Evolution of global snow drought characteristics from 1850 to 2100

Environmental Research Letters (IOP) | June 6th, 2023

Examining the Contribution of the Observed Global Warming Trend to the California Droughts of 2012/13 and 2013/14

American Meteorological Society (AMS) | September 30th, 2014

In this study, we examine the November–February California droughts of 2012/13 and 2013/14. During 2013/14, California had its warmest and third driest rainy se

In this study, we examine the November–February California droughts of 2012/13 and 2013/14. During 2013/14, California had its warmest and third driest rainy season on record (1895–2014), while the 2012/13 season registered as the 45th warmest and 38th driest (Vose et al. 2014). The 2013 January–December calendar year was the driest on record (Water CA 2014). These consecutive below-normal seasons conspired with warm temperatures to reduce California’s snowpack to the second lowest level since 1960, when recording began, with snowpack at 24% of normal (Water CA 2014). Between January 2013 and January 2014, satellite observations documented dramatic snowpack-related land cover change (NASA Earth Observatory 2014): in 2014, the Cascade, Sierra Nevada, and Coastal ranges were almost completely devoid of snow. In February and March of 2014, air temperatures were extremely warm (NOAA NCDC 2014; HPRC 2014), and U.S. Geological Survey (USGS) observations indicated extreme or moderate hydrologic drought (USGS 2014) and high levels of vegetation stress (VegDRI 2014). The state declared a drought emergency (NIDIS 2014). While it is too soon to assess the full impact of the 2012/13 and 2013/14 California droughts, they seem likely to substantially impact the state’s ability to generate hydrologic power, support agriculture, reduce the risk of forest and bush fires, and protect fragile ecosystems (Huffington Post 2014). *Chapter 4, Explaining Extreme Events of 2013 from a Climate Perspective, Bull. Amer. Meteor. Soc., 95 (9)

Exploring the Origins of Snow Drought in the Northern Sierra Nevada, California

American Meteorological Society (AMS) | February 22nd, 2018

The concept of snow drought is gaining widespread interest as the climate of snow-dominated mountain watersheds continues to change. Warm snow drought is defined

The concept of snow drought is gaining widespread interest as the climate of snow-dominated mountain watersheds continues to change. Warm snow drought is defined as above- or near-average accumulated pre- cipitation coinciding with below-average snow water equivalent at a point in time. Dry snow drought is defined as below-average accumulated precipitation and snow water equivalent at a point in time. This study contends that such point-in-time definitions might miss important components of how snow droughts originate, persist, and terminate. Using these simple definitions and a variety of observations at monthly, daily, and hourly time scales, the authors explore the hydrometeorological origins of potential snow droughts in the northern Sierra Nevada from water years 1951 to 2017. This study finds that snow droughts can result from extreme early season precipitation, frequent rain- on-snow events, and low precipitation years. Late-season snow droughts can follow persistent warm and dry periods with effects that depend upon elevation. Many snow droughts were characterized by lower snow fractions and midwinter peak runoff events. These findings can guide improved evaluations of historical and potential future snow droughts, particularly with regards to how impacts on water resources and mountain ecosystems may vary depending on how snow droughts originate and evolve in time.

Exploring the Potential for Water-Limited Agriculture in the San Joaquin Valley

Public Policy Institute of California (PPIC) | July 21st, 2022

The rollout of California’s Sustainable Groundwater Management Act (SGMA) is altering the state’s agricultural landscape. As groundwater sustainability measures are

The rollout of California’s Sustainable Groundwater Management Act (SGMA) is altering the state’s agricultural landscape. As groundwater sustainability measures are implemented and water scarcity increases, at least half a million acres are projected to come out of irrigated production in the San Joaquin Valley, the state’s agricultural heartland. Rather than widespread land idling—which comes with unintended consequences such as dust, weeds, pests, and soil degradation — a switch from summer irrigated crops to winter crops produced with limited water (including winter cereals and forage crops, among others) might keep some of this land in production. Although water-limited agriculture faces large hurdles, some promising aspects warrant further exploration.

Exploring the Spatially Compounding Multi‐Sectoral Drought Vulnerabilities in Colorado's West Slope River Basins

American Geophysical Union (AGU) | November 9th, 2024

Exploring Water System Vulnerabilities in California's Central Valley Under the Late Renaissance Megadrought and Climate Change

American Geophysical Union (AGU) | April 24th, 2025

Extreme and persistent drought in California and Patagonia during medieval time

Nature Portfolio (Springer Nature) | June 16th, 1994

STUDIES from sites around the world1–5 have provided evidence for anomalous climate conditions persisting for several hundred years before about AD 1300. Early workers

STUDIES from sites around the world1–5 have provided evidence for anomalous climate conditions persisting for several hundred years before about AD 1300. Early workers emphasized the temperature increase that marked this period in the British Isles, coining the terms 'Mediaeval Warm Epoch' and 'Little Climatic Optimum', but many sites seem to have experienced equally important hydrological changes. Here I present a study of relict tree stumps rooted in present-day lakes, marshes and streams, which suggests that California's Sierra Nevada experienced extremely severe drought conditions for more than two centuries before ad ∼ 1112 and for more than 140 years before ad ∼ 1350. During these periods, runoff from the Sierra was significantly lower than during any of the persistent droughts that have occurred in the region over the past 140 years. I also present similar evidence from Patagonia of drought conditions coinciding with at least the first of these dry periods in California. I suggest that the droughts may have been caused by reorientation of the mid-latitude storm tracks, owing to a general contraction of the circumpolar vortices and/or a change in the position of the vortex waves. If this reorientation was caused by mediaeval warming, future natural or anthropogenically induced warming may cause a recurrence of the extreme drought conditions.

Final Environmental Impact Statement Post-2026 Operational Guidelines and Strategies for Lake Powell and Lake Mead

U.S. Bureau of Reclamation (USBR) | July 31st, 2026

The Colorado River Basin (Basin) provides essential water supplies to approximately 40 million people, nearly 5.5 million acres of agricultural lands, and habitat for eco

The Colorado River Basin (Basin) provides essential water supplies to approximately 40 million people, nearly 5.5 million acres of agricultural lands, and habitat for ecological resources across seven states which includes broad areas in the Southwestern United States (U.S.) and Northwestern United Mexican States (Mexico). Prudent management of the Basin is critically important because the Colorado River is the foundation for diverse resources across a large geographic region and faces exceptional challenges from prolonged drought and future uncertainty. States, tribes, and Mexico rely on the Colorado River to support essential municipal, agricultural, environmental, cultural, and hydropower needs. These resources are now at significant risk: since the onset of the current drought in 2000, the Basin’s primary reservoirs, Lake Powell and Lake Mead, have fallen to historically low elevations. Several of the major reservoir- and water-management documents and agreements developed to guide Colorado River operations through the persistently dry conditions expire in 2026, including the 2007 Colorado River Interim Guidelines for Lower Basin Shortages and Coordinated Operations for Lake Powell and Lake Mead (2007 Interim Guidelines; Reclamation 2007), the 2019 Colorado River Drought Contingency Plans (Reclamation 2019), and key international agreements between the U.S. and Mexico. Despite the significance of these agreements, actions taken over the past two decades have not been sufficiently robust to prevent continued decline of the reservoirs through the prolonged drought. The Secretary of the Interior (Secretary), acting through the Bureau of Reclamation (Reclamation), proposes adoption of new guidelines and coordinated management strategies to address Lake Powell and Lake Mead through their full operating ranges to take effect when the current agreements expire in 2026. Volume I Executive Summary Cover, Abstract, Table of Contents, and Acronyms Chapter 1. Purpose and Need Chapter 2: Description of Alternatives Chapter 3: Affected Environment and Environmental Consequences Chapter 4: Consultation and Coordination Volumes II,  III, IV Click here to be taken to Reclamation for Supporting Appendices, Preparers, References, Glossary, and Index

Frontiers in Ecology and the Environment: Alteration of streamflow magnitudes and potential ecological consequences: a multiregional assessment

Ecological Society of America (Wiley) | October 19th, 2010

Human impacts on watershed hydrology are widespread in the US, but the prevalence and severity of streamflow alteration and its potential ecological consequences have not

Human impacts on watershed hydrology are widespread in the US, but the prevalence and severity of streamflow alteration and its potential ecological consequences have not been quantified on a national scale. We assessed streamflow alteration at 2888 streamflow monitoring sites throughout the conterminous US. The magnitudes of mean annual (1980–2007) minimum and maximum streamflows were found to have been altered in 86% of assessed streams. The occurrence, type, and severity of streamflow alteration differed markedly between arid and wet climates. Biological assessments conducted on a subset of these streams showed that, relative to eight chemical and physical covariates, diminished flow magnitudes were the primary predictors of biological integrity for fish and macroinvertebrate communities. In addition, the likelihood of biological impairment doubled with increasing severity of diminished streamflows. Among streams with diminished flow magnitudes, increasingly common fish and macroinvertebrate taxa possessed traits characteristic of lake or pond habitats, including a preference for fine-grained substrates and slow-moving currents, as well as the ability to temporarily leave the aquatic environment.

Funding Opportunity for Voluntary Participation in the Lower Colorado Conservation and Efficiency Program

U.S. Bureau of Reclamation (USBR) | October 12th, 2022