Water Utilities and Drought Planning: Indices, Triggers, Stages, and Response David Yates, David Purkey, Liz Mansfield CPASW 7 March 2008

Inland Empire Utility Agency, S. California Regional Utility Alliance in California, CABY Colorado Springs, CO Boston, MA Durham, NC Palm Beach County, FL New York City, NY Portland, OR AwwaRF/NCARThe Water Utility Story NYC IEUA

Decision Analysis Approach

Water Utilities and Climate Information Streamflow is the primary climate surrogate. Planning is based on assumption of Stationarity Should we assume Stationarity is Dead? Milly et al. 2008, Stationarity Is Dead: Whither Water Management?, Science

El Dorado Irrigation District Sac

EID- Shared Vision Model Drought Plan Built On: –Model of 3-year worst-case dry year sequence –Historic hydrology –Historic Demands Supply Demand

EID- Shared Vision Model Drought Plan Built On: –Model of 3-year worst-case dry year sequence –Historic hydrology –Historic Demands Supply Demand Streamflow PerCap & Pop Reliability

Drought Plan Development Estimate water supply conditions Determine savings that each Drought Stage will likely produce Define the indicators and triggers to give expected results (e.g. reliability target) Test when drought conditions are likely to cause operational issues How soon curtailment would have to start to be effective.

Shared Vision Model Water supply scenarios, rights and restrictions under low flow conditions Build in drought indices Test drought triggers by various stage scenarios Test various trigger plans, including current plans User–friendly, transparent, dynamic and consensus-based

Drought Plan Indicators Indicators include: –Water Yr Type –ENSO –Reservoir levels –Streamflow –Define a Supply Remain Index Indicators are modeled in the SVM

EID Drought Plan Triggers EID SRI Trigger Plan Summary Table MonthENSOSRI Last month's stage This month's stage MayAny <0.601 <=0.75 1,2,3 Last months stage June - Sept Any< <0.35*<0.120,1,22 <0.35*< Any >0.750,1,2,30 SRI tuned to achieve reliability for the worst drought of record

Drought Plan Response Drought Stage 3 Severely Restricted Water Supplies Up to 50% Total Supply Reduction Drought Stage 2 Moderately Restricted Water Supplies Up to 30% Total Supply Reduction Drought Stage 1 Slightly Restricted Water Supplies Up to 15% Total Supply Reduction Drought Stage Zero - Ongoing Conservation. Normal 0% Total Supply Reduction Drought stageWater supply conditions Preliminary Drought Stage Definitions

EID Drought Plan Triggers – Supply Remaining Index (SRI)

SVM Dashboard Reliability Supply Demand The Plan

Drought Stage 1 Actions Voluntary community response Total demand reduction goal of up to 15% (GDPUD treated water customers only) GDPUD managed supply of up to 50% raw water cutbacks Monitor indicators and demands Monthly Drought Interagency Coordination Committee meetings (DICC) Initiate public outreach

Drought Stage 2 Actions Voluntary community response (EID has potential mandatory phase) Total demand reduction goal of up to 30% (GDPUD treated water customers only) GDPUD managed supply of up to 50% raw water cutbacks Monitor indicators and demands weekly Weekly Drought Interagency Coordination Committee meetings (DICC) Intensify public outreach

Stage 3: Customer Response Needs Mandatory community response Total demand reduction goal of up to 50% (GDPUD treated water customers only) GDPUD managed supply of up to 100% raw water cutbacks Monitor indicators and demands weekly Weekly Drought Interagency Coordination Committee meetings (DICC) Intensify public outreach

Adding Climate Information Climate Driven DSS (WEAP) –Can disaggregate the demands –Look at Environmental conditions –Other competing Uses –Tradeoffs/ Benefits and Costs Just starting to work with EID on advancing their drought plan –Michael Hanemann from UC Berkley (resource economist)

Integrated watershed hydrology and water planning model GIS-based, graphical drag & drop interface. Physical simulation of water demands and supplies. Additional simulation modeling: user-created variables and modeling equations. Scenario management capabilities. Seamless watershed hydrology, water quality and financial modules Developed by the Stockholm Environment Institute, Bostons USAs office

El Dorado Irrigation District

North Fork American at North Fork Dam

Middle Fork American at Foresthill