DWR’s 2070 extreme climate change scenarios enable exploration of the vulnerability of and opportunities for water supply at the potential bounds of future climate change conditions. These scenarios were originally developed as part of the public benefit uncertainty analysis for the California Water Commission’s Water Storage Investment Program (WSIP) (dataset available here: https://data.cnra.ca.gov/dataset/climate-change-projections-wsip-2030-2070). In 2018, DWR’s Sustainable Groundwater Management Program (SGMP) furnished these extreme scenarios for use by Groundwater Sustainability Agencies (GSAs) (dataset available here: https://data.cnra.ca.gov/dataset/sgma-climate-change-resources). Specifically, downscaled global climate model (GCM) projections were provided for two future climate periods, including a 2030 central tendency, a 2070 central tendency, and two 2070 extreme scenarios to establish a range of projected conditions. **Since then, DWR collaborated with Lawrence Berkeley National Laboratory to improve the fidelity of these long-range planning datasets, resulting in this update of the 2070 extreme scenarios.** The 2070 extreme scenario update utilizes an improved climate period analysis method to better capture the GCM-projected change in temperature and precipitation. The updated dataset improves downscaled climate change extreme conditions considered for water supply that features both statewide coverage of hydrologic variables and managed flows within California’s inter-regional water conveyance system. **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.

This data release contains results from a simple monthly water budget that includes water supply and consumptive use for thermoelectric, irrigation, and public supply for 12-digit Hydrologic Unit Codes (HUC12) across the conterminous United States for water years 2010-2020. These results were produced using an analysis pipeline that ingests water supply, consumptive use, and routing information and accumulates and routes the water balance through the HUC12 network (Miller and others, 2024; https://doi.org/10.5066/P14MPRDE ). Water budget results also include an assessment of supply and use imbalances within the context of historical climatic conditions to calculate a surface water supply and use index and when considering a range of environmental flow allocation methods.

This data release contains Mann-Kendall trend results (p-values and Theil-Sen slope values) of water use data in either 8-digit Hydrologic Unit Code (HUC08) or Van Metre hydrologic regions across the conterminous United States (CONUS) for the period 2000-2020. Trends are computed for 7 timesteps: annual, winter (Dec, Jan, Feb), spring (Mar, Apr, May), summer (Jun, Jul, Aug), fall (Sep, Oct, Nov), high (Apr-Sep), and low (Oct-Mar) from three monthly HUC12 water-use datasets: public supply (Luukkonen, and others, 2023), irrigation (Martin, and others, 2023; Haynes and others, 2023), and thermoelectric (Galanter, and others, 2023; Gorman and others, 2023). Trends are computed on withdrawals, consumptive use, and the ratio of consumptive use to total withdrawal types for each of the three water use categories. In addition, trends were calculated for all withdrawals across the three categories (summing HUC12 datasets). Trends in thermoelectric data and all withdrawals are limited to the period 2008-2020. In addition to the trends data in “trends_modelled_wateruse.csv”, this dataset includes several files in the “trends.zip” folder that were used to download modelled output data, calculate trends (volumetric and Regional Kendall), and visualize trends across water-use categories and hydrologic units.

California Water Code Section 10004.6 requires the California Department of Water Resources (DWR) to quantify current and future water conditions in the state. This information is published in the California Water Plan (Water Plan), which is updated every five years. Water Plan Updates 2005, 2009, 2013, 2018 and 2023 have progressively developed a Water Evaluation And Planning (WEAP) model for assessing the impacts of climate change on California water resources and infrastructure, as well as the adaptation strategies needed and available to improve regional water resilience. Update 2023 brought significant improvements to input data and process in the model as described in the model documentation provided in the resources. The current WEAP model is called the WEAP-CVPA model as it covers the Central Valley of California at the planning area scale. The model was run on WEAP version 2021.0.2.2 but is compatible with newer versions of WEAP based on limited testing. Included in this dataset is: * The model itself with input files provided as a zip file * A link to SEI’s website where the software to run and view the model can be downloaded * The documentation for the model that was released as part of the California Water Plan Update 2023 * 4 CSVs with the post processed data from the study that were used to create the Future Scenarios Interactive Data Explorer, separated by summary vs detailed response surface as well as by planning area metrics vs points of interest metrics * A link to the Future Scenarios Interactive Data Explorer where the post processed results and response surfaces available at the planning area level * The raw exports from the model of the level 2070 that were post processed to create the data that informed the Water Plan Update 2023 * Spatial Boundaries for Water Plan Planning Areas which were used as the basis for spatial areas in the WEAP model