State Water Project and Central Valley Project Drought Contingency Plan May 1, 2021 – September 30, 2021

California Department of Water Resources (DWR) | May 28th, 2021

This Drought Contingency Plan (Drought Plan) is prepared by the California Department of Water Resources (DWR) and the U.S. Bureau of Reclamation (Reclamation) in an effo

This Drought Contingency Plan (Drought Plan) is prepared by the California Department of Water Resources (DWR) and the U.S. Bureau of Reclamation (Reclamation) in an effort to provide updated information about areas of potential concern given the current dry hydrology of 2021. DWR and Reclamation operate the State Water Project (SWP) and the Central Valley Project (CVP), respectively, to the 2020 Record of Decision (ROD) as analyzed in the 2019 U.S. Fish and Wildlife Service (USFWS) Biological Opinion and 2019 National Marine Fisheries Service (NMFS) Biological Opinion on the Coordinated Long-Term Operation of the Central Valley Project and the State Water Project (Collectively the 2019 Biological Opinions), and DWR also operates the SWP to the 2020 California Department of Fish and Wildlife (CDFW) Incidental Take Permit (ITP). This updated Drought Plan will be submitted by DWR to CDFW in response to Condition 8.21 of CDFW’s ITP. Concurrently, this plan will be shared with the Water Operations Management Team (WOMT) which includes representatives from DWR, Reclamation, USFWS, NMFS, CDFW, and the State Water Resources Control Board (SWRCB) (collectively referred to as Agencies). This report was first drafted in February and subsequently updated in March, April, and May 2021.

State Water Project Long-Term Drought Plan

California Department of Water Resources (DWR) | May 21st, 2024

The 2024 State Water Project (SWP) Long-Term Drought Plan consolidates information and actions taken during past droughts along with descriptions of the actions taken by

The 2024 State Water Project (SWP) Long-Term Drought Plan consolidates information and actions taken during past droughts along with descriptions of the actions taken by the SWP to plan for and prepare for future droughts.

Statement from ADWR Director Tom Buschatzke and CAP General Manager Ted Cooke in response to the U.S. Department of the Interior announcement of actions to protect the Colorado River system and 2023 Operating Conditions for Lake Powell and Lake Mead

Arizona Department of Water Resources (ADWR) | August 16th, 2022

Statement of Camille Calimlim Touton, Commissioner, Bureau of Reclamation U.S. Department of the Interior Before the Senate Committee on Energy and Natural Resources June 14, 2022

Senate Committee on Energy and Natural Resources | June 14th, 2022

"The Colorado River Basin is in the 23rd year of a historic drought. Both Lake Powell and Lake Mead – the two largest reservoirs in the United States – are at histori

"The Colorado River Basin is in the 23rd year of a historic drought. Both Lake Powell and Lake Mead – the two largest reservoirs in the United States – are at historically low levels with a combined storage capacity of 28 percent of capacity. While Reclamation and its partners have been successful in conserving water in Lake Mead and Colorado River System reservoirs, more needs to be done as the system reaches critically low water levels. The system is at a tipping point. An example of how Tribal Nations and water managers have addressed these conditions is shown in how, over the past 15 years, approximately 4.6 million acre-feet (maf) have been conserved in Lake Mead through voluntary measures by the three Lower Basin States, Tribal Nations, and Mexico. This has been accomplished through the creation of Intentionally Created Surplus, system conservation water, water for Mexico’s water reserve under Minutes 318, 319, and 323, as well as other water conservation efforts. At current water levels, these measures add 70 feet to Lake Mead’s elevation and delayed the first shortage declaration by six years. Over the past few years, Reclamation has worked with the Upper and Lower Basin States, Tribes, and stakeholders on Colorado River Drought Contingency Plans (DCPs), which were implemented in 2019. The DCPs provide a framework for additional actions to help the basin adapt to drought. An example of this is a 2021 Lower Basin Memorandum of Understanding, called the 500 Plus Plan. The plan, developed under both the DCP and 2021 MOU, aims to conserve additional water above what is required under a Lower Basin shortage condition and contributions under the Lower Basin DCP. The 500 Plus Plan parties have identified and are funding projects in each of the three Lower Basin States, and the projects include tribal, agricultural, and municipal water users. On May 3, 2022, Reclamation announced two separate drought response actions that will help increase Lake Powell storage by nearly 1.0 maf over the next 12 months (May 2022 through April 2023). The two actions include: 1. Approximately 500,000 acre-feet of water will be released from Flaming Gorge Reservoir, located approximately 455 river miles upstream of Lake Powell, pursuant to an agreement as part of the Upper Basin Drought Contingency Plan (adopted in 2019); and 2. Another 480,000 acre-feet will be left in Lake Powell by reducing Glen Canyon Dam’s annual release volume from 7.48 maf to 7.00 maf, as outlined in the 2007 Interim Guidelines that control operations of Glen Canyon Dam and Hoover Dam. Regarding current conditions, in March 2022 Lake Powell dropped below elevation 3,525 feet, meaning the reservoir was less than 35 feet above the minimum power pool of 3,490 feet (i.e., minimum elevation at which hydropower can be generated). According to the May 2022 Most Probable 24-Month Study, the April-July runoff forecast into Lake Powell is 3.80 maf, or 59 percent of average. Lake Powell’s water surface elevation is projected to end the calendar year at 3,522.94 feet (22 percent full). Lake Mead is projected to reach an elevation of 1,039.92 feet (27 percent full) on December 31, 2022. While not official until the August 2022 24-Month Study, a shortage condition for the Lower Basin is projected in calendar year 2023. Looking to the future, Reclamation is preparing to develop new operating guidelines given that the 2007 Interim Guidelines expire in 2026. Reclamation is targeting initiating a formal National Environmental Policy Act (NEPA) process in early 2023. Technical information and lessons learned from management under the current guidelines will be very helpful as the basin strives to develop new guidelines that are durable and drought resilient. Additionally, collaboration and involvement by partners and stakeholders (Tribal Nations, States, water districts, etc.) will be paramount for the effort to be successful. Prior to the start of the formal NEPA process, Reclamation is preparing to issue a “pre-scoping” Federal Register notice (targeting the week of June 20) to ask for input on both the stakeholder engagement process and the substantive elements and strategies for post-2026 operations. Despite the actions taken by the Department and Reclamation, significant and additional conservation actions are required to protect the Colorado River system infrastructure and the long-term stability of the system."

Statistical Downscaling Using Localized Constructed Analogs (LOCA)*

American Meteorological Society (AMS) | December 2nd, 2014

A new technique for statistically downscaling climate model simulations of daily temperature and precipitation is introduced and demonstrated over the western United Sta

A new technique for statistically downscaling climate model simulations of daily temperature and precipitation is introduced and demonstrated over the western United States. The localized constructed analogs (LOCA)method produces downscaled estimates suitable for hydrological simulations using amultiscale spatial matching scheme to pick appropriate analog days fromobservations. First, a pool of candidate observed analog days is chosen by matching the model field to be downscaled to observed days over the region that is positively correlated with the point being downscaled, which leads to a natural independence of the downscaling results to the extent of the domain being downscaled. Then, the one candidate analog day that best matches in the local area around the grid cell being downscaled is the single analog day used there. Most grid cells are downscaled using only the single locally selected analog day, but locations whose neighboring cells identify a different analog day use a weighted combination of the center and adjacent analog days to reduce edge discontinuities. By contrast, existing constructed analog methods typically use a weighted average of the same 30 analog days for the entire domain. By greatly reducing this averaging, LOCA produces better estimates of extreme days, constructs a more realistic depiction of the spatial coherence of the downscaled field, and reduces the problem of producing too many light-precipitation days. The LOCA method is more computationally expensive than existing constructed analog techniques, but it is still practical for downscaling numerous climate model simulations with limited computational resources.

Storing Water for the Environment: Operating Reservoirs to Improve California’s Freshwater Ecosystems

Public Policy Institute of California (PPIC) | August 23rd, 2022

Large reservoirs like those that rim the Central Valley are essential for managing water in California’s highly variable climate. They provide multiple benefits includi

Large reservoirs like those that rim the Central Valley are essential for managing water in California’s highly variable climate. They provide multiple benefits including water supply, hydropower, flood management, and recreation. However, construction and operation of these reservoirs have also imposed significant environmental costs, including native fishes’ loss of access to high-quality habitat above dams and degradation of freshwater ecosystems below them. Moreover, regulatory uncertainty for water users is rising as these ecosystems decline. California needs a new approach for managing environmental water in its large reservoirs, particularly as the climate warms and droughts become more intense.

Strum Und Drand – California’s Remarkable Storm-Drought Connection

International Association for Hydro-Environment Engineering and Research | May 31st, 2019

Storm and drought are essentially the whole story of water and life in California in ways that have always made hydro-environmental engineering a unique proposition th

Storm and drought are essentially the whole story of water and life in California in ways that have always made hydro-environmental engineering a unique proposition there. To begin with, California experiences larger year-to-year variations in precipitation than elsewhere in the US, with standard deviations of annual precipitation between 30-50% of long-term averages, compared to 10-30% nearly everywhere else. California’s annual precipitation totals routinely vary from as little as 50% to more than 200% of long-term averages, with those dry excursions forming our droughts. This extreme variability arises because California’s Mediterranean climate only provides a limited seasonal window of precipitation events, and within that period a small number of storms deliver most of the State’s precipitation each year. If a few extra large storms reach California in a given winter, we can have a very wet year indeed; if some are lacking, we face drought. But the storm-drought connection is deeper and more pervasive in California than anywhere else in the US.

Supplement to the 2007 Colorado River Interim Guidelines for Lower Basin Shortages and the Coordinated Operations for Lake Powell and Lake Mead

U.S. Bureau of Reclamation (USBR) | May 6th, 2024

This ROD revises the 2007 Interim Guidelines for the near-term operation of Glen Canyon and Hoover Dams to address the potential for continued low-runoff conditions in th

This ROD revises the 2007 Interim Guidelines for the near-term operation of Glen Canyon and Hoover Dams to address the potential for continued low-runoff conditions in the Basin. Reclamation has concluded that the potential impacts of low-runoff conditions pose unacceptable risks to routine operations of Glen Canyon and Hoover Dams during the remainder of the interim period (through the end of the 2026 operating year) and that modified operating guidelines need to be expeditiously developed.

Synergies between climate anomalies and hydrological modifications facilitate estuarine biotic invasions

Ecology Letters (Wiley) | June 6th, 2011

Environmental perturbation, climate change and international commerce are important drivers for biological invasions. Climate anomalies can further increase levels of hab

Environmental perturbation, climate change and international commerce are important drivers for biological invasions. Climate anomalies can further increase levels of habitat disturbance and act synergistically to elevate invasion risk. Herein, we use a historical data set from the upper San Francisco Estuary to provide the first empirical evidence for facilitation of invasions by climate extremes. Invasive zooplankton species did not become established in this estuary until the 1970s when increasing propagule pressure from Asia coincided with extended drought periods. Hydrological management exacerbated the effects of post‐1960 droughts and reduced freshwater inflow even further, increasing drought severity and allowing unusually extreme salinity intrusions. Native zooplankton experienced unprecedented conditions of high salinity and intensified benthic grazing, and life history attributes of invasive zooplankton were advantageous enough during droughts to outcompete native species and colonise the system. Extreme climatic events can therefore act synergistically with environmental perturbation to facilitate the establishment of invasive species.

The 1976-1977 California Drought - A Review

California Department of Water Resources (DWR) | May 1st, 1978

This is the fifth and final Department of Water Resources' report on the 1976-1977 California drought, the worst in the State's history, which saw 1976, the fourth-driest

This is the fifth and final Department of Water Resources' report on the 1976-1977 California drought, the worst in the State's history, which saw 1976, the fourth-driest year of record, give way to 1977, the driest ever.  These reports provide the most comprehensive documentation of a drought in history. The 1976-1977 drought has again shown the finite nature of our resourcees and our limited ability to control nature.  This report, prepared by the Department's Drought Information Center, updates the August 1977 report and places the entire two-year period in perspective.  It documents the impact of the drought and details the response by federal, State, and local governments and the public. This report also discusses lessons learned from the drought and suggest future actions to enable us to better use our State's limited water resources.