HEC-WAT (Watershed Analysis Tool)

Introduction

The U.S. Army Corps of Engineers (USACE) conducts water resources management studies. These studies begin with the definition of problems, issues, and opportunities and continue through the planning process by formulating, evaluating, and comparing alternatives with various analyses to determine impacts so that appropriate decisions may be made. The studies often require hydrologic, hydraulic, economic, and social impact analyses. In most cases, varying sections within a USACE office or through a Project Delivery Team (PDT) perform these impact analyses independently with the reporting and visualization of modeling results through independent models. For the project study, coordination, file/data sharing, logistics, reporting of modeling results, and status reporting are often a problem for the modeling teams as well as project management. 

The Institute for Water Resources, Hydrologic Engineering Center (CEIWR-HEC) developed the Watershed Analysis Tool (HEC-WAT) to meet the USACE requirements of performing water resources studies in a comprehensive, systems based approach. Modeling teams will benefit because teams will be able to develop models in a closely coordinated manner using a shared schematic; track progress of other models; and, automatically retrieve results from previous model runs through the shared schematic, thus assuring a more efficient and coordinated result. A graphical user interface (GUI) would allow data and results sharing, common schematic assembly, definition and representation of alternatives, model setup, editing and implementation, and direct data and results visualization. The management team would benefit through the use of a tool that employs a common interface by being able to track project status through each modeling component and being able to display results during public and project status meetings. 

For over two decades, USACE has required that all USACE planning processes address the Nation's water resources needs in a systems context while using risk analysis. From within USACE there is very little guidance and few tools to support this requirement. For this reason, HEC has added an option to HEC-WAT that will analyze complex riverine systems while implementing the flood risk management and systems requirements. The new compute option, Flood Risk Analysis (FRA), will allow a user to perform plan formulation or system performance analyses while incorporating risk analysis.

HEC-WAT provides a framework that streamlines and integrates tools commonly applied by USACE District and Division offices used when performing a water resources management study. The basic building block of the HEC-WAT framework is an HEC developed concept labeled "plug-in". By using the plug-in concept HEC-WAT incorporates individual pieces of software such as:

HEC-RAS - River Analysis System
HEC-HMS - Hydrologic Modeling System
HEC-ResSim - Reservoir Simulation
HEC-FIA - Flood Impact Analysis
HEC-DSSVue -HEC Data Storage System (DSS) Visual Utility Engine

The plug-in architecture allows the software to work together in a coordinated fashion so that water resources, and economic decisions can be made from the same interface.   Additional plug-ins may be offered by HEC, other USACE organizations, or other non-USACE entities – responsibility for the behavior of each plug-in depends on that plug-in's development team.  The HEC-WAT team can only provide limited support for plug-ins developed by others and the models using them.

Purpose

The purpose of the HEC-WAT software is to help USACE study teams perform the necessary hydrologic, hydraulic, and consequence planning analyses that is required for water resource studies. The HEC-WAT framework allows a multi-disciplinary PDT to perform water resources studies in a comprehensive, systems based approach by building, editing and running models commonly applied by multi-disciplinary teams and saving and displaying data and results in a coordinated fashion.  

The terminology, analysis procedures, and output used by HEC-WAT are consistent with the requirements of USACE guidance and policy. HEC-WAT is designed to facilitate:

• The entry of the appropriate data into each of the individual modeling programs. 
• Trade-off analyses as all study alternatives will eventually be created within the HEC-WAT using consistent schematics, data, and tools. Their results will be easier to compare and contrast thus making the trade-off analysis easier to perform. 
• The analytical process and enhanced coordination among study team members, while producing more consistent results, and shared displays. 
• The definition of alternatives through schematic representations, model identification and sequencing, and tabular formats.
• The study status by reviewing reports in the HEC-WAT. During any given study, the manager or any other member of the project delivery team (PDT) will be able to determine the study status. 
• The reviewing of modeling results at all modeled locations without the direct knowledge of how any of the individual models develop those results. Those attending meetings will be able to see the results directly rather than reading the results from a few locations in a hard copy report or poster. 

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