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Northern Sacramento Valley Conjunctive Water Management Investigation Public Workshop December 8, 2010 The Glenn-Colusa Irrigation District and The Natural.

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Presentation on theme: "Northern Sacramento Valley Conjunctive Water Management Investigation Public Workshop December 8, 2010 The Glenn-Colusa Irrigation District and The Natural."— Presentation transcript:

1 Northern Sacramento Valley Conjunctive Water Management Investigation Public Workshop December 8, 2010 The Glenn-Colusa Irrigation District and The Natural Heritage Institute 12/8/20101

2 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 12/8/20102

3 How Does The Proposed Project Work?

4 4 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 12/8/2010

5 10 Spring (no inflow) Summer (no inflow) Fall-Winter (inflow) Spring (no inflow) 8 Project Reservoir Operation Baseline Reservoir Operation Re-Operation Case 1- Reservoir Refills Reservoir Full 100 Deliveries = 50 Target Carryover = Reservoir Full 100 Reservoir Full 100 Flood Release = 20 Inflow = Inflow = 70 Flood Release = Reservoir Full Target Carryover = 40 Deliveries = 60 40

6 10 Project Reservoir Operation Baseline Reservoir Operation Re-operation Case 2- Reservoir Does Not Refill Reservoir Full 100 Reservoir Full 100 Deliveries = 50 Target Carryover = Reservoir Partially Full 80 Target Carryover = 40 Deliveries = Target Carryover = 40 Deliveries = Target Carryover = 40 Deliveries = Reservoir Partially Full 70 Spring (no inflow) Summer (no inflow) Fall-Winter (inflow) Spring (no inflow) Summer (no inflow) Inflow = 30 Flood Release = 0 70 Inflow = 30 Flood Release = 0 80 GW Groundwater = 10 40

7 Project Performance Summary Project Scenario 2 Evaluated with Revised Model Including Biological Opinions, Forecast-based Operation and Minimum Reservoir Release Criteria 12/8/20107 Performance Metric Sac R (Shasta) Feather R (Oroville) Total number of years in simulation ( )82 Number of years no project releases made6245 Number of years project releases made2037 Average annual (82 years) project release, (TAF) (Roughly 2/3 environmental and 1/3 ag benefits) Cumulative benefit over 82 years (TAF) = 25 2, ,460 Maximum year project release (TAF) (Includes environmental and ag) Number of years payback pumping is needed411 Average annual (82 years) project pumping (TAF) Cumulative pumping over 82 years (TAF) = Maximum year project pumping (TAF) (Maximums do not occur in same year) 100 Average annual (82 years) reservoir refill from surplus flows (TAF)23 Spillage of payback water0-2

8 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? 12/8/20108

9 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? Questions, continued How Does The Proposed Project Work? 12/8/20109

10 What are the existing contractual obligations? Public wants assurance that there is adequate thought going into monitoring and mitigation. Questions, continued How Does The Proposed Project Work? 12/8/201010

11 Investigation Tools and Data

12 Overview of Analysis Tools 12/8/201012

13 13 Groundwater Model Area and Grid Density Sacramento Orland Unit GCID Butte Basin Willows 12/8/2010 Chico

14 14 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 /8/2010

15 15 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 12/8/2010

16 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? 12/8/201016

17 Project Benefits

18 Questions Project Benefits What are the project benefits? Are there benefits to the groundwater systems and were they considered in the economic analysis? 12/8/201018

19 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 12/8/201019

20 Project Impacts

21 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? 12/8/201021

22 22 Typical Sacramento Valley GW Hydrograph (Butte Co.) 12/8/2010

23 Sacramento Valley Water Uses and Sources by County

24 Peak Year Project Pumping (100 TAF 1 ) in Relation to Estimated Annual Baseline Pumping Area Estimated Baseline Pumping (TAF) Project Pumping as % of Area Baseline Butte County41124% Glenn and Colusa Counties63516% Butte, Glenn and Colusa Counties 1,04610% Northern Sacramento Valley (Butte, Glenn, Colusa, Tehama and Shasta Counties) 1,3238% Entire Sacramento Valley (Source: GW model water budgets) 2,500 +/-4% 12/8/ Peak year project pumping is 100 TAF in the Butte Basin and in GCID but the two not occur in the same year based on the 1922 through 2003 modeling

25 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)? 12/8/201025

26 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. Questions, continued Project Impacts 12/8/201026

27 Comparison of Drawdown from Modeling and Averaged for Impact Analysis 12/8/ Potential Impact Zones: Worst Case, New Wells Regional Aquifer Drawdown in Aug 1990, Scenario 1, New Well Field Figure 11-15, p from Modeling Report, Feb 2010

28 Next Steps Draft and Final Investigation Report Additional public meetings Phase 2 12/8/201028


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