Large-Scale Environments of Successive Atmospheric River Events Leading to Compound Precipitation Extremes in California

American Meteorological Society (AMS) | February 18th, 2022

Successive atmospheric river (AR) events—known as AR families—can result in prolonged and elevated hydrological impacts relative to single ARs due to the lack of reco

Successive atmospheric river (AR) events—known as AR families—can result in prolonged and elevated hydrological impacts relative to single ARs due to the lack of recovery time between periods of precipitation. Despite the outsized societal impacts that often stem from AR families, the large-scale environments and mechanisms associated with these compound events remain poorly understood. In this work, a new reanalysis-based 39-yr catalog of 248 AR family events affecting California between 1981 and 2019 is introduced. Nearly all (94%) of the interannual variability in AR frequency is driven by AR family versus single events. Using k-means clustering on the 500-hPa geopotential height field, six distinct clusters of large-scale patterns associated with AR families are identified. Two clusters are of particular interest due to their strong relationship with phases of El Niño–Southern Oscillation (ENSO). One of these clusters is characterized by a strong ridge in the Bering Sea and Rossby wave propagation, most frequently occurs during La Niña and neutral ENSO years, and is associated with the highest cluster-average precipitation across California. The other cluster, characterized by a zonal elongation of lower geopotential heights across the Pacific basin and an extended North Pacific jet, most frequently occurs during El Niño years and is associated with lower cluster-average precipitation across California but with a longer duration. In contrast, single AR events do not show obvious clustering of spatial patterns. This difference suggests that the potential predictability of AR families may be enhanced relative to single AR events, especially on subseasonal to seasonal time scales.

Lessons from California’s 2012–2016 Drought

American Society of Civil Engineers (ASCE) | October 1st, 2018

California’s 5-year drought has ended, even as its aftermath lingers. From 2012–2016 much or all of California was under severe drought conditions, with gre

California’s 5-year drought has ended, even as its aftermath lingers. From 2012–2016 much or all of California was under severe drought conditions, with greatly diminished precipitation, snowpack, and streamflow and higher temperatures. Water shortages to forests, aquatic ecosystems, hydroelectric power plants, rural drinking water supplies, agriculture, and cities caused billions of dollars in economic losses, killed millions of forest trees, brought several fish species closer to extinction, and caused inconvenience and some expense to millions of households and businesses. The drought also brought innovations and improvements in water management, some of which will better prepare California for future droughts. This paper summarizes the magnitude and impacts of the 2012–2016 California drought. The paper then reviews innovations arising from the drought in the larger historical context of water management in California. Lessons for California and for modern drought management are then discussed. Droughts in modern, well-managed water systems serving globalized economies need not be economically catastrophic, but will always have impacts and challenges, particularly for native ecosystems. In California and every other water system, droughts usefully expose weaknesses and inadequate preparation in water management. In this regard for California, managers of ecosystems and small rural water supplies had the most to learn.

Letter from John J. Entsminger, General Manager, Southern Nevada Water Authority, to Debra Haland, Secretary, U.S. Department of Interior

Southern Nevada Water Authority (SNWA) | August 15th, 2022

Letter in support of the Temporary Urgency Change Petition (TUCP)

California State Water Resources Control Board (SWRCB) | February 19th, 2023

Levee Failures in the Sacramento-San Joaquin River Delta: Characteristics and Perspectives

Texas A&M University | December 15th, 2011

Between 1850 and 1922, agriculturalists built 1,700 kilometers of levees to convert 250,000 hectares of tidal marsh to farmland where the San Joaquin and Sacramento River

Between 1850 and 1922, agriculturalists built 1,700 kilometers of levees to convert 250,000 hectares of tidal marsh to farmland where the San Joaquin and Sacramento Rivers enter the San Francisco Bay (the Delta). Drained, farmed and isolated from the water channels, the organic soils behind the levees subsided to elevations as low as 8 meters below sea level, turning "levees" into "dams" that hold back water constantly. Engineers built water transfer projects in the mid-20th century, transferring water from the south Delta to 25 million Californians who now rely on the "dams" accidentally converted into supply channels. In 1972, however, a levee failure caused a salt-water intrusion into the Delta, raising the prominence of the polemic Peripheral Canal which, if built would replace the levees in the trans-Delta water transport role. Levee failures in 2004 (the Delta) and 2005 (New Orleans) have re-ignited the debate, fueled by comments made by public officials who warned that the Delta levees posed more risk of failure than did the pre-Katina Louisiana levees. This background motivates two research questions: What are the social perspectives regarding levee failures of the experts managing the Delta; and what is the history of levee failures that might support their perspectives? The research employed Q-Method to identify and describe four social perspectives: Delta Sustainers, Abandon the Levees, Levee Pragmatists, and Multi-Purpose Levee Advocates. A critical element underlying differences among the perspectives revolved around the perceived history of failures of Delta levees. This dissertation employed semi-structured interviews, archival record searches, and historic map and aerial photograph comparisons to compile a history of 265 levee failures since 1868, many of which are referenced to location, segment, and levee type. In addition, the dissertation compiled a list of emergency repairs and successful flood-fights. The history of failures indicates that important levees of the Delta have performed significantly better than previously identified. Sharing these social perspectives and research results among the key actors addressing Delta issues may lead to improved consensus decisions.

Liquid Assets: Improving Management of the State's Groundwater Resources

Legislative Analyst's Office (LAO) | March 24th, 2010

California’s water system is facing a series of challenges affecting water availability, reliability, and delivery. Reevaluating how groundwater is managed is necessary

California’s water system is facing a series of challenges affecting water availability, reliability, and delivery. Reevaluating how groundwater is managed is necessary if it is to achieve its full potential as a reliable source of water. In this report, we present the Legislature with a series of actions that would be phased in over a period of time to address current and emerging groundwater management issues, including bringing science and law together to accurately reflect the physical interconnection of surface water and groundwater.

Lithologic and ground-water data for monitoring sites in the Mojave River and Morongo ground-water basins, San Bernardino County, California, 1992-98

U.S. Geological Survey (USGS) | July 1st, 2002

Lithologic and ground-water data were collected at 85 monitoring sites constructed in the Mojave Water Agency Management area in San Bernardino County, California, as par

Lithologic and ground-water data were collected at 85 monitoring sites constructed in the Mojave Water Agency Management area in San Bernardino County, California, as part of a series of cooperative studies between the U.S. Geological Survey and the Mojave Water Agency. The data are being used to evaluate and address water-supply and water-quality issues. This report presents a compilation of the data collected at these sites from 1992 through 1998, including location and design of the monitoring sites, lithologic data, geophysical logs, ground-water-level measurements, and water-quality analyses. One to five small (generally 2-inch) diameter wells were installed at each of the 85 monitoring sites to collect depth-dependent hydrologic data. Lithologic logs were compiled from descriptions of drill cuttings collected at each site and from observations recorded during the drilling of the borehole. Generalized stratigraphic columns were compiled by grouping similar lithologic units. Geophysical logs provide information on the character of the lithologic units and on the presence of ground water and the chemical characteristics of that water. Water-level and water-quality data were collected periodically from the sites during 1992 through 1998. 

Long-term groundwater depletion in the United States

National Groundwater Association (NGWA) | December 15th, 2014

The volume of groundwater stored in the subsurface in the United States decreased by almost 1000 km3 during 1900–2008. The aquifer systems with the three largest volu

The volume of groundwater stored in the subsurface in the United States decreased by almost 1000 km3 during 1900–2008. The aquifer systems with the three largest volumes of storage depletion include the High Plains aquifer, the Mississippi Embayment section of the Gulf Coastal Plain aquifer system, and the Central Valley of California. Depletion rates accelerated during 1945–1960, averaging 13.6 km3/year during the last half of the century, and after 2000 increased again to about 24 km3/year. Depletion intensity is a new parameter, introduced here, to provide a more consistent basis for comparing storage depletion problems among various aquifers by factoring in time and areal extent of the aquifer. During 2001–2008, the Central Valley of California had the largest depletion intensity. Groundwater depletion in the United States can explain 1.4% of observed sea‐level rise during the 108‐year study period and 2.1% during 2001–2008. Groundwater depletion must be confronted on local and regional scales to help reduce demand (primarily in irrigated agriculture) and/or increase supply.

Los Angeles Basin Stormwater Conservation Study: Task 2 Water Supply & Water Demand Projections

U.S. Bureau of Reclamation (USBR) | December 1st, 2014

The Los Angeles County Flood Control District (LACFCD) partnered with the U.S. Department of the Interior, Bureau of Reclamation (Reclamation) to collaborate on t

The Los Angeles County Flood Control District (LACFCD) partnered with the U.S. Department of the Interior, Bureau of Reclamation (Reclamation) to collaborate on the Los Angeles Basin Stormwater Conservation Study (LA Basin Study). The purpose of the LA Basin Study is to study long-term water conservation and flood control impacts from projected climate conditions and population changes in the Los Angeles Basin. The LA Basin Study will recommend potential changes to the operation of stormwater capture systems, modifications to existing facilities, and development of new facilities that could help resolve future water supply and flood control issues. The recommendations will be developed through identifying alternatives and conducting trade-off analyses. For Task 2 of the LA Basin Study, Water Supply and Water Demand Projections, existing and projected water supplies and demands were characterized for the LA Basin Study Area (Study Area) out to 2095, with consideration of projected climate change effects. It is important to note that this Task 2 report inventories projected available supplies (i.e., potential supplies), and does not make assumptions for the volume of each supply source that will actually be used to meet projected demands, nor the facilities necessary to access and serve those supplies. This determination would require more in-depth integrated supply and demand planning to predict and analyze the multitude of factors that influence water supply and use decisions such as policy, cost, environmental factors, reliability, etc. This Task 2 report is intended to provide a supply and demand basis for understanding the potential need and benefit of additional stormwater capture systems that could be implemented across the region by the LACFCD and its partners. Given that stormwater is a local and relatively inexpensive source of supply, it must be a critical and substantial part of the LA Basin water supply portfolio that could help meet demands through 2095 and beyond.

Los Angeles Basin Stormwater Conservation Study: Task 3.1 Climate Change and Hydrologic Projections Appendices

U.S. Bureau of Reclamation (USBR) | October 1st, 2013

Reclamation’s Technical Service Center (TSC) performed Task 3.1 of the LA Basin Study—to develop and evaluate projected future climate conditions related to precipita

Reclamation’s Technical Service Center (TSC) performed Task 3.1 of the LA Basin Study—to develop and evaluate projected future climate conditions related to precipitation frequency over the Los Angeles Basin. The subtasks were to: Consider existing projections of climate change in the LA Basin Study area Determine appropriate climate scenarios for use in developing precipitation and potential evaporation input datasets to support subsequent hydrologic modeling Prepare data (hourly precipitation and potential evaporation) for input into the LACFCD’s Watershed Management Modeling System (WMMS) Determine storm event frequency for planning purposes The data, methods, and results from Task 3.1 are documented in this report. Results from these four subtasks were then transmitted to LACFCD, who used these results as input in their WWMMS as part of Task 3.2 of the LA Basin Study. LACFCD is preparing a companion report with the results from the hydrologic modeling.