Addressing Stakeholder Science Needs for Integrated Drought Science in the Colorado River Basin

U.S. Geological Survey (USGS) | May 31st, 2022

Advances in Sub-seasonal to Seasonal Prediction Relevant to Water Management in the Western United States

American Meteorological Society (AMS) | July 21st, 2022

Water management in the semi-arid western United States (U.S.) is a challenging endeavor that evolves from year to year based on large-scale atmospheric and oceanic condi

Water management in the semi-arid western United States (U.S.) is a challenging endeavor that evolves from year to year based on large-scale atmospheric and oceanic conditions. This region has frequently experienced prolonged periods of drought with substantial socioeconomic impacts; the most recent instance involves California entering its third consecutive drought year. As context for the economic implications of drought, California’s enacted state budget for the Fiscal Year 2021-22 authorizes more than $600 million for the California Department of Water Resources for providing immediate drought support to local water agencies (CA State Budget 2021a); this amount is part of a package of more than $5 billion over four years for water resilience and drought preparedness (CA State Budget 2021b). For drought preparedness, state and local water managers would like to rely on skillful forecasts on timescales that span the spectrum between weather forecasts and climate predictions. Despite recent improvements in developing sub-seasonal (2- to 6-weeks lead) and seasonal (2- to 6-months lead) prediction systems that compete with and/or outperform existing dynamical and statistical models (e.g., Gibson et al. 2021, Switanek et al. 2020, DeFlorio et al. 2019), forecasting limitations have hindered crucial management decisions for western U.S. water managers, especially related to longer-lead planning, budgeting, resource allocation, and better preparedness for wet and dry extremes (DeFlorio et al. 2021). Improved understanding of physical phenomena and processes governing weather and climate extremes and utilization of emerging forecast methodologies are critical to developing skillful S2S forecast products relevant to water management.

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

University of California Giannini Foundation of Agricultural Economics | May 14th, 2015

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 agri

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.

Allocating California’s Water: Directions for Reform

Public Policy Institute of California (PPIC) | November 11th, 2015

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 wate

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.

Alternative management paradigms for the future of the Colorado and Green Rivers

U.S. Department of Agriculture (USDA) | January 28th, 2021

The Colorado River is among the most extensively managed river systems in the world. The river’s headwaters are within the Rocky Mountains in the United States. From t

The Colorado River is among the most extensively managed river systems in the world. The river’s headwaters are within the Rocky Mountains in the United States. From there, it flows through the arid lands of the Colorado Plateau and the Basin-and-Range to its delta in northwestern Mexico. Here, the river is the only significant water supply in an otherwise starkly arid landscape and has long been called “America’s Nile.” It provides a critical water supply for nearly four million acres of irrigated land, municipal supplies for 30 million people located within and outside the basin, and more than 4,200 MW of hydropower generation capacity. The Colorado River and some of its tributaries also provide an existing or potential water supply for at least 15 Native American tribes. The river flows through seven National Wildlife Refuges, four National Recreation Areas, and five National Parks. Today, the annual consumptive uses and losses of streamflow in the basin typically exceed the amount of water available, and the river rarely flows into the Gulf of California. The impacts of climate change are likely to decrease future runoff and intensify droughts, thereby threatening current and future uses in the basin. Clearly, new ways of thinking about and managing the river need to be sought and implemented.

Amplified impacts of multi-year La Niñas on soil moisture compared to single-year La Niñas

Nature Portfolio (Springer Nature) | August 14th, 2025

This study examines December-January-February (DJF) soil moisture responses to multi-year (MY) and single-year (SY) La Niñas using a 2200-year CESM1 simulation, AGCM exp

This study examines December-January-February (DJF) soil moisture responses to multi-year (MY) and single-year (SY) La Niñas using a 2200-year CESM1 simulation, AGCM experiments, and observational data. Four regions where MY La Niñas amplify SY La Niñas’ impacts on soil moisture were identified: North America, Australia, the Middle East, and the Sahel. SY La Niñas typically cause soil moisture drying in the Middle East and North America and wetting in Australia and the Sahel. MY La Niñas enhance these effects in the second DJF due to the strengthening of precipitation anomalies or the accumulation of precipitation-induced soil moisture anomalies, except in the Sahel where wetting is driven in part by evapotranspiration anomalies. Soil moisture variations are linked to La Niña-induced sea surface temperature changes in the Indian Ocean (for Australia and the Middle East) and the Pacific Ocean (for North America). These amplified effects are largely supported by the observed MY La Niña events from 1948 to 2022. These findings emphasize the need to integrate MY La Niñas into regional agriculture and water resource management strategies to better anticipate and mitigate their impacts.

An Abrupt Decline in Global Terrestrial Water Storage and Its Relationship with Sea Level Change

Nature Portfolio (Springer Nature) | November 4th, 2024

An Assessment of Potential Severe Droughts in the Colorado River Basin

American Water Resources Association (AWRA) | September 15th, 2022

Analysis of Colorado River Basin Storage Suggests Need For Immediate Action

John Fleck | September 11th, 2025

Anatomy of a range contraction: Flow–phenology mismatches threaten salmonid fishes near their trailing edge

National Academy of Sciences (NAS) | March 31st, 2025

Climate change is redistributing life on Earth, with profound impacts for ecosystems and human well-being. While repeat surveys separated by multidecadal intervals can de

Climate change is redistributing life on Earth, with profound impacts for ecosystems and human well-being. While repeat surveys separated by multidecadal intervals can determine whether observed shifts are in the expected direction (e.g., poleward or upslope due to climate change), they do not reveal their mechanisms or time scales: whether they were gradual responses to environmental trends or punctuated responses to disturbance events. Here, we document population reductions and temporary range contractions at multiple sites resulting from drought for three Pacific salmonids at their ranges’ trailing edge. During California’s 2012 to 2016 historic multiyear drought, the 2013 to 2014 winter stood apart because rainfall was both reduced and delayed. Extremely low river flows during the breeding season (“flow–phenology mismatch”) reduced or precluded access to breeding habitat. While Chinook (Oncorhynchus tshawytscha) experienced a down-river range shift, entire cohorts failed in individual tributaries (steelhead trout, O. mykiss) and in entire watersheds (coho salmon, O. kisutch). Salmonids returned to impacted sites in subsequent years, rescued by reserves in the ocean, life history diversity, and, in one case, a conservation broodstock program. Large population losses can, however, leave trailing-edge populations vulnerable to extinction due to demographic stochasticity, making permanent range contraction more likely. When only a few large storms occur during high flow season, the timing of particular storms plays an outsized role in determining which migratory fish species are able to access their riverine breeding grounds and persist.