlation is causal or coincidental. Close