South Coast

Review of the Colorado River Interim Guidelines for Lower Basin Shortages and Coordinated Operations for Lake Powell and Lake Mead

U.S. Bureau of Reclamation (USBR) | December 18th, 2020

Spurred by an ongoing multi-year drought, decreasing system storage, and growing demands for Colorado River Water, in December 2007, Secretary of the Interior (Se

Spurred by an ongoing multi-year drought, decreasing system storage, and growing demands for Colorado River Water, in December 2007, Secretary of the Interior (Secretary) Kempthorne approved the Record of Decision (ROD) for the Colorado River Interim Guidelines for Lower Basin Shortages and the Coordinated Operations for Lake Powell and Lake Mead (Guidelines) (U.S. Department of the Interior [Department], 2007). The Guidelines, which are anticipated to be in place for an interim period through 2026, provide operating criteria for Lake Powell and Lake Mead including provisions designed to provide a greater degree of certainty to water users about timing and volumes of potential water delivery reductions, and additional operating flexibility to conserve and store water in the system. The interim nature of the Guidelines provided the opportunity to gain valuable experience for the management of Lake Powell and Lake Mead under modified operations and improve the basis for making future operational decisions, whether during the interim period or after. The requirement to document this experience is set forth in Section XI.G.7.D. of the ROD: “Beginning no later than December 31, 2020, the Secretary shall initiate a formal review for purposes of evaluating the effectiveness of these Guidelines. The Secretary shall consult with the Basin States in initiating this review” (7.D. Review). In December 2019, Secretary Bernhardt directed the Bureau of Reclamation (Reclamation) to begin a review of the Guidelines in early 2020. This Report is the culmination of that process. This Report documents Reclamation’s operational experience and provides a retrospective evaluation of whether operations and actions specified by the Guidelines have adhered to common themes and been effective with respect to the purpose stated in the ROD. The results of this evaluation are not intended to imply correctness of any particular operational provision or recommend future policies or actions. Reclamation anticipates that this Report will be a valuable source of information during upcoming activities in support of post-2026 operations – but expects this Report to be only one of many sources of information that will be available to guide that process and inform upcoming decisions on operations. Reclamation recognizes there are other areas of interest beyond the scope of this Report that should be considered in future discussions. These topics include but are not limited to the impacts to environmental, recreational, hydropower, and water quality resources, how to meaningfully engage perspectives from a diverse group of partners and stakeholders, and other recommendations from tribes, states and other stakeholders. Reclamation anticipates that additional studies and activities will be undertaken and used to inform discussions related to future operations of Lake Powell and Lake Mead. Click here for Final Report, Appendix A – Operational Documentation for Lake Powell and Lake Mead Operations Under the Colorado River 2007 Interim Guidelines Years 2008 to 2019

Ridging associated with drought in western and southwestern United States: characteristics, trends and predictability

American Meteorological Society (AMS) | April 1st, 2020

Persistent winter ridging events are a consistent feature of meteorological drought across the western and southwestern United States. In this study, a ridge detection al

Persistent winter ridging events are a consistent feature of meteorological drought across the western and southwestern United States. In this study, a ridge detection algorithm is developed and applied on daily geopotential height anomalies to track and quantify the diversity of individual ridge characteristics (e.g., position, frequency, magnitude, extent, and persistence). Three dominant ridge types are shown to play important, but differing, roles for influencing the location of landfalling atmospheric rivers (ARs), precipitation, and subsequently meteorological drought. For California, a combination of these ridge types is important for influencing precipitation deficits on daily through seasonal time scales, indicating the various pathways by which ridging can induce drought. Furthermore, both the frequency of ridge types and reduced AR activity are necessary features for explaining drought variability on seasonal time scales across the western and southwestern regions. The three ridge types are found to be associated in different ways with various remote drivers and modes of variability, highlighting possible sources of subseasonal-to-seasonal (S2S) predictability. A comparison between ridge types shows that anomalously large and persistent ridging events relate to different Rossby wave trains across the Pacific with different preferential upstream locations of tropical heating. For the “South-ridge” type, centered over the Southwest, a positive trend is found in both the frequency and persistence of these events across recent decades, likely contributing to observed regional drying. These results illustrate the utility of feature tracking for characterizing a wider range of ridging features that collectively influence precipitation deficits and drought.

Rising Seas and Electricity Infrastructure: Potential Impacts and Adaptation Actions for San Diego Gas & Electric

California Energy Commission (CEC) | August 31st, 2018

Part A: Rising sea levels pose a threat to California’s energy infrastructure and the coastal communities that it serves. To better understand this threat, this

Part A: Rising sea levels pose a threat to California’s energy infrastructure and the coastal communities that it serves. To better understand this threat, this study analyzed the exposure of San Diego Gas & Electric Company (SDG&E) electricity assets in San Diego County to climate change- driven coastal wave flooding, tidal inundation, and coastal erosion. The study found that the greatest potential direct impacts are damage to four substations in the Mission Bay and San Diego Bay areas. By modeling the potential costs to customers from unserved energy due to service disruptions driven by exposed substations, this study found economic impacts could— under an extreme sea level rise scenario in the late 21st century compounded by a 100 year storm-- range from $1.2 billion to $25 billion, assuming no adaptation actions are taken. Nearby communities could also experience indirect impacts if critical customers served by the substations—such as sewage pumping stations, hospitals, airports, and ports—are affected by outages. For other asset types, potential direct impacts are expected in the form of increased maintenance and repair costs. The research team identified a range of potential adaptation measures to build resilience to potential impacts. The application of flexible adaptation pathways emerged through the study as the best approach to improve implementation of these measures in the face of future uncertainty. Rather than selecting adaptation measures based only on what is known today, flexible adaptation pathways help establish information that that should be tracked, termed signposts, to help navigate uncertainty, set thresholds that trigger adaptation actions, and determine if an adaptation plan is meeting its objectives. Using these pathways, four initial climate adaptation actions were identified for SDG&E: 1) enhance coastal storm prediction and response, 2) identify signposts and thresholds that indicate when the need for an adaptation decision is approaching, 3) conduct consultations with regional stakeholders to identify opportunities to improve community-wide resilience, and 4) improve and fine-tune cost-benefit analysis methods to increase accuracy and confidence in cost-benefit estimates that incorporate climate change. Click here for Part B of the report, Potential Climate Change Impacts and Adaptation Actions for Gas Assets in the San Diego Gas and Electric Company Service Area, CEC, 2018

Risk-Informed Future Climate Scenario Development for the State Water Project Delivery Capability Report

California Department of Water Resources (DWR) | August 24th, 2023

This report introduces and documents an extensive effort undertaken by the California Department of Water Resources (DWR) to develop risk-informed future climate scenario

This report introduces and documents an extensive effort undertaken by the California Department of Water Resources (DWR) to develop risk-informed future climate scenarios for the State Water Project (SWP) Delivery Capability Report (DCR), a report issued by the SWP every two years. These reports present DWR’s analysis of the SWP system and planning information for users of SWP water. The analysis provides information about how climate change, regulatory, and operational considerations affect SWP delivery capability. Specifically, the report must provide “…under a range of hydrologic conditions, the then existing overall delivery capability of the project facilities and the allocation of that capacity to each contractor. The range of hydrologic conditions shall include the historic extended dry cycle and long-term average.” (Settlement Agreement 2003).

Risks of ocean acidification in the California Current food web and fisheries: ecosystem model projections

Wiley | January 12th, 2017

The benefits and ecosystem services that humans derive from the oceans are threatened by numerous global change stressors, one of which is ocean acidification. Here, we d

The benefits and ecosystem services that humans derive from the oceans are threatened by numerous global change stressors, one of which is ocean acidification. Here, we describe the effects of ocean acidification on an upwelling system that already experiences inherently low pH conditions, the California Current. We used an end‐to‐end ecosystem model (Atlantis), forced by downscaled global climate models and informed by a meta‐analysis of the pH sensitivities of local taxa, to investigate the direct and indirect effects of future pH on biomass and fisheries revenues. Our model projects a 0.2‐unit drop in pH during the summer upwelling season from 2013 to 2063, which results in wide‐ranging magnitudes of effects across guilds and functional groups. The most dramatic direct effects of future pH may be expected on epibenthic invertebrates (crabs, shrimps, benthic grazers, benthic detritivores, bivalves), and strong indirect effects expected on some demersal fish, sharks, and epibenthic invertebrates (Dungeness crab) because they consume species known to be sensitive to changing pH. The model's pelagic community, including marine mammals and seabirds, was much less influenced by future pH. Some functional groups were less affected to changing pH in the model than might be expected from experimental studies in the empirical literature due to high population productivity (e.g., copepods, pteropods). Model results suggest strong effects of reduced pH on nearshore state‐managed invertebrate fisheries, but modest effects on the groundfish fishery because individual groundfish species exhibited diverse responses to changing pH. Our results provide a set of projections that generally support and build upon previous findings and set the stage for hypotheses to guide future modeling and experimental analysis on the effects of OA on marine ecosystems and fisheries.

River Floods Under Wetter Antecedent Conditions Deliver Coarser Sediment to the Coast

American Geophysical Union (AGU) | April 13th, 2025

Increasing hydrologic volatility—more extreme rain, and larger variations between wet and dry years—has become apparent in some regions, but few data exist to determi

Increasing hydrologic volatility—more extreme rain, and larger variations between wet and dry years—has become apparent in some regions, but few data exist to determine how intensifying hydrologic extremes affect sedimentary systems. Using uniquely high-resolution records of fluvial suspended sediment and coastal morphology, we quantify sedimentary responses from a steep, 357-km2 watershed in California under extreme wet and dry hydrologic conditions. In years with multiple 2- to 10-year floods, fluvial sediment coarsened significantly as the wet season progressed, with late-season floods delivering dominantly sand-sized material to the coast. Greater and coarser sediment supply under wetter antecedent conditions affected nearshore geomorphic evolution for 4–5 years. The watershed and coastal changes we documented point to an increasing role of sediment-related hazards (flooding and hillslope erosion) and resources (nearshore accretion) as wet seasons intensify.

Rivers of California

Pacific Gas & Electric Company (PG&E) | July 1st, 1962

Rules and Regulations of the Borrego Springs Watermaster

Superior Court of California, County of Orange | February 23rd, 2021

Safe Clean Water Water for Los Angeles County Residents

Los Angeles County Department of Public Works (LACDPW) | November 7th, 2017

We live in a water-scarce area, and forces outside of our control can threaten our local water resources, including lakes, rivers and beaches. LA Count

We live in a water-scarce area, and forces outside of our control can threaten our local water resources, including lakes, rivers and beaches. LA County residents rely heavily on imported water from the Sierra Mountains, the Central Valley and even from states as far away as Colorado. Climate change is causing more and more extreme weather conditions, making these remote sources more unreliable . The impacts of the recent five-year drought were widely felt here. Rainfall is an essential, local source of LA’s water . Rain runs through local rivers, creeks and streams and can be absorbed underground, replenishing groundwater, which is a local source of drinking water. However, because so much of our region is paved over, when we do experience heavy rain, too much of that precious water is lost to the ocean before we can capture it for use. Our local water resources are also threatened by toxins and pollution as stormwater runs through streets and over-paved areas into our rivers, creeks and streams. Pollution flows onto our beaches and into the ocean, posing a public health risk and harming marine life.

Salinity of deep groundwater in California: Water quantity, quality, and protection

National Academy of Sciences (NAS) | July 12th, 2016

Deep groundwater aquifers are poorly characterized but could yield important sources of water in California and elsewhere. Deep aquifers have been developed for oil and g

Deep groundwater aquifers are poorly characterized but could yield important sources of water in California and elsewhere. Deep aquifers have been developed for oil and gas extraction, and this activity has created both valuable data and risks to groundwater quality. Assessing groundwater quantity and quality requires baseline data and a monitoring framework for evaluating impacts. We analyze 938 chemical, geological, and depth data points from 360 oil/gas fields across eight counties in California and depth data from 34,392 oil and gas wells. By expanding previous groundwater volume estimates from depths of 305 m to 3,000 m in California’s Central Valley, an important agricultural region with growing groundwater demands, fresh [<3,000 ppm total dissolved solids (TDS)] groundwater volume is almost tripled to 2,700 km3, most of it found shallower than 1,000 m. The 3,000-m depth zone also provides 3,900 km3 of fresh and saline water, not previously estimated, that can be categorized as underground sources of drinking water (USDWs; <10,000 ppm TDS). Up to 19% and 35% of oil/gas activities have occurred directly in freshwater zones and USDWs, respectively, in the eight counties. Deeper activities, such as wastewater injection, may also pose a potential threat to groundwater, especially USDWs. Our findings indicate that California’s Central Valley alone has close to three times the volume of fresh groundwater and four times the volume of USDWs than previous estimates suggest. Therefore, efforts to monitor and protect deeper, saline groundwater resources are needed in California and beyond.