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Data Set

PPIC Delta Water Accounting

These spreadsheets contain all data, sources, and methods used in the 2022 report Tracking Where Water Goes in a Changing Sacramento–San Joaquin Delta, Technical Appendix: Methods and Detailed Results for 1980–2021 and its accompanying policy brief of the same name. This study and dataset update the information in the 2017 report A New Approach to Accounting for Environmental Water: Insights from the Sacramento-San Joaquin Delta.

The Delta is operated according to regulations that assign water flowing into the Delta to various purposes. These spreadsheets contain estimates of the outflow needed to meet these regulations, including protection of water quality for in-Delta agricultural and municipal and industrial (M&I) uses and Delta exports (collectively referred to here as “system outflow”), and protection of water quality and flows for ecological uses (“ecosystem outflow”), along with water for in-Delta and export uses (“water depletions”), and water that exceeds these demands and regulatory requirements (“uncaptured outflow”). The spreadsheets also contain annual estimates of watershed-level sources (runoff, net changes in storage, and imports from the Trinity River) and upstream depletions. The main datasets cover the period 1980‒2021, a time during which significant regulatory changes affected the apportionment of Delta inflows and in which there was significant warming in California. The file also includes annual longer term estimates (1922‒2021) of runoff, depletions, and outflow, along with long-term estimates of temperature for California (1896‒2021).

The file contains an index; documentation that describes the variables used; three spreadsheets for 1980‒2021 Delta water accounting at different time scales—daily, monthly, and annual by calendar year (CY), and annual by water year (WY); a spreadsheet with different datasets for in-Delta use and depletion estimates (1980‒2021); a spreadsheet with daily estimates of unimpaired flow (1980‒2021); a spreadsheet with long-term (1922‒2021) watershed-level data on sources and depletions; and a spreadsheet with long-term data on California temperatures (1896‒2021). It also includes a succinct description of the methods, and a spreadsheet with the model to obtain water flows from salinity standards in the Delta.

The data were obtained following the description included in the Technical Appendix. Below are some of the main input sources. (Additional sources used in this update are listed in the individual spreadsheets.):

DAYFLOW: An estimate of daily average Delta Outflow. Department of Water Resources.

California Data Exchange Center (CDEC). Department of Water Resources.

Delta Islands Consumptive Use Model (DICU). For DICU documentation:
DWR (1995). “Estimation of Delta Island Diversions and Return Flows”. State of California. Department of Water Resources. Division of Planning. February 1995.

G-Model: Used to obtain water flows from salinity standards in the Delta. For G-model documentation:
Denton, R.A. 1993 “Accounting for Antecedent Conditions in Seawater Intrusion Modeling -Applications for the San Francisco Bay-Delta.” Hydraulic Engineering 93, Vol. 1 pp. 448-453 Proceedings of ASCE National Conference on Hydraulic Engineering, San Franc

Denton, R. (1993). “Antecedent flow-salinity relations: Application to Delta planning models.” Contra Costa Water District. December, 1993.

Sullivan, G. D., and Denton, R. (1994). “Report on Clean Water Act X2 Water Quality Standards.” Contra Costa Water District. February, 1994.

For Carriage water documentation see: Denton, R. (2006). “Refining CCWD’s Salinity-Outflow Model”. Contra Costa Water District. April 25, 2006.

State Water Project Annual Report of Operations. Department of Water Resources.

For a detailed analysis of this data, see Tracking Where Water Goes in a Changing Sacramento–San Joaquin Delta Technical Appendix: Methods and Detailed Results for 1980–2021.

For questions concerning this dataset, please contact Greg Gartrell.

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