Development of Recommended Flow Targets to Support Biological Integrity Based on Regional Flow-ecology Relationships for Benthic Macroinvertebrates in Southern California Streams

Southern California Coastal Water Research Project | March 23rd, 2017

Changes to instream flow are known to be one of the major factors that affect the health of biological communities. Regulatory, monitoring, and management programs are in

Changes to instream flow are known to be one of the major factors that affect the health of biological communities. Regulatory, monitoring, and management programs are increasingly using biological community composition, particularly benthic invertebrates, as one measure of instream conditions, stormwater project performance, or regulatory compliance with NPDES or other requirements and regulations. Understanding the relationship between changes in flow and changes in benthic invertebrate communities is, therefore, critical to informing decisions about ecosystem vulnerability, causes of stream and watershed degradation, and priorities for future watershed management. There are many approaches to developing flow-ecology relationships that relate hydrologic change to responses in instream biological communities that can be used to establish management targets. The Ecological Limits of Hydrologic Alteration (ELOHA) framework (Poff et al. 2010) provides a way to assess the effect of flow alteration on the condition of biological communities (vs. individual taxa) on a regional basis. Consequently, it is a useful approach for setting targets across a wide range of geographies and stream types where comprehensive detailed site-specific investigations are not practical. The framework includes elements of stream classification, estimation of flow alteration and development of flow ecology relationships based on the response of biological communities to changes in flow.

Development of Stage-Frequency Curves in the Sacramento-San Joaquin Delta for Climate Change and Sea Level Rise

California Energy Commission (CEC) | August 27th, 2018

Future changes in hydrologic patterns and sea level rise will impact water levels in the Sacramento-San Joaquin Delta (Delta), the hub of California’s water supply sys

Future changes in hydrologic patterns and sea level rise will impact water levels in the Sacramento-San Joaquin Delta (Delta), the hub of California’s water supply system and an important ecosystem and agricultural area. An important tool for flood management is stage frequency curves which indicate how often certain water levels (or stage) occur. The Delta poses inherent complexity in the determination of stage-frequency and requires a number of considerations. One needs to account for river flows coming into the Delta, as well as the effect of tides from the Delta’s connection to the ocean through San Francisco Bay. During storms, Delta water levels are also affected by storm surge from the advancing storm fronts coming from the Pacific Ocean. Under climate change, Delta water levels will also be affected by rising sea levels and expected changes in hydrology, such as shifts in timing and amount of precipitation and runoff and changes in how much of our precipitation falls as rain or snow (referred to as climate change hydrology in this paper). With these taken into consideration, this study lays out the assumption and method used to develop stage-frequency curves in the Delta for three different conditions: current hydrology conditions, current hydrology with sea level rise, and late-century climate change hydrology with sea level rise. In addition, water surface elevation profiles along the Sacramento and San Joaquin rivers for various magnitudes of flood events were compared to the top of levee elevations. Both the stage-frequency curves and the water surface elevation profiles comparisons to top of levee elevations provide valuable information to water resources planners and were applied to inform life and flood risk analysis for the Delta in the Central Valley Flood Protection Plan 2017 Update.

Development of the Lower Sacramento Valley Flood-Control System: Historical Perspective

American Society of Civil Engineers (ASCE) | July 1st, 2008

Natural physical conditions and the politics of flood management provide the historical context for structural flood control that underlies modern flood hazards in the S

Natural physical conditions and the politics of flood management provide the historical context for structural flood control that underlies modern flood hazards in the Sacramento Valley. The valley is a broad, low plain with backswamp basins that were frequently inundated prior to Anglo-American settlement, continuing until the modern flood-control system was established. Early attempts to emulate the Mississippi River single-channel levee strategy failed repeatedly in the Sacramento Valley due to high flow variability, mining sedimentation, lack of a coordinated levee system, and the inability of the main channels to carry most of the flood flows. Hydraulic mining caused massive sedimentation in major east-side tributaries, such as the Feather, Yuba, Bear, and American Rivers, and in the Sacramento River below the Feather River confluence. This sedimentation led to a flood-control design that relied on levees with narrow cross-channel spacings to promote channel scour and facilitate navigation. Even without sedimentation, floods were not contained within channels, but were largely conveyed through a system of low-land basins. In the early twentieth century, an innovative channel bypass system was adopted that emulates the natural system by routing excess flood waters over a series of weirs and through broad, channelized bypasses that cross the basins. This system has been successful in reducing the extent of frequent inundations of broad lowland areas of the valley. It is in need of maintenance and improvement, however, and cannot eliminate the risk of future flooding in low areas behind levees that are being rapidly developed.

DGMETA (Version 1): Dissolved Gas Modeling and Environmental Tracer Analysis Computer Program

U.S. Geological Survey (USGS) | January 8th, 2021

DGMETA (Dissolved Gas Modeling and Environmental Tracer Analysis) is a Microsoft Excel-based computer program that is used for modeling air-water equilibrium conditions f

DGMETA (Dissolved Gas Modeling and Environmental Tracer Analysis) is a Microsoft Excel-based computer program that is used for modeling air-water equilibrium conditions from measurements of dissolved gases and for computing concentrations of environmental tracers that rely on air-water equilibrium model results. DGMETA can solve for the temperature, salinity, excess air, fractionation of gases, or pressure/elevation of water when it is equilibrated with the atmosphere. Models are calibrated inversely using one or more measurements of dissolved gases such as helium, neon, argon, krypton, xenon, and nitrogen. Excess nitrogen gas, originating from denitrification or other sources, also can be included as a fitted parameter or as a separate calculation from the dissolved gas modeling results. DGMETA uses the air-water equilibrium models to separate measured concentrations of gases and isotopes of gases into components that are used for tracing water in the environment. DGMETA calculates atmospheric dry-air mole fractions (mixing ratios) for transient atmospheric gas tracers such as chlorofluorocarbons, sulfur hexafluoride, and bromotrifluoromethane (Halon-1301); and concentrations of tritiogenic helium-3 and radiogenic helium-4, which accumulate from the decay of tritium in water and the decay of uranium and thorium in rocks, respectively. Sample data can be graphed to identify applicable models of excess air, samples that contain excess nitrogen gas, or samples that have partially degassed, for example. Monte Carlo analysis of errors associated with dissolved gas equilibrium model results can be carried through computations of environmental tracer concentrations to provide robust estimates of error. In addition, graphical routines for separating helium sources using helium isotopes are included to refine estimates of tritiogenic helium-3 when terrigenic helium from mantle or crustal sources is present in samples. Environmental tracer concentrations and their errors computed from DGMETA can be used with other programs, such as TracerLPM (Jurgens and others, 2012), to determine groundwater ages and biogeochemical reaction rates. DGMETA also produces output files in a format that meets the U.S. Geological Survey open data requirements for documentation of model inputs and outputs. DGMETA is a versatile and adaptable program that allows users to add solubility data for new gases, modify the existing set of gas solubility data, modify the default set of gases used for modeling, choose calculations based on real (non-ideal) gas behavior, and select various concentration units for data entry and results to match laboratory reports and study objectives. DGMETA comes with a set of gases widely used in hydrology and oceanography and many gases include multiple solubilities from previous work. Seventeen dissolved gases are included in the default version of the program: noble gases (helium, neon, argon, krypton, and xenon), reactive gases (nitrogen, oxygen, methane, carbon dioxide, carbon monoxide, hydrogen, and nitrous oxide), and environmental tracers (chlorofluorocarbon-11, chlorofluorocarbon-12, chlorofluorocarbon-113, sulfur hexafluoride, and Halon-1301).  

Dimension reduction approach for understanding resource-flow resilience to climate change

Nature Portfolio (Springer Nature) | June 15th, 2024

Dioxin Issue Paper: Expert Panel Response and Recommendations

Bay Area Clean Water Agencies (BACWA) | February 11th, 2010

Congeners of dioxins and furans have been found in the San Francisco Bay in several species of fish sometimes used for human consumption, causing the State of California

Congeners of dioxins and furans have been found in the San Francisco Bay in several species of fish sometimes used for human consumption, causing the State of California to issue an interim fish consumption advisory. This fish consumption advisory has been used by the US Environmental Protection Agency and the State of California as a basis for placing the Bay on the State’s list of impaired waterways required by the Clean Water Act. As a consequence, water quality-based discharge limits for dioxins are now being placed into NPDES permits for dischargers to the Bay where dioxins or furans have been detected in effluents. At the request of the Bay Area Clean Water Agencies (BACWA), an association of municipal wastewater treatment utilities, the San Francisco Estuary Institute convened a panel of three qualified experts to review the factual case and to make recommendations. As a starting point, BACWA prepared a draft “Dioxin Issue Paper” on February 15, 2008, detailing the environmental problem, the regulatory context, and the specific  difficulties presented by dioxin-related effluent limits in permits. The draft Dioxin Issue Paper also outlined an array of possible regulatory strategies which might help resolve the difficulties faced by dischargers, ranging from strategies related to impairment listing to strategies related to NPDES permit issuance. Panel members were asked to review the draft Dioxin Issue Paper, make recommendations for improvement, and respond to a number of questions posed by the San Francisco Estuary Institute. The Panel met in Oakland, California, on February 22, 2008, at the San Francisco Estuary Institute. We were joined by representatives of the San Francisco Bay Regional Water Quality Control Board, the US Environmental Protection Agency, BACWA, and others with expertise in the field. Subsequently, we held numerous conference calls and agreed that we would address the questions posed by the Institute in both short- and long-term contexts. For the short term, we agreed upon recommendations that could help alleviate some of the dioxin-related regulatory difficulties faced by municipal wastewater treatment plants. For the long-term, however, we agreed that the problems faced by the dischargers are best addressed by solutions for the dioxin contamination problems in the Bay as a whole. We therefore also agreed to recommend a series of steps towards developing an integrated multi-media strategy for reducing dioxin levels in the San Francisco Bay.

Direct potable reuse: a future imperative

International Water Association (IWA) Publishing | March 1st, 2011

As a result of population growth, urbanization, and climate change, public water supplies are becoming stressed, and the chances of tapping new water supplies for

As a result of population growth, urbanization, and climate change, public water supplies are becoming stressed, and the chances of tapping new water supplies for metropolitan areas are getting more difficult, if not impossible. As a consequence, existing water supplies must go further. One way to achieve this objective is by increased water reuse, particularly in supplementing municipal water supplies. Although water reuse offers many opportunities it also involves a number of problems. A significant cost for nonpotable water reuse in urban areas is associated with the need to provide separate piping and storage systems for reclaimed water. In most situations, the cost of a dual distribution system has been prohibitive and thus, has limited implementation for water reuse programs. The solution to the problem of distribution is to implement direct potable reuse (DPR) of purified water in the existing water distribution system. The purpose of this paper is to consider (a) a future in which DPR will be the norm and (b) the steps that will need to be taken to make this a reality. Following an overview, the rationale for DPR, some examples of DPR projects, technological and implementation issues, and future expectations are examined.

Disappearing Arctic sea ice reduces available water in the American west

American Geophysical Union (AGU) | March 24th, 2004

Recent decreases in Arctic sea ice cover and the probability of continued decreases have raised the question of how reduced Arctic sea ice cover will influence extrapo

Recent decreases in Arctic sea ice cover and the probability of continued decreases have raised the question of how reduced Arctic sea ice cover will influence extrapolar climate. Using a fully coupled earth system model, we generate one possible future Arctic sea ice distribution. We use this ‘‘future’’ sea ice distribution and the corresponding sea surface temperatures (SSTs) to run a fixed SST and ice concentration experiment with the goal of determining direct climate responses to the reduction in Arctic sea ice that is projected to occur in the next 50 years. Our results indicate that future reductions in Arctic sea ice cover could significantly reduce available water in the American west and highlight the fact that the most severe impacts of future climate change will likely be at a regional scale.

DISB Review of Bay Delta Conservation Plan/California WaterFix Partially Recirculated Draft EIR/EIS

Delta Stewardship Council (Delta Council) | October 1st, 2015

We have reviewed the partially Recirculated Draft Environmental Impact Report/ Supplemental Draft Environmental Impact Statement for the Bay Delta Conservation Plan/Calif

We have reviewed the partially Recirculated Draft Environmental Impact Report/ Supplemental Draft Environmental Impact Statement for the Bay Delta Conservation Plan/California WaterFix (herein, "the Current Draft"). We focused on how fully and effectively it considers and communicates the scientific foundations for assessing the environmental impacts of water conveyance alternatives. The review is attached and is summarized below. The Current Draft contains a wealth of information but lacks completeness and clarity in applying science to far-reaching policy decisions. It defers essential material to the Final EIR/EIS and retains a number of deficiencies from the Bay Delta Conservation Plan Draft EIR/EIS. The missing content includes: 1. Details about the adaptive-management process, collaborative science, monitoring, and the resources that these efforts will require; 2. Due regard for several aspects of habitat restoration: landscape scale, timing, long-term monitoring, and the strategy of avoiding damage to existing wetlands; 3. Analyses of how levee failures would affect water operations and how the implemented project would affect the economics of levee maintenance; 4. Sufficient attention to linkages among species, landscapes, and management actions; effects of climate change on water resources; effects of the proposed project on San Joaquin Valley agriculture; and uncertainties and their consequences; 5. Informative summaries, in words, tables, and graphs, that compare the proposed alternatives and their principal environmental and economic impacts. The effects of California WaterFix extend beyond water conveyance to habitat restoration and levee maintenance. These interdependent issues of statewide importance warrant an environmental impact assessment that is more complete, comprehensive, and comprehensible than the Current Draft.

DISB Review of the Draft EIR/EIS for the Bay Delta Conservation Plan

Delta Stewardship Council (Delta Council) | May 15th, 2014

The Delta Reform Act of 2009 (§85320(c)) instructs the Delta Independent Science Board to review the Bay Delta Conservation Plan (BDCP) Draft Environmental Impact Report

The Delta Reform Act of 2009 (§85320(c)) instructs the Delta Independent Science Board to review the Bay Delta Conservation Plan (BDCP) Draft Environmental Impact Report/Environmental Impact Statement (DEIR/DEIS) and to submit our comments to the Delta Stewardship Council and the California Department of Fish and Game. We have focused our review on the adequacy of the science and the validity of the conclusions drawn from that science. The accompanying document constitutes our legislatively mandated review. We commend the preparers of the Draft BDCP documents for assembling and analyzing mountains of scientific information, and for exploring environmental impacts of many proposed BDCP actions. The preparers faced a bewildering array of regulatory requirements and economic, social, and political pressures. We find, however, that the science in this BDCP effort falls short of what the project requires. We highlight our concerns in the attached report. The report, in turn, draws on our detailed responses to charge questions from the Delta Stewardship Council (Appendix A) and on our reviews of individual chapters in the DEIR/DEIS (Appendix B). Our concerns raise issues that, if not addressed, may undermine the contributions of BDCP to meeting the co-equal goals for the Delta.