Classifying California’s stream thermal regimes for cold-water conservation

PLOS | August 20th, 2021

Stream temperature science and management is rapidly shifting from single-metric driven approaches to multi-metric, thermal regime characterizations of streamscapes. Giv

Stream temperature science and management is rapidly shifting from single-metric driven approaches to multi-metric, thermal regime characterizations of streamscapes. Given considerable investments in recovery of cold-water fisheries (e.g., Pacific salmon and other declining native species), understanding where cold water is likely to persist, and how coldwater thermal regimes vary, is critical for conservation. California’s unique position at the southern end of cold-water ecosystems in the northern hemisphere, variable geography and hydrology, and extensive flow regulation requires a systematic approach to thermal regime classification. We used publicly available, long-term (> 8 years) stream temperature data from 77 sites across California to model their thermal regimes, calculate three temperature metrics, and use the metrics to classify each regime with an agglomerative nesting algorithm. Then, we assessed the variation in each class and considered underlying physical or anthropogenic factors that could explain differences between classes. Finally, we considered how different classes might fit existing criteria for cool- or cold-water thermal regimes, and how those differences complicate efforts to manage stream temperature through regulation. Our results demonstrate that cool- and cold-water thermal regimes vary spatially across California. Several salient findings emerge from this study. Groundwater-dominated streams are a ubiquitous, but as yet, poorly explored class of thermal regimes. Further, flow regulation below dams imposes serial discontinuities, including artificial thermal regimes on downstream ecosystems. Finally, and contrary to what is often assumed, California reservoirs do not contain sufficient cold-water storage to replicate desirable, reach-scale thermal regimes. While barriers to cold-water conservation are considerable and the trajectory of cold-water species towards extinction is dire, protecting reaches that demonstrate resilience to climate warming remains worthwhile.

Clean Water Act Jurisdiction Following the U.S. Supreme Court's Decision in Rapanos v. United States & Carabell v. United States

U.S. Environmental Protection Agency (EPA) | December 2nd, 2008

Congress enacted the Clean Water Act ("CWA" or "the Act") "to restore and maintain the chemical, physical, and biological integrity of the Nation's waters." One

Congress enacted the Clean Water Act ("CWA" or "the Act") "to restore and maintain the chemical, physical, and biological integrity of the Nation's waters." One of the mechanisms adopted by Congress to achieve that purpose is a prohibition on the discharge of any pollutants, including dredged or fill material, into "navigable waters" except in compliance with other specified sections of the Act. In most cases, this means compliance with a permit issued pursuant to CWA §402 or §404. The Act defines the term "discharge of a pollutant" as "any addition of any pollutant to navigable waters from any point source" and provides that "[t]he term `navigable waters' means the waters of the United States, including the territorial seas[,]." In Rapanos, the Supreme Court addressed where the Federal government can apply the Clean Water Act, specifically by determining whether a wetland or tributary is a "water of the United States." The justices issued five separate opinions in Rapanos (one plurality opinion, two concurring opinions, and two dissenting opinions), with no single opinion commanding a majority of the Court. The Rapanos Decision Four justices, in a plurality opinion authored by Justice Scalia, rejected the argument that the term "waters of the United States" is limited to only those waters that are navigable in the traditional sense and their abutting wetlands. However, the plurality concluded that the agencies' regulatory authority should extend only to "relatively permanent, standing or continuously flowing bodies of water" connected to traditional navigable waters, and to "wetlands with a continuous surface connection to" such relatively permanent waters . Justice Kennedy did not join the plurality's opinion but instead authored an opinion concurring in the judgment vacating and remanding the cases to the Sixth Circuit Court of Appeals.  Justice Kennedy agreed with the plurality that the statutory term "waters of the United States" extends beyond water bodies that are traditionally considered navigable." Justice Kennedy, however, found the plurality's interpretation of the scope of the CWA to be "inconsistent with the Act's text,structure,andpurpose[,]" and he instead presented a different standard for evaluating CWA jurisdiction over wetlands and other waterbodies.' Justice Kennedy concluded that wetlands are"waters of the United States" "if the wetlands, either alone or in combination with similarly situated lands in the region, significantly affect the chemical, physical, and biological integrity of other covered waters more readily understood as `navigable.' When, in contrast, wetlands' effects on water quality are speculative or insubstantial, they fall outside the zone fairly encompassed by the statutory term 'navigable waters.' Four justices, in a dissenting opinion authored by Justice Stevens, concluded that EPA's and the Corps' interpretation of "waters of the United States" was a reasonable interpretation of the Clean Water Act. When there is no majority opinion in a Supreme Court case, controlling legal principles may be derived from those principles espoused by five or more justices. Thus, regulatory jurisdiction under the CWA exists over a water body if either the plurality's or Justice Kennedy's standard is satisfied. Since Rapanos, the United States has filed pleadings in a number of cases interpreting the decision in this manner. The agencies are issuing this memorandum in recognition of the fact that EPA regions and Corps districts need guidance to ensure that jurisdictional determinations, permitting actions, and other relevant actions are consistent with the decision and supported by the administrative record. Therefore, the agencies have evaluated the Rapanos opinions to identify those waters that are subject to CWA jurisdiction under the reasoning of a majority of the justices. This approach is appropriate for a guidance document. The agencies will continue to monitor implementation of the Rapanos decision in the field and recognize that further consideration of jurisdictional issues, including clarification and definition of key terminology, may be appropriate in the future, either through issuance of additional guidance or through rulemaking.

Clean Watersheds Needs Survey 2012

U.S. Environmental Protection Agency (EPA) | December 13th, 2012

Clear Lake Watershed and Lake Remediation

University of California, Davis (UC Davis) | December 9th, 2024

The main goal of this joint effort between the University of California Davis, Tahoe Environmental Research Center (UCD-TERC), and the United States Geological Survey (US

The main goal of this joint effort between the University of California Davis, Tahoe Environmental Research Center (UCD-TERC), and the United States Geological Survey (USGS), is to develop the watershed and in-lake monitoring and modeling needed to:  Better understanding of the processes contributing to poor water quality;  Predict watershed and lake responses to changing environmental conditions; and,  Evaluate the impacts and unintended consequences of potential management and restoration activities. 

Clearer Structure, Cleaner Water: Improving Performance and Outcomes at the State Water Boards

Little Hoover Commission | January 1st, 2009

The Little Hoover Commission on Thursday urged the governor and the Legislature to reform the State Water Resources Control Board and nine Regional Water Quality Control

The Little Hoover Commission on Thursday urged the governor and the Legislature to reform the State Water Resources Control Board and nine Regional Water Quality Control Boards by expanding the state board to nine members, with five members representing statewide interests and four drawn on a rotating basis from the nine regional board chairpersons, whose positions would become full-time. In addition, the Commission called for a revamped appeals process; to improve the use of data and science in water quality regulatory processes; and urged the water boards to focus on new ways to solve modern water quality problems and set priorities. In its report, Clearer Structure, Cleaner Water: Improving Performance and Outcomes at the State Water Boards, the Commission also recommends refocusing both the state board and regional boards on policy-making and updating basin plans. During its study, the Commission found that the water boards face increasingly complex water quality problems, caused in part by hard-to-regulate sources such as urban and agricultural runoff. The Commission also found that a decentralized governance structure, with nine regional water quality boards operating with distinct policies and processes, hinders accountability and transparency. The result is a system that has lost the confidence of most stakeholders. To restore accountability and increase focus on clean-water outcomes, the Commission recommends strengthening the relationship between the state and regional boards. “The governance structure for water quality regulation in California is 40 years old and is ill-prepared to handle modern problems,” Little Hoover Commission Chairman Daniel Hancock said. “Major reform is needed to help protect and improve water quality, which is a key to the state’s future.”

Clearing the Waters: A Focus on Water Quality Solutions

Pacific Institute | March 22nd, 2010

Every day, 2 million tons of sewage and industrial and agricultural waste are poured into the world’s waters. The result is that more people die from unsafe water annua

Every day, 2 million tons of sewage and industrial and agricultural waste are poured into the world’s waters. The result is that more people die from unsafe water annually than from all forms of violence, including war. A new Pacific Institute report released by the United Nations Environment Programme (UNEP) for World Water Day, March 22, 2010, lays out steps and solutions to address our urgent water-quality challenges––and they start with awareness and will to action. “A wide range of human activities affect water quality. The health of our ecosystems––and our communities––depends on how we act now,” said Achim Steiner, executive director of UNEP. “Improving and protecting water quality means healthier ecosystems, improved human well-being, and more secure livelihoods, both for ourselves and for future generations.” The new United Nations report, Clearing the Waters: A Focus on Water Quality Solutions, details how water quality is as important as water quantity for satisfying human and environmental needs, yet has received far less investment, scientific support, and public attention. Prepared by the Pacific Institute, one of the world’s leading nonprofit research organizations on freshwater issues, the UNEP report is part of the World Water Day 2010 effort to bring global attention to the need for clean, safe water––and action and policy to address water pollution. “Improving water quality, whether by preventing pollution, treating wastewater before disposal, or restoring the quality of waterways, requires increased awareness and political will,” said Peter Gleick, president of the Pacific Institute. “The consequences of inaction are stark: water-quality problems affect our health, reduce agricultural productivity, impose additional costs on industrial production, and degrade ecosystem services––with costs to local populations and governments.”

Climate Change and Future Water Availability in the United States, Chapter E of U.S. Geological Survey Integrated Water Availability Assessment—2010–20

U.S. Geological Survey (USGS) | January 15th, 2025

The following are the key points of this chapter:  The steady rise in global temperature as a result of human activity is causing changes in Earth’s water cycle.

The following are the key points of this chapter:  The steady rise in global temperature as a result of human activity is causing changes in Earth’s water cycle. The amount of water stored within and moving between vapor, liquid and frozen components of the water cycle is shifting, with significant consequences for water availability. Climatic drivers underlie regional or local changes in water supply and their socioeconomic impacts. Threats to the quantity and quality of water available for humans and ecosystems in North America include increases in drought, aridification, and fire weather; heavy precipitation and flooding; cryosphere decline; rising surface-water temperatures; and saltwater intrusion in coastal areas. An understanding of how changes in the major climatic drivers impact the water cycle and the accurate simulation of impacts in hydrological models are crucial to predicting future water availability and developing adaptation strategies to ensure human and ecosystem water supplies. Companion chapters: U.S. Geological Survey Integrated Water Availability Assessment—2010–20, Chapter A Water Supply in the Conterminous United States, Alaska, Hawaii, and Puerto Rico, Water Years 2010–20, Chapter B Status of Water-Quality Conditions in the United States, 2010–20, Chapter C  Water Use Across the Conterminous United States, Water Years 2010–20, Chapter D  Integrated Water Availability in the Conterminous United States, 2010–20, Chapter F 

Climate change and variability drive increasing exposure of marine heatwaves across US estuaries

Nature Portfolio (Springer Nature) | March 6th, 2025

Marine heatwaves (MHWs) are among the greatest threats to marine ecosystems, and while substantial advances have been made in oceanic MHWs, little is known about estuarin

Marine heatwaves (MHWs) are among the greatest threats to marine ecosystems, and while substantial advances have been made in oceanic MHWs, little is known about estuarine MHWs. Utilizing a temperature dataset spanning over two decades and 54 stations distributed across 20 estuaries in the United States National Estuarine Research Reserve System, we present a comprehensive analysis of estuarine MHW characteristics and trends. Long-term climate-change-driven warming is driving more frequent MHWs along the East Coast, and if trends continue, this region will be in a MHW state for ~ 1/3 of the year by the end of the century. In contrast, the vast majority of the West Coast showed no trends, highlighting the potential for future thermal refugia. The West Coast was more strongly influenced by climate variability through the enhancement/suppression of MHWs during different phases of climate modes, suggesting long-term predictability potential. These results can provide guidance for management actions and planning in these critical environments.

Climate Change Scenarios for Air and Water Temperatures in the Upper San Francisco Estuary: Implications for Thermal Regimes and Delta Smelt

University of California, Davis (UC Davis) | June 10th, 2024

Climate-driven aerobic habitat loss in the California Current System

American Association for the Advancement of Science (AAAS) | May 15th, 2020

Climate warming is expected to intensify hypoxia in the California Current System (CCS), threatening its diverse and productive marine ecosystem. We analyzed past region

Climate warming is expected to intensify hypoxia in the California Current System (CCS), threatening its diverse and productive marine ecosystem. We analyzed past regional variability and future changes in the Metabolic Index, a species-specific measure of the environment’s capacity to meet temperature-dependent organismal oxygen demand. Across the traits of diverse animals, exhibits strong seasonal to interdecadal variations throughout the CCS, implying that resident species already experience large fluctuations in available aerobic habitat. For a key CCS species, northern anchovy, the long-term biogeographic distribution and decadal fluctuations in abundance are both highly coherent with aerobic habitat volume. Ocean warming and oxygen loss by 2100 are projected to decrease below critical levels in 30 to 50% of anchovies’ present range, including complete loss of aerobic habitat—and thus likely extirpation—from the southern CCS. Aerobic habitat loss will vary widely across the traits of CCS taxa, disrupting ecological interactions throughout the region.