Philosophy

HEC-WAT (Watershed Analysis Tool) is a model integration tool, designed to facilitate a multi-disciplinary team's evaluation of the performance of water resources projects in a systems context. The HEC-WAT software empowers a multi-disciplinary team with a common graphical user interface (GUI) and computational platform which leverages a powerful array of plugin software, including HEC-HMS, HEC-ResSim, HEC-RAS, and HEC-FIA. The software also provides common data storage, data management, mapping, graphics, and results reporting capabilities. HEC-WAT serves as a hydrologic and hydraulic studies counterpart to the Corps Water Management System (CWMS) HEC-RTS software, which fulfills a similar role for real-time water management and flood forecasting.Many teams using HEC-WAT reduce the time required for initial model development by repurposing the CWMS models developed for real-time water management, which exist for most watersheds where USACE is involved in water management decisions.

The United States Army Corps of Engineers (USACE) is charged with managing the nation's water resources - requiring studies of proposed actions or changes in the watershed, during which product delivery teams (PDTs) of engineers, planners, economists, and others work together to define the problems, issues, and opportunities in the study scope, and then evaluation of impacts to inform the decision making process. These studies often require hydrologic, hydraulic, economic, environmental, and social impact analyses - requiring extensive coordination, file/data sharing, logistics, reporting of modeling results, and status reporting between modeling teams, as well as project management staff.

HEC-WAT is designed to facilitate:

• Entry of the appropriate data into each of the modeling programs is incorporated into the HEC-WAT framework.
  
• The analytical process and enhanced coordination among study team members, while producing more consistent results and displays.
  
• The definition of alternatives through schematic representations, model identification and sequencing, and tabular formats.
  
• The assessment of study status by reviewing HEC-WAT outputs and reports.
  
• The review of modeling results at all modeled locations without the direct knowledge of how the individual models generate those results. Those attending meetings can view the results system-wide rather than reading the results for a few locations in a hard copy report or poster.

Supporting USACE Flood Risk Management Policy

USACE flood risk management (FRM) policy requires that USACE analyze risk and uncertainty in a systems-based life-cycle approach to flood consequences. The system response must be captured such as showing how the performance or likelihood of failure or one system or project in a watershed may have impacts on other locations and projects - such as a sequence of levee systems along a river where the failure of one will result in changes in the loading of another. HEC-WAT includes functionality in the Flood Risk Analysis compute option to analyzes complex riverine systems for both FRM impacts and other impacts, while implementing the flood risk management and systems requirements, thus enabling teams perform plan formulation or system performance analyses in alignment with this guidance. The terminology, analysis procedures, and output for the FRA compute option are consistent with USACE guidance and requirements.

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Features

This central framework will allow study team members to: load GIS (geographic information system) based layers shapefiles and DEMs (digital elevation model); establish stream networks and schematics; identify locations (common computation points) where models share information; define the modeling software applications and their compute sequence order; import existing models; and, develop new models. The HEC-WAT framework also aids in organizing and developing study alternatives; provide the ability to access and execute modeling software applications directly; and, allows users to view and compare alternative results. The following is a description of the major capabilities of HEC-WAT:

User Interface

The HEC-WAT program provides a Graphical User Interface (GUI) that streamlines and integrates the water resource tools commonly applied by USACE district and division offices so that more efficient and coordinated modeling and planning may be performed. The HEC-WAT framework enables a coordinated approach for a user to create and use a water resources study within this environment, providing dialogs for file management, data entry and editing, and viewing output. The interface provides for the following functions:

• File Management
• Data Entry, Importing, and Editing
• Tabulation and Graphical Displays of Results
• Reporting Features

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Plug-In Architecture

HEC-WAT does not replace existing software but rather provides a framework that allows existing software to work together in a coordinated manner. The integration of the individual pieces of software within the HEC-WAT framework uses a "plug-in" architecture, eliminating the requirement for code changes in HEC-WAT to support additional software or upgrade versions of software used within HEC-WAT. The plug-in concept supports additional plug-ins being developed for software that might be included in the HEC-WAT framework in the future. HEC-WAT provides the analysis framework and the individual pieces of software provides the technical mechanics within the framework (i.e., editing, reporting capability, computational analyses, etc.). The individual pieces of software do not contain any HEC-WAT specific code.

The primary set of software includeed in the HEC-WAT framework is:

• HEC-HMS (Hydrologic Modeling System)
• HEC-RAS (River Analysis System)
• HEC-ResSim (Reservoir System Simulation)
• HEC-FIA (Flood Impact Aanalysis)

Additional plugins have been developed for use within HEC-WAT and are included in the standard HEC-WAT release, and study teams have developed custom plugins for their unique needs.

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A Systems-informed Approach to Modeling Risk and Uncertainty

The HEC-WAT framework also includes a flood risk analysis (FRA) compute option, which provides tools that will help a planner address the issues faced during a USACE planning study, and specifically addresses the requirement for systems, watershed, and uncertainty analyses. The FRA compute builds on the HEC-WAT framework to provide a convenient method of implementing a nested Monte Carlo analysis across multiple models for assessing flood risk management as well as other water resources mission areas of USACE - allowing a PDT to perform plan formulation or system performance analyses while incorporating requirements to incorporate risk and uncertainty in their decision-making.

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