**5. Selected state-of-the-art generalized modeling systems**

The four user-oriented generalized models in Table 1 provide comprehensive capabilities for a broad spectrum of river/reservoir system modeling applications. ResSim, MODSIM, WRAP, and RiverWare are distinctly different from each other. However, as a group, the four alternative modeling systems are representative of the current state-of-the-art of professional practice in the United States in analyzing complex problems and issues in managing rivers and reservoir systems.

The Corps Water Management System (CWMS) is the automated information system used by the USACE nationwide to support real-time operations of flood control, navigation, and multiple-purpose reservoir systems (Fritz et al., 2002). The CWMS is an integrated system of hardware and software that compiles and processes hydrometeorology, watershed, and project status data in real-time. A map-based user-friendly interface facilitates modeling and evaluation of river/reservoir system operations. CorpsView, a spatial visualization tool developed by the HEC based on commercially available geographic information system (GIS) software, provides a direct interface to GIS products and associated attribute information. The CWMS combines data acquisition/management tools with simulation models which include HEC-HMS (Hydrologic Modeling System), HEC-ResSim (Reservoir Simulation), HEC-RAS (River Analysis System), and HEC-FIA (Flood Impact Analysis).

The HEC-5 Simulation of Flood Control and Conservation Systems model (Hydrologic Engineering Center 1998) has been used since the 1970's in many USACE and non-USACE studies, including investigations of storage reallocations and other operational modifications at existing reservoirs, feasibility studies for proposed new projects, and support of real-time operations. The HEC plans to eventually replace HEC-5 with HEC-ResSim. However, HEC-5 is still available at the HEC website and continues to be applied

HEC-5 simulates multiple-purpose reservoir system operations for inputted unregulated stream flows and reservoir evaporation rates using a variable time interval. A monthly or weekly time step may be used during periods of normal or low flows in combination with a daily or hourly time step during flood events. HEC-5 makes release decisions to empty flood control pools and to meet user-specified diversion and instream flow targets based on reservoir storage levels and stream flows at downstream locations. Flood routing options include modified Puls, Muskingum, working R&D, and average lag. Optional analysis capabilities include computation of expected annual flood damages and water supply firm

The HEC Prescriptive Reservoir Model (HEC-PRM) was developed in conjunction with studies of reservoir systems in the Missouri and Columbia River Basins. Later applications include studies of systems in California, Florida, and Panama (Draper et al., 2003; Watkins et al., 2004). HEC-PRM is a network flow programming model designed for prescriptive applications involving minimization of a cost based objective function. Reservoir release decisions are made based on minimizing costs associated with convex piecewise linear penalty functions associated with various purposes including hydroelectric power, recreation, water supply, navigation, and flood control. Schemes have also been devised to also include non-economic components in the objective function. HEC-PRM applications to

The four user-oriented generalized models in Table 1 provide comprehensive capabilities for a broad spectrum of river/reservoir system modeling applications. ResSim, MODSIM, WRAP, and RiverWare are distinctly different from each other. However, as a group, the four alternative modeling systems are representative of the current state-of-the-art of professional practice in the United States in analyzing complex problems and issues in

by various model-users.

date have used a monthly time interval.

managing rivers and reservoir systems.

**5. Selected state-of-the-art generalized modeling systems** 

yields.

The four modeling systems were developed by water agencies and university research entities and have been extensively applied in both the U.S. and other countries. The software was developed for application by model-users other than the original developers and is accessible by water management professionals throughout the world. The ResSim, MODSIM, and WRAP software and documentation can be downloaded free-of-charge at the websites listed in Table 1. RiverWare is a proprietary software product which is available for a licensing fee as described at the website shown in Table 1. The four software packages all run on personal computers operating under Microsoft Windows and all have also been executed with other computer systems as well. RiverWare was developed primarily for Unix workstations though it also is used on personal computers with Microsoft Windows.

The four alternative modeling systems and their predecessors have evolved through many versions over more than twenty years of research and development, with new versions being released periodically. The modeling capabilities provided by each of the models have changed significantly over time in the past and continue to be improved and expanded.
