Sacramento River

Increasing water cycle extremes in California and in relation to ENSO cycle under global warming

Nature Portfolio (Springer Nature) | October 21st, 2015

Since the winter of 2013–2014, California has experienced its most severe drought in recorded history, causing statewide water stress, severe economic loss and

Since the winter of 2013–2014, California has experienced its most severe drought in recorded history, causing statewide water stress, severe economic loss and an extraordinary increase in wildfires. Identifying the effects of global warming on regional water cycle extremes, such as the ongoing drought in California, remains a challenge. Here we analyse large-ensemble and multi-model simulations that project the future of water cycle extremes in California as well as to understand those associations that pertain to changing climate oscillations under global warming. Both intense drought and excessive flooding are projected to increase by at least 50% towards the end of the twenty-first century; this projected increase in water cycle extremes is associated with a strengthened relation to El Niño and the Southern Oscillation (ENSO)—in particular, extreme El Niño and La Niña events that modulate California’s climate not only through its warm and cold phases but also its precursor patterns.

Independent Forensic Team Report: Oroville Dam Spillway Incident

California Department of Water Resources (DWR) | January 5th, 2018

The Oroville Dam spillway incident was caused by a long-term systemic failure of the California Department of Water Resources (DWR), regulatory, and general i

The Oroville Dam spillway incident was caused by a long-term systemic failure of the California Department of Water Resources (DWR), regulatory, and general industry practices to recognize and address inherent spillway design and construction weaknesses, poor bedrock quality, and deteriorated service spillway chute conditions. The incident cannot reasonably be “blamed” mainly on any one individual, group, or organization. During service spillway operation on February 7, 2017, water injection through both cracks and joints in the chute slab resulted in uplift forces beneath the slab that exceeded the uplift capacity and structural strength of the slab, at a location along the steep section of the chute . The uplifted slab section exposed the underlying poor quality foundation rock at that location to unexpected severe erosion, resulting in removal of additional slab sections and more erosion . Responding to the damage to the service spillway chute necessitated difficult risk tradeoffs while the lake continued to rise. The resulting decisions, made without a full understanding of relative uncertainties and consequences, allowed the reservoir level to rise above the emergency spillway weir for the first time in the project’s history, leading to severe and rapid erosion downstream of the weir and, ultimately, the evacuation order. . . . There were many opportunities to intervene and prevent the incident , but the overall system of interconnected factors operated in a way that these opportunities were missed. Numerous human , organizational, and industry factors led to the physical factors not being recognized and properly addressed, and to the decision-making during the incident.

Independent Panel Review of the Bay Delta Conservation Plan prepared for The Nature Conservancy and American Rivers

Nature Conservancy | September 19th, 2013

Two non-­governmental organizations, The Nature Conservancy (TNC) and American Rivers (AR), are evaluating their options for engagement with the Bay Delta Conservation P

Two non-­governmental organizations, The Nature Conservancy (TNC) and American Rivers (AR), are evaluating their options for engagement with the Bay Delta Conservation Plan (BDCP). If approved, the Plan would become a Habitat Conservation Plan (HCP) under the federal Endangered Species Act and a Natural Communities Conservation Plan (NCCP) under California law. The purpose of the Plan is to allow for construction of new water diversion facilities in the Sacramento-­San Joaquin Delta while also protecting aquatic and terrestrial species that may be adversely affected by the project and accompanying changes in the State Water Project (SWP) and Central Valley Project (CVP) operations. The Plan also includes habitat restoration and a commitment to assist in the conservation and recovery of species that are listed for protection under the federal and state Endangered Species Acts. With financial support from the S.D. Bechtel, Jr. Foundation, Saracino and Mount, LLC, convened an independent panel of experts, with technical support from NewFields, Inc., to evaluate portions of the Plan. The panel, working jointly with TNC and AR, developed a series of technical and legal questions about the Plan. This report provides answers to these questions, along with limited recommendations on how to improve BDCP. To simplify analysis, this review focuses on conditions for federally listed fishes during the Early Long Term (ELT), a decade after a permit would be issued (approximately year 2025). These are described in detail in the BDCP Effects Analysis and accompanying Environmental Impact Statement/Environmental Impact Report. We compared the performance of three different scenarios: a No Action Alternative (NAA) where no new North Delta diversion facility is constructed, a High Outflow Scenario (HOS) where the facilities are operated in a way that allows for occasional high spring and fall outflows, and a Low Outflow Scenario (LOS) with lower spring and fall outflows. The review also emphasizes in-­Delta and Sacramento River watershed conditions during the ELT, with less attention to San Joaquin River conditions and fishes. Although multiple data sources were used in this analysis, most hydrologic data came from CALSIM simulations conducted by BDCP consultants. The Panel strongly cautions about the conclusions drawn from these simulations. Flow simulations have three compounding uncertainties that can lead to significant error: (1) uncertainty in system understanding and future conditions, (2) model uncertainties (particularly the relationships between 1-­, 2-­, and 3-­dimensional models), and (3) behavioral/regulatory uncertainty where the models cannot capture the scope of human behavior in operating the projects under various conditions. These uncertainties, which are not described in BDCP documents well, makes all of our conclusions contingent on the projects actually being operated as simulated.

Independent Review Panel (IRP) Report for the 2014 Long-Term Operations Biological Opinions (LOBO) Annual Science Review

Delta Stewardship Council (Delta Council) | December 1st, 2014

Independent Review Panel (IRP) Report for the 2015 Long-Term Operations Biological Opinions (LOBO) Annual Science Review

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

This report presents findings and opinions of the Independent Review Panel (IRP) assembled by the Delta Science Program to inform the National Marine Fisheries Service (N

This report presents findings and opinions of the Independent Review Panel (IRP) assembled by the Delta Science Program to inform the National Marine Fisheries Service (NMFS) and the U.S. Fish & Wildlife Service (USFWS) as to the efficacy of water operations and certain regulatory actions prescribed by their respective Long-term Operations Biological Opinions’ (LOBO) Reasonable and Prudent Alternative Actions (RPAs) as applied from October 1, 2014 through September 30, 2015 (Water Year 2015).  This year’s annual review focused primarily on: (1) Shasta Reservoir and Sacramento River temperature monitoring, modeling, and management, (2) the River Assessment for Forecasting Temperature (RAFT) decision support tool (model), (3) an Enhanced Particle Tracking Model (E-PTM), and (4) a USFWS report on past, present, and future approaches to incidental take of Delta Smelt.  After reviewing a required set of written documents (Appendix 1), the IRP convened at a public workshop in Sacramento, CA on 5-6 November 2015. The first day of the 2-day workshop included agency presentations and provided a forum for the IRP to interact and consider information presented on water operations, temperature modeling, monitoring and RPA Actions as implemented in yet another critically dry 2015 water year. On the second day, the IRP deliberated in a private session beginning at 9:00 a.m. in order to prepare and present their initial findings at the public workshop at 2:00 p.m., after which there was an opportunity for agency representatives, members of the public, and the IRP members to comment and otherwise exchange impressions and information. Subsequent IRP communication and deliberations were conducted via email and conference calls in the course of drafting this final report. Click here for federal agency response letter

Independent Review Panel (IRP) Report for the 2017 Long-term Operations Biological Opinions (LOBO) Biennial Science Review (January 24, 2018)

Delta Stewardship Council (Delta Council) | January 31st, 2018

Independent Review Panel Report for the 2016 California WaterFix Aquatic Science Peer Review

Delta Stewardship Council (Delta Council) | May 12th, 2016

This report presents the findings of the 2016 California WaterFix Aquatic Science Peer Review. An Independent Review Panel was convened by the Delta Science Program to pr

This report presents the findings of the 2016 California WaterFix Aquatic Science Peer Review. An Independent Review Panel was convened by the Delta Science Program to provide the National Marine Fisheries Service (NMFS), U.S. Fish and Wildlife Service (USFWS), and California Department of Fish and Wildlife (CDFW) with an independent scientific evaluation of the methods and approaches for developing the joint Biological Opinion requirements and analyses prepared for the CDFW 2081(b) Incidental Take Permit application for the California WaterFix. The Panel was charged with reviewing: (1) selected sections of the Biological Assessment (BA) that seeks to predict the effects of the WaterFix project on Endangered Species Act (ESA)-listed species and their designated critical habitats, (2) the draft Analytical Approach to developing the joint Biological Opinion (AABO) and (3) the proposed methods for assessing project effects on Longfin Smelt. After reviewing a set of documents (Appendix 1), the Panel participated in a public meeting in Sacramento, CA on April 5-6, 2016. On the first day of this meeting, the Panel interacted with agency representatives following their presentations on the three topics above. On day 2, the Panel communicated and discussed its preliminary findings to agency representatives and the public. This report summarizes the Panel’s findings and recommendations in full detail.

Independent Review Panel Report for the 2016-2017 California WaterFix Aquatic Science Peer Review Phase 2A

Delta Stewardship Council (Delta Council) | March 7th, 2017

This report presents the Phase 2A findings of the 2016-2017 California WaterFix (CWF) Aquatic Science Peer Review. An Independent Review Panel (Panel; Appendix 1) was con

This report presents the Phase 2A findings of the 2016-2017 California WaterFix (CWF) Aquatic Science Peer Review. An Independent Review Panel (Panel; Appendix 1) was convened by the Delta Science Program to provide the National Marine Fisheries Service (NMFS), U.S. Fish and Wildlife Service (USFWS), and California Department of Fish and Wildlife (CDFW) to obtain the views of experts not involved in the CWF Endangered Species Act (ESA) consultation and 2081(b) permit on the use of best available scientific information as it pertains to analyses of effects on aquatic California ESA (CESA)-listed species in the California WaterFix Incidental Take Permit Application [2081(b) application]. The agencies further requested review of the Adaptive Management Framework proposed to integrate future scientific research, monitoring, and decision making during construction and operations of CWF. Accordingly, the Panel was charged specifically with reviewing: (1) the draft Adaptive Management Framework for CWF and (2) the 2081(b) application analyses of the CWF impacts of take for winter-run Chinook Salmon, spring-run Chinook Salmon, Delta Smelt, and Longfin Smelt. After reviewing the charge (Appendix 2) and a set of prescribed documents (Appendix 3), the Panel participated in a public meeting in Sacramento, California on December 8-9, 2016. On the first day of this meeting, the Panel interacted with agency representatives following their presentations on the topics above. On the second day, the Panel communicated and discussed its preliminary findings to agency representatives and the public (Appendix 4).

Influence of agricultural managed aquifer recharge on nitrate transport: The role of soil texture and flooding frequency

Soil Science Society of America (SSSA) | June 9th, 2021

Agricultural managed aquifer recharge (Ag-MAR) is a concept in which farmland is flooded during the winter using excess surface water to recharge the underlying groundwat

Agricultural managed aquifer recharge (Ag-MAR) is a concept in which farmland is flooded during the winter using excess surface water to recharge the underlying groundwater. In this study, we show how different recharge practices affect NO3− leaching and mineralization–denitrification processes in different soil systems. Two contrasting soil textures (sand and fine sandy loam) from the Central Valley, Califor- nia, were repeatedly flooded with 15 cm of water at varying time intervals in field and soil column experiments. Nitrogen species (NO3–, NH4+, total N), total C, dis- solved O2, and moisture content were measured throughout the experiments. Results show that when flooding occurs at longer intervals (every 1–2 wk), N mineralization increases, leading to an increase of mobile NO3− in the upper root zone and leach- ing of significant quantities of NO3− from both soil textures (137.3 ± 6.6% [sand] and 145.7 ± 5.8% [fine sandy loam] of initial residual soil NO3−) during subsequent flooding events. Laboratory mineralization incubations show that long flooding inter- vals promote mineralization and production of excess NO3− at rates of 0.11–3.93 mg N kg–1 wk–1 (sand) and 0.08–3.41 mg N kg–1 wk–1 (fine sandy loam). Decreasing the flooding frequency to 72 h reduces potential mineralization, decreasing the amount of NO3− leached during flooding events (31.7 ± 3.8% [sand] and 64.7 ± 10.4% [fine sandy loam] of initial residual soil NO3–). The results indicate that implementing recharge as repeated events over a long (multiple-week) time horizon might increase the total amount of NO3− potentially available for leaching to groundwater.

Influence of temperature and precipitation variability on near-term snow trends

Climatic Change (Springer) | October 17th, 2014

Snow is a vital resource for a host of natural and human systems. Global warming is projected to drive widespread decreases in snow accumulation by the end of the century

Snow is a vital resource for a host of natural and human systems. Global warming is projected to drive widespread decreases in snow accumulation by the end of the century, potentially affecting water, food, and energy supplies, seasonal heat extremes, and wildfire risk. However, over the next few decades, when the planning and implementation of current adaptation responses are most relevant, the snow response is more uncertain, largely because of uncertainty in regional and local precipitation trends. We use a large (40-member) single-model ensemble climate model experiment to examine the influence of precipitation variability on the direction and magnitude of near-term Northern Hemisphere snow trends. We find that near-term uncertainty in the sign of regional precipitation change does not cascade into uncertainty in the sign of regional snow accumulation change. Rather, temperature increases drive statistically robust consistency in the sign of future near-term snow accumulation trends, with all regions exhibiting reductions in the fraction of precipitation falling as snow, along with mean decreases in late-season snow accumulation. However, internal variability does create uncertainty in the magnitude of hemispheric and regional snow changes, including uncertainty as large as 33 % of the baseline mean. In addition, within the 40-member ensemble, many mid-latitude grid points exhibit at least one realization with a statistically significant positive trend in net snow accumulation, and at least one realization with a statistically significant negative trend. These results suggest that the direction of near-term snow accumulation change is robust at the regional scale, but that internal variability can influence the magnitude and direction of snow accumulation changes at the local scale, even in areas that exhibit a high signal-to-noise ratio.