1. CALIFORNIA DEPARTMENT OF WATER RESOURCES
A Flood Management Focused Vulnerability Pilot Study of the Tuolumne Watershed
April 22nd, CWEMF
Romain Maendly, CA DWR, but…
A much bigger team which includes multiple colleagues from USACE, Academia and DWR

2. Outline Why this project – Background, goals, project overview
General study design for vulnerability assessment
Adaptive planning strategy
Uncertainty
Reservoir vulnerability
Identification of Adaptation measures (adaptive planning process)

3. Background and Purpose
Past studies have shown increasing flood risk in the Central Valley in the future due to climate change.
2017 CVFPP Update Climate Change Study has integrated climate change risks in flood planning in the Central Valley.
This project aims to enhance and extend climate change vulnerability assessment efforts and improve stakeholder understanding.
Uncertainty
Reservoir vulnerability
Identification of Adaptation measures (adaptive planning process)

4. Goals 4 2 1 3
Change in Temperature (C)
Change in Precipitation (%) 30 20 10
Projected Range of Likely Climate Changes by 2050
Quantify deep uncertainties in flood and drought prediction under climate change
Formulate a systematic framework for assessing future risks and developing economically efficient, robust, and flexible plans to mitigate risk
Inform other project/planning efforts

5. General Study Design This Presentation Previous Presentation
Global Climate Model Projections
Operations and Planning Models (HEC-WAT)
Previous Presentation
Weather Generator – Produce a time-series of meteorological variables
Adaptive Planning
Weather Generator
Systematic Climate Perturbations
System Response Surface/
Stress Test
System Base Performance/Probabilistic Vulnerability Assessment

6. HEC-WAT System Based Performance HMS RES SIM RAS FIA Weather Generator
HEC-WAT Integrates different HEC modeling software into one modeling tool, streamlining the modeling process.
Weather Generator
Simulation Data and Results (DSS)

7. HEC-HMS Model Overview
27 total subbasins
Unimpaired flow simulation
Calibration points: Unimpaired inflow to each reservoir and Dry Modesto
Results compared to daily unimpaired flow estimates from Steiner FERC model
Meteorological Model Inputs
Net Radiation (Short + Longwave) from LIVNEH (daily)
Precipitation & Temperature from NLDAS-2 (hourly)
ET by Priestley-Taylor
Snowmelt: Temperature Index
Elevation Bands: Roughly every 500’ above 4500’, but some adjustment to have band area > 10%
Dan Steiner FERC Model
Runtime Improvements

8. HEC-ResSim Model Overview
Combined Irrigation Canals
Don Pedro
Three upstream reservoirs
Combined Canals
San Joaquin Pipeline
Inflow from HMS
Original Model setup for flood operations
Using the model to model thousands of years of continuous hydrology.
Want to model non-flood operations for carryover storage
Runtime improvements
Historical data used to calibrate and validate the model

9. HEC-RAS Model Overview
Based from CVFED Model
Calibrated with the 2011 and 2017 events
Model handles extreme events (~320,000cfs)

10. HEC-FIA The inventory is a combination of point structure data from:
CVFPP 2017 Update’s HEC-FDA
And, the National Structure Inventory
Warning System/Time Feedback based on local input
Calibrated based on the 1997 and 2017 events

11. Vulnerability Assessment Metrics
Flood Risk
Expected Annual Damage / Life Loss
Population and Assets in 100yr Floodplain
Water Supply/Irrigation
Don Pedro storage on Apr 1st , July 1st and Oct 1st
Don Pedro deliveries to irrigation channel
Environmental
San Joaquin River Basin Index
Evapotranspiration
Metrics which will be evaluated:
Expected Annual Damage ($/Year)
Expected Annual Life Loss (#people/Year)
Annual Exceedance Probabilities (AEP) of flow/damage/life loss
Population in 100yr floodplain (#people)
Value of assets in 100yr floodplain ($)
Don Pedro storage on Apr 1st , July 1st and Oct 1st
Annual frequency of Don Pedro dead pool/top of cons elevation
Don Pedro deliveries to irrigation channel (Acres-feet/Year)
San Joaquin River Basin Index
Annual snowpack (SWO on Apr 1st)
Evapotranspiration (Acres/Year)
Precipitation, Temp, Solar Radiation (in / *C / W-m-2)

12. Vulnerability Assessment Example
Annual Average Inflow Volume: 1.9 MAF
Don Pedro Inflow Volume Change
(Oct01-Sep30)
Change in Volume (TAF) 4
Worse than Historical
Maintain current performance
Current conditions estimate
1000 years of model simulations
at each point 3
+200TAF
Change in Temperature (C) 2 1 30 20 10 10 20 30
Change in Precipitation (%)

13. Vulnerability Assessment Example
Annual Average Inflow Volume: 1.9 MAF
Don Pedro Water Supply Season
(Average Flow Volume: 983 TAF)
Don Pedro Flood Control Season (Average Flow Volume: 915 TAF)
+350TAF
-150TAF

14. Likelihoods Patrick Ray and Casey 2015 Dependencies
We are treating GCM as a independent

15. Likelihoods

16. Likelihoods

17. Vulnerability Assessment Example
Annual Average Inflow Volume: 1.9 MAF
Don Pedro Water Supply Season
(Average Flow Volume: 983 TAF)
Don Pedro Flood Control Season (Average Flow Volume: 915 TAF)

18. Integrated Adaptation Strategies Envisioned
Based on the system’s vulnerabilities, formulate robust actions and flexible plan to deal with future risks and uncertainties.
Flood-MAR
Floodplain transitory storage
Conservation easements
By-pass
FIRO
Increase capacity of infrastructures
Integrating water management activities, from headwaters to groundwater, can add sustainability and resiliency in water management systems, including maximizing water supply portfolios and supporting multiple benefits.
Projects/actions that foster sustainability and integrated water resources management

19. Adaptation Analysis Example
Current Expected Life Loss based on the 2017 CVFPP Update:
 149 life at risk
2067 life loss projection using median climate change projection (~3 °C and +4.5% Precip.)
 420 life at risk (+271)
What if the median projection is median projection is wrong?
Hypothetical Expected Annual Life Loss
+271 life at risk

20. DWR Use of Decision Scaling
CA 4th Climate Change Assessment
“Climate Change Risk Faced by the California Central Valley Water Resource System”
Climate Action Plan
Phase II: Analysis Guidance
Phase III: Vulnerability Assessment and Adaptation Plan.
Flood-MAR Program
Merced Reconnaissance Study
CVFPP 2022 Update
Tuolumne Watershed Pilot Study
Potential additional pilots
Phase II: Climate Change Analysis Guidance – This phase of planning develops a framework and guidance for consistent incorporation and alignment of analysis for climate change impacts in DWR’s project and program planning activities
Phase III: DWR’s Climate Change Vulnerability Assessment and Adaptation Plan (VA/AP) – The VA/AP describes, evaluates, and quantifies the vulnerabilities of DWR’s assets and business to potential climate change impacts.
Session 12: Tuesday Morning
10:00 – 11:45 am

21. Next Steps Vulnerability Assessments Identify Adaptive Strategies
Documentation
Continue to Engage and Communicate the Study Status with Locals and other Stakeholders

22. Questions Romain Maendly, California Department of Water Resources
Romain.