HEC-ResSim

Overview

HEC-ResSim (Reservoir System Simulation) is designed to simulate operations at one or more projects (reservoirs, diversions, and locks and dams) for a variety of operational goals and constraints. HEC-ResSim is fundamental to the CWMS software suite, as it simulates real-time dam operations to meet approved Water Control Plan (WCP) rules such as flood management, low flow augmentations, hydropower, system operations, and guide curve operations. In addition to providing Water Managers (WM) with simulations that meet approved WCPs, HEC-ResSim provides the capability for WMs to enter operational overrides based upon institutional knowledge and WM judgement. This allows them to refine operational forecasts and/or to evaluate impacts of deviating from WCPs due unforeseen circumstances, such as outlet structure closures, temporary restrictions upstream or downstream, or emergency situations.

Funded Activities

Accomplishments

Finalize and Release HEC-ResSim 3.5 (CWMS 3.4)

HEC-ResSim 3.5 was released in August 2024, and the software's User's Manual was published online for the first time. As compared with HEC-ResSim's previous release timeline, HEC-ResSim 3.5 was released in almost half the time, a significant step in shortening the release cycle. 

This activity included final standalone testing, final bug fixes, final benchmark resolution, and documentation. The development and standalone testing of the HEC-ResSim 3.5 release candidate was completed in February 2024, making the release candidate available for integration testing with CWMS and HEC-WAT while the user documentation and resolution of outstanding benchmark differences were completed over the next six months. The standalone testing included standard compute tests (benchmark tests against results from HEC-ResSim 3.3) and focused manual testing for new or expanded features related to hydropower, OSI, lookback options, variants, global variables, vertical datum, disabling rules, release allocation, prescribe release rules, water accounting, Monte Carlo alternatives, ensembles, HEC-DSS 7, and Java 11.

Given general program budget and time limitations, compromises were made to release with existing bugs and incomplete features rather than attempting to fix all issues and wait much longer for release, known issues were documented in the User's Manual. Of most impact to CWMS users are the compromises made with respect to OSI, vertical datum, and variants. Many interface and functional issues have been identified for the the OSI feature, but it was determined that there was more value in releasing version 3.5 sooner than making OSI improvements. Planned OSI documentation improvements were deferred based on a change in priorities, and funding used to complete additional integration testing for the CWMS 3.4 release. The HEC-ResSim vertical datum feature was designed with HEC-DSS 6 and found to be incompatible with the new implementation of vertical datum in HEC-DSS 7. A major overhaul will be needed for vertical datum to function in the HEC-ResSim version 4.0 series. CWMS watersheds that rely on storing vertical datum will need to remove the information as this capability is marked as Do Not Use. Finally, the variants feature that allows CWMS and HEC-WAT to create their own copies of alternatives was found to be problematic for some users, so a new design was developed and planned for HEC-ResSim version 4.0.

Test and Document Water Quality Capabilities within HEC-ResSim 4.0 (CWMS 3.5)

Numerous bugs were fixed and several new WQ capabilities were added to the software. The HEC-ResSim WQ feature was tested with CAVI and a path for a minimally viable product for CWMS 3.5 and HEC-ResSim 4.0 was mapped out.

HEC-ResSim 4.0 Development (CWMS 3.5)

HEC-ResSim 4.0 development has been ongoing since 2017, but finalizing the HEC-ResSim 3.5 release candidate allowed the team's primary focus to shift to HEC-ResSim 4.0. The 4.0 code is hosted on HEC DevNet, and uses DevOps tooling, which is a great stride in improving the HEC-ResSim development process and release cycle. Major accomplishments for this activity in FY24 include: the code dependency was updated and tested with Monolith 5.0 (the latest shared HEC code); the code was updated to Java 11; initial benchmark tests were run against the final HEC-ResSim 3.5 results; and a framework was planned and implemented for automating the benchmark compute tests. Additional work included increasing the investment in bug fixes and code structure improvements.

HEC-ResSim CAVI Integration Testing

Manual tests were created and run to test HEC-ResSim from within the CAVI in CWMS 3.4. The tests included:

• running the DSS conversion script to convert files from version 6 to version 7, and then running HEC-ResSim within the CAVI
• verifying existing forecasts that included HEC-ResSim opens and results can be viewed within the CAVI
• testing the Operation Support Interface (OSI) from within the CAVI
• testing Global Variables within the OSI
• verifying Save to Base works properly within the CAVI
• verifying Replace from Base works properly within the CAVI

Field Support and Documentation Updates

The MMC hosted monthly working sessions on the CWMS Modeling Group within Microsoft Teams, allowing HEC-ResSim modelers to receive support from experts. The HEC-ResSim/CWMS team participated in these meetings to provide field support, answer questions, and demonstrate important capabilities of the software to attendees. The team also provided one-on-one support to offices on an ad-hoc basis throughout the year. Discourse also provided an interface for users to submit their questions and get expert support.