**4.2 Models developed by state water agencies in the United States**

CALSIM consists of the generalized Water Resources Integrated Modeling System (WRIMS) combined with input datasets for the interconnected California State Water Project and federal Central Valley Project. The California Department of Water Resources in partnership with the U.S. Bureau of Reclamation developed the WRIMS and CALSIM modeling system (Draper et al., 2004) to replace an earlier California Department of Water Resources model.

The generalized WRIMS and California CALSIM are designed for evaluating operational alternatives for large, complex river systems. The modeling system integrates a simulation language for defining operating criteria, a linear programming (LP) solver, and graphics capabilities. The monthly time step simulation model is based on a LP formulation that minimizes a priority-based penalty function of delivery and storage targets. The LP model is solved for each month. Adjustment computations are performed after the LP solution to deal with nonlinear aspects of modeling complex system operations. A feature called the

software products developed with government funding in the U. S. are made accessible to the professional water management community without charging a fee for the software.

However, reservoir/river system models are developed throughout the world. Three examples of the many non-U.S.-based modeling systems are cited as follows. The proprietary MIKE BASIN, WEAP, and OASIS software products were developed and are marketed by organizations that provide consulting services in applying the models. The developers and others have applied the models to reservoir/river systems throughout the

The Danish Hydraulic Institute (http://www.dhi.dk/) has developed a suite of models dealing with various aspects of hydraulics, hydrology, and water resources management. MIKE BASIN, the reservoir/river system component of the DHI family of software, integrates geographic information system capabilities with modeling river basin management. MIKE BASIN simulates multiple-purpose, multiple-reservoir systems based on a network formulation of nodes and branches. Time series of monthly inflows to the stream system are provided as input. Various options are provided for specifying reservoir

The Water Evaluation and Planning (WEAP) System developed by the Stockholm Environmental Institute (http://www.weap21.org/) is a reservoir/river/use system water balance accounting model that allocates water from surface and groundwater sources to different types of demands. The modeling system is designed as a tool for maintaining water balance databases, generating water management scenarios, and performing policy

The Operational Analysis and Simulation of Integrated Systems (OASIS) model developed by HydroLogics, Inc. (http://www.hydrologics.net/) is based on linear programming. Reservoir operating rules are expressed as goals and constraints defined by the model-user using a patented scripting language that is similar to the Water Resources Engineering

CALSIM consists of the generalized Water Resources Integrated Modeling System (WRIMS) combined with input datasets for the interconnected California State Water Project and federal Central Valley Project. The California Department of Water Resources in partnership with the U.S. Bureau of Reclamation developed the WRIMS and CALSIM modeling system (Draper et al., 2004) to replace an earlier California Department of Water Resources model. The generalized WRIMS and California CALSIM are designed for evaluating operational alternatives for large, complex river systems. The modeling system integrates a simulation language for defining operating criteria, a linear programming (LP) solver, and graphics capabilities. The monthly time step simulation model is based on a LP formulation that minimizes a priority-based penalty function of delivery and storage targets. The LP model is solved for each month. Adjustment computations are performed after the LP solution to deal with nonlinear aspects of modeling complex system operations. A feature called the

Simulation Language (WRESL) in the WRIMS-CALSIM model discussed next.

**4.2 Models developed by state water agencies in the United States** 

**4.1 Models developed by international research and consulting organizations** 

operating rules and allocating water between water users.

world.

analyses.

Water Resources Engineering Simulation Language (WRESL) was developed for the model to allow the user to express reservoir/river system operating requirements and constraints. The user-supplied statements written in the WRESL language are used by the model to define the LP formulation. Time series data are stored, manipulated, and plotted using the Hydrologic Engineering Center (1995, 2009) Data Storage System (HEC-DSS), which is also used with WRAP, discussed later, as well as with HEC-ResSim and other HEC simulation models.

The Texas Water Development Board (TWDB) Surface Water Resources Allocation Model and Multiple-Reservoir Simulation and Optimization Model simulate and optimize the operation of an interconnected system of reservoirs, hydroelectric power plants, pump canals, pipelines, and river reaches using a monthly computational time step. The daily time step MONITOR also simulates complex surface water storage and conveyance systems operated for hydroelectric power, water supply, and low flow augmentation (Martin, 1983, 1987). The TWDB has adopted the WRAP modeling system, described later, for statewide and regional planning studies conducted in recent years, replacing these early TWDB models.

The early TWDB models, original California Department of Water Resources model, and the original versions of HEC-PRM and MODSIM discussed later are all based on the same network flow programming solution algorithm. An early version of WRAP was also developed using the same algorithm, but another simulation approach was actually adopted for WRAP. The original solution algorithms in HEC-PRM and MODSIM were later replaced with much more computationally efficient network flow programming algorithms.
