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A 1,200-year perspective of 21st century drought in southwestern North America

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A 1,200-year perspective of 21st century drought in southwestern North America
Proceedings of the National Academy of Sciences (PNAS) | December 11, 2009...
Summary
A key feature of anticipated 21st century droughts in Southwest North America is the concurrence of elevated temperatures and increased aridity. Instrumental records...
A key feature of anticipated 21st century droughts in Southwest North America is the concurrence of elevated temperatures and increased aridity. Instrumental records and paleoclimatic evidence for past prolonged drought in the Southwest that coincide with elevated temperatures can be assessed to provide insights on temperature-drought relations and to develop worst-case scenarios for the future. In particular, during the medieval period, ∼AD 900–1300, the Northern Hemisphere experienced temperatures warmer than all but the most recent decades. Paleoclimatic and model data indicate increased temperatures in western North America of approximately 1 °C over the long-term mean. This was a period of extensive and persistent aridity over western North America. Paleoclimatic evidence suggests drought in the mid-12th century far exceeded the severity, duration, and extent of subsequent droughts. The driest decade of this drought was anomalously warm, though not as warm as the late 20th and early 21st centuries. The convergence of prolonged warming and arid conditions suggests the mid-12th century may serve as a conservative analogue for severe droughts that might occur in the future. The severity, extent, and persistence of the 12th century drought that occurred under natural climate variability, have important implications for water resource management. The causes of past and future drought will not be identical but warm droughts, inferred from paleoclimatic records, demonstrate the plausibility of extensive, severe droughts, provide a long-term perspective on the ongoing drought conditions in the Southwest, and suggest the need for regional sustainability planning for the future.

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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 (USDA), 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 Measure of Snow: Case Studies of the Snow Survey and Water Supply Forecasting Program

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A Measure of Snow: Case Studies of the Snow Survey and Water Supply Forecasting Program
U.S. Department of Agriculture (USDA), Natural Resources Conservation Service | September 1, 2010...
Summary
Snow depth and snow water content data have been collected and disseminated throughout the W estern United States for over 100 years. Early...

Snow depth and snow water content data have been collected and disseminated throughout the W estern United States for over 100 years. Early Snow Survey and Water Supply Forecasting data were gathered through the efforts of university scientists. In 1935, the Soil Conservation Service (SCS) was given $36,000 to establish a formal cooperative Snow Survey and Water Supply Forecasting (SSWSF) Program. The agency was charged with the responsibility for “conducting Snow Survey and Water Supply Forecast s and forecasting of irrigation water supplies.” The new program would also develop consistent methods for measuring snow and reliable models for water supply forecasting.

Using a case study approach, this report assesses the various uses of data gathered and published by the SSWSF Program and estimates the value of those data in terms of both the market and non-market values of the information. Additionally, it evaluate s the relative merits of maintaining the program as a publicly funded program as opposed to privatizing the program.

This study finds that the SSWSF Program is generating both market and non-market benefits to the U.S. economy and to U.S. society as a whole that are worth significantly more than the cost of the program. Should climate variability increase — as is expected by many of those interviewed in the course of completing this study, and as current climate research strongly suggests — the value of the information provided by the SSWSF Program will increase accordingly.

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A Perspective on the Drought in California
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A Perspective on the Drought in California
Legislative Analyst's Office | November 21, 1991...
Summary
Despite heavy rains in March 1991, California continues to face a serious near-term water problem resulting from five years of drought. In fact,...
Despite heavy rains in March 1991, California continues to face a serious near-term water problem resulting from five years of drought. In fact, the amount of water in storage on October 1, 1991 was about equal to the amount in storage one year ago—a year in which strict conservation measures were imposed in some areas and there were significant reductions in water supplies for many agricultural users. In this paper, we provide background information on California's water system, the impact of the drought, water needs in the future, and legislative options for coping with water supply limitations.

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A tale of two California droughts: Lessons amidst record warmth and dryness in a region of complex physical and human geography

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A tale of two California droughts: Lessons amidst record warmth and dryness in a region of complex physical and human geography
American Geophysical Union (AGU) | November 19, 2015...
Summary
The state of California has experienced the worst drought in its historical record during 2012–2015. Adverse effects of this multi year event have been...
The state of California has experienced the worst drought in its historical record during 2012–2015. Adverse effects of this multi year event have been far from uniformly distributed across the region, ranging from remarkably mild in most of California’s densely populated coastal cities to very severe in more rural, agricultural, and wildfire-prone regions. This duality of impacts has created a tale of two very different California droughts—highlighting enhanced susceptibility to climate stresses at the environmental andsocioeconomic margins of California. From a geophysical perspective, the persistence of related atmospheric anomalies has raised a number of questions regarding the drought’s origins—including the role of anthropogenic climate change. Recent investigations underscore the importance of understanding the underlying physical causes of extremes in the climate system, and the present California drought represents an excellent case study for such endeavors. Meanwhile, a powerful El Niño event in the Pacific Ocean offers the simultaneous prospect of partial drought relief but also an increased risk of flooding during the 2015–2016 winter—a situation illustrative of the complex hydroclimatic risks California and other regions are likely to face in a warming world.

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Addressing Institutional Vulnerabilities in California’s Drought Water Allocation, Part 1: Water Rights Administration and Oversight During Major Statewide Droughts, 1976–2016

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Addressing Institutional Vulnerabilities in California’s Drought Water Allocation, Part 1: Water Rights Administration and Oversight During Major Statewide Droughts, 1976–2016
California Natural Resources Agency | August 30, 2018...
Summary
Climate change has already begun to affect California’s hydrology and water resources, and droughts are likely to become more frequent, longer, and more...

Climate change has already begun to affect California’s hydrology and water resources, and droughts are likely to become more frequent, longer, and more intense in the future (see Section 2.2.4). This project is designed to help state water governance and decision-making structures adapt to this changing climatic reality. We focus on how one of California’s primary water management institutions, the State Water Resources Control Board (Board), has responded in the past, and could better respond in the future, to droughts and their attendant challenges, including water shortage, uncertainty, and conflict.

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Addressing Institutional Vulnerabilities in California’s Drought Water Allocation, Part 2: Improving Water Rights Administration and Oversight for Future Droughts

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Addressing Institutional Vulnerabilities in California’s Drought Water Allocation, Part 2: Improving Water Rights Administration and Oversight for Future Droughts
California Natural Resources Agency | August 30, 2018...
Summary
In California, droughts are likely to become more frequent, longer, and more intense in the future, posing increasing challenges for water management, and...
In California, droughts are likely to become more frequent, longer, and more intense in the future, posing increasing challenges for water management, and raising the stakes for effective drought response. This project aims to help state water governance and decision-making structures adapt to the changing climatic reality. In a companion report in this volume, we analyzed the strategies the State Water Resources Control Board (Board) used for water rights administration and oversight during the last four major statewide droughts. Our findings suggest that more proactive planning and preparation, enabling reduced reliance on in-drought improvisation, would improve the Board’s future drought responses. This report builds on that retrospective analysis with specific recommendations.

Click here for Part 1.

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Agricultural Irrigation in This Drought: Where is the Water and Where Is It Going?
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Agricultural Irrigation in This Drought: Where is the Water and Where Is It Going?
University of California Giannini Foundation of Agricultural Economics | May 14, 2015...
Summary
In the midst of its fourth year of drought, California now faces an estimated reduction in surface-water availability of 8.8 million acre-feet (maf)...
In the midst of its fourth year of drought, California now faces an estimated reduction in surface-water availability of 8.8 million acre-feet (maf) out of 29 maf in agricultural applied water statewide. However, groundwater, the buffer water supply during drought, is replacing about 6.2 maf of surface water via additional pumping. This increased groundwater pumping is in addition to the 1.5 maf of annual average groundwater overdraft in the Central Valley. The net reduction of 2.6 maf in the total supply in 2015 may result in about 564,000 acres fallowed statewide, or about 120,000 more acres than last year's fallowing estimates.

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Allocating California’s Water: Directions for Reform
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Allocating California’s Water: Directions for Reform
Public Policy Institute of California (PPIC) | November 11, 2015...
Summary
California’s water allocation system hampers its ability to meet the state’s needs, especially in times of drought. At its heart is an unusually...
California’s water allocation system hampers its ability to meet the state’s needs, especially in times of drought. At its heart is an unusually complex array of water rights. This report summarizes challenges and suggests reforms to strengthen the state’s ability to weather droughts and shifting economic demands for water, while maintaining the existing seniority of water rights.

Read a summary of the report’s policy recommendations.

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Anthropogenic warming has increased drought risk in California

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Anthropogenic warming has increased drought risk in California
National Academy of Sciences | March 2, 2015...
Summary
California is currently in the midst of a record-setting drought. The drought began in 2012 and now includes the lowest calendar-year and 12-mo...

California is currently in the midst of a record-setting drought. The drought began in 2012 and now includes the lowest calendar-year and 12-mo precipitation, the highest annual temperature, and the most extreme drought indicators on record. The extremely warm and dry conditions have led to acute water shortages, ground- water overdraft, critically low streamflow, and enhanced wildfire risk. Analyzing historical climate observations from California, we find that precipitation deficits in California were more than twice as likely to yield drought years if they occurred when conditions were warm. We find that although there has not been a substantial change in the probability of either negative or moderately negative precipitation anomalies in recent decades, the occurrence of drought years has been greater in the past two decades than in the preceding century. In addition, the probability that precipitation deficits co-occur with warm conditions and the probability that precipitation deficits produce drought have both increased. Climate model experiments with and without anthropogenic forcings reveal that human activities have increased the probability that dry precipitation years are also warm. Further, a large ensemble of climate model realizations reveals that additional global warming over the next few decades is very likely to create ∼100% probability that any annual-scale dry period is also extremely warm. We therefore conclude that anthropogenic warming is increasing the probability of co-occurring warm–dry conditions like those that have created the acute human and ecosystem impacts associated with the “exceptional” 2012–2014 drought in California.

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A 1,200-year perspective of 21st century drought in southwestern North America

A 1,200-year perspective of 21st century drought in southwestern North America

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

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: Case Studies of the Snow Survey and Water Supply Forecasting Program

A Measure of Snow: Case Studies of the Snow Survey and Water Supply Forecasting Program

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A Perspective on the Drought in California

A Perspective on the Drought in California

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A tale of two California droughts: Lessons amidst record warmth and dryness in a region of complex physical and human geography

A tale of two California droughts: Lessons amidst record warmth and dryness in a region of complex physical and human geography

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Addressing Institutional Vulnerabilities in California’s Drought Water Allocation, Part 1: Water Rights Administration and Oversight During Major Statewide Droughts, 1976–2016

Addressing Institutional Vulnerabilities in California’s Drought Water Allocation, Part 1: Water Rights Administration and Oversight During Major Statewide Droughts, 1976–2016

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Addressing Institutional Vulnerabilities in California’s Drought Water Allocation, Part 2: Improving Water Rights Administration and Oversight for Future Droughts

Addressing Institutional Vulnerabilities in California’s Drought Water Allocation, Part 2: Improving Water Rights Administration and Oversight for Future Droughts

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Agricultural Irrigation in This Drought: Where is the Water and Where Is It Going?

Agricultural Irrigation in This Drought: Where is the Water and Where Is It Going?

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Allocating California’s Water: Directions for Reform

Allocating California’s Water: Directions for Reform

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Anthropogenic warming has increased drought risk in California

Anthropogenic warming has increased drought risk in California

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