HEC-HMS

Overview

HEC-HMS (Hydrologic Modeling System) is a software application designed to simulate the complete hydrologic processes of watershed systems, primarily for flood forecasting, water availability studies, urban drainage, flow forecasting, and reservoir spillway design. HEC-HMS is widely used by engineers, hydrologists, and water resource professionals across the U.S. and internationally. It’s designed to be flexible, scalable, and compatible with other HEC tools.

Key Capabilities:

• Rainfall-runoff modeling: Simulates how precipitation translates into runoff within a watershed.
• Hydrologic routing: Models the movement of water through rivers, channels, and reservoirs.
• Loss modeling: Includes methods for estimating infiltration and surface runoff.
• Baseflow and snowmelt modeling: Accounts for subsurface contributions and snow processes.
• Forecasting and real-time operations: Supports real-time flow forecasting when integrated with systems like CWMS.

Planned Activities

Develop New Tutorials and Host Webinars

As new or enhanced features are added to HEC-HMS, the team will develop tutorials and webinars to help inform users and support modelers in using these updates effectively.

Planned topics include:

• How to use the automated forecast optimization tool
• How to apply recent improvements of blending
• How to georeference existing projects and modify subbasin and reach delineations

Test HEC-HMS in HEC-RTS

Testing HEC-HMS builds within HEC-RTS is crucial to maintaining compatibility between the two applications as they evolve. Conducting these tests before each release helps minimize potential issues for users in the field. Over the past few years, the team has placed a strong emphasis on improving testing procedures and will continue to build on those efforts moving forward.

Support Field Operations

The team will continue to offer direct support to users who encounter HEC-HMS-related issues within HEC-RTS. This support ensures that users can resolve problems quickly and continue using the software for their water management operations. For assistance, please contact the HEC Modeling Team via Discourse, Microsoft Teams, or by reaching out directly.

Fix Bugs

When bugs are reported—either by users or the development team—they are investigated to determine their root causes. The team then works to correct the underlying issues. Once fixes are implemented, the updated code undergoes rigorous testing to confirm that the problems have been fully resolved and that no new issues have been introduced. A new version of the software is released to users only after this testing is successfully completed. A portion of this funding is directly allocated for the full migration of DSS version 6 to DSS version 7. 

Improve Automated Optimization

In FY25, the team developed a new automated optimization feature for use with forecast simulations in HEC-HMS, reaching a Minimum Viable Product (MVP) stage. Continued funding will support the expansion of this feature by adding enhanced functionality to the forecast optimization capability.

Design the Capability for Plots to Display Prior Results

HEC-HMS currently displays only the most recent results after a computation. The team plans to expand this capability by allowing plots to retain and display previous results. This will help users compare model runs and track changes over time. Implementation will occur over several years.

Enable Existing Snowmelt Plots in HEC-RTS

While HEC-HMS includes snowmelt plots, these are not currently accessible from HEC-RTS. The team will work to make these plots viewable in HEC-RTS so users can quickly analyze snowmelt results without switching to HEC-HMS.

Implement Changes to Allow Users to Clear All Zonal Edits and Element Overrides

This enhancement would add a button to the Combined Parameter Editor, allowing users to clear all manually entered zonal edits and element overrides in one step. This ensures quick removal of user inputs which override other model settings.