The Watershed Analysis Tool (HEC-WAT) software developed by the U.S. Army Corps of Engineers' Hydrologic Engineering Center (HEC) is a model integration tool that allows multi-disciplinary teams to perform water resources studies following USACE guidance and best-practices. HEC-WAT implements a framework that enables evaluation of study alternatives under comprehensive, systems-based approach while incorporating evaluation of risk and uncertainty in a standard process – as required by USACE guidance for hydrologic studies, including EM 1110-2-1619 Risk-based Analysis for Flood Damage Reduction Studies and EM 1110-2-1420 Hydrologic Engineering Requirements for Reservoirs. HEC-WAT promotes the collaborative building, editing, and running of models commonly applied by multi-disciplinary teams, including the saving and displaying of data and results in an organized manner - increasing reproducibility and transparency in outcomes. Performing a risk analysis in a systems approach is an underpinning of the HEC-WAT framework - implemented as a nested Monte Carlo simulation process in the "Flood Risk Analysis" (FRA) compute option. While primarily developed for quantification of risk and uncertainty on flood risk management (FRM) projects, the flexibility of HEC-WAT allows this approach to be applied to many other aspects of watershed system performance including evaluation of changes in hydrology and reservoir operations on hydropower, water supply, navigation, recreation, and ecosystem benefits. The FRA compute option supports the analysis of complex riverine systems while implementing USACE policy for evaluation of flood risk with both uncertainty and systems-based approaches. The HEC-WAT software also allows users to organize their model runs into study alternatives and simulations that represent them - allowing comparison of proposed projects or changes in the watershed while maintaining a comparable baseline condition.

HEC-WAT 1.1 is designated as 'CoP Preferred' by the HH&C CoP as an engineering software tool. HEC-WAT 1.1 has not been certified as a model for evaluation of economic and life-safety consequences with USACE Planning studies – we recommend studies needing to perform these analyses to use HEC-WAT to develop the required inputs for HEC-FDA, applying HEC-WAT to evaluate uncertainty where the watershed processes or system interactions are significant, and develop HEC-FDA inputs from the HEC-WAT results (such as flow-frequency, stage-frequency, unregulated-regulated flow transforms or flow-stage transforms). Improvements to carrying forward additional information to quantify modeled uncertainty from HEC-WAT into HEC-FDA is part of an ongoing work unit between the HEC-WAT and HEC-FDA teams.

This website provides information about the HEC-WAT software, including a page with downloads for the latest official release of HEC-WAT, complementary plugins, example studies, and links to the HEC-WAT users manual, quick start guide, and resources for resolving issues encountered while using HEC-WAT, reporting bugs, and suggest improvements. Unfortunately, HEC is unable to provide phone or email technical support to non-USACE customers. However, HEC encourages anyone who finds an issue in our software, to please report it through the Bug Report section of the Contact Us page of this website. Please review our Support Policy page for details.