The Science of Non-native Species in a Dynamic Delta

Delta Stewardship Council (Delta Council) | May 21st, 2022

Invasion of non-native species is one of the greatest global threats to the integrity of ecosystems and one of the five main drivers of ecosystem change. When a new speci

Invasion of non-native species is one of the greatest global threats to the integrity of ecosystems and one of the five main drivers of ecosystem change. When a new species becomes part of the ecosystem, it can alter the food web, nutrient and contaminant cycling, abundances of other species, and habitat structure. The resultant changes in ecosystem services (e.g. water quality, water flow, fisheries, endangered species) and even ecosystem stability can impact a broad range of stakeholders and impinge on the responsibilities of many government agencies. The California San Francisco Bay-Delta ecosystem is one of the world’s most invaded estuaries. Indeed, non-native species comprise much of today’s Delta ecosystem. Non-native species threaten the Delta Plan’s coequal goals of “protecting, restoring, and enhancing the Delta ecosystem,“ and “providing a more reliable water supply for California” as well as state and federal objectives for preserving native species and ecosystems. The Delta Reform Act of 2009 recognized the importance of this issue and stipulated that the Delta Plan should restore a healthy ecosystem by promoting “self-sustaining, diverse populations of native and valued species by reducing the risk of take and harm from invasive species.” Reducing the impact of non-native species is also a core strategy highlighted in the Ecosystem Amendment to California’s Delta Plan.

The Scientist and Engineer in Court

American Geophysical Union (AGU) | January 1st, 1983

Published by the American Geophysical Union as part of the Water Resources Monograph Series, Volume 8. The gavel goes down, the witness is called and sworn in: "Will y

Published by the American Geophysical Union as part of the Water Resources Monograph Series, Volume 8. The gavel goes down, the witness is called and sworn in: "Will you tell the truth, the whole truth, and nothing but the truth, so help you God?" Every court day scientists and engineers take this oath, yet few know the duties of an expert witness and fewer still know the procedures in a lawsuit. Unprepared for the courtroom, they watch a drama unfold without benefit of the plot (Ball, 1975). Courtrooms swirl with costume and ceremony. Jury, judge, and spectators assume roles: audience, director, trier of the facts. And the lawyers! Lawyers are the key dramatis personae. Protagonist and antagonist confront one another as lawyers argue their clients cases in the courtroom. They object endlessly. They cross-examine opposing witnesses mercilessly. They speak an opaque jargon of "laches," "remittitur" and "stare decisis." They speak Latin: "ab initio," "in pari causa," "lex loci actus." They speak old French: "estoppel," "fee simple," "voire dire." And they speak law-speak: "abuse of discretion," "clearly erroneous," "malice aforethought" (Mellinkoff, 1963). They call contrary versions of the same story true. They plead for understanding and compassion. They mix independent variables called "facts" and a dependent variable called "law" into an argumentative gruel for court consumption. Then it's over, and the judge delivers his or her opinion. One lawyer calls it the decision of the decade, a magnificent example of benign, reasoned law. The other darkly threatens to appeal all the way to the Supreme Court, if necessary, to relieve an onerous and oppressive injustice. All of this is fascinating theatre, but to the unprepared scientist or engineer, the drama has none of the charm and all of the clarity of a Japanese "Noh" play.

The season for large fires in Southern California is projected to lengthen in a changing climate

Nature Portfolio (Springer Nature) | February 17th, 2022

Southern California is a biodiversity hotspot and home to over 23 million people. Over recent decades the annual wildfire area in the coastal southern California region h

Southern California is a biodiversity hotspot and home to over 23 million people. Over recent decades the annual wildfire area in the coastal southern California region has not significantly changed. Yet how fire regime will respond to future anthropogenic climate change remains an important question. Here, we estimate wildfire probability in southern California at station scale and daily resolution using random forest algorithms and downscaled earth system model simulations. We project that large fire days will increase from 36 days/year during 1970–1999 to 58 days/year under moderate greenhouse gas emission scenario (RCP4.5) and 71 days/year by 2070–2099 under a high emission scenario (RCP8.5). The large fire season will be more intense and have an earlier onset and delayed end. Our findings suggest that despite the lack of a contemporary trend in fire regime, projected greenhouse gas emissions will substantially increase the fire danger in southern California by 2099.

The Seasonal Cycle of Surface Soil Moisture

American Meteorological Society (AMS) | June 29th, 2022

The seasonal cycle contributes substantially to soil moisture temporal variability in many parts of the world, with important implications for seasonal forecasting releva

The seasonal cycle contributes substantially to soil moisture temporal variability in many parts of the world, with important implications for seasonal forecasting relevant to agriculture and the health of humans and ecosystems. There is considerable spatial variability in the seasonal cycle of soil moisture, yet a lack of global observations has hindered the development of parsimonious theories explaining that variability. Here, we use 6 years of global satellite observations to describe and explain the seasonal cycle of surface soil moisture globally. An unsupervised clustering algorithm is used to identify five distinct seasonal cycle regimes. Each seasonal cycle regime typically arises in both hemispheres, on multiple continents, and across substantially different local climates. To explain this spatial variability, we then show that the observed seasonal cycle regimes are reproduced very well by a simple but physically based water balance model, which only uses precipitation and downwelling surface shortwave radiation as inputs, and includes no free parameters. Surprisingly, no information on vegetation or land cover is required. To our knowledge, this is the first characterization of the seasonal cycle of surface soil moisture based on global observations.

The seven Colorado River Basin states letter to the U.S. Bureau of Reclamation, 5/22/23

U.S. Bureau of Reclamation (USBR) | May 22nd, 2023

The shrinking Great Salt Lake contributes to record high dust-on-snow deposition in the Wasatch Mountains during the 2022 snowmelt season

Environmental Research Letters (IOP) | June 15th, 2023

The source of water derived from wells— Essential factors controlling the response of an aquifer to development

American Society of Civil Engineers (ASCE) | May 1st, 1940

The paper presented herewith, as a Ground Water Note, was first published by the American Society of Civil Engineers in its Civil Engineering magazine (p. 277-280

The paper presented herewith, as a Ground Water Note, was first published by the American Society of Civil Engineers in its Civil Engineering magazine (p. 277-280) for May 1940. A number of years ago the Ground Water Branch reprinted the paper in limited quantity for distribution to the field offices and some field personnel. The original paper is faithfully reproduced herein, except for minor changes in notation to conform with current Branch usage. Theis’ extremely lucid discussion of the source of water discharged by wells should be clearly understood by all who would attempt to analyze how a preexisting balanced hydraulic system will adjust to newly imposed well discharge.

The Stakes are Rising: Lessons on Engaging Coastal Communities on Climate Adaptation in Southern California

Cities and the Environment | November 16th, 2017

Preparing for climate change is rising as a priority for many public policy agendas, driving a demand for information that allows communities to identify both cur

Preparing for climate change is rising as a priority for many public policy agendas, driving a demand for information that allows communities to identify both current and projected vulnerabilities to climate change at local and regional levels. In response, a developing climate change adaptation service sector is bringing science and technical training to policy-makers. Approaching adaptation planning through a regional lens is critical, due to the large number of stakeholders and the intensely interconnected nature of geographies, communities, and economies. Decisions made in one jurisdiction will undoubtedly affect its neighbors. In this emerging field, boundary organizations play a unique role in building capacity across jurisdictions and bridging the gaps among various community, science and government stakeholders. The University of Southern California (USC) Sea Grant Program, located in Los Angeles, has developed a robust stakeholder engagement process to help communities plan for the impacts of climate change along the urbanized coastline. In 2016, USC Sea Grant analyzed its climate change adaptation outreach program to gain insights about its effectiveness. Drawing from this analysis, this paper explores: 1) stakeholder processes; 2) communications methods, particularly the challenges of communicating scientific information; 3) barriers to planning and implementation; 4) how to identify community needs; and, 5) what kinds of investments have been made to meet those needs. Four primary lessons are identified: 1) place-based boundary organizations can be an effective broker in establishing trust among stakeholders; 2) the ever-evolving and complex nature of climate science can overwhelm stakeholders and stall progress, so it is important to emphasize key messages provided by the scientific information, rather than dive deep into technical details and methods; 3) adaptive management is a promising approach to help communities move forward; and, 4) lack of significant and sustained funding for adaptation will continue to limit progress, however, even modest investments made at the right time can be impactful. Finally, the paper discusses the challenges USC Sea Grant faced in the first six years of its climate adaptation outreach program, and provides thoughts on how to help communities continue to advance their adaptation planning goals in the years to come.

The State of the Sierra Nevada’s Forests

Sierra Nevada Conservancy | October 2nd, 2014

There is a growing understanding that many Sierra Nevada forests are not healthy and that overgrown forests are susceptible to disease and intense wildfire. There is like

There is a growing understanding that many Sierra Nevada forests are not healthy and that overgrown forests are susceptible to disease and intense wildfire. There is likewise broad consensus that science-based ecological restoration of our Sierra Nevada forests must be dramatically increased in order stem the tide of large, uncharacteristic wildfires. These wildfires threaten the very lifeblood of California -- the forested watersheds of the Sierra Nevada. The State of Sierra Nevada’s Forests Report identifies the wide range of benefits provided by our Sierra Nevada forests and watersheds that are at risk: The Region is the origin of 60% of California’s developed water supply. These watersheds are the primary source of fresh water flowing into the Sacramento-SanJoaquin Delta, California’s water “hub.” The forests of the Sierra Nevada store massive amounts of carbon, assisting in the state’sefforts to combat climate change. The forests and watersheds provide crucial habitat to hundreds of species. The area provides world-class recreational opportunities enjoyed by millions from around the world. The Region is a major producer of wood products and hydro-electric power. Key findings of this report include the following: The United States Forest Service Region 5 (USFS) estimates that between six and nine million acres of lands for which they have management responsibility are in need of restoration. In order to return these lands to ecological health, a two to three times increase in the pace and scale of ecological restoration must occur. The amount of area consumed by fire in the Sierra Nevada continues to increase. More land has burned in the first four-and-a-half-years of this decade than seven entire decades in the past. Between 1984 and 2010, there was a significant increase in the number of acres within a forest fire burning at high-intensity, from an average of 20% in mid-1980s to over 30% by 2010. High-intensity burn areas can experience runoff and erosion rates five to ten times greater than low- or moderate-intensity burn areas. The sediment that is carried in the runoff not only degrades water quality and damages infrastructure, it fills reservoirs, reducing storage capacity. The 2013 Rim Fire, the largest fire in the recorded history of the Sierra Nevada, burned 257,000 acres, almost 40% of which was at high intensity. Estimates are that that fire produced the same amount of greenhouse gas emissions that 2.3 million vehicles produce in a year.

The State Water Project Delivery Capability Report 2023 Addendum - Impacts of Subsidence

California Department of Water Resources (DWR) | May 7th, 2025

The purpose of this addendum is to show how ongoing subsidence effects on the California Aqueduct will impact operation of the State Water Project (SWP). The addendum pro

The purpose of this addendum is to show how ongoing subsidence effects on the California Aqueduct will impact operation of the State Water Project (SWP). The addendum provides information to SWP water users about a potential range of water delivery impacts over the next 20 years if no corrective action is taken to address the subsidence effects. However, the California Department of Water Resources (DWR) is committed to restore the conveyance capacity of the California Aqueduct and has an engineering plan for near-term fixes. DWR is also working with its partners to secure additional funding sources for this work. DWR is confident that the California Aqueduct capacity will be restored and the SWP will not see the impacts outlined in this addendum. Thus, long-term water supply planning activities by water users should rely on the potential future SWP allocation results presented in the 2023 Delivery Capability Report (DCR 2023) released in 2024.