understanding the delta - an engineering perspective

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