Global warming precipitation accumulation increases above the current‐climate cutoff scale

National Academy of Sciences (NAS) | February 7th, 2017

Precipitation accumulations, integrated over rainfall events, can be affected by both intensity and duration of the storm event. Thus, although precipitation intensity

Precipitation accumulations, integrated over rainfall events, can be affected by both intensity and duration of the storm event. Thus, although precipitation intensity is widely projected to increase under global warming, a clear framework for predicting accumulation changes has been lacking, despite the importance of accumulations for societal impacts. Theory for changes in the probability density function (pdf) of precipitation accumulations is presented with an evaluation of these changes in global climate model simulations. We show that a simple set of conditions implies roughly exponential increases in the frequency of the very largest accumulations above a physical cutoff scale, increasing with event size. The pdf exhibits an approximately power-law range where probability density drops slowly with each order of magnitude size increase, up to a cutoff at large accumulations that limits the largest events experienced in current climate. The theory predicts that the cutoff scale, controlled by the interplay of moisture convergence variance and precipitation loss, tends to increase under global warming. Thus, precisely the large accumulations above the cutoff that are currently rare will exhibit increases in the warmer climate as this cutoff is extended. This indeed occurs in the full climate model, with a 3 C end-of-century global-average warming yielding regional increases of hundreds of percent to >1,000% in the probability density of the largest accumulations that have historical precedents. The probabilities of unprecedented accumulations are also consistent with the extension of the cutoff.

Global water gaps under future warming levels

Nature Portfolio (Springer Nature) | January 30th, 2025

Governing California Through Climate Change

Little Hoover Commission | July 1st, 2014

State government, which guided California through the instability of the Great Depression, managed the profound disruptions of World War II and steered, during following

State government, which guided California through the instability of the Great Depression, managed the profound disruptions of World War II and steered, during following decades, one of the nation’s great population, development and innovation booms, faces again an historic governing challenge in climate change. A $2 trillion annual economy and the needs of nearly 40 million residents ride on the outcome of the state’s preparations and response. Climate change, which most scientists believe has already begun, promises decades of wilder weather and great uncertainty regarding the scale of annual precipitation, wildfire activity, sea level rise and daily temperatures. These changes have powerful implications for agricultural production, air quality, real estate values, electricity generation, public health and California’s renowned quality of life.

Grand Challenges to Delta Science: Planning for Science in a Dynamic System (Draft)

Delta Stewardship Council (Delta Council) | May 23rd, 2024

The Delta Science Program is in the process of updating the Delta Science Plan for the third iteration. The Delta Science Plan is a collaboratively developed plan, stipul

The Delta Science Program is in the process of updating the Delta Science Plan for the third iteration. The Delta Science Plan is a collaboratively developed plan, stipulated in the Delta Plan, that aims to provide the vision, principles, and approaches for coordinating Delta science actors and communicating the outcomes of science activities and their management implications to decision-makers.

Green Light for Adaptive Policies on the Colorado River

Water (MDPI) | December 21st, 2021

The Colorado River is a critical source of water supply for 40 million people in nine states spanning two nations in western North America. Overallocated in the 20th cent

The Colorado River is a critical source of water supply for 40 million people in nine states spanning two nations in western North America. Overallocated in the 20th century, its problems have been compounded by climate change in the 21st century. We review the basin’s hydrologic and water management history in order to identify opportunities for adaptive governance to respond to the challenge of reduced system flows and distill the ingredients of past successes. While significant advances have been made in the first two decades of the 21st century, these past actions have not been sufficient to halt the declines in the basin’s reservoirs. We find that the mix of federal, state, and local responsibility creates challenges for adaptation but that progress can be made through a combination of detailed policy option development followed by quick action at hydrologically driven moments of opportunity. The role of directives and deadlines from federal authorities in facilitating difficult compromises is noted. The current state of dramatically decreased overall flows has opened a window of opportunity for the adoption of water management actions that move the river system toward sustainability. Specific measures, based on the existing institutional framework and on policy proposals that have circulated within the Colorado River community, are suggested.

Greenhouse Gas Emissions Calculator for the Water Sector: User’s Manual

U.S. Bureau of Reclamation (USBR) | September 24th, 2013

The Santa Ana Watershed Basin Study (Basin Study) is a collaborative effort by the Santa Ana Watershed Project Authority (SAWPA) and the Bureau of Reclamation (Reclamatio

The Santa Ana Watershed Basin Study (Basin Study) is a collaborative effort by the Santa Ana Watershed Project Authority (SAWPA) and the Bureau of Reclamation (Reclamation), authorized under the Sustain and Manage America's Resources for Tomorrow SECURE Water Act (Title IX, Subtitle F of Public Law 111-11). The Basin Study complements SAWPA’s Integrated Regional Water Management (IRWM) planning process, also known as their “One Water One Watershed” (OWOW) Plan. It refines the watershed’s water projections, and identifies potential adaptation strategies, in light of projected effects of climate change. The Climate Change Analysis for the Santa Ana River Watershed (SARW) is a contributing section to the Basin Study. The Greenhouse Gas (GHG) Emissions Calculator was developed as a tool to support the Climate Change Analysis. It was developed to evaluate mitigation strategies, while the Climate Change Analysis focused primarily on adaption and vulnerability analysis. Development of the tool began in 2012 and was completed in August 2013. This report explains the methods used to develop the calculator and provides instructions on how to use it by introducing examples. The examples focus on the SARW to show how to develop a GHG emissions baseline, evaluate what it would take to meet specific GHG emission reduction goals, and illustrate how the GHG Emissions Calculator can be used to analyze projects. Chapter 1 provides an introduction to the project, a literature review, and a summary of California’s GHG legislation. The methods used in the GHG Emissions Calculator can be found in Chapter 2. A guide showing users what data is needed and how to enter that data can be found in Chapter 3. Chapter 4 provides an introduction to the SARW, the GHG emission baseline for the SARW, discusses varies scenarios to reduce GHG emissions, and compares those reduction scenarios. In Chapter 5 SAWPA’s 20 finalist for the Integrated Regional Water Management (IRWM) funding were analyzed using the GHG Emissions Calculator. The GHG Emission Calculator is a decision-making tool that can be used to explore the links between water resources, energy, and GHG emissions. It can be used to determine water supply and energy demands for the study area, in addition to GHG emissions from 1990 to 2050. It can be used to analyze a study area ranging from a city block to an entire watershed, regardless of the level of detailed data available. The GHG Emissions calculator is a vital tool for decision makers when developing water supply plans for the future. It is also equipped to evaluate long term GHG emission reduction potential for new projects that will alter the water supply portfolio.

Greenhouse gas emissions from US irrigation pumping and implications for climate-smart irrigation policy

Nature Portfolio (Springer Nature) | January 23rd, 2024

Ground water and climate change

Nature Portfolio (Springer Nature) | November 25th, 2012

As the world's largest distributed store of fresh water, ground water plays a central part in sustaining ecosystems and enabling human adaptation to climate variability a

As the world's largest distributed store of fresh water, ground water plays a central part in sustaining ecosystems and enabling human adaptation to climate variability and change. The strategic importance of ground water for global water and food security will probably intensify under climate change as more frequent and intense climate extremes (droughts and floods) increase variability in precipitation, soil moisture and surface water. Here we critically review recent research assessing the impacts of climate on ground water through natural and human-induced processes as well as through groundwater-driven feedbacks on the climate system. Furthermore, we examine the possible opportunities and challenges of using and sustaining groundwater resources in climate adaptation strategies, and highlight the lack of groundwater observations, which, at present, limits our understanding of the dynamic relationship between ground water and climate.

Groundwater microbiomes balance resilience and vulnerability to hydroclimatic extremes

Nature Portfolio (Springer Nature) | August 20th, 2025

Growing human-induced climate change fingerprint in regional weekly fire extremes

Nature Portfolio (Springer Nature) | April 23rd, 2025