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

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)

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)

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

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

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)

HEC-HMS Model Overview 27 total subbasins Unimpaired flow simulation Calibration points: Unimpaired inflow to each reservoir and Dry Creek @ 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

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

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

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

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)

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 (%)

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

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

Likelihoods

Likelihoods

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)

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

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

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

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

Questions Romain Maendly, California Department of Water Resources Romain. Maendly@water.ca.gov