A rapid approach to modeling hyporheic flow at instream geomorphic features

<jats:p>Restoration planning teams need a rapid, repeatable way to identify and quantify hyporheic flows in streams. Current approaches are often only qualitative or require complex models and large datasets that are not practical for rapid analysis. This technical note introduces a simple workflow that couples 2D surface-water models (Hydrologic Engineering Center’s River Analysis System [HEC-RAS]) with 3D groundwater models (Groundwater Modeling System [GMS] and MODFLOW) to quantify hyporheic residence times, flow-path lengths, and exchange rates. The workflow fills a gap between qualitative indicators and data-intensive detailed modeling (e.g., computational fluid dynamics) and provides a rapid screening tool for hyporheic assessment. We demonstrate the workflow with an example application in riffle-pool features on the Concho River, Texas. The workflow provides outputs that can be mapped and tabulated to rank sites, prioritize reaches, and target field data needs in support of restoration planning studies. The outputs provide a consistent basis to compare existing conditions with concept designs that modify channel geometry and define performance measures aligned with project objectives. The scope of this technical note is limited to the hydraulic modeling workflow, and the intended audience is surface-water modelers with a basic understanding of hydrogeologic principles. Field data collection guidance and linking hyporheic flows to ecological indicators are briefly summarized.</jats:p>