Development of the HEC-Water Quality Engine began in 2016 to fulfill two main objectives:

  1. To begin extending water quality modeling capabilities to major HEC watershed modeling software products. The HEC-RAS (River Analysis System) program has included water quality modeling capabilities since version 4.0 (2006). By integrating water quality into the HEC-ResSim and HEC-HMS (Hydrologic Modeling System) programs, there will be support for linking water quality through different models and simulating the full range of conditions found in large watersheds - from upper basins, to reservoir systems, to lower river systems. While the HEC-5Q model (RMA, 1998) previously allowed users to simulate water quality in reservoir systems, it is now no longer supported or distributed by HEC.
  2. To streamline the process of modeling of reservoir releases for water quality objectives. Previous modeling options were labor intensive. Flows were simulated using release decision software such as HEC-ResSim. Those flows were then used to drive a water quality simulation, with a different software package. Finally, the water quality results were used to adjust and re-run the reservoir release simulation in a trial-and-error manner. By integrating water quality modeling capabilities directly into the HEC-ResSim software, the iterative process of determining reservoir releases for water quality objectives is addressed directly.

Since the software's initial beta releases, it has been successfully applied to several federally-managed reservoirs and reservoir systems, including:

  • the Russian River watershed (Lake Sonoma and Lake Mendocino),
  • the Upper Sacramento watershed (Lake Shasta, Trinity Lake, and others),
  • the Lower American watershed (Folsom Lake), 
  • the Stanislaus watershed (New Melones Reservoir), and
  • sections of the Columbia River watershed (Snake and Clearwater River reservoirs)

These applications have helped drive development of the software, including its integration into the modeling framework program HEC-WAT (Watershed Analysis Tool) and the Corps Water Management System (CWMS). 

The first official release of the software was packaged with HEC-ResSim 4.0 in 2025.