US Army Corps of Engineers
Hydrologic Engineering Center

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Water Quality

Four water quality modules (Temperature, GCSM, NSMI, NSMII) have been integrated into HEC-RAS for performing water quality analysis. The one-dimensional (1D) HEC-RAS water quality modeling capabilities have been used to support studies for Total Maximum Daily Load (TMDL) analysis, military installations, and environmental impact studies. Recent studies include the Columbia-Snake River watershed, Missouri River, lower Minnesota River, Calleguas Creek, and the Patuxent River.

Riparian Vegetation Simulation Module (RVSM)

RVSM was integrated into HEC-RAS to simulate the interactions between flow and riparian vegetation on floodplains. For each timestep in of an HEC-RAS-RVSM simulation, HEC-RAS computes water surface elevation, discharge, average velocity, energy slope of each cross section. RVSM uses these variables to simulate the impacts of these variables on the riparian vegetation lifecycle and computes the impacts of riparian vegetation on channel roughness (Manning’s n values), which alters the river hydraulics. The new roughness values replace the previous values in the HEC-RAS model and are used to compute new hydraulic variables for the next time step.

Modeled and observed dissolved oxygen, Lower Minnesota River HEC-RAS water quality model.

The new water quality capabilities will be available in HEC-RAS v5.1, targeted for release in FY20.

Last Updated: 02/28/2019