Colorado River Storage Project of 1956

U.S. Bureau of Reclamation (USBR) | April 11th, 1956

Colorado River water supply is predictable on multi-year timescales owing to long-term ocean memory

Nature Portfolio (Springer Nature) | October 9th, 2020

Skillful multi-year climate forecasts provide crucial information for decision-makers and resource managers to mitigate water scarcity, yet such forecasts remain challen

Skillful multi-year climate forecasts provide crucial information for decision-makers and resource managers to mitigate water scarcity, yet such forecasts remain challenging due to unpredictable weather noise and the lack of dynamical model capability. Here we demonstrate that the annual water supply of the Colorado River is predictable up to several years in advance by a drift-free decadal climate prediction system using a fully coupled climate model. Observational analyses and model experiments show that prolonged shortages of water supply in the Colorado River are significantly linked to sea surface temperature precursors including tropical Pacific cooling, North Pacific warming, and southern tropical Atlantic warming. In the Colorado River basin, the water deficits can reduce crop yield and increase wildfire potential. Thus, a multi-year prediction of severe water shortages in the Colorado River basin could be useful as an early indicator of subsequent agricultural loss and wildfire risk.

Comment Letter on the Draft Water Resilience Portfolio for the State of California

Pacific Institute | February 7th, 2020

This comment letter conveys summary comments and suggestions on the draft Water Resilience Portfolio released by California state agencies, drawing on the considerable ex

This comment letter conveys summary comments and suggestions on the draft Water Resilience Portfolio released by California state agencies, drawing on the considerable experience Pacific Institute has around themes of water efficiency, stormwater management, and the Salton Sea. The letter was authored by staff at Pacific Institute and directed to the Governor’s Water Portfolio Program at the California Natural Resources Agency.

Comments on and Protest of Temporary Urgency Change Petition Regarding Delta Water Quality

California State Water Resources Control Board (SWRCB) | February 17th, 2023

Community and Grower Engagement in Multibenefit Land Repurposing

Environmental Defense Fund (EDF) | June 10th, 2022

Community estimate of global glacier mass changes from 2000 to 2023

Nature Portfolio (Springer Nature) | February 19th, 2025

Glaciers are indicators of ongoing anthropogenic climate change1. Their melting leads to increased local geohazards2, and impacts marine3 and terrestrial4,5 ecosystems, r

Glaciers are indicators of ongoing anthropogenic climate change1. Their melting leads to increased local geohazards2, and impacts marine3 and terrestrial4,5 ecosystems, regional freshwater resources6, and both global water and energy cycles7,8. Together with the Greenland and Antarctic ice sheets, glaciers are essential drivers of present9,10 and future11,12,13 sea-level rise. Previous assessments of global glacier mass changes have been hampered by spatial and temporal limitations and the heterogeneity of existing data series14,15,16. Here we show in an intercomparison exercise that glaciers worldwide lost 273 ± 16 gigatonnes in mass annually from 2000 to 2023, with an increase of 36 ± 10% from the first (2000–2011) to the second (2012–2023) half of the period. Since 2000, glaciers have lost between 2% and 39% of their ice regionally and about 5% globally. Glacier mass loss is about 18% larger than the loss from the Greenland Ice Sheet and more than twice that from the Antarctic Ice Sheet17. Our results arise from a scientific community effort to collect, homogenize, combine and analyse glacier mass changes from in situ and remote-sensing observations. Although our estimates are in agreement with findings from previous assessments14,15,16 at a global scale, we found some large regional deviations owing to systematic differences among observation methods. Our results provide a refined baseline for better understanding observational differences and for calibrating model ensembles12,16,18, which will help to narrow projection uncertainty for the twenty-first century11,12,18. Click here for more about the Glacier Mass Balance Intercomparison Exercise 

Community Perspectives on SGMA Implementation

University of California, Davis (UC Davis) | June 13th, 2019

The Sustainable Groundwater Management Act (SGMA) of 2014 represents a historic opportunity to achieve long-term sustainable groundwater management and protect th

The Sustainable Groundwater Management Act (SGMA) of 2014 represents a historic opportunity to achieve long-term sustainable groundwater management and protect the drinking water supplies of hundreds of small and rural low-income communities that rely on this shared resource, especially in the San Joaquin Valley. Prior research, however, indicates that few of these communities are represented in the Groundwater Sustainability Agencies (GSAs) formed to implement the new law. This raises questions about other forms of community involvement, and concerns about the extent to which small and rural drinking-water interests are being incorporated into the process. This report details the results of twenty-three interviews with thirty-one representatives of small, low-income communities who rely on groundwater for their drinking-water supplies. The findings suggest community stakeholders are highly interested in SGMA and desire to be involved in its implementation, which many deemed indispensable for the future of their communities. Many are actively participating or following the process, including by serving on boards and committees, attending meetings and workshops, and monitoring meeting minutes and agendas. The experience of small and rural communities with SGMA is predictably diverse. Some interviewees have had very positive experiences thus far and are hopeful about the ways SGMA could benefit their communities and regions in the future. Others have felt overlooked or intentionally excluded. Yet many similarities also arose across the interviews including six common challenges and concerns about SGMA implementation: 1. Resource constraints to participation: Lack of staff, small budgets, in-house experts and an inability to pay for outside services/support limited communities’ formal participation in GSA governance and attendance and involvement in SGMA meetings. 2. Accessibility: Additional factors limiting the accessibility of the SGMA process included day-time meetings, language barriers, the proliferation of board and committee meetings, and irregular and unclear meeting schedules and notices. 3. Transparency: A lack of transparency in GSA decision-making as well as limited access to the data and information being used to develop Groundwater Sustainability Plans (GSPs) were common concerns for interviewees. 4. Lack of formal representation: The relegation of communities to advisory, rather than decision-making, roles in the SGMA process was also a common concern. 5. Limited opportunities to provide meaningful input and feedback: Whether participating as a decision-maker, committee member or as a member of the public attending meetings, many were frustrated at the lack of opportunities to provide meaningful input into decisions or on draft documents due to short turnaround times, not being provided necessary background or materials, and limited opportunities for public comment and open discussion. 6. Lack of addressing drinking water interests and priorities: Overwhelmingly, interviewees reported that drinking water interests, especially water quality and domestic wells, were not part of their local SGMA conversations, leading many to be skeptical that SGMA would have drinking-water benefits. Best practices detailed by interviewees with particularly positive experiences and suggestions and recommendations from all of the interviewees, however, demonstrate ample opportunities to address these issues and increase the integration of drinking-water stakeholders and interests into sustainable groundwater management. Targeted efforts to reduce barriers to participation, improve communication and transparency, and promote diverse representation could go a long way to ensuring the “consideration” and “active involvement” of this important, historically marginalized, stakeholder group. For example, communities can educate their GSA about drinking-water priorities and the variety of regulations and requirements public water systems must comply with and coordinate with other small and rural communities to elevate and advocate for drinking water needs. GSAs should incorporate available public data into Groundwater Sustainability Plans (GSPs) while developing plans to fill data gaps, provide ample time for feedback on staggered and sequential GSP sections and streamline and increase interaction with stakeholders in meetings. State agencies should consider requiring or incentivizing collaborative community projects be included in GSPs, and community representation in GSP development and implementation as well as provide funding to support meaningful community involvement in all phases of SGMA implementation.

Comparison of U.S. Geological Survey and Bureau of Reclamation Water-Use Reporting in the Colorado River Basin

U.S. Geological Survey (USGS) | September 2nd, 2019

The use of water in the United States is arguably one of the most important factors determining water availability at any specific place and time. Numerous local, State,

The use of water in the United States is arguably one of the most important factors determining water availability at any specific place and time. Numerous local, State, and Federal entities develop, compile, and report water-use data, which can lead to confusing or conflicting information. This report was authored jointly by the U.S. Geological Survey (USGS) and Bureau of Reclamation (Reclamation) to compare and contrast the two agencies’ water-use information programs in the Colorado River Basin. The report also describes the legal drivers for each program, clarifies confusing terminol- ogy, compares the methods used, and contrasts the information reported by each agency. This detailed comparison demon- strates that these two Federal agencies have different missions, different programmatic drivers, and different user communi- ties, all of which lead to different approaches to water-use data collection, analysis, and reporting. This report highlights those differences and explains why the USGS and Reclamation programs exist and how the data serve different user communities. Even though the two water-use programs are different by design and purpose, the program comparison presented in this report has identified opportunities for closer coordination and sharing of information between the USGS and Reclamation, as well as program components where agency collaboration can improve water-use estimate methodologies. This comparison effort emphasizes that it is incumbent upon each agency to clearly define the meaning of the terms used and the appropri- ate application of the reported information to avoid confusion or the accidental misuse of the information. An additional benefit of this comparison effort is the formation of a joint USGS/ Reclamation water-use team that will continue to investigate opportunities to expand and coordinate future water-use data compilation and reporting.

Competition for water induced by transnational land acquisitions for agriculture

Nature Portfolio (Springer Nature) | January 26th, 2022

The ongoing agrarian transition from smallholder farming to large-scale commercial agriculture promoted by transnational large-scale land acquisitions (LSLAs) often aims

The ongoing agrarian transition from smallholder farming to large-scale commercial agriculture promoted by transnational large-scale land acquisitions (LSLAs) often aims to increase crop yields through the expansion of irrigation. LSLAs are playing an increasingly prominent role in this transition. Yet it remains unknown whether foreign LSLAs by agribusinesses target areas based on specific hydrological conditions and whether these investments compete with the water needs of existing local users. Here we combine process-based crop and hydrological modelling, agricultural statistics, and georeferenced information on individual transnational LSLAs to evaluate emergence of water scarcity associated with LSLAs. While conditions of blue water scarcity already existed prior to land acquisitions, these deals substantially exacerbate blue water scarcity through both the adoption of water-intensive crops and the expansion of irrigated cultivation. These effects lead to new rival water uses in 105 of the 160 studied LSLAs (67% of the acquired land). Combined with our findings that investors target land with preferential access to surface and groundwater resources to support irrigation, this suggests that LSLAs often appropriate water resources to the detriment of local users.

Conceptual and Numerical Models of Dissolved Solids in the Colorado River, Hoover Dam to Imperial Dam, and Parker Dam to Imperial Dam, Arizona, California, and Nevada

U.S. Geological Survey (USGS) | August 28th, 2018

Conceptual and numerical models were developed to understand and simulate monthly flow-weighted dissolved-solids concentrations in the Colorado River at Imperial

Conceptual and numerical models were developed to understand and simulate monthly flow-weighted dissolved-solids concentrations in the Colorado River at Imperial Dam. The ability to simulate dissolved-solids concentrations at this location will help the Bureau of Reclamation satisfy the binational agreement on the volume and salinity of Colorado River water delivered to Mexico. A robust spatial- and temporal-resolution dataset that consists of river discharge and dissolved-solids concentration and load information between January 1990 and September 2016 for 10 sites on canals, drains, tributaries, and the main stem of the Colorado River between Hoover and Imperial Dams was generated. Daily mean dissolved-solids concentrations were estimated and monthly mean dissolved-solids loads were computed for each site. Spatial and temporal load patterns, and historical and current controls on loads and concentrations, were analyzed in order to develop a conceptual model of dissolved- solids transport between Hoover and Imperial Dams. Two numerical models describing the relations between dissolved- solids concentrations and components controlling dissolved-solidsconcentrations and loads were developed, calibrated, and verified. Between January 1990 and September 2016, there was a 98.8-million-acre-feet loss of water and a 57.0-million-ton loss of dissolved-solids load from the Colorado River between Hoover and Imperial Dams. Between Hoover and Parker Dams, about 69.0 million acre-feet of water was lost and 51.1 million tons of dissolved solids were lost; between Parker and Imperial Dams, about 29.8 million acre-feet of water was lost and 5.9 million tons of dissolved solids were lost. Water was removed from the river at a relatively consistent rate over the 25-year study period through water transfers to California and Arizona, evapotranspiration from crop irrigation, transpiration processes of riparian vegetation, and evaporation from the river main stem. Dissolved solids were removed from the river between Hoover and Parker Dams at a relatively constant rate through water transfers to California and Arizona, and water pumped from the river for irrigation within the Mohave Valley. A small amount of dissolved solids are gainedby the river from inflow from the Bill Williams River. Between Parker and Imperial Dams, however, dissolved solids were not removed from the river at a consistent rate over the study period. Dissolved solids were generally removed from the river from 1990 to 2012, then gained by the river from 2012 to 2015, and then removed from the river from 2015 through 2016. Dissolved solids are assumed to be removed from the river and accumulated within the floodplain sediments and aquifers during irrigation processes; some dissolved solids may also be removed from the river through uptake by crops and riparian vegetation. Dissolved solids accumulated on the landscape and in the floodplain aquifer during irrigation are transported to the river during periods when the hydraulic gradient between the floodplain aquifer and the river is increased, causing a gain in dissolved solids in the river. Dissolved-solids gains in the river occur during periods of relatively low river discharge, such as during the winter months and during drier climatic conditions. Two numerical models were developed and coefficientswere estimated by using data from a May 2008-September 2016 calibration period. One model simulates concentrations at Imperial Dam based on the Colorado River system downstream from Parker Dam, and the other model simulates concentrations at Imperial Dam based on the Colorado River system downstreamfrom Hoover Dam. Both models simulated monthly flow-weighted concentrations of dissolved solids for the Colorado River at Imperial Dam, which corresponded well with observed concentrations for the entire study period. The models are more sensitive to input variables of monthly discharge of the ColoradoRiver below Parker Dam and monthly flow-weighted dissolved-solids concentrations of the Colorado River below Hoover Dam and Parker Dam than to the rate of change in concentration with respect to time and the combined discharge of the Colorado River Indian Reservation Main Canal and the Palo Verde Canal. The calibrated models can be used to run scenarios of future monthlyflow-weighted dissolved-solids concentrations in the ColoradoRiver at Imperial Dam. Although the models are expected to provide concentration estimates within 18 milligrams per liter (Parker Dam to Imperial Dam model) to 22 milligrams per liter (Hoover Dam to Imperial Dam model), 95 percent of the time, the error of future scenarios increases as uncertainty in the estimated future input variables increases.