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A Measure of Snow: A Report Based on Case Studies of The Snow Survey and Water Supply Forecasting Program

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A Measure of Snow: A Report Based on Case Studies of The Snow Survey and Water Supply Forecasting Program
U.S. Department of Agriculture Natural Resources Conservation Service | November 1, 2008...
Summary
Snow depth and snow water content data have been collected and disseminated throughout the Western United States for over 100 years. Early snow survey and...

Snow depth and snow water content data have been collected and disseminated throughout the Western United States for over 100 years. Early snow survey and water supply data were gathered through the efforts of university scientists, beginning with the work of Dr. James E. Church. In 1935, the Soil Conservation Service (SCS), now the United States Department of Agriculture (USDA) Natural Resources Conservation Service (NRCS), established a formal cooperative Snow Survey and Water Supply Forecasting (SS-WSF) Program. The Agency was charged with responsibility for “conducting snow survey and water supply forecasts and the forecasting of irrigation water supplies.” The new Program would also develop consistent methods for measuring snow and reliable models for accurate water supply forecasting.

Administered by NRCS, the SS-WSF Program has grown into a network of more than 1,200 manually-measured snow courses and over 750 automated Snowpack Telemetry (SNOTEL) weather stations in 13 Western States, including Alaska. (See map on page 4.) The SS-WSF Program provides manual snow course data collected by NRCS conservation professionals, automated SNOTEL data, and modeled water supply/streamflow volume data as well as issues streamflow forecasts for over 740 locations in the West. The data and the related reports and forecasts, are made available—in near real time for the automated SNOTEL sites—to private industry; to Federal, State, and local government entities; and to private citizens through an extensive Internet delivery system and other distribution channels.

With 50-80 percent of the water supply in the West arriving in the form of snow, data on the snowpack provides critical information to decision-makers and water managers throughout the West. The basic data become even more valuable when used in concert with partner organizations to provide water supply forecasting tailored to meet end-user needs. According to researchers from multiple U.S. and international agencies, research centers, and academia, changes in the world’s climate have resulted in a loss of predictability in weather, precipitation, and water transport and accumulation patterns. It is anticipated that the value the SS-WSF Program provides to society will increase over time as climate variability increases.

Recently a study was done to see who uses SS-WSF data, how the data are used, and the value of the data. Users of the data were interviewed and specific events and activities were analyzed. This publication is based on that study.

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A rationale for effective post-fire debris flow mitigation within forested terrain

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A rationale for effective post-fire debris flow mitigation within forested terrain
Geoenvironmental Disasters, Springer | May 25, 2018...
Summary
Watersheds recently burned by wildfires are recognized as having an increased susceptibility to debris flow occurrence. The great majority occur within the first 2...
Watersheds recently burned by wildfires are recognized as having an increased susceptibility to debris flow occurrence. The great majority occur within the first 2 years following wildfires. These debris flows are generated primarily through the process of progressive entrainment of material eroded from hillslopes and channels by surface runoff and appears independent of the vegetative community burned. The decreased likelihood of debris flows over time is linked to the restoration of hydrologic function as vegetative cover and soil infiltration functioning return to pre-fire conditions. An exception to this pattern of post-wildfire debris flow susceptibility occurs in burned drainage basins with forest cover. A second, later period of increased debris flow susceptibility due to infiltration-triggered landslides can occur in burned forested basins. This later period of debris flow susceptibility is largely attributable to the fire-induced tree mortality and subsequent decay of tree root networks decreasing soil strength on steep hillslopes which produces an increased likelihood of debris flow occurrence 3 to 10 or more years after the wildfire. Consequently, post-fire mitigation measures in forested terrain must address the risk posed by debris flows caused by progressive entrainment during the 2 years following the wildfire and debris flows due to infiltration-induced debris slides three or more years later. Mitigation for the later debris flows in forested terrain involves identification of areas with infiltration-induced debris slides coincident with concentrations of fire-killed trees. Timely reforestation of these areas after a wildfire limits the loss of soil strength from decaying roots.

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A study of methods to estimate debris flow velocity

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A study of methods to estimate debris flow velocity
Landslides, Springer | September 16, 2019...
Summary
Debris flow velocities are commonly back-calculated from superelevation events which require subjective estimates of radii of curvature of bends in the debris flow...
Debris flow velocities are commonly back-calculated from superelevation events which require subjective estimates of radii of curvature of bends in the debris flow channel or predicted using flow equations that require the selection of appropriate rheological models and material property inputs. This research investigated difficulties associated with the use of these conventional velocity estimation methods. Radii of curvature estimates were found to vary with the extent of the channel investigated and with the scale of the media used, and back-calculated velocities varied among different investigated locations along a channel. Distinct populations of Bingham properties were found to exist between those measured by laboratory tests and those back-calculated from field data; thus, laboratory-obtained values would not be representative of field-scale debris flow behavior. To avoid these difficulties with conventional methods, a new preliminary velocity estimation method is presented that statistically relates flow velocity to the channel slope and the flow depth. This method presents ranges of reasonable velocity predictions based on 30 previously measured velocities.

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California Water Plan 2013: Mountain Counties Regional Report
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California Water Plan 2013: Mountain Counties Regional Report
Department of Water Resources | October 30, 2014...
Summary
As the State works to solve the water crisis in California, the potential for redirected impacts in the Mountain Counties Area is acute....
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.

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California’s Water: Protecting Headwaters
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California’s Water: Protecting Headwaters
Public Policy Institute of California (PPIC) | October 1, 2016...
Summary
Mountainous regions provide most of the state’s water supply. But major problems loom— from a growing risk of wildfires to a shrinking snowpack....

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.

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Environmental Health Risks from Abandoned Mines in the Sierra Nevada
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Environmental Health Risks from Abandoned Mines in the Sierra Nevada
The Sierra Fund | June 9, 2014...
Summary
The widespread pollution from Gold Rush mining activities, including mercury, arsenic and lead, constitutes the oldest and longest neglected environmental justice problem in...
The widespread pollution from Gold Rush mining activities, including mercury, arsenic and lead, constitutes the oldest and longest neglected environmental justice problem in California. The effects of this pollution on human health and the environment are only now beginning to be addressed.

Today, the effects of historic mining pollution are an invisible but very real threat to people who live, work or recreate in the Sierra Nevada. Toxins of concern include mercury, arsenic, lead and asbestos. There is little information about these potential exposures available to Sierra residents. State-issued fish consumption advisories in the region
do not provide site-specific advice for many locations people fish, or the species people eat.

In 2006, The Sierra Fund, in partnership with California State University Chico, conducted a survey of Sierra clinics. This study found that not one of 13 surveyed clinics included information on mercury in fish as part of their maternal/infant health programs, whether caught locally or not. Additionally, the study learned that none of the clinics surveyed administer an environmental health history form, so it is difficult to connect current health problems to environmental exposures.

In order to address this lack of information and provide a springboard for more research, The Sierra Fund conducted three pilot studies of potential environmental exposures in 2009 and 2010 and a pilot outreach program to present these findings to Sierra communities in 2013-14. This report summarizes findings and recommendations from these efforts, in order to encourage continued research into these potentially serious health exposures.

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Estimates of Natural and Unimpaired Flows for the Central Valley of California: Water Years 1922-2014 (draft)
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Estimates of Natural and Unimpaired Flows for the Central Valley of California: Water Years 1922-2014 (draft)
California Department of Water Resources (DWR) | March 1, 2016...
Summary
Estimating regional water supplies that would have occurred absent human activities is a common practice in water resources planning. In this report, such...

Estimating regional water supplies that would have occurred absent human activities is a common practice in water resources planning. In this report, such theoretical water supply estimates are referred to as “unimpaired” flow. Since 1980, the Department of Water Resources (Department) has periodically published estimates of Central Valley unimpaired flows. In spite of the Department’s previous attempts to distinguish between natural conditions and its calcula tion of theoretical unimpaired flows, unimpaired flow estimates have frequently been used as a surrogate measure of natural conditions, presumably because natural flow estimates were unavailable. A major objective of this report is to clarify the conceptua l differences between natural and unimpaired flows.

In this report, the term “unimpaired” flow is used to describe a theoretically available water supply assuming existing river channel conditions in the absence of (1) storage regulation for water supply a nd hydropower purposes and (2) stream diversions for agricultural and municipal uses. Unimpaired flow estimates are theoretical in that such conditions have not occurred historically. In pristine watersheds which have undergone little land use change, unim paired flow estimates provide a fixed frame of reference to develop relationships between precipitation, runoff, and water supply based on long - term hydrologic records. For many years these relationships were based on the assumption of stationarity, i.e. that the past is a good indicator of the future. However, global warming now requires hydrologists and water resources managers to analyze non-stationary processes, requiring more sophisticated tools and techniques to quantify future water supplies. This report updates and extends the Department’s previous published estimates of unimpaired flows for 24 Central Valley sub-basins and the Delta. Monthly unimpaired flows are presented for water years 1922 - 2014.

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Estimating reservoir sedimentation rates at large spatialand temporal scales: A case study of California

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Estimating reservoir sedimentation rates at large spatialand temporal scales: A case study of California
Water Resources Research, American Geophysical Union (AGU) | December 25, 2009...
Summary
Previous reservoir sedimentation models have ignored two key factors for large spatial and temporal modeling of multiple reservoirs: trapping by upstream dams and decreasing sediment...
Previous reservoir sedimentation models have ignored two key factors for large spatial and temporal modeling of multiple reservoirs: trapping by upstream dams and decreasing sediment trapping as reservoirs fill. We developed a spreadsheet-based model that incorporates both factors. Using California as a case study, we used measured sedimentation rates to estimate sediment yields for distinct geomorphic regions and applied those rates to unmeasured reservoirs by region. Statewide reservoirs have likely filled with 2.1 billion m3 of sediment to date, decreasing total reservoir capacity by 4.5%. About 200 reservoirs have likely lost more than half their initial capacity to sedimentation.

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Forest Management (Resource Management Strategy)
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Forest Management (Resource Management Strategy)
California Department of Water Resources (DWR) | July 29, 2016...
Summary
Forest lands in California, the majority of which are in the middle to high elevation foothills and mountains, produce a diverse array of...
Forest lands in California, the majority of which are in the middle to high elevation foothills and mountains, produce a diverse array of resources such as water, timber, native vegetation, fish, wildlife, and livestock, and outdoor recreation. However, the water produced by these forests has economic value that equals or exceeds that of any other forest resource (Krieger 2001; California Department of Forestry and Fire Protection 2003).

Most of California’s major rivers and a substantial portion of its runoff originate in these forests; therefore, most of California’s major water development projects are tied strongly to forested watersheds.

Forest management activities can affect water quantity and quality. This strategy focuses on forest management activities, on both public and privately-owned forest lands, whose goals specifically include improvement of the availability and quality of water for downstream users.

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Improving the Health of California’s Headwater Forests
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Improving the Health of California’s Headwater Forests
Public Policy Institute of California (PPIC) | September 18, 2017...
Summary
California’s headwater forests are not thriving under current management practices, and changes are needed to make them more resilient to periodic drought and...
California’s headwater forests are not thriving under current management practices, and changes are needed to make them more resilient to periodic drought and long-term climate change. More active management of these lands is needed to improve forest health, reduce the risk of major wildfires and pest infestations, and maintain the flow of benefits provided by this critical natural infrastructure.

Decades of fire suppression, an emphasis on short-term management priorities, weather extremes, and a warming climate have set the stage for the decline in forest resilience. Two-thirds of the state’s surface water supply originates in these mountainous forests. California stands to lose timber production, wildlife habitat, recreational opportunities, and water supply if this vital natural infrastructure continues to decline. Management options exist—prescribed fire, managed wildfire, mechanical thinning, and forest pest treatments—that can help rebuild resilience in these forests and prepare them for a challenging future.

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