l 07 rulebasedresops

7/23/2019 L 07 RuleBasedResOps

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Hydrologic Engineering Center

Rule-BasedReservoir Operation

HEC-ResSim



Outline

Review Zones and Guide Curve Operation

Go over some Terms & Definitions

Take a quick look at the available Rule Types

Discuss the different Release Limit Types

Walk through ResSim’s Release Decision Logic

Understand Conflicts

Generate releases and interpret decisions

Look forward to Further Complexities



Review…

What are reservoir storage zones ?

Zones partition reservoir storage amongdifferent purposes.

“Top ofCon.”

E l e v a t i o n

S t o r a g e

Water ConservationZone

Flood ControlZone



Review…

What is a guide-curve?The seasonally variable target pool elevation

The desired water storage level

What is Guide-curve operation?

Release or store to get back to guide curve.

Release water when

flood pool is

encroached

Store water to refillconservation pool

E l e v

a t i o n

S t o

r a g e


Flood ControlZone

E l e v

a t i o n

S t o

r a g e


Flood ControlZone



Review…

What is an operating rule ?

A rule is an objective for, or constraint on, the operation

of a reservoir or system of reservoirs.

When evaluated, a ResSim rule specifies an operational

goal or constraint as a desired limit on the range of

allowable releases.



Range of Allowable Releases – the minimum andmaximum values that the release can be whilesatisfying the governing physical and operationalconstraints on the reservoir.

Terms & Definitions

R e l e a s e

( c f s )

0

75,000

50,000

25,000

Physical Release

Capacity - Max

Physical Release

Capacity - Min1 2

Range of

Allowable

Releases



Terms & Definitions

Rule Priority describes the order in which the rulesare computed and applied to the region of allowablereleases.

Order of the rules in each zone

indicates priority –

the rule at the top of the list

has the highest priority

in that zone.



Rule Types

1. Release Function (at-site)2. Flow Rate of Change Limit

3. Elevation Rate of Change Limit

4. Downstream Control Function

5. Induced Surcharge

6. Tandem Operation

7. Hydropower – Schedule

8. Hydropower – Power Guide Curve9. Hydropower – Time Series Requirement

10. Hydropower – System Schedule

11. Pump Schedule

12. User Defined (Scripted)

O D RO D R

R

R

R

R

O

O

O

O

O

O D R

*A rule can be applied to:

O=Outlet

D=Dam or Group

R=Reservoir



Max Limit

A l l o w a b l e r a n g e o f

r e l e a s e s ( c f s )

0

15,000

10,000

5,000

Flow Limit Types

Min Limit

A l l o w a b l e r a n g e

o f


0

15,000

10,000

5,000

Specified Limit

A l l o w a b l e r a n g e

o f


0

15,000

10,000

5,000

Decreasing

Rate of Change


r e l e a s e s ( c f s

)

0

15,000

10,000

5,000

Increasing

Rate of Change


r e l e a s e s ( c f s

)

0

15,000

10,000

5,000



Examples - Release Rules

1. “Maintain at least 150 cfs

in the tailwater channel

throughout the year.”

2. “The tailwater channel hasa capacity of 10,000 cfs.”

3. “During the non-growing season, the maximumrelease can linearly increase from 11,000 when the

reservoir pool level is 711 feet to 20,000 cfs at poollevel of 712 feet.” (not illustrated)

A l l o w

a b l e

r a n g e

o f

r e

l e a s e s ( c f s )

0

15,000

10,000

5,000

1.

2.



1. “Release below Crazy Mountain Dam must not

increase by more more than 3,000 cfs per hour.”

2. “Release below CrazyMountain Dam must

not decrease by more

more than 1,000 cfs

per hour.” A l l o w a b l e

r a n g e

o f


0

15,000

10,000

5,0001.

2.

Assume that the previousrelease was 5,000 cfs

Examples -Flow Rate-of-Change Rules



Example –Elevation Rate of Change

1. “Do not allow the pool to

fill by a rate that is more

than 1 ft/hr.”

2. “Pool drawdown rate

should not exceed

0.25 ft/hr.” A l l o w a b l e

r a n g e

o f


0

15,000

10,000

5,000

1.

2.



1. Determine physical limitations

2. Apply operation rules to identify region ofallowable releases

3. Calculate desired guide-curve release

4. Decide which release applies

5. Release!

Walking through…The Release Decision Logic



1. Determine physical limitations Use Pool Elev -> Lookup Maximum Release Capacity

Use Release -> determine Max and Min Release Ability using Rate-of-Change constraints

R e l e a s e s ( c f s )

0

15,000

10,000

5,000




2. Apply operating rules … Use Current Pool Elevation -> Get Current Zone and its Rules

Evaluate Rules in Priority Order, narrowing the range of allowablereleases as appropriate

R e l e a s e s ( c f s )

0

15,000

10,000

5,000

0 1 2 3 40. Physical Capacity1. IROC - 3000 cfs2. Max Release - 10,000 cfs3. Min Release – 700 cfs4.Allowable Range: 700-8000 cfs





(When pool elevation is above guide curve…)

Net Inflow + Current pool elevation (685 ft)

Guide-curve elevation (683 ft)

Δ Elevation (+2 ft)

Δ Storage/ time-step

Desired GC release (26,000 cfs)

Δ Elev.




4. Decide !

(when pool elevation is above guide curve…)

?

Is Guide-Curve releasewithin allowable range?

Yes Make GC release

No Make allowable release that isclosest to GC release (8,000 cfs)

R e l e a s e

( c f

s )

30,000

20,000

10,000

GC

RD

AR

GC: desired guide curve releaseRD: release decisionAR: allowable range





(When pool elevation is below guide curve…)

Net Inflow + Current pool elevation (678 ft)

Guide-curve elevation (683 ft)

Δ Elevation (-5 ft)

Need to store water…

Desired GC release (0 cfs)

Δ Elev.




R e l e a s e

( c f s )

0

30,000

20,000

10,000

4. Decide !

(when pool elevation is below the guide curve…)

?Is Guide-Curve release

within allowable range?

Yes Make GC release

NoMake allowable release that isclosest to GC release (150 cfs)

GC: desired guide curve releaseRD: release decisionAR: allowable range

GC

AR

RD




Conflicts

What is a conflict? Webster’s says: “A .. struggle resulting from incompatible or

opposing needs, drives, wishes, or external or internaldemands”

In ResSim context - a situation when one goal or constraint

(rule) desires a release limit that is incompatible with therelease limit desired by another goal or constraint.

Example: A minimum rule calls for a release of 5,000 cfs but due to

downstream local flow and channel capacity, the reservoirshould not release more than 2000 cfs.



Resolving Conflicts

Priority resolves (addresses) virtually all

conflicts…

The priority stack that governs ResSim release

decisions:

1. Physical Limitations

2. The prioritized Operating Rules

3. Desired Guide Curve Release



Resolving Conflicts…

What happens if…

The Desired GC Release is outside the Allowable

Range?

The release will be the limit of the allowable range

closer to the Desired GC Release.



Resolving Conflicts

What happens if…

An operating rule prescribes a release limitoutside the range defined by the physical limits?

In general, the rule’s desired release will be capped(adjusted) by the physical limit.

But, Let’s be more specific…



Resolving Conflicts…

What if…

A minimum rule calls for a release greater than themaximum physical limit?

Since a minimum rule cannot force the reservoir torelease more than it is able, the rule will pull theminimum limit of the allowable range up to themaximum (physical) limit (the range will become asingle value) .



R e l e a s e

( c f s )

HEC-ResSim will try to make the

release that is closest to thatdesired by GC operation and theregion of releases allowed byoperating rules.

Physical limitations override(16,000 cfs), so GC and op rulesmay be violated.

Resolving Conflicts

When Guide-Curve and operating rules conflictwith physical limitations …

0

30,000

20,000

10,000

GC: desired guide curve releaseRD: release decisionAR: allowable range (rules only)PC: physical capacity

PC

GC

AR RD



Is this a Conflict?

A power rule calls for 5 MWHs to be generatedduring the next hour. But the pool elevation is solow, your 80 MW plant can only produce 3 MWHsduring the next hour.

Yes. The power rule is in conflict with the physical limitations of the reservoir.

How is this resolved?

ResSim will release to generate the 3 MWHs.The power rule is violated and constrained, butNOT ignored.



Is this a conflict?

The pool is below guide curve but a minimum rulecalls for a 1000 cfs release.

Yes. The minimum rule is in conflict with thedesired guide curve release.

What is the desired guide curve release?

How is this resolved?

ResSim will release 1000 cfs. The guide curve

operation is violated, but NOT ignored. Iteffectively forces the release to the minimum ofthe allowable range.

0.



Is this a conflict?

A minimum rule calls for a 1000 cfs release all yearlong. Another minimum rule calls for 2000 cfs duringthe Spring growing season. It is now May 15th.

No. The 1000 cfs min does not preclude a larger

release.

What is the effect of these rules?

Remember the rule of thumb!....

The minimum limit of the allowable range ofreleases will be set to 2000 cfs.



A Rule of Thumb

When a sequence of minimum rules are togetherin the rule stack, their relative priority does notmatter – the highest min “Wins”.

Similarly…

When a sequence of maximum rules are togetherin the rule stack, their relative priority does notmatter – the lowest max “Wins”.



Interpreting Release Decisions…

Use the SimulationModule to verifyand refine yourreservoir operations

Right-click on areservoir, view…

Reservoir Editor

Plots & Reports

Release Decision

Report



Interpreting Release Decisions…

View results through: The Release Decision

Reports

Plots (Flow & Elevationhydrographs)

Summary Reports



Adding Complexities…

Zone-specific rules Prioritizing rules

Rising/Falling Conditions

Operating for a downstream location

Seasonally Varying Release and DownstreamControl Functions

Hydropower rules (and zones)

Induced surcharge (minimum required release

based on inflow and storage) Jointly operating multiple reservoirs (for same

flow objective and/or a balanced pool state)



And MORE Complexities…

Separate rules for outlets, dams, and reservoirs Allocating Releases

Prioritizing or Balancing Releases across the

reservoir outlets

Outlet Outages and Capacity Overrides Decision Schedules

Allowing the reservoir to make release decisions at

intervals greater than the compute time-step.

Release overrides

Release specified timestep by timestep; ignore

operating rules



Take-home points

12 types of operating rules are available in HEC-ResSim

Physical constraints and Reservoir operating rules limitthe range of allowable releases

Current inflow and pool elevation, previous release,

physical limitations, applicable operating rules, anddesired guide-curve release all factor into releasedecisions

Priority resolves conflicts – it determines who “wins”

Use release, elevation, and release decision reports toidentify active rule

l 07 rulebasedresops

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