1. HEC-ResSim 3.3 New Features to Support Complex Studies
It’s a Small World, Managing our Water Resources
USSD 2017 Annual Meeting & Conference
HEC-ResSim 3.3 New Features to Support Complex Studies
Presented by: Joan Klipsch, USACE-IWR-HEC

2. Overview What is HEC-ResSim?
Sources of Complexity for Reservoir Modeling
New Features in ResSim to meet the needs of Complex Studies
Firm Yield Determination
Water Accounts
Ensemble Alternatives
Monte Carlo Analysis

3. What is HEC-ResSim?
HEC-ResSim is a software product for simulating reservoir operations of one or more reservoirs in a river system.
It is designed for watershed-scale modeling of a system of reservoirs to support real-time decision-making and complex study projects.

4. More about HEC-ResSim…
HEC-ResSim models can be built to respond to extreme storm events and continue to manage under extreme drought.
HEC-ResSim can be used by itself or as part of an integrated suite of software tools
CWMS – Corps Water Management System
HEC-WAT – Watershed Analysis Tool

5. Sources of Complexity Competing Demands Conditional Demands
Flood Control
Water Supply
Hydropower
Ecosystems and Threatened & Endangered Species
Recreation
Navigation
Conditional Demands
Drought Contingency Operation
Seasonality
Water Supply, M&I – Municipal and Industrial, Agriculture, seasonal & out of phase with natural availability
Hydropower – maintain head, unnatural pulse flows
Flood control refers to all methods used to reduce or prevent the detrimental effects of flood waters. Flood relief refers to methods used to reduce the effects of flood waters or high water levels.

6. Sources of Complexity Watershed Scale Large models Reservoir Systems
Multiple reservoirs & control points
Long distances
Spans multiple climates
Reservoir Systems
with shared objectives
With local constraints

7. Sources of Complexity Increased Uncertainty
Changing Climate  greater weather variability and extremes
Changing Environment  development & land use, fires, drought, …
Changing Demands  growing population, conservation efforts, technology, …

8. New Complex Analysis Features
Firm Yield Determination – a simulation tool in ResSim that…
performs successive iterations of an alternative (compute)…
while adjusting the magnitude of a demand rule (adjust)…
until the reservoir(s) operating for that demand “just empty” during the critical dry period (converge).

10. Firm Yield Determination

11. Firm Yield Determination

12. New Complex Analysis Features
Water Accounts…
Specified as a quantity of storage in a reservoir “guaranteed” for use by a single water user or purpose.
Account is debited when releases are made to meet demands for this user or purpose (based on associated rule)
Account is credited with the account’s share of inflow

13. New Complex Analysis Features
Water Accounts…
Will “short” the demand if the water account empties.
Added to ResSim as part of the Yield Analysis features so that yield of an account can be determined.

14. Water Account Yield

15. New Complex Analysis Features
Ensemble Alternatives
An alternative type that iterates through a ensemble set of inflow time series data to allow the modeler to evaluate risk of a specified operation.
Added as a part a multi-agency effort to study risk-based reservoir operation.
Standard plots recognize ensemble alternatives and plot results accordingly.
One override specification applies to all members.

16. Ensemble Alternatives

17. Ensemble Results

18. New Complex Analysis Features
Monte Carlo Analysis
An alternative type in ResSim that allows the user to identify one or more input variables that may be randomly sampled within a user- specified distribution.
The user can also specify one or more output variables to be used to analyze the impact of the varied input.
ResSim will repeatedly compute the alternative, sampling a new value for each input variable to be used for each iteration.

19. Monte Carlo Analysis
When defining the output variables, the user can also specify convergence criteria for one or more of the output variables.
If used, the convergence criteria can stop the sampling before the maximum number of iterations is reached.

20. Monte Carlo Analysis Sampled starting pool elevation
Output variable, with convergence, max simulated pool elevation
55 seconds, 26 iterations, 99% confidence, < 0.1% rel error
Min 10 iterations
Max 1000 iterations

22. Coming Soon Watch the HEC website for the release of HEC-ResSim 3.3
Due: June 2017