Historical and future relations between large storms and droughts in California

University of California, Davis (UC Davis) | July 14th, 2016

California precipitation varies more dramatically from year to year than elsewhere in the conterminous United States. This paper analyzes the extent to which contribution

California precipitation varies more dramatically from year to year than elsewhere in the conterminous United States. This paper analyzes the extent to which contributions of the wettest days to overall precipitation dictate the state’s precipitation seasonality and frequent multiyear periods of drought (as precipitation deficit) and plenty is analyzed, historically and in projections of future climates. The wettest 5% of wet days in California contribute about a third of precipitation but about two-thirds of the variance of water-year precipitation. Year-to-year fluctuations in precipitation strongly reflect year-to-year fluctuations of contributions from the largest storms, with the large-storm contributions explaining about twice as much precipitation fluctuation as do contributions from all remaining storms combined. This extreme dominance of large storms is largely unique to California within the United States. In climate-change projections, eight of ten climate models considered here yield increases in precipitation from the largest storms, and when the increases are large, total precipitation follows suit. All of the models project declines in contributions from the smaller storms and models projecting total-precipitation declines reflect this decline. Projected changes in variance of water-year precipitation reflect changes in variance of large-storm contributions. The disproportionately large overall contributions from California’s largest storms, and their outsized year-to-year variability, ensure that the state’s largest storms dictate the state’s regimes of wet and dry spells, historically and in climate-change projections.

Historical Ecology and Landscape Change in the Central Laguna de Santa Rosa

San Francisco Estuary Institute (SFEI) | May 12th, 2017

This study synthesizes a diverse array of data to examine the ecological patterns, ecosystem functions, and hydrology that characterized a central portion of the Laguna d

This study synthesizes a diverse array of data to examine the ecological patterns, ecosystem functions, and hydrology that characterized a central portion of the Laguna de Santa Rosa during the mid-19th century, and to analyze landscape changes over the past 150 years. The primary purpose of this study was to help guide restoration actions and other measures aimed at reducing nutrient loads within this portion of the Laguna de Santa Rosa watershed. Prior to Euro-American modification of the landscape, the Laguna de Santa Rosa (hereafter, “Laguna”) supported a diverse and extensive array of wetland and riparian habitat types ranging from tule marshes and willow forests to wet meadows and vernal pools. As one of the largest wetland complexes in northern California, the Laguna was a productive ecosystem that was home to vast numbers of resident and migratory birds, fish, mammals, and other wildlife. It was this diversity and productivity that made the Laguna a focal element of the Santa Rosa Plain for generations of native Pomo people, and for 19th-century Spanish and American settlers. Today, the Laguna continues to provide vital habitat for a host of native plants and animals, and has been recognized by the Ramsar Convention on Wetlands as a Wetland of International Importance (Ramsar 2017). However, as the population of the area has grown and land use modifications have intensified over the past 150 years, the Laguna has experienced a variety of impacts stemming from urban and agricultural development. These impacts include substantial loss of native wetland and riparian habitats, channelization of streams, alterations to streamflow and sediment dynamics, invasion of non-native species, and water quality impairments. While the Laguna still exhibits elements of its former character, the modern Laguna represents a landscape profoundly altered by over a century and a half of both direct and indirect modifications. As residents and land managers look to improve the ecological health of the Laguna and restore lost ecological functions, an understanding of what the landscape was like in the recent past, and how it has changed over time, provides a valuable starting place for envisioning its future potential.

Historical Ecology and Landscape Change in the Central Laguna de Santa Rosa

San Francisco Estuary Institute (SFEI) | March 1st, 2017

This study synthesizes a diverse array of data to examine the ecological patterns, ecosystem functions, and hydrology that characterized a central portion of the Laguna d

This study synthesizes a diverse array of data to examine the ecological patterns, ecosystem functions, and hydrology that characterized a central portion of the Laguna de Santa Rosa during the mid-19th century, and to analyze landscape changes over the past 150 years. The primary purpose of this study was to help guide restoration actions and other measures aimed at reducing nutrient loads within this portion of the Laguna de Santa Rosa watershed.

Historical Ecology of the Los Angeles River Watershed and Environs, Infrastructure for a Comprehensive Analysis

University of Southern California (USC) | June 15th, 2020

Historical Expenditures and Current and Future Funding Needs

California Department of Water Resources (DWR) | December 13th, 2018

This document supports information contained in the California Water Plan Update 2018. The purpose of this document is to provide a description of California’s water re

This document supports information contained in the California Water Plan Update 2018. The purpose of this document is to provide a description of California’s water resources management historical expenditures and the existing funding needs in the State. The historical expenditure data includes capital and ongoing public agencies’ (State, local, and Federal agencies) historical expenditures. Historical expenditure data is organized by management action type and water sectors. In this document, capital management actions include infrastructure development, repair, replacement or rehabilitation. Ongoing actions include planning, data management, tracking and reporting, operations, and maintenance. Historical expenditure data is provided for State fiscal year 2005/2006 (2006) to 2014/2015 (2015). This timeframe was selected due to data availability at the local, State, and Federal levels. This document also provides information on the accrued interest on debt from State general obligation (GO) bonds.  This document provides information pertaining to the projected existing water management funding needs and existing water management funding gap. Projected water management funding need was estimated from planned and proposed management actions collected from State, local, and Federal agencies.  Historical expenditure and funding need information is used in the California Water Plan Update 2018 to provide context and data for inclusion into the funding analysis, described in the Funding Scenario Analysis supporting document. 

Historical Fresh Water and Salinity Conditions in the Western Sacramento-San Joaquin Delta and Suisun Bay

Contra Costa Water District (CCWD) | February 23rd, 2010

The watershed of the Sacramento–San Joaquin Delta (Delta) provides drinking water to more than 23 million Californians as well as irrigation water for millions of acres

The watershed of the Sacramento–San Joaquin Delta (Delta) provides drinking water to more than 23 million Californians as well as irrigation water for millions of acres of agriculture in the Central Valley. The Delta itself is a complex estuarine ecosystem, with populations of many native species now in serious decline. The Delta estuary as we know it began to form about 6,000 years ago, following the end of the last ice age. Because the estuary is connected to the Pacific Ocean through San Francisco Bay, seawater intrusion causes the salinity of Suisun Bay and the Delta to vary depending on hydrological conditions. This seawater intrusion into the Delta affects estuarine species as well as drinking water and irrigation water supplies. Successful restoration of the Delta ecosystem requires an understanding of the conditions under which native species evolved. Contra Costa Water District’s report on “Historical Fresh Water and Salinity Conditions in the Western Sacramento-San Joaquin Delta and Suisun Bay” presents a detailed review of more than 100 years of studies, monitoring data, scientific reports, and modeling analyses that establish an historical record of the salinity conditions in the Western Delta and Suisun Bay.

Historical Seawater Intrusion Map Pressure 180-Foot Aquifer - 500 mg/L or Greater Chloride Areas

Monterey County Water Resources Agency (MCWRA) | April 11th, 2018

History and Sources of Co-Occurring Pesticides in an Abstraction Well Unraveled by Age Distributions of Depth-Specific Groundwater Samples

American Chemical Society (ACS) | November 24th, 2019

When groundwater-based drinking water supply becomes contaminated, the timing and source of contamination are obvious questions. However, contaminants often have diffuse

When groundwater-based drinking water supply becomes contaminated, the timing and source of contamination are obvious questions. However, contaminants often have diffuse sources and different contaminants may have different sources even in a single groundwater well, making these questions complicated to answer. Age dating of groundwater has been used to reconstruct contaminant travel times to wells; however, critics have highlighted that groundwater flow is often complex with mixing of groundwater of different ages. In drinking water wells, where water is typically abstracted from a large depth interval, such mixing is even more problematic. We present a way to overcome some of the obstacles in identifying the source and age of contaminants in drinking water wells by combining depth-specific sampling with age tracer modeling, particle tracking simulations, geological characterization, and contaminant properties. This multitool approach was applied to a drinking water well, where bentazon and dichlorprop contamination was found to have different pollutant sources and release histories, even though both pesticides can be associated with the same land use. Bentazon was derived from recent application to a golf course, while dichlorprop was derived from agricultural use more than 30 years ago. The advantages, limitations, and pitfalls of the proposed course of action are then further discussed.

History and Sources of Co-Occurring Pesticides in an Abstraction Well Unraveled by Age Distributions of Depth-Specific Groundwater Samples

American Chemical Society (ACS) | November 24th, 2019

When groundwater-based drinking water supply becomes contaminated, the timing and source of contamination are obvious questions. However, contaminants often have diffuse

When groundwater-based drinking water supply becomes contaminated, the timing and source of contamination are obvious questions. However, contaminants often have diffuse sources and different contaminants may have different sources even in a single groundwater well, making these questions complicated to answer. Age dating of groundwater has been used to reconstruct contaminant travel times to wells; however, critics have highlighted that groundwater flow is often complex with mixing of groundwater of different ages. In drinking water wells, where water is typically abstracted from a large depth interval, such mixing is even more problematic. We present a way to overcome some of the obstacles in identifying the source and age of contaminants in drinking water wells by combining depth-specific sampling with age tracer modeling, particle tracking simulations, geological characterization, and contaminant properties. This multitool approach was applied to a drinking water well, where bentazon and dichlorprop contamination was found to have different pollutant sources and release histories, even though both pesticides can be associated with the same land use. Bentazon was derived from recent application to a golf course, while dichlorprop was derived from agricultural use more than 30 years ago. The advantages, limitations, and pitfalls of the proposed course of action are then further discussed.

History of Legislation and Policy Formation of the Central Valley Project

U.S. Department of Agriculture (USDA) | March 15th, 1946