8 Model Description

The goal of this model is to illustrate the value and opportunities of a regional approach to water management, particularly in meeting the needs of both fish and people. Answering this challenge is becoming increasingly important as instream requirements are modified to address the salmon listing on the Endangered Species Act. The CRYSTAL model simulates water system response to different scenarios (e.g., How will increased flow requirements for the salmon affect the reliability of the urban water supply? When might water use curtailments be necessary? Can water in one basin be used to support fish production in another?). With such tools, regional decision-makers and the public can better understand the consequences of important policy and infrastructure decisions.

Predicting the availability and potential uses of water in the Puget Sound is an important component of the PRISM project. The Department of Civil and Environmental Engineering is creating a regional model of water supply and instream flow needs of the cities of Seattle, Tacoma, and Everett. This model integrates the separate water supply systems to better utilize existing regional resources, viewing the Puget Sound as one watershed.

How CRYSTAL was created

Existing models of the Seattle and Tacoma water supply systems were translated and enhanced. Models of the Everett water supply system and the Snohomish Hydropower system were also created. These models were combined to create the CRYSTAL model: a dynamic simulation model that operates on a weekly time-step while simulating water supply operations. Operations of interest include weekly reservoir operating policies, municipal and industrial water supply diversions, and instream fish flow provisions.

CRYSTAL's Future

The water resources model will be integrated with the PRISM model using a mass balance approach. The model will use data generated by the atmospheric MM5 model and the hydrological DHSVM model to predict flows on the major water supply rivers (e.g., Cedar, Green, Snohomish). These flows will be used to determine the probable amount of water that will be available to meet urban demands and fish flow requirements over a multi-year period. The water resources component of PRISM will also work with the urban planners to determine if the existing water distribution system will be adequate to meet regional population growth in those areas where it is most likely to occur.

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