abhishek singh, phd, pe 2019/aw… · abhishek singh, phd, pe incorporating uncertainty into...
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Abhishek Singh, PhD, PE
Incorporating Uncertainty into Integrated Regional Water Resources Planning
Oct 1, 2019
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Planning under Uncertainty
• Planning with certainty is a rare luxury
• Planning under uncertainty is the norm
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Outline
• Planning under uncertainty• 5-steps for uncertainty assessment• Case-Study – Texas water planning• Lessons learned
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The Planning Process
Now
How we get there
Decisio
ns, Acti
ons
Future
Where w
e want
to be
Success
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Planning under Uncertainty
Now
How we get there
Decisio
ns, Acti
onsWhere w
e want
to be
Future?
Success
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• Account for uncertainty
Alternatives?
• Ignore uncertainty• Deterministic• Reactive• Near-Term
• Probabilistic• Scenarios• Adaptive• Long-Term
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Planning under Uncertainty• How do we maximize our chance of success given
everything we do not know?
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5-step Program
1. Identify Uncertainties • Known Unknowns/Unknown Unknowns
2. Characterize Uncertainties
3. Relate Uncertainty to Key Decisions
4. Assess Sensitivity to/Importance of Uncertainties
5. Manage Uncertainty• Reduce Uncertainty
• Increase Reliability/Reduce Risk
• Increase Resilience
• Monitor, Measure, and Adapt
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Case Study
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Texas Water Planning Framework• Regional water planning
process for resilient water supply– Drought of record– Deterministic
• Stake-holder driven process– Regional water planning
groups• 50-year planning horizon
– Updated every 5 years
•
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Objective
• Methodology to inform decision-makers how to characterize and account for uncertainty in regional water resources planning– Build on the current (deterministic) water planning
framework
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Methodology
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Uncertainty Characterization
• Uncertainty in demand– Population projections– Water usage rates
• Uncertainty in supplies– Water supplies in future droughts – Climate-change impacts
• Create multiple demand and supply scenarios
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Demand Scenarios
• 6 Pop. Proj. x 3 usage rate = 18 demand scenarios
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
500,000 1,000,000 1,500,000 2,000,000 2,500,000
2050 Population
Rela
tive
Lik
elih
ood
0.12
0.14
0.16
0.18
0.2
0.22
0.24
Year
Hig
her
than
Ave
rage
Per
-Cap
ita
Usa
ge R
ate
(ac-
ft/Y
) High Usage Rate
Low Usage Rate
Avg. Usage Rate
0%
5%
10%
15%
20%
25%
30%
150,000 200,000 250,000 300,000 350,000 400,000 450,000
2050 Demand (ac-ft/yr)
Rela
tive
Lik
elih
ood
High UsageAvg. Usage
Low Usage
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Supply Scenarios
• LCRA/SAWS Climate Change Study used as basis for modeling uncertainty in climate
• 2 GCMs x 2 Future Emission Scenarios + 1 Baseline = 5 Supply Scenarios
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Supply Scenarios
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Water Needs Scenarios
• Water Need = Water Demand – Water Supply
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Water Needs Scenarios
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Evaluating Projects
• Baseline strategy = Conservation and Reuse (C&R)– Meets (deterministic) projected water needs (10,000 AFY)– Only 22% reliable
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Evaluating Projects
• 6 potential strategies to meet the deficit
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Project Portfolios
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Cost-Reliability Trade-Off
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Sensitivity to Uncertainty
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Sensitivity to Uncertainty
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Summary
• Framework to plan under uncertainty based on existing planning framework
• Identified and characterized key uncertainties in demands and supplies
• Developed project portfolios to improve reliability of water plan
• Evaluated trade-offs in cost and reliability to rank and select project portfolios
•
Other Planning Studies…
Other Planning Studies…
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Lessons Learned
• Demonstrate importance of considering uncertainty– ‘Baseline’ solution not reliable
• Having a well-defined deterministic planning framework is key
• Start simple – easier to communicate ideas to stakeholders– Sequentially add ‘layers’ of uncertainty– Scenarios keep things ‘real’– Sensitivity analysis shows importance of different uncertainties
• Enables more robust decision making•
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