Trends in atmospheric patterns conducive to seasonal precipitation and temperature extremes in California seasonal precipitation and temperature extremes

American Association for the Advancement of Science (AAAS) | April 1st, 2016

Recent evidence suggests that changes in atmospheric circulation have altered the probability of extreme climate events in the Northern Hemisphere. We investigate northe

Recent evidence suggests that changes in atmospheric circulation have altered the probability of extreme climate events in the Northern Hemisphere. We investigate northeastern Pacific atmospheric circulation patterns that have historically (1949–2015) been associated with cool-season (October-May) precipitation and temperature extremes in California. We identify changes in occurrence of atmospheric circulation patterns by measuring the similarity of the cool-season atmospheric configuration that occurred in each year of the 1949–2015 period with the configuration that occurred during each of the five driest, wettest, warmest, and coolest years. Our analysis detects statistically significant changes in the occurrence of atmospheric patterns associated with seasonal precipitation and temperature extremes. We also find a robust increase in the magnitude and subseasonal persistence of the cool-season West Coast ridge, resulting in an amplification of the background state. Changes in both seasonal mean and extreme event configurations appear to be caused by a combination of spatially non-uniform thermal expansion of the atmosphere and reinforcing trends in the pattern of sea level pressure. In particular, both thermal expansion and sea level pressure trends contribute to a notable increase in anomalous northeastern Pacific ridging patterns similar to that observed during the 2012–2015 California drought. Collectively, our empirical findings suggest that the frequency of atmospheric conditions like those during California’s most severely dry and hot years has increased in recent decades, but not necessarily at the expense of patterns associated with extremely wet years.

Trends in Snowfall versus Rainfall in the Western United States

American Meteorological Society (AMS) | September 15th, 2006

The water resources of the western United States depend heavily on snowpack to store part of the wintertime precipitation into the drier summer months. A well-documented

The water resources of the western United States depend heavily on snowpack to store part of the wintertime precipitation into the drier summer months. A well-documented shift toward earlier runoff in recent decades has been attributed to 1) more precipitation falling as rain instead of snow and 2) earlier snowmelt. The present study addresses the former, documenting a regional trend toward smaller ratios of winter-total snowfall water equivalent (SFE) to winter-total precipitation (P) during the period 1949–2004. The trends toward reduced SFE are a response to warming across the region, with the most significant reductions occurring where winter wet-day minimum temperatures, averaged over the study period, were warmer than 5°C. Most SFE reductions were associated with winter wet-day temperature increases between 0° and 3°C over the study period. Warmings larger than this occurred mainly at sites where the mean temperatures were cool enough that the precipitation form was less susceptible to warming trends. The trends toward reduced SFE/P ratios were most pronounced in March regionwide and in January near the West Coast, corresponding to widespread warming in these months. While mean temperatures in March were sufficiently high to allow the warming trend to produce SFE/P declines across the study region, mean January temperatures were cooler, with the result that January SFE/P impacts were restricted to the lower elevations near the West Coast. Extending the analysis back to 1920 shows that although the trends presented here may be partially attributable to interdecadal climate variability associated with the Pacific decadal oscillation, they also appear to result from still longer-term climate shifts.

Tri-County Water Authority Groundwater Sustainability Plan

Tri-County Water Authority | December 18th, 2019

Tulare Lake Subbasin Groundwater Sustainability Plan

Kings County Farm Bureau | January 29th, 2020

Tulare Lake Subbasin Groundwater Sustainability Plan -- Amended

Mid-Kings River Groundwater Sustainability Agency | July 26th, 2022

The Tulare Lake Subbasin submitted a single GSP in January 2020 to the Department of Water Resources (DWR). DWR was required to determine whether the GSP conformed to the

The Tulare Lake Subbasin submitted a single GSP in January 2020 to the Department of Water Resources (DWR). DWR was required to determine whether the GSP conformed to the specific requirements of SGMA. In a letter dated January 28, 2022, DWR determined that that the GSP is incomplete. DWR stated that the GSP was considered incomplete as it “does not define undesirable results or set sustainable management criteria for groundwater levels, subsidence, and water quality in the manner consistent with SGMA and the GSP regulations.” Upon receiving the incomplete determination, the Subbasin had 180 days to address the identified deficiencies and submit a revised GSP by July 27, 2022. The GSAs are submitting this 2022 Amended GSP to address the three deficiencies outlined in the determination letter. The 2022 Amended GSP consists of clean and redline strike out versions of the 2020 GSP and the attached 2022 GSP Addendum. The 2022 GSP Addendum was prepared to specifically address the incomplete determination letter from DWR. Sections of this document have been edited since the original submittal in 2020 and direct the reader to the Addendum for further details. Due to size, this file has been divided. Part 1, Part 2, Part 3, Part 4, Part 5, Part 6

Tulare Lake Subbasin Probationary Hearing Draft Report

California State Water Resources Control Board (SWRCB) | October 12th, 2023

The State Water Board recognizes that significant efforts were made by local public agencies in the Tulare Lake Subbasin since the passage of SGMA to form groundwater sus

The State Water Board recognizes that significant efforts were made by local public agencies in the Tulare Lake Subbasin since the passage of SGMA to form groundwater sustainability agencies (GSAs) and then develop detailed technical and other information supporting the adoption and implementation of a groundwater sustainability plan (GSP) for the subbasin. Despite those efforts, in January of 2022, DWR reviewed the GSP to determine if it met SGMA’s requirements and found it to be incomplete. Following revisions made by the GSAs in the subbasin, DWR reevaluated the GSP in March of 2023, determined it to be inadequate, and referred the subbasin to the State Water Board, as required by SGMA. Consistent with SGMA, the State Water Board may now consider whether to designate the Tulare Lake Subbasin as a “probationary basin,” a term that is used in SGMA to describe the first stage of state intervention. Click here for Appendix to the report.

Tulare Lake Subbasin Probationary Hearing Final Staff Report

California State Water Resources Control Board (SWRCB)nia | March 29th, 2024

State Water Board staff have identified specific deficiencies in the Tulare Lake Subbasin 2022 GSP and have outlined potential corrective actions to address those specifi

State Water Board staff have identified specific deficiencies in the Tulare Lake Subbasin 2022 GSP and have outlined potential corrective actions to address those specific deficiencies. The Final Staff Report also incorporates deficiencies identified by DWR’s determination. Deficiencies that have been identified within the GSP relate to: * Chronic lowering of groundwater levels with insufficient management criteria. * Continued land subsidence (sinking). * Further degradation of groundwater quality.

Tule Subbasin Probationary Hearing Draft Staff Report

California State Water Resources Control Board (SWRCB) | March 1st, 2024

The State Water Board recognizes that local public agencies in the Tule Subbasin significant efforts since the passage of SGMA to form groundwater sustainability agencies

The State Water Board recognizes that local public agencies in the Tule Subbasin significant efforts since the passage of SGMA to form groundwater sustainability agencies (GSAs) and then develop detailed technical and other information supporting the adoption and implementation of six groundwater sustainability plans (GSPs) for the subbasin. Despite those efforts, in January of 2022, DWR reviewed GSPs to determine if the GSPs met SGMA’s requirements and found it to be incomplete. Following revisions made by the GSAs in the subbasin, DWR reevaluated the GSPs in March of 2023, determined the GSPs to be inadequate, and referred the subbasin to the State Water Board, as required by SGMA. Consistent with SGMA, the State Water Board may now consider whether to designate the Tule Subbasin as a “probationary basin,” a term that is used in SGMA to describe a basin in the first stage of state intervention.

Tule Subbasin Probationary Hearing Final Staff Report

California State Water Resources Control Board (SWRCB) | August 30th, 2024

Board staff identified specific deficiencies in the Tule Subbasin 2022 GSPs and outlined potential corrective actions to address those specific deficiencies. • Chron

Board staff identified specific deficiencies in the Tule Subbasin 2022 GSPs and outlined potential corrective actions to address those specific deficiencies. • Chronic lowering of groundwater levels with insufficient management criteria. • Continued land subsidence (sinking). • Further degradation of groundwater quality. • Depletions of interconnected surface water.

Tuolumne Watershed Diversions without Hetch Hetchy Reservoir: Comparison of Interties to Cherry and Don Pedro Reservoirs

Environmental Defense Fund (EDF) | February 14th, 2005

Without storing water in Hetch Hetchy Valley, additional conveyance facilities could allow the San Francisco Public Utilities Commission to divert supplies from storage i

Without storing water in Hetch Hetchy Valley, additional conveyance facilities could allow the San Francisco Public Utilities Commission to divert supplies from storage in other Tuolumne River watershed reservoirs. The most obvious potential locations for additional conveyance are at Don Pedro Reservoir or at Holm Powerplant below Cherry Reservoir. Computer modeling, using a 73 year hydrologic record, indicates that either a Don Pedro Intertie or a Cherry Intertie would allow the SFPUC to deliver more than 95 percent of customer demand without diminishing system reliability. Some additional supplies would be needed in dry years to replace the loss of Hetch Hetchy Reservoir.