Transcript Northern Sacramento Valley Conjunctive Water Management

Northern Sacramento Valley
Conjunctive Water Management
Investigation
Public Workshop
December 8, 2010
The Glenn-Colusa Irrigation District and
The Natural Heritage Institute
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Workshop Objective & Process
• Objective
– Respond to questions from October 21, 2010
workshop 1
• Process
– Organized questions into topics
– Describe each topic
– Provide response
– Engage in discussion
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How Does The Proposed
Project Work?
Re-operate Surface Reservoirs with
Groundwater “Backstop”
• Reservoir re-operation
– Additional releases to meet program objectives
(North of Delta water supply and environmental enhancement)
– Expect reservoir refill from surplus surface flows
– Honor existing CVP and SWP delivery obligations and
operations constraints
• Groundwater operation
– Pump groundwater to “repay” reservoirs if storage conditions put
contract deliveries or temperature control at risk
– Groundwater used in lieu of surface entitlements that then
remain in storage
– Minimize or avoid GW impacts
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Re-Operation Case 1- Reservoir Refills
Baseline
Reservoir
Operation
Spring
(no inflow)
Summer
(no inflow)
Reservoir
Full
Target
Carryover = 50
100
Reservoir
Full
Project
Reservoir
Operation
50
Fall-Winter
(inflow)
Spring
(no inflow)
Inflow = 70
Reservoir
Full
100
100
8
Deliveries = 50
Flood
Release = 20
Target
Carryover = 40
Inflow = 70
Reservoir
Full
100
100
10
100
40
Deliveries = 60
Flood
Release = 10
Re-operation Case 2- Reservoir Does Not Refill
Spring
(no inflow)
Reservoir
Full
Baseline
Reservoir
Operation
100
Reservoir
Full
Project
Reservoir
Operation
10
100
Summer
(no inflow)
Target
Carryover = 50
Fall-Winter
(inflow)
Spring
(no inflow)
Summer
(no inflow)
Inflow = 30
Reservoir
Partially Full
Target
Carryover = 40
50
80
80
40
Deliveries = 50
Flood Release = 0
Target
Carryover = 40
40
Deliveries = 60
Deliveries = 40
Inflow = 30
Reservoir
Partially Full
Target
Carryover = 40
70
70
40
Flood Release = 0
Deliveries = 30
Groundwater = 10
40
GW
Project Performance Summary
Project Scenario 2 Evaluated with Revised Model Including Biological
Opinions, Forecast-based Operation and Minimum Reservoir Release Criteria
Sac R
(Shasta)
Feather R
(Oroville)
Total number of years in simulation (1922-2003)
82
82
Number of years no project releases made
62
45
Number of years project releases made
20
37
Average annual (82 years) project release, (TAF)
(Roughly 2/3 environmental and 1/3 ag benefits)
Cumulative benefit over 82 years (TAF) =
25
30
2,050
2,460
180
102
4
11
Average annual (82 years) project pumping (TAF)
Cumulative pumping over 82 years (TAF) =
2
164
9
738
Maximum year project pumping (TAF)
(Maximums do not occur in same year)
100
100
Average annual (82 years) reservoir refill from surplus flows (TAF)
23
23
Performance Metric
Maximum year project release (TAF)
(Includes environmental and ag)
Number of years “payback” pumping is needed
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Spillage of payback water
7
0
-2
Questions
How Does The Proposed Project Work?
• Can you do just reservoir re-operation
without doing the pumping for repayment?
• Where does the water for environmental
enhancements and other project benefits
come from?
• How does the payback water get used?
• How do the project benefits compare to
the frequency and magnitude of payback?
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Questions, continued
How Does The Proposed Project Work?
• How would the reservoir releases be
measured?
• How would it be determined that water
needs to be repaid…what triggers
reservoir payback?
• Which aquifer are we talking about, the
deep or shallow?
• Does the study address the total
groundwater picture?
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Questions, continued
How Does The Proposed Project Work?
• What are the existing contractual
obligations?
• Public wants assurance that there is
adequate thought going into monitoring
and mitigation.
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Investigation Tools and Data
Overview of Analysis Tools
Other
User Input
Environmental
Objectives
Target River Flows
GW Pumping
Reservoir Ops
Other Assumptions
Surface Water
Model
Ground Water
Model
SW-GW Interaction
CalSim Results
System Operation
With
Conjunctive Management
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Groundwater Model Area and Grid Density
Chico
Orland Unit
Butte Basin
Willows
GCID
Sacramento
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Groundwater Flow Model
• Regional scale with high spatial detail
– 5,950 square miles (3.8 million acres)
– 88,922 surface nodes
– 7 vertical layers
• Aquifer properties based on analysis of more
than 1,000 production wells
• Calibration
– Static calibration for year 2000
– Water levels from 257 monitoring wells
• Monthly time step, 1982 through 2003
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Surface Water Operations Model
• Spreadsheet-based for ease and speed of
operation
• Re-operates Shasta and Oroville Reservoirs
relative to a baseline condition depicted by
CalSim II outputs (1922 through 2003)
• Driven by additional target deliveries for:
– Environmental restoration in Sac and Feather Rivers
– Unmet Sac Valley agricultural demands
• Various operational constraints
• Uses generalized SW-GW interaction functions
derived from GW model
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Questions
Investigation Tools and Data
• Why are critical dry years not used in the
analysis?
• What is the time-step used to develop the
groundwater model? Is the time-step
appropriate for capturing localized effects
of day to day well operation and aquifer
response?
• Were economic impacts beyond just
project costs and benefits considered,
such as impacts to specific segments of
the agricultural community?
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Project Benefits
Questions
Project Benefits
• What are the project benefits?
• Are there benefits to the groundwater
systems and were they considered in the
economic analysis?
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Project Benefits
• Increased Sac Valley surface water supply
– More local benefit (water supply) from CVP
and SWP
– Reduced overall reliance on Sac Valley
groundwater, though increased local pumping
in certain years
• Improved habitat in Sac and Feather
Rivers through
– Recovery of salmon populations
– Ecosystem sustainability
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Project Impacts
Questions
Project Impacts
• What are the impacts of groundwater
pumping in the valley on foothill aquifers?
• What are the critical recharge months in
the upper reaches? In the area in general?
• Project pumping may be a small share of
Valley wide pumping but what proportion
is it of pumping within the project area?
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Typical Sacramento Valley GW
Hydrograph (Butte Co.)
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Sacramento Valley Water Uses and
Sources by County
Peak Year Project Pumping (100 TAF1) in Relation
to Estimated Annual Baseline Pumping
Estimated
Baseline
Pumping (TAF)
Project Pumping
as % of Area
Baseline
Butte County
411
24%
Glenn and Colusa Counties
635
16%
Butte, Glenn and Colusa
Counties
1,046
10%
Northern Sacramento Valley
(Butte, Glenn, Colusa, Tehama
and Shasta Counties)
1,323
8%
2,500 +/-
4%
Area
Entire Sacramento Valley
(Source: GW model water
budgets)
1
Peak year project pumping is 100 TAF in the Butte Basin and in GCID but the
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two not occur in the same year based on the 1922 through 2003 modeling
Questions
Project Impacts
• Is the interconnection between streams
and underlying aquifers sufficiently defined
to predict the effects of even modest
changes in groundwater levels (e.g., Butte
and Big Chico Creeks)?
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Questions, continued
Project Impacts
• What is the extent of the impact on
domestic (and other wells)? You show 0 to
6 feet, but you also say that near the wells
that are pumping payback water it could
be 50 or 60 feet? Even a few feet can
have a large impact. This needs to be
clarified.
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Comparison of Drawdown from Modeling
and Averaged for Impact Analysis
Potential Impact Zones:
Worst Case, New Wells
Regional Aquifer Drawdown in Aug
1990 , Scenario 1, New Well Field
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Figure 11-15, p.11-16 from Modeling Report, Feb 2010
Next Steps
• Draft and Final Investigation Report
• Additional public meetings
• Phase 2
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