understanding the delta - an engineering perspective
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UNDERSTANDING THE DELTA -
AN ENGINEERING PERSPECTIVE
Richard A. DentonWater Resources Manager
Contra Costa Water District
Location of Delta and Relationship to CALFED Bay-Delta Program Solution Area
Geographic Scope of
Solution
Geographic Scope of Problem Identification
Sacramento
Sacramento River
San Joaquin
River
Stockton
Suisun Marsh
Major California
Rivers
Water Projectsand Major Rivers
in California
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
Sacramento
San Joaquin
Delta Outflow
SWP and CVPExports
Vallejo, Solano
CCWD - three intakes
Contra Costa Water District
Contributions to Delta Outflow(Annual Average = 28 Million Acre-Feet)
Sacramento
Yolo
EastsideStreamsSan Joaquin
Precipitation
Data Source: DWR Delta Atlas
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
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
Yellow diamonds represent dams in California
“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
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
Delta Cross Channeland Georgiana Slough
DCC
GeorgianaSlough
SacramentoRiver
SacramentoRiver
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
1999 Cross-Channel Closure
Salinity impact in Old River at Holland Tract due to DCC closure from October 19 to November 9, 1999
0
50
100
150
200
250
300
350
220 230 240 250 260 270 280 290 300 310 320 330 340 350 360Julian Day 1999
Chl
orid
es (m
g/L)
Model - with Closure Model - No Closure
Field Data
Closed
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
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
Rock SloughIntake (CCWD)
Old River Intake(CCWD)
Redirected Water Quality Impacts
Poor Quality
San Joaquin Inflow
Proposals for Conveying WaterThrough or Around the Delta
· Peripheral Canal (1982)
· Through Delta - channel widening
· Chain of Lakes
· CALFED Modified Through-Delta Alternative
· Towing water bags
Peripheral CanalIsolated conveyance
around the Delta
29,000 cfs capacity
Hood
ExportPumps
Sacramento River
ThroughDelta AlternativeInundated Islands
Setback Levees
CALFED THROUGH-DELTA CONVEYANCE
CentralDeltaIntake
Concept
(not carried forward)
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)
Los Vaqueros Reservoir Contra Costa Water District
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)
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
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 studies
of 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.
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
Los VaquerosReservoir
Chipps Island
Export Pumps
CollinsvilleRoeIsland
Salinity-Outflow Model
Chipps Island Daily Electrical Conductivity -- 1988
0
2
4
6
8
10
12
14
16
88.0 88.1 88.2 88.2 88.3 88.4 88.5 88.6
1988
Chi
pps
EC
(m
S/cm
)
Field EC Data
Salinity-Outflow Model (straight Delta outflow)
Jan Feb Mar Apr May Jun Jul
Antioch Tide
-2
-1
0
1
2
3
4
1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35
March 2000
Tid
al S
tage
(Fee
t)
Hourly
Tidally-Filtered Stage
Tidal Filling and Draining
Storage of Water within
Delta because of 14-Day
Cycle of Mean Water Level
Calculation of Suisun Bay Salinity based on Present and Previous Outflows
from Delta
Salinity-Outflow Model
Net Delta Outflow
“Actual” Delta
Outflow
Salinity at Chipps Island
Salinity-Outflow Model
Chipps Island Daily Electrical Conductivity -- 1988
0
2
4
6
8
10
12
14
16
88.0 88.1 88.2 88.2 88.3 88.4 88.5 88.6
1988
Chi
pps
EC
(m
S/cm
)
Field EC Data
Salinity-Outflow Model (straight Delta outflow)
Salinity-Outflow Model (tidal filling and draining)
Jan Feb Mar Apr May Jun Jul
For More Information
CALFED Bay-Delta Programwww.calfed.ca.gov
Cal. Department of Water Resourceswww.dwr.water.ca.gov
Contra Costa Water Districtwww.ccwater.com
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
MontezumaSloughControl
Structure
Suisun Marsh
Suisun Bay
SUISUN MARSH SALINITY CONTROL GATES
SacramentoRiver
San JoaquinRiver
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
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
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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