Climate Change and the Delta

University of California, Davis (UC Davis) | October 1st, 2016

Climate change amounts to a fast approaching, “new” stressor in the Sacramento–San Joaquin Delta system. In response to California’s extreme natural hydroclimatic

Climate change amounts to a fast approaching, “new” stressor in the Sacramento–San Joaquin Delta system. In response to California’s extreme natural hydroclimatic variability, complex water-management systems have been developed, even as the Delta’s natural ecosystems have been largely devastated. Climate change is projected to challenge these management and ecological systems in different ways that are characterized by different levels of uncertainty. Future precipitation changes are less certain, with as many climate models projecting wetter conditions as drier. Warmer temperatures will likely enhance evaporation and raise water temperatures. Consequently, climate change is projected to yield both more extreme flood risks and greater drought risks. Effects on the Delta ecosystem that are traceable to warming include sea level rise, reduced snowpack, earlier snowmelt and larger storm-driven streamflow, warmer and longer summers, warmer summer water temperatures, and water-quality changes. These changes and their uncertainties will challenge the operations of water projects and uses throughout the Delta’s watershed and delivery areas. Although the effects of climate change on Delta ecosystems may be profound, the end results are difficult to predict, except that native species will fare worse than invaders. Successful preparation for the coming changes will require greater integration of monitoring, modeling, and decision-making across time, variables, and space than has been historically normal.

Climate Change and the Delta: A Synthesis (Public Review Draft)

Delta Stewardship Council (Delta Council) | March 23rd, 2018

The Delta Reform Act of 2009 (Water Code Section 85066) requires that the Delta Stewardship Council adopt a Delta Plan (the Plan) to achieve the coequal goals of providin

The Delta Reform Act of 2009 (Water Code Section 85066) requires that the Delta Stewardship Council adopt a Delta Plan (the Plan) to achieve the coequal goals of providing a more reliable water supply for California and protecting, restoring, and enhancing the Delta ecosystem (Water Code Section 85000). In the time since the Plan was adopted in 2013, a significant shift in State planning for Delta ecosystem protection, restoration, and enhancement has occurred, prompting review of the Delta Plan to  examine whether its strategies are still suited to achieve the ecological goals of the Delta Reform Act. As such, the Delta Stewardship Council (Council) is developing an amendment of the Plan’s Chapter 4, Protect, Restore, and Enhance the Delta Ecosystem. Council staff are reviewing the best-available science to inform amendment of Chapter 4 of the Delta Plan. To support this effort, Council staff have developed three science  synthesis papers. This paper focuses on the effects of climate change in the Delta and is accompanied by two other papers focused on the Delta ecosystem (terrestrial and  aquatic resources) and restoration. Climate change is of interest for the Chapter 4  amendment given recent rapid advancements in research on climate change and its  effects on the Delta ecosystem that have occurred since the Delta Plan was adopted in  2013 (Dettinger et al. 2016). Climate change has the potential to significantly affect the Delta ecosystem by raising  air and water temperatures, changing the timing and volume of flows into and through  the Delta, increasing tidal inundation with sea-level rise (SLR), and increasing salinity  intrusion into the Delta. Climate change is recognized as a global stressor in Chapter 4 of the 2013 Delta Plan, but the effects of climate change on Delta ecosystems are  discussed only briefly and with limited consideration of management strategies that address the issue. Chapter 4 of the Delta Plan identifies five key stressors to the Delta  ecosystem and core strategies for addressing each. Climate change has interrelated  effects on all five core strategy areas: Delta flows, habitat, water quality, non-native 28 species, and hatcheries and harvest management. The Delta Reform Act specifies consideration of “the future impact of climate change and sea-level rise” (Water Code Section 85066), and identifies a restoration timeline horizon of 2100 (Water Code Section 85302). More generally, Executive Order B-30-15, signed by Governor Brown in April 2015, requires that State agencies incorporate climate change into planning and investment decisions, and that they prioritize natural infrastructure and actions for climate preparedness.

Climate change impacts on water resources and hydropower potential in the Upper Colorado River Basin

Journal of Hydrology (Elsevier) | April 23rd, 2015

Precipitation projections from climate models vary up to 16%; flow projections revealed greater differences, up to 50%. The climate models projected increase in t

Precipitation projections from climate models vary up to 16%; flow projections revealed greater differences, up to 50%. The climate models projected increase in temperature at low elevations with extreme seasonality at high elevations, although summer temperatures increased at all elevations. The models projected a 60% decline in precipitation at lower elevations and a 74% increase at high elevations, although precipitation declined during the summer months at all elevations. Using the A2 scenario an overall decrease in annual flow was predicted, attributed to a reduction in precipitation and increasing temperature trends; however, this was not consistent during the winter months, which showed an increase in precipitation at high elevations and a modest temperature increase during the winter and resulted in an increase in stream flow. The responses to climate change on reservoir levels varied basin-wide due to variability in precipitation, evapotranspiration, and stream flow. Simulations indicated that water levels in Blue Mesa Reservoir (the largest reservoir in the UCRB) would decline by more than 70% with increasing annual temperatures. Reservoirs with smaller surface areas to the volume ratio were not significantly impacted by evapotranspiration. Our results indicate that hydropower management strategies in the UCRB must adapt to potential climate change, but the required adaptations are dependent on several factors including reservoir size and location.

Climate Change Risks Faced by the California Central Valley Water Resource System

California Energy Commission (CEC) | ?

Observed climate trends and projections of accelerated future change have motivated several studies of the impacts of climate change on water resources management in Cal

Observed climate trends and projections of accelerated future change have motivated several studies of the impacts of climate change on water resources management in California. This paper presents a methodology that improves on previous approaches, revealing fundamental climate change risks to one of the State of California’s key water resource systems — the integrated California Central Valley System (CCVS). By using a bottom-up decision scaling approach, starting with a systematic climate change stress test of the performance of the system to changes in temperature and precipitation, specific vulnerabilities to the system are identified. This study also improves on previous water resource vulnerability analyses by incorporating and evaluating a much wider range of inter-annual precipitation variability than has previously been used. By drawing from the 1,100-year (reconstructed dendrochronology) record of Sacramento and San Joaquin river flows, vulnerabilities to low frequency natural climate variability are analyzed in concert with expected potential climate changes. The results of this analysis provide a comprehensive summary of the sensitivity of the system to climate change. This paper provides results and discussion of select future system performance metrics at 2050. Results indicate that declines in almost every category (e.g., supply, storage, delta outflow) of system performance are likely. The likelihood of severely degraded future performance is especially high for north-of-Delta carryover storage and Delta exports. The results of this study are expected to provide water managers and decision-makers with more actionable science because they provide probabilistic results that can be used in more traditional risk management approaches to planning of climate change adaptation investment decisions.

Climate Change Scenarios for Air and Water Temperatures in the Upper San Francisco Estuary: Implications for Thermal Regimes and Delta Smelt

University of California, Davis (UC Davis) | June 10th, 2024

Collateral Damage: A citizen’s guide to fish kills and habitat degradation at the state and federal water project pumps in the Delta

Bay Institute | March 1st, 2012

Large-scale fish kills and habitat destruction aren’t an unusual occurrence at the giant federal and state pumps that export water from the Sacramento-San Joaquin Delta

Large-scale fish kills and habitat destruction aren’t an unusual occurrence at the giant federal and state pumps that export water from the Sacramento-San Joaquin Delta to agribusinesses and cities in the southern half of the state. These events are business as usual. • Every day, between 870 and 61,000 fish – including from 200 to 42,000 native and endangered fishes – are “salvaged” at the pumps. Most die in the process. • On average, over 9 million fish – representing the twenty fish species considered in this report – are “salvaged” each year at the pumps. As many as 15 million fish of all species encountered are “salvaged” each year. • Up to 40% of the total population of the endangered delta smelt and 15% of the endangered winter-run population of Chinook salmon are killed at the pumps in some years. In the first half of 2011, over 8.6 million splittail were salvaged. • Salvage estimates drastically underestimate the problem. The numbers do not factor in the results of “indirect” mortality, as high levels of export pumping disrupt fish migration, shrink the amount of non-lethal habitat available to fish species, and remove vast amounts of biomass, including fish eggs and larvae too small to be screened at the pumps. • Export pumping causes the lower San Joaquin River to flow backwards most of the year and removes the equivalent of 170 railroad boxcars of water – and the accompanying fish, other organisms, and nutrients – from the Delta ecosystem every minute. • Large numbers of fish being entrained is a problem even for species that are not currently listed as “endangered.” Killing large numbers of fish year after year cuts off population growth in response to favorable conditions and can start the species on a downward path to extinction. As the species declines, the population impacts of entrainment become proportionately larger. • Entrainment is a real problem. But the same interests in the Delta export community who claim that it isn’t also back constructing expensive new conveyance facilities such as a peripheral canal or tunnel to solve the problem that they say doesn’t exist.

Colorado River Accounting and Water Use Report - Arizona, California, and Nevada, Interior Region 8: Lower Colorado Basin

U.S. Bureau of Reclamation (USBR) | May 13th, 2022

Colorado River Accounting and Water Use Report: Arizona, California, and Nevada

U.S. Bureau of Reclamation (USBR) | May 15th, 2024

In accordance with Article V of the Consolidated Decree of the United States Supreme Court in Arizona v. California et al. 547 U.S. 150 (2006) (Consolidated Decree): �

In accordance with Article V of the Consolidated Decree of the United States Supreme Court in Arizona v. California et al. 547 U.S. 150 (2006) (Consolidated Decree): “The United States shall prepare and maintain, or provide for the preparation and maintenance of, and shall make available, annually and at such shorter intervals as the Secretary of the Interior shall deem necessary or advisable, for inspection by interested persons at all reasonable times and at a reasonable place or places, complete, detailed and accurate records of: (A) Releases of water through regulatory structures controlled by the United States; (B) Diversions of water from the mainstream, return flow of such water to the stream as is available for consumptive use in the United States or in satisfaction of the Mexican Treaty obligation, and consumptive use of such water. These quantities shall be stated separately as to each diverter from the mainstream, each point of diversion, and each of the States of Arizona, California and Nevada; (C) Releases of mainstream water pursuant to orders therefor but not diverted by the party ordering the same, and the quantity of such water delivered to Mexico in satisfaction of the Mexican Treaty or diverted by others in satisfaction of rights decreed herein. These quantities shall be stated separately as to each diverter from the mainstream, each point of diversion, and each of the States of Arizona, California and Nevada; (D) Deliveries to Mexico of water in satisfaction of the obligations of Part III of the Treaty of February 3, 1944, and, separately stated, water passing to Mexico in excess of treaty requirements; (E) Diversions of water from the mainstream of the Gila and San Francisco Rivers and the consumptive use of such water, for the benefit of the Gila National Forest.” This Colorado River Accounting and Water Use Report: Arizona, California, and Nevada presents the records compiled pursuant to the Consolidated Decree for Calendar Year 2023. Copies of this and previous years’ reports may be found on the Bureau of Reclamation’s website.

Colorado River Basin August 2022 24-Month Study

U.S. Bureau of Reclamation (USBR) | August 16th, 2022

Colorado River Drought Contingency Plan Authorization

United States Congress | April 16th, 2019

Authorized Drought Contingency Plans (DCPs) for the Upper and Lower Colorado River Basins, which required reduced Lower Basin deliveries beyond previous curtailment plans

Authorized Drought Contingency Plans (DCPs) for the Upper and Lower Colorado River Basins, which required reduced Lower Basin deliveries beyond previous curtailment plans at specified Lake Mead storage levels, committed Reclamation to additional water conservation efforts, and put in place plans to coordinate Upper Basin operations to enhance Lake Powell storage levels and prevent the loss of hydropower generation.