This data release includes data containing projections of unimpaired hydrology, reservoir storage, and downstream managed flows in the Sacramento River/San Joaquin River watershed, California for scenarios of future climate change generated for the CASCaDE2 project (Computational Assessments of Scenarios of Change for the Delta Ecosystem, phase 2). Code used to produce the data is also included. The dataset is produced using a multiple-model approach. First, downscaled global climate model outputs are used to drive an existing Variable Infiltration Capacity/Variable Infiltration Capacity Routing (VIC/RVIC) model of Sacramento/San Joaquin hydrology, resulting in projections of daily, unimpaired flows throughout the watershed. A management model, CASCaDE2-modified CalSim (C2-CalSim), uses these projections as inputs and produces monthly estimates of reservoir and other infrastructure operations and resulting downstream managed flows. The CASCaDE2 resampling algorithm (CRESPI), also uses the projected daily unimpaired flows, along with historical managed flows, to estimate the daily variability in managed flows throughout the watershed. The monthly and daily managed-flow estimates are combined in a way that preserves the multi-decadal variability and century-scale trends produced by the C2-CalSim model and the day-to-day variability produced by the CRESPI algorithm. The resulting data are analyzed and processed to produce tables, figures, and text for the associated publications. To reduce the data release's size, data from a given step in the analysis that are not used in a subsequent step have not been included in this data release. All code generated by the USGS to produce the data in this data release is also included. This includes all code to download and preprocess external data; to set up and control the RVIC model runs; to modify, set up, and control runs of the CalSim 2 model; to implement and run the CRESPI algorithm; to postprocess and analyze model outputs; and to produce published figures, tables and text that includes calculated values. A detailed README file is included with instructions for running the code, including how to obtain the external RVIC and CalSim 2 models.

Understanding the effects of climate change is a substantial challenge in estuarine systems because the mixing of freshwater and ocean water adds complexity to climate change projections. Such climate change projections have been conducted in the San Francisco Estuary as part of the U.S. Geological Survey’s CASCaDE Project. In this project, we assessed downscaled air temperature data from 10 Global Climate Change models under 2 Representative Concentration Pathway (RCP) trajectories for greenhouse gas concentrations for three regions of the upper San Francisco Estuary: Suisun and Grizzly Bays, Suisun Marsh, and the legal Delta. We also utilized previously derived regression models to estimate future water temperatures at 16 locations within the upper estuary based on the projected air temperature data.

Understanding the effects of climate change is a substantial challenge in estuarine systems because the mixing of freshwater and ocean water adds complexity to climate change projections. Such climate change projections have been conducted in the San Francisco Estuary as part of the U.S. Geological Survey’s CASCaDE Project. In this project, we assessed downscaled air temperature data from 10 Global Climate Change models under 2 Representative Concentration Pathway (RCP) trajectories for greenhouse gas concentrations for three regions of the upper San Francisco Estuary: Suisun and Grizzly Bays, Suisun Marsh, and the legal Delta. We also utilized previously derived regression models to estimate future water temperatures at 16 locations within the upper estuary based on the projected air temperature data.

This dataset includes simulated streamflow and sediment discharge for major tributaries contributing to Clear Lake, California. Historical hourly streamflow and sediment for each tributary location were outputs from an Hydrological Simulation Program - FORTRAN (HSPF) model. The historical data is available at an hourly time step from October 1980 to March 2024. The future time series were generated from the calibrated historical HSPF model and four CMIP6 bias corrected climate change scenarios: EC-Earth3, MPI-ESM1-2-HR, MIROC6, and TaiESM1, each using the" business as usual or medium warming scenarios from the SSP370 emissions forcing and socioeconomic pathway. The daily data are available for the same locations but at a daily time step from October 1980 to September 2099. Model inputs and outputs for each of the 11 sub models are located in the Model Archive child item.

This dataset includes processed climate change datasets related to climatology, hydrology, and water operations. The climatological data provided are change factors for precipitation and reference evapotranspiration gridded over the entire State. The hydrological data provided are projected stream inflows for major streams in the Central Valley, and streamflow change factors for areas outside of the Central Valley and smaller ungaged watersheds within the Central Valley. The water operations data provided are Central Valley reservoir outflows, diversions, and State Water Project (SWP) and Central Valley Project (CVP) water deliveries and select streamflow data. Most of the Central Valley inflows and all of the water operations data were simulated using the CalSim II model and produced for all projections. These data were originally developed for the California Water Commission’s Water Storage Investment Program (WSIP). The WSIP data used as the basis for these climate change resources along with the technical reference document are located here: https://data.cnra.ca.gov/dataset/climate-change-projections-wsip-2030-2070. Additional processing steps were performed to improve user experience, ease of use for GSP development, and for Sustainable Groundwater Management Act (SGMA) implementation. Furthermore, the data, tools, and guidance may be useful for purposes other than sustainable groundwater management under SGMA. Data are provided for projected climate conditions centered around 2030 and 2070. The climate projections are provided for these two future climate periods, and include one scenario for 2030 and three scenarios for 2070: a 2030 central tendency, a 2070 central tendency, and two 2070 extreme scenarios (i.e., one drier with extreme warming and one wetter with moderate warming). The climate scenario development process represents a climate period analysis where historical interannual variability from January 1915 through December 2011 is preserved while the magnitude of events may be increased or decreased based on projected changes in precipitation and air temperature from general circulation models. ## 2070 Extreme Scenarios Update, September 2020 DWR has collaborated with Lawrence Berkeley National Laboratory to improve the quality of the 2070 extreme scenarios. The 2070 extreme scenario update utilizes an improved climate period analysis method known as "quantile delta mapping" to better capture the GCM-projected change in temperature and precipitation. A technical note on the background and results of this process is provided here: https://data.cnra.ca.gov/dataset/extreme-climate-change-scenarios-for-water-supply-planning/resource/f2e1c61a-4946-4863-825f-e6d516b433ed. *Note: the original version of the 2070 extreme scenarios can be accessed in the archive posted here: https://data.cnra.ca.gov/dataset/sgma-climate-change-resources/resource/51b6ee27-4f78-4226-8429-86c3a85046f4*

This report summarizes estimates of “natural” and “unimpaired” flows for all areas in the Central Valley tributary to the Sacramento – San Joaquin Delta (Delta) for the period spanning water years 1922-2014. A major objective of this report is to clarify the conceptual differences between natural and unimpaired flows. In spite of the Department’s previous attempts to distinguish between natural conditions and its calculation of theoretical unimpaired flows, unimpaired flow estimates have frequently been used as a surrogate measure of natural conditions, presumably because natural flow estimates were unavailable. This report contains the Department’s first published estimates of natural flows; these estimates are derived from complex simulation models and are based on published estimates of natural vegetation cover and associated evapotranspiration.

This dataset includes processed climate change datasets related to climatology, hydrology, and water operations. The climatological data provided are change factors for precipitation and reference evapotranspiration gridded over the entire State. The hydrological data provided are projected stream inflows for major streams in the Central Valley, and streamflow change factors for areas outside of the Central Valley and smaller ungaged watersheds within the Central Valley. The water operations data provided are Central Valley reservoir outflows, diversions, and State Water Project (SWP) and Central Valley Project (CVP) water deliveries and select streamflow data. Most of the Central Valley inflows and all of the water operations data were simulated using the CalSim II model and produced for all projections. These data were originally developed for the California Water Commission’s Water Storage Investment Program (WSIP). The WSIP data used as the basis for these climate change resources along with the technical reference document are located here: https://data.cnra.ca.gov/dataset/climate-change-projections-wsip-2030-2070. Additional processing steps were performed to improve user experience, ease of use for GSP development, and for Sustainable Groundwater Management Act (SGMA) implementation. Furthermore, the data, tools, and guidance may be useful for purposes other than sustainable groundwater management under SGMA. Data are provided for projected climate conditions centered around 2030 and 2070. The climate projections are provided for these two future climate periods, and include one scenario for 2030 and three scenarios for 2070: a 2030 central tendency, a 2070 central tendency, and two 2070 extreme scenarios (i.e., one drier with extreme warming and one wetter with moderate warming). The climate scenario development process represents a climate period analysis where historical interannual variability from January 1915 through December 2011 is preserved while the magnitude of events may be increased or decreased based on projected changes in precipitation and air temperature from general circulation models. ## 2070 Extreme Scenarios Update, September 2020 DWR has collaborated with Lawrence Berkeley National Laboratory to improve the quality of the 2070 extreme scenarios. The 2070 extreme scenario update utilizes an improved climate period analysis method known as "quantile delta mapping" to better capture the GCM-projected change in temperature and precipitation. A technical note on the background and results of this process is provided here: https://data.cnra.ca.gov/dataset/extreme-climate-change-scenarios-for-water-supply-planning/resource/f2e1c61a-4946-4863-825f-e6d516b433ed. *Note: the original version of the 2070 extreme scenarios can be accessed in the archive posted here: https://data.cnra.ca.gov/dataset/sgma-climate-change-resources/resource/51b6ee27-4f78-4226-8429-86c3a85046f4*

This report summarizes estimates of “natural” and “unimpaired” flows for all areas in the Central Valley tributary to the Sacramento – San Joaquin Delta (Delta) for the period spanning water years 1922-2014. A major objective of this report is to clarify the conceptual differences between natural and unimpaired flows. In spite of the Department’s previous attempts to distinguish between natural conditions and its calculation of theoretical unimpaired flows, unimpaired flow estimates have frequently been used as a surrogate measure of natural conditions, presumably because natural flow estimates were unavailable. This report contains the Department’s first published estimates of natural flows; these estimates are derived from complex simulation models and are based on published estimates of natural vegetation cover and associated evapotranspiration.

This report summarizes estimates of “natural” and “unimpaired” flows for all areas in the Central Valley tributary to the Sacramento – San Joaquin Delta (Delta) for the period spanning water years 1922-2014. A major objective of this report is to clarify the conceptual differences between natural and unimpaired flows. In spite of the Department’s previous attempts to distinguish between natural conditions and its calculation of theoretical unimpaired flows, unimpaired flow estimates have frequently been used as a surrogate measure of natural conditions, presumably because natural flow estimates were unavailable. This report contains the Department’s first published estimates of natural flows; these estimates are derived from complex simulation models and are based on published estimates of natural vegetation cover and associated evapotranspiration.

The hydrologic modeling approach used to predict functional flows relies on daily streamflow data from gages operated by the U.S. Geological Survey (USGS) in California. This dataset contains, for each of 219 gages, a collection of metrics computed on each water year for the period of record to and including Water Year 2016.