Use of Intra ‐ Seasonal and Seasonal Forecasts to Reduce Risk in Regional Public Water Supply Management Chris Martinez University of Florida Agricultural and Biological Agricultural and Biological Engineering Engineering
Overview • Project Partners • Project Background & Goals • Methods • Results • Lessons Learned • Relevance Funded by NOAA’s Climate Program Office SARP-Water program Agricultural and Biological Engineering
Percentage of Background Water by Source • Current sources: 1998 • Groundwater (13 wellfields) 100% • Tampa Bypass Canal/Hillsborough River • Alafia River 11% • C.W. Bill Young off ‐ stream reservoir 2008 • Desalination Plant 28% 61% 9% (12-month moving average) 2012 Groundwater Permit Pre ‐ 1998 192 MGD 45.5% 45.5% 1998 158 MGD 2002 121 MGD Agricultural and Biological 2008 90 MGD Engineering
Source Allocation Decisions • Multiple decision scales: • Water year plan (6 ‐ months prior) • Month to month adjustments • Operational decisions (weekly) • Multiple constraints: • Permitted groundwater (12 ‐ month moving average) • Minimum streamflows • Streamflow extraction ratio (maintain Fluoride limit) • Costs of different sources Agricultural and Biological Engineering
Project Goals • Integrate forecast information into decision making – Multiple temporal scales – Relevant spatial scales – Integrate forecasts into suite of models used by Tampa Bay Water • System ‐ wide Decision Support – What is the system ‐ wide benefit/risk of adopting forecast information? – What is the reliability of the current system? – Value judgments under different scenarios? Agricultural and Biological Engineering
Links Between Climate/Hydrologic Information and Decisions by Tampa Bay Water Required Information Decision Climate/Hydrology Time-Scale Set Prices and monthly 18 months •Estimate of initial reservoir volume Source Allocation for in advance •Scenarios of historical conditions water-year •Demand forecasts Update water-year Monthly, •Precipitation and Streamflow Allocations out to 12 forecasts months Operational Weekly, •Precipitation, Streamflow and Allocations out to 4 Demand forecasts weeks Agricultural and Biological Engineering
“Typical” Water Year Reservoir Reservoir Max Min Oct --- Nov --- Dec --- Jan --- Feb --- Mar --- Apr --- May --- Jun --- Jul --- Aug --- Sep Filling Max Reservoir Groundwater Using Reservoir use Max Direct Surface Water use • Estimate of end of year reservoir level needed for plan for next water year • Greater than expected groundwater pumping impacts next water year plan • Seasonal forecasts can be used to determine expected higher/lower groundwater pumping in winter months Agricultural and Biological Engineering
Different Products for Different Time ‐ Scales • Operational – Ensemble Precipitation, Streamflow and Demand forecasts derived from medium ‐ range forecast products • Monthly/Seasonal – Probabilistic Precipitation and Streamflow/Withdrawal Climate ‐ based Forecasts • Water ‐ Year – Decision Support, taking into account previous and next 12 months Agricultural and Biological Engineering
Current Historical Forecast Forecast Analogs Operational Time ‐ scale • +/ ‐ 30 day search window • 100 analog forecasts • Forecast analogs using the ESRL/PSD GFS Retrospective forecast Historical Observations archive (Stations or NARR) 1 ‐ 15 day • 2.5° x 2.5 ° • • 1979 ‐ present Ensemble of • Analog selection can be Hydrologic tailored to need Forecasts http://www.esrl.noaa.gov/psd/forecasts/ Agricultural and Biological reforecast/ Engineering
Precipitation Forecast Skill 0.35 Day 1 Day 2 0.3 Day 3 Day 5 CRPSS: Continuous 0.25 Day 7 Ranked Probability Skill 0.2 CRPSS Score 0.15 0.1 1 0.05 0.8 0 0.6 J F M A M J J A S O N D F(x) ‐ 0.05 0.4 Forecast 0.2 Observation 0 0.35 24 ‐ hr 48 ‐ hr 1 2 3 4 5 6 72 ‐ hr 5 ‐ day 0.3 x week ‐ 1 week ‐ 2 0.25 ∞ 2 [ ] dx ∫ = − 0.2 CRPS F(x) F (x) CRPSS o 0.15 − ∞ 0.1 CRPS 0.05 = − Forecast CRPSS 1 0 CRPS Ref Agricultural and Biological J F M A M J J A S O N D ‐ 0.05 Engineering
Monthly/Seasonal Time ‐ scale • Forecast analogs using CFS retrospective forecast archive http://cfs.ncep.noaa.gov/ – Week 2 – Monthly – Seasonal • Climate ‐ based probability of exceedance streamflow forecasts Agricultural and Biological Engineering
Correlation of Streamflow w/ ENSO Probability of Lagged Niñ03.4 Exceedance Streamflow Forecasts Season Posterior probability of streamflow Streamflow Forecast conditioned on predictor Streamflow Agricultural and Biological Exceedance Probability (%) Engineering
Decision Support + Scenarios • Inputs: – Forecasted Demand – Forecasted Withdrawal • Outputs: – Optimized source ‐ water allocations based on preferences/constraints – End of year reservoir volume Agricultural and Biological Engineering
Lessons Learned • There is a learning curve associated with using weather/climate datasets!!! (for hydrologists/engineers, at least…) • Limited number of forecasted variables archived in retrospective archives may limit usefulness Agricultural and Biological Engineering
Relevance • Tools/approaches that can easily be replicated in other regions – Analog forecasts – Exceedance streamflow forecasts Agricultural and Biological Engineering
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