South Lahontan

Quantifying the Relationship Between Atmospheric River Origin Conditions and Landfall Temperature

American Geophysical Union (AGU) | October 11th, 2022

The temperature of landfalling atmospheric rivers (ARs) has direct implications for regional water resources. Compared to cool ARs, warm ARs can result in more surface ru

The temperature of landfalling atmospheric rivers (ARs) has direct implications for regional water resources. Compared to cool ARs, warm ARs can result in more surface runoff and flooding, less water availability via low snow accumulations and enhanced snowmelt, and greater challenges for storm forecasting and reservoir operations. Based on case studies, ARs with subtropical origin locations and warm origin conditions are assumed to be associated with warmer landfall temperatures—though, to date, this has not yet been demonstrated systematically. We analyze North Pacific ARs that made landfall along the West Coast of North America from 1980 to 2017. We find that ARs originating over the subtropical Pacific Ocean near Hawaii (“Pineapple Express”-type ARs) are indeed 1.5°C warmer and 2 kg/m2 moister in winter than ARs originating elsewhere. We extend this analysis for the full study population of ARs by quantifying AR origin conditions, including the spatial distribution of origin temperature, moisture content, and integrated vapor transport (IVT). We use fixed effects multivariate regression to quantify the relative influence of the origin conditions on landfall temperature. Our regression models show that AR origins with lower latitudes, longer AR lifetimes, and stronger IVT are associated with warmer landfall temperatures and that ARs that start warm generally stay warm. We also find that the phase of the El Niño/Southern Oscillation does not exhibit a consistent relationship with AR landfall temperature. Overall, our results partially affirm—yet also complicate—common assumptions about the role of different origin conditions in landfalling AR temperature.

Racanelli Decision: Detailed summary of the decision

Department of Justice (DOJ) | November 16th, 2007

At their meeting on October 25, 2007, the Delta Vision Blue Ribbon Task Force members asked for a summary of United States v. State Water Resources Control Board (1986) 1

At their meeting on October 25, 2007, the Delta Vision Blue Ribbon Task Force members asked for a summary of United States v. State Water Resources Control Board (1986) 182 Cal.App.3d 82, commonly referred to as the “Racanelli Decision,” after the appellate judge who wrote the opinion. We repeat the Court’s own very short summary of the case, followed by a more detailed summary of the decision.

Rapid decline of California’s native inland fishes: a status assessment

University of California, Davis (UC Davis) | November 1st, 2010

Degradation of freshwater ecosystems is a global crisis best understood through intensive study of well-studied regional faunas. A quantitative protocol was used

Degradation of freshwater ecosystems is a global crisis best understood through intensive study of well-studied regional faunas. A quantitative protocol was used to determine conservation status of all 129 freshwater fishes native to California. Seven (5%) are extinct; 34 (26%) qualified for listing as endangered or threatened species; 32 (25%) were rated as imperiled, qualifying as California Species of Special Concern, with potential for listing; 34 (26%) rated being on a watch list and 22 (17%) were found to be relatively secure. Of 31 species officially listed under federal and state endangered species acts, 17 (55%) clearly qualified for listing under our criteria and 12 (39%) were rated as species of special concern. Conversely, of 34 extant species with the lowest ratings under our criteria, only 17 (50%) were officially listed. Climate change, area occupied and anthropogenic threats had the largest negative impact on status. Of the 15 categories of anthropogenic threats analyzed, those most likely to diminish status were alien species, agriculture and dams. Overall, 83% of California’s freshwater fishes are extinct, endangered, or in decline, a 16% increase since 1995 and a 21% increase since 1989. The decline seen in California’s inland fishes is probably typical of declines in areas that are less well documented, indicating a strong need for better methods of conservation of freshwater ecosystems.

Recent decreases in snow water storage in western North America

Nature Portfolio (Springer Nature) | May 22nd, 2023

Mountain snowpacks act as natural water towers, storing winter precipitation until summer months when downstream water demand is greatest. We introduce a Snow Storage Ind

Mountain snowpacks act as natural water towers, storing winter precipitation until summer months when downstream water demand is greatest. We introduce a Snow Storage Index (SSI), representing the temporal phase difference between daily precipitation and surface water inputs—sum of rainfall and snowmelt into terrestrial systems—weighted by relative magnitudes. Different from snow water equivalent or snow fraction, the SSI represents the degree to which the snowpack delays the timing and magnitude of surface water inputs relative to precipitation, a fundamental component of how snow water storage influences the hydrologic cycle. In western North America, annual SSI has decreased (p 

Recharge Area Identification, Utilization, and Protection Resource Management Strategy

California Department of Water Resources (DWR) | April 29th, 2024

This resource management strategy (RMS) advances water supply augmentation, resilience, and equity in California by providing summaries of the state of knowledge, applica

This resource management strategy (RMS) advances water supply augmentation, resilience, and equity in California by providing summaries of the state of knowledge, applications, and available information and resources on recharge area identification, utilization, and protection.

Recharge Net Metering to Enhance Groundwater Sustainability

University of California, Berkeley (UC Berkeley) | April 2nd, 2018

Groundwater sustainability depends on balancing aquifer inflows and outflows. Extraction (pumping of groundwater, typically for human use) and recharge (inflow of

Groundwater sustainability depends on balancing aquifer inflows and outflows. Extraction (pumping of groundwater, typically for human use) and recharge (inflow of water to an aquifer from the land surface and streams) are central components of this water balance. Often, increasing demands for groundwater are exacer- bated by stresses on limited surface water supplies. Changes in land use and shifting climate can result in less infiltration of precipitation into the ground, reducing recharge. Increasing water scarcity has led to increased pumping, and in turn, unsustainable management of groundwater in many basins, resulting in depleted supplies, degraded water quality, and other impacts.

Recommendations to the State Water Resources Control Board Pursuant to California Water Code Section 10609

California Department of Water Resources (DWR) | September 29th, 2022

The Department of Water Resources (DWR) is pleased to provide the following recommendations developed in response to the 2018 Legislation (Senate Bill 606 [Hertzberg] and

The Department of Water Resources (DWR) is pleased to provide the following recommendations developed in response to the 2018 Legislation (Senate Bill 606 [Hertzberg] and Assembly Bill 1668 [Friedman]) enacted in support of “Making Water Conservation a California Way of Life.” The Legislation included provisions for advancing urban water use efficiency through developing and implementing various water use efficiency standards, variances for unique uses of water, and commercial, industrial, and institutional (CII) performance measures, among other requirements. Full reports detailing our methods, technical analyses, studies, public input, and recommendations will follow. These recommendations for long-term urban water use efficiency reflect technical considerations, public input, and the imperative to continue California’s progress in urban efficient use of water for future generations. If adopted DWR's recommendations on outdoor residential and CII water use on landscapes with dedicated irrigation meters, combined with the indoor residential water use standard recommendations submitted to the Legislature jointly by DWR and State Water Resources Control Board (State Water Board), pursuant to Water Code 10609.4 (b)(1), would result in expected long-term water savings of approximately 450,000 acre-feet per year starting in 2030 – considering 2019 population and 2017-2019 water use data, the water savings are enough to supply about 1.6 million homes or 4.7 million residents for both indoor and outdoor annual water needs.

Reconstructing the Mediaeval low stands of Mono Lake, Sierra Nevada, California, USA

Holocene (Sage Journals) | December 1st, 2019

Palaeosimulations of Mono Lake covering the past 2 kyr have been conducted using a water balance model forced with tree-ring derived inflow estimates. The results show tw

Palaeosimulations of Mono Lake covering the past 2 kyr have been conducted using a water balance model forced with tree-ring derived inflow estimates. The results show two low stands, during the ninth to tenth and twelfth to thirteenth centuries, that agree well in timing and magnitude with those described by Stine (1987, 1990, 1994) on the basis of geomorphic evidence and relict trees and shrubs exposed on Mono Lake's artificially exposed shorelands. The lake simulation provides independent corroboration of the timing and magnitude of Stine's drought-induced low stands and supports the accuracy of tree-ring-derived estimates of Mediaeval precipitation and runoff reductions in the central Sierra Nevada. Specifically, we estimate that during the two Mediaeval droughts, centennial average precipitation and river runoff in the central Sierra Nevada reached as low as 75% of the twentieth century values, with multidecade averages as low as 60—65%. In both magnitude and duration, these droughts far exceed anything experienced in the region during modern times. An analysis of the spatial patterns of reconstructed drought indices shows that the particular `two drought' Mono Lake low stand signal was focused over central and southern California, indicating the dominant role of boreal winter precipitation deficits. In this respect, the `Great Sierra Nevada droughts' were somewhat distinct from the more general Great Basin/far western Plains pattern of Mediaeval aridity over the western USA.

Regional Ground-Water Evapotranspiration and Ground-Water Budgets, Great Basin, Nevada

U.S. Geological Survey (USGS) | July 1st, 2000

Regional water table (1994) and water-level changes in the Morongo Basin, San Bernardino County, California

U.S. Geological Survey (USGS) | July 1st, 1995

The Morongo Basin is in the Mojave Desert region of southern California, about 100 mi east of Los Angeles. Ground water is virtually the sole source of water in the Moro

The Morongo Basin is in the Mojave Desert region of southern California, about 100 mi east of Los Angeles. Ground water is virtually the sole source of water in the Morongo Basin. Increased pumping to meet the needs of an increasing resident population has resulted in ground-water overdraft in parts of the ground-water basin. Most of the water resources of the basin are managed by the Mojave Water Agency (MWA) and the U.S. Marine Corps Air/Ground Combat Center at Twentynine Palms (USMCAGCC). To help manage the ground-water resources, the MWA and the U.S. Marine Corps, Department of the Navy, requested the U.S. Geological Survey (USGS) to construct a regional water-table map of the Morongo ground-water basin. The purposes of this study were to construct a regional water-table map and determine areas of water-level change in the Morongo Basin. Existing data were evaluated and water levels were measured in selected wells throughout the Morongo Basin. Water-level measurements were used to construct a regional water-table map for 1994 conditions (fig. 1), and available historical water levels were used to construct hydrographs (shown in fig. 1) and determine water-level change at selected wells. Results of this study will aid the USGS in evaluating its current ground-water monitoring network in the Morongo Basin. In addition, information gained through this study will contribute to ongoing projects in the area, such as the Regional Aquifer-System Analysis (RASA) of Southern California.