2018 Clear Creek Technical Team Annual Report for the Coordinated Long-Term Operations Biological Opinion

Delta Stewardship Council (DSC) | July 1st, 2019

2022 Drought Plan Klamath Project, Oregon-California Interior Region 10, California-Great Basin

U.S. Bureau of Reclamation (USBR) | April 29th, 2022

The Klamath Project (Project) delivers water for irrigation purposes to up to approximately 230,000 acres in southern Oregon and northern California when water is availab

The Klamath Project (Project) delivers water for irrigation purposes to up to approximately 230,000 acres in southern Oregon and northern California when water is available. The Project relies upon several primary water sources to meet irrigation demands including water from Upper Klamath Lake (UKL), Clear Lake Reservoir, and Gerber Reservoir, and from the Klamath and Lost rivers. The Project’s water supplies (Project Supply or Supplies) have been impacted by the severe drought conditions currently affecting the Klamath Basin in southern Oregon and northern California. This 2022 Drought Plan describes the background for and the process of allocating the available Project Supply during the 2022 spring/summer irrigation season (April 15 through September 30, 20222), consistent with the contract priorities that exist within the Project.

A western United States snow reanalysis dataset over the Landsat era from water years 1985 to 2021

Scientific Data (Nature) | November 7th, 2022

Water stored in mountain snowpacks (i.e., snow water equivalent, SWE) represents an important but poorly characterized component of the terrestrial water cycle. The Weste

Water stored in mountain snowpacks (i.e., snow water equivalent, SWE) represents an important but poorly characterized component of the terrestrial water cycle. The Western United States snow reanalysis (WUS–SR) dataset is novel in its combination of spatial resolution (~500 m), spatial extent (31°–49° N; 102°–125° W), and temporal continuity (daily over 1985–2021). WUS–SR is generated using a Bayesian framework with model-based snow estimates updated through the assimilation of cloud-free Landsat fractional snow-covered area observations. Over the WUS, the peak SWE verification with independent in situ measurements show correlation coefficient, mean difference (MD), and root mean squared difference (RMSD) of 0.77, −0.15 m, and 0.28 m, respectively. The effects of forest cover and Landsat image availability on peak SWE are assessed. WUS–SR peak SWE is well correlated (ranging from 0.75 to 0.91) against independent lidar-derived SWE taken near April 1st, with MD

Asymmetric emergence of low-to-no snow in the midlatitudes of the American Cordillera

Nature Climate Change | November 14th, 2022

Societies and ecosystems within and downstream of mountains rely on seasonal snowmelt to satisfy their water demands. Anthropogenic climate change has reduced mountain sn

Societies and ecosystems within and downstream of mountains rely on seasonal snowmelt to satisfy their water demands. Anthropogenic climate change has reduced mountain snowpacks worldwide, altering snowmelt magnitude and timing. Here the global warming level leading to widespread and persistent mountain snowpack decline, termed low-to-no snow, is estimated for the world’s most latitudinally contiguous mountain range, the American Cordillera. We show that a combination of dynamical, thermodynamical and hypsometric factors results in an asymmetric emergence of low-to-no-snow conditions within the midlatitudes of the American Cordillera. Low-to-no-snow emergence occurs approximately 20 years earlier in the southern hemisphere, at a third of the local warming level, and coincides with runoff efficiency declines (8% average) in both dry and wet years. The prevention of a low-to-no-snow future in either hemisphere requires the level of global warming to be held to, at most, +2.5 °C.

California forest die-off linked to multi-year deep soil drying in 2012–2015 drought

Nature Geoscience | July 1st, 2019

Widespread episodes of recent forest die-off have been tied to the occurrence of anomalously warm droughts, although the underlying mechanisms remain inadequately

Widespread episodes of recent forest die-off have been tied to the occurrence of anomalously warm droughts, although the underlying mechanisms remain inadequately understood. California’s 2012–2015 drought, with exceptionally low precipitation and warmth, and widespread conifer death, provides an opportunity to explore the chain of events leading to forest die-off. Here, we present the spatial and temporal patterns of die-off and moisture deficit during California’s drought, based on field and remote sensing observations. We found that die-off was closely tied to multi-year deep-rooting-zone drying, and that this relationship provides a framework with which to diagnose and predict mortality. Marked tree death in an intensively studied Sierra Nevada forest followed a four-year moisture overdraft, with cumulative 2012–2015 evapotranspiration exceeding precipitation by ~1,500 mm, and subsurface moisture exhaustion to 5–15-m depth. Observations across the entire Sierra Nevada further linked tree death to deep drying, with die-off and moisture overdraft covarying across latitude and elevation. Unusually dense vegetation and warm temperatures accelerated southern Sierran evapotranspiration in 2012–2015, intensifying overdraft and compounding die-off by an estimated 55%. Climate change is expected to further amplify evapotranspiration and moisture overdraft during drought, potentially increasing Sierran tree death during drought by ~15–20% °C−1.

California Hydraulic Mining under the Caminetti Act

Scientific American | July 21st, 1900

The gold deposits of California are, for a large part, contained in gravel beds once the channel of rivers which formed the drainage of the west slope of th

The gold deposits of California are, for a large part, contained in gravel beds once the channel of rivers which formed the drainage of the west slope of the Sierra Nevada Mountains. In the course of ages new rivers were formed, leaving the ancient gravel beds elevated often hundreds of feet above the river beds of the present. The depth of the gravel in the old channels is often several hundred feet and the width across them frequently one-half mile, while their courses may be traced for thirty or forty miles in length in detached sections, which are the remnants of once continuous beds. Denudation and the cutting down of the present streams has removed parts of the ancient channels and they often disappear below the surface for several miles underneath coverings of lava which have been spread over them ...  Hydraulic mining became an immense industry. At the time when it had reached its greatest development it was estimated that more than one hundred millions of dollars had been invested in the construction of water supplies, mining plant, tunnels, and flumes, and more than two million dollars have been spent in the equipment of a single mine. Everything was upon an immense scale, and the amounts of gravel removed were in proportion. So large, in fact, that the material washed into the streams caused blockages over spreading agricultural lands in the Sacramento Valley, obstructing and raising the beds of the navigable rivers which enter San Francisco Bay, causing inundations at times of flood, and generally making its influence noticeable 200 miles from the seat of mining. In 1880 it was estimated that in the bed of the Yuba River alone there were stored more than one hundred and forty million cubic yards of accumulations, and the bed of the river had spread over a width of two and one-half miles between the side levees built to confine the spread of the deposits.

California Water Plan 2013: Mountain Counties Regional Report

California Department of Water Resources (DWR) | October 30th, 2014

As the State works to solve the water crisis in California, the potential for redirected impacts in the Mountain Counties Area is acute. It is critical that the State rec

As the State works to solve the water crisis in California, the potential for redirected impacts in the Mountain Counties Area is acute. It is critical that the State recognize the significance and importance of the Sierra Nevada mountain range to the local communities, the environment, the Delta, and all of California, now and for future generations. Water resource managers are working with elected officials, governmental agencies, businesses, farmers and conservationists on innovative programs for watershed management, water use efficiency, conservation, reuse, and recycling. Water managers and others in the region are actively balancing the water supplies that support both a vibrant economy and a healthy environment. They are also continually improving the management of surface and groundwater sources to sustain this important balance for this region and California. Statewide Significance Water is the number one resource exported from the Sierra Nevada, and the 16-county Mountain Counties Area is the primary source for most of that exported water. The Mountain Counties Area is over 15,700 square miles and represents 9.9 percent of the state. More than 40 percent of California’s developed water supply originates in the Mountain Counties area serving end users throughout the state. -The reservoirs in the region produce hydroelectricity to supply homes and businesses in the western United States. Mountain Counties has more hydroelectric generation facilities than any other region in California. - Agriculture in this region feeds the state and the world and is an economic driver for California’s economy. Recreation and tourism in the Sierra Nevada mountains help communities thrive economically as guests come from all over the world to hike, ski, fish, raft, and boat. Water stored behind designated reservoirs in the ten major watershed areas have dedicated in-stream flow releases designed to meet the many beneficial uses for the environment, agriculture, and urban users and provides storage to reduce the magnitude of flood flows.

California’s Water: Protecting Headwaters

Public Policy Institute of California (PPIC) | October 1st, 2016

Mountainous regions provide most of the state’s water supply. But major problems loom— from a growing risk of wildfires to a shrinking snowpack. This brief outlin

Mountainous regions provide most of the state’s water supply. But major problems loom— from a growing risk of wildfires to a shrinking snowpack. This brief outlines ways California and the federal government—the largest landowner in headwater areas—could address critical problems in these areas. This publication is part of a briefing kit that summarizes a dozen of the state’s most pressing water management issues.

Climate change decisive for Asia’s snow meltwater supply

Nature Climate Change | June 24th, 2021

Streamflow in high-mountain Asia is influenced by meltwater from snow and glaciers, and determining impacts of climate change on the region’s cryosphere is essential to

Streamflow in high-mountain Asia is influenced by meltwater from snow and glaciers, and determining impacts of climate change on the region’s cryosphere is essential to understand future water supply. Past and future changes in seasonal snow are of particular interest, as specifics at the scale of the full region are largely unknown. Here we combine models with observations to show that regional snowmelt is a more important contributor to streamflow than glacier melt, that snowmelt magnitude and timing changed considerably during 1979–2019 and that future snow meltwater supply may decrease drastically. The expected changes are strongly dependent on the degree of climate change, however, and large variations exist among river basins. The projected response of snowmelt to climate change indicates that to sustain the important seasonal buffering role of the snowpacks in high-mountain Asia, it is imperative to limit future climate change.

Climate change is increasing the likelihood of extreme autumn wildfire conditions across California

Environmental Research Letters, IOP Publishing | August 20th, 2020

California has experienced devastating autumn wildfires in recent years. These autumn wildfires have coincided with extreme fire weather conditions during periods of stro

California has experienced devastating autumn wildfires in recent years. These autumn wildfires have coincided with extreme fire weather conditions during periods of strong offshore winds coincident with unusually dry vegetation enabled by anomalously warm conditions and late onset of autumn precipitation. In this study, we quantify observed changes in the occurrence and magnitude of meteorological factors that enable extreme autumn wildfires in California, and use climate model simulations to ascertain whether these changes are attributable to human-caused climate change. We show that state-wide increases in autumn temperature (~1 °C) and decreases in autumn precipitation (~30%) over the past four decades have contributed to increases in aggregate fire weather indices (+20%). As a result, the observed frequency of autumn days with extreme (95th percentile) fire weather—which we show are preferentially associated with extreme autumn wildfires—has more than doubled in California since the early 1980s. We further find an increase in the climate model-estimated probability of these extreme autumn conditions since ~1950, including a long-term trend toward increased same-season co-occurrence of extreme fire weather conditions in northern and southern California. Our climate model analyses suggest that continued climate change will further amplify the number of days with extreme fire weather by the end of this century, though a pathway consistent with the UN Paris commitments would substantially curb that increase. Given the acute societal impacts of extreme autumn wildfires in recent years, our findings have critical relevance for ongoing efforts to manage wildfire risks in California and other regions.