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UNDERSTANDING THE DELTA - AN ENGINEERING PERSPECTIVE

This article provides an engineering perspective on the Delta and its importance, goals, and proposed engineering approaches for achieving those goals.

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UNDERSTANDING THE DELTA - AN ENGINEERING PERSPECTIVE

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  1. UNDERSTANDING THE DELTA - AN ENGINEERING PERSPECTIVE Richard A. Denton Water Resources Manager Contra Costa Water District

  2. Location of Delta and Relationship to CALFED Bay-Delta Program Solution Area Sacramento Sacramento River Suisun Marsh San Joaquin River Geographic Scope of Problem Identification Stockton Geographic Scope of Solution

  3. Major CaliforniaRivers

  4. Water Projectsand Major Riversin California

  5. Importance of the Delta • Source of Drinking Water for 22 Million People • 750 Plant & Animal Species • Supports $27 billion Agricultural Industry • Local Homes and Infrastructure • 80% of the State’s Commercial Salmon Fisheries • California’s Trillion Dollar Economy

  6. Sacramento Vallejo, Solano Delta Outflow CCWD - three intakes San Joaquin SWP and CVP Exports

  7. Contra Costa Water District

  8. Contributions to Delta Outflow(Annual Average = 28 Million Acre-Feet) Data Source: DWR Delta Atlas

  9. DELTA GOALS* • Ensure good water quality for fish, for drinking water, agriculture and other beneficial uses • Restore sustainable ecosystem and improve aquatic and terrestrial habitats • Reduce mismatch between water supply and demand • Improve structural integrity of Delta levee system and other facilities * Based on CALFED Bay-Delta Program Goals

  10. ENGINEERING APPROACHES FOR ACHIEVING GOALS • Barriers/Tide Gates • Water quality • Fish • Water levels • Increased Flows • San Joaquin River Recirculation Study • Fish Screens and Fish Salvage • New or Improved Conveyance • Increased pumping capacity • New or expanded storage • Groundwater conjunctive use • Off-stream or on-stream surface storage • In-Delta storage

  11. Yellow diamonds represent dams in California

  12. “SOFT PATH” PROPOSALS FOR ACHIEVING GOALS • Watershed Protection and Source Control • Advanced Drinking Water Treatment • Ultraviolet Disinfection • Membranes • Improved Water Use Efficiency • Conservation • Reclamation • Water Transfers • Removal of Barriers to Fish Migration • Dam removal on smaller tributaries • Wetland and Riparian Habitat Restoration

  13. Barriers/Tide Gates • Delta Cross-Channel Gates • Water Quality • Fish • South Delta Improvement Program • Water Levels (for farmers) • Fish (Head of Old River Barrier) • Improved circulation for water quality

  14. Georgiana Slough DCC Sacramento River Sacramento River Delta Cross Channel and Georgiana Slough

  15. Delta Cross-Channel • Operated by U.S. Bureau of Reclamation • Designed to increase flow of fresh Sacramento water into Central Delta (water quality) • Closed at high flows to avoid Delta flooding • May cause out-migrating salmon to stray • Closed Nov-Jan (up to 45 days) and May-June (14 days) (fish) • Oct-Nov 1999 closure for fish caused Delta water quality standards to be violated

  16. 1999 Cross-Channel Closure

  17. CALFED Cross-Channel Experiments • Goal is to protect fish as they move downstream without degrading Delta water quality • What is effect of only closing gates only on ebb tide (when flow and fish moving downstream)? • No impact on water quality • Do fish move during day or at night? • What is effect of only leaving gate open one flood tide per day (i.e., 6 hours)? • Some impact on water quality

  18. CALFED South Delta Improvement Program • Head of Old River barrier for fish • Three operable barriers for agricultural water levels and quality • Maintains water levels in channels for South Delta farmers (eastern side of barriers) • Creates some circulation for water quality for farmers • New fish screens for CVP and SWP export pumps • Channel dredging • Increased SWP export pumping • Agricultural drainage reduction near CCWD intakes

  19. Redirected Water Quality Impacts Rock Slough Intake (CCWD) Poor Quality San Joaquin Inflow Old River Intake (CCWD)

  20. Proposals for Conveying Water Through or Around the Delta • Peripheral Canal (1982) • Through Delta - channel widening • Chain of Lakes • CALFED Modified Through-Delta Alternative • Towing water bags

  21. Peripheral Canal Isolated conveyance around the Delta 29,000 cfs capacity Hood Export Pumps

  22. Sacramento River Through Delta Alternative Inundated Islands Setback Levees

  23. CALFED THROUGH-DELTA CONVEYANCE

  24. CentralDeltaIntakeConcept(not carried forward)

  25. New or Expanded Storage Proposals • Los Vaqueros Expansion (add 400 TAF) • Raise Shasta Dam (add 300 TAF) • In-Delta Storage (250 TAF) • Sites Reservoir near Willows (1.9 MAF) • Expanded San Joaquin reservoir storage, e.g., Friant (add 250-700 TAF) • Groundwater storage (500 TAF - 1 MAF)

  26. Los Vaqueros Reservoir Contra Costa Water District

  27. CCWD LOS VAQUEROS PROJECT • 100,000 acre-feet off-stream reservoir for water quality and emergency water supply • New 250 cfs screened diversion off Old River • Blending water released from Los Vaqueros when needed to meet 65 mg/L delivered goal • Provides ecosystem benefits because: • CCWD takes water from reservoir during low flow periods (water quality) • CCWD ceases diverting from Delta for 30 days in spring (fish protection)

  28. CCWD LOS VAQUEROS PROJECT • 1987 -- Project planning and design begins • Sept. 1994 -- Construction of reservoir began • Summer 1997 -- First diversions from new intake • Jan. 1998 -- Reservoir construction completed (first reservoir completed in California in 10 years) • Jan. 1999 -- Reservoir full for first time • July 1999 -- Los Vaqueros Project wins ASCE Outstanding Civil Engineering Achievement Award

  29. CALFED LOS VAQUEROS RESERVOIR EXPANSION STUDIES • Identified in CALFED Record of Decision • Would improve Bay-Area urban water quality and supply reliability • Increase reservoir from 100 TAF up to 500 TAF. • CCWD has contracted with DWR to perform studiesof expansion. • Closely coordinated with CALFED Bay Area Blending/Exchanges studies: • Physical interconnections between agencies. • Sharing of high quality water supplies to enhance delivered water quality for Bay Area users.

  30. SWRCB Estuarine Habitat Standards • Adopted by State Water Board in 1994 • Require 2 ppt salinity to be east of Roe Island, Chipps Island and Collinsville for a given number of days for the months of February through June • Number of days at each location determined from runoff to Delta in previous month • Number of days based on recreating flow conditions during 1968-1975 • Number of days developed from historical flow data using CCWD’s salinity-outflow model

  31. Collinsville Roe Island Chipps Island Los Vaqueros Reservoir Export Pumps

  32. Salinity-Outflow Model

  33. Tidal Filling and Draining

  34. Salinity-Outflow Model “Actual” Delta Outflow Salinity at Chipps Island Net Delta Outflow Calculation of Suisun Bay Salinity based on Present and Previous Outflows from Delta Storage of Water within Delta because of 14-Day Cycle of Mean Water Level

  35. Salinity-Outflow Model

  36. For More Information CALFED Bay-Delta Program www.calfed.ca.gov Cal. Department of Water Resources www.dwr.water.ca.gov Contra Costa Water District www.ccwater.com

  37. CALFED PROGRAM AREAS • Ecosystem Restoration • Water Quality • Governance • Water Supply Reliability • Watersheds • Storage • Conveyance • Environmental Water Account • Water Use Efficiency (conservation and recycling) • Water Transfers • Levees • Science

  38. SUISUN MARSH SALINITY CONTROL GATES Sacramento River Suisun Marsh Montezuma Slough Control Structure Suisun Bay San Joaquin River

  39. ENGINEERING TOOLS • Hydrologic and reservoir operation models • Hydrodynamic transport models • Contaminant transport models, e.g., salt transport • Statistical correlations • salinity-outflow • fish-flow • Conceptual fish population models • Fish “transport” models

  40. How the system is run • Northern California Hydrology: • Wet year: 4 months with rain, 8 dry • Dry year: 2 or 3 months with rain, 9 or 10 dry • Critically dry: 3 or 4 storms in a year • Major water sources: • Sierra snowfall • Basin rainfall • Local rain and groundwater

  41. Tidal Influence • Flows in Channels • Tides up to 500,000 cubic feet per second • Outflow typically 3,000 cfs to 100,000 cfs • Tides and seawater intrusion • Tides bring in seawater, river flows push it back • Good water quality if outflow is 7,000 cfs or more • Outflow is less than 5,000 cfs September through December

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