2.5  General Overview of the CRYSTAL Model

The CRYSTAL Model is an integrated model that makes use of both the Powersim simulation environment and a Microsoft EXCEL Spreadsheet. The model uses 60 years of weekly streamflow data for the four rivers in the model. The model also incorporates operating rules, instream flow requirements, and other weekly operating constraints. Results from the model are generated and stored so that comparisons between runs can me made.

CRYSTAL simulates weekly system operation over a period specified by the user incorporating historic streamflow data and projected water demands. Typically, a user is interested in how the system performs. The model can also be made to run over as many as 60 consecutive years.

The model tracks weekly averaged streamflows, flows into the Green, Cedar, South Fork Tolt, and Sultan Rivers, reservoir releases and elevations, water demands throughout the system, system shortfall, and instream flow characteristics. In total, the model has over 2,500 variables, all of which assume values for each and every week of simulation. If a user investigates one year of streamflow records, they generate some 130,000 variables, all in less than 10 seconds of run time (given a relatively fast PC). The entire record of 62 years can be run in approximately 5 minutes.

Currently the model makes available to the user streamflow data from 1930 through 1993 and demand forecast for the years 2000 through 2040. The model can be viewed as a series of mass balance equations that track water as it enters the system and follows its movement to the distribution system. Additional streamflow data can be added to the model with a minimum of effort and future demands can be easily updated.