CE 385 D Water Resources Planning and Management

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CE 385 D Water Resources Planning and Management

• Simulating System Performance
• Daene C. McKinney

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Operating Rules

• Allocate releases among purposes, reservoirs, and
  time intervals
• In operation (as opposed to design), certain
  system components are fixed
• Active and dead storage volume
• Power plant and stream channel capacities
• Reservoir head-capacity functions
• Levee heights and flood plain areas
• Monthly target outputs for irrigation, energy,
  water supply, etc
• Others are variable Allocation of
• stored water among reservoirs
• stored and released water among purposes
• stored and released water among time intervals

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Standard Operating Policy

• Reservoir operating policy - release as function
  of storage volume and inflow
• Rt Rt(St,Qt)

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Hedging Rule

• Reduce releases in times of drought (hedging) to
  save water for future releases in case of an
  extended period of low inflows.

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System Simulation
Operating Policy
Allocation Policy

• Create network representation of system
• Need inflows for each period for each node
• For each period
• Perform mass balance calculations for each node
• Determine releases from reservoirs
• Allocate water to users

Done?
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Example

• Using unregulated river for irrigation
• Proposed Reservoir
• Capacity K 40 million m3 (active)
• Demand D 30 ? 40 ? 45 million m3
• Winter instream flow 5 mil. m3 min.
• 45 year historic flow record available
• Evaluate system performance for a 20 year period
• Simulate
• Two seasons/year, winter (1) summer(2)
• Continuity constraints
• Operating policy

Flow statistics
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Summer Operating Policy
Storage at beginning of summer
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Performance Evaluation

• How well will the system perform?
• Define performance criteria
• Indices related to the ability to meet targets
  and the seriousness of missing targets
• Simulate the system to evaluate the criteria
• Interpret results
• Should design or policies be modified?

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Performance Criteria - Reliability

• Reliability Frequency with which demand was
  satisfied
• Define a deficit as
• Then reliability is
• where n is the total number of simulation periods
  

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Performance Criteria - Resilience

• Resilience probability that once the system is
  in a period of deficit, the next period is not a
  deficit.
• How quickly does system recover from failure?

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Performance Criteria - Vulnerability

• Vulnerability average magnitude of deficits
• How bad are the consequences of failure?

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Simulate the System
Reservoir operating policy
Allocation policy
Policies
Hydrologic time series
Model output
System
Input
Output
Model
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Uncertainty

• Deterministic process
• Inputs assumed known.
• Ignore variability
• Assume inputs are well represented by average
  values.
• Over estimates benefits and underestimates losses

• Stochastic process
• Explicitly account for variability and
  uncertainty
• Inputs are stochastic processes
• Historic record is one realization of process.

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Simulate the System
Reservoir operating policy
Allocation policy
Distribution of inputs
Policies
Generate multiple input sequences
Compute statistics of outputs
System
Get multiple output sequences
Model
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The Simulation

• Simulate reservoir operation
• Perform 23 equally likely simulations
• Each simulation is 20 years long
• Each simulation uses a different sequence of
  inflows (realization)

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Example Realization 1
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Results
Average failure frequency 0.165 Average
reliability 1- 0.165 0.835 83.5 Actual
failure frequency ? 0, 0.40 Actual Reliability
? 100, 60
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Physical Environment Feedback Sub Model to FAV
Local Physical Environment (tides, freshwater
flow)

Heavy metals
Riparian Vegetation
Salinity
Nutrients
DO
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Surface, Subsurface Light

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Wind, Flow Velocity
Temp
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Substrate Org Matter
FAV Establishment and Growth
FAV Patch

Dispersal


Small Substrate Grain Size


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Subsurface Light
Lars Anderson, UC Davis Stuart Siegel, WWR Mark
Stacey, UCB