Mark Anderson, a CH2M HILL senior technologist and project manager, will be presenting on this topic, co-authored by Glen George (City of Tacoma, Washington), Chistopher Johnson (City of Tacoma, Washington), Baha Mirghani (CH2M HILL), and Mark Anderson (CH2M HILL), at the World Environmental and Water Resources Congress (EWRI) in Albuquerque, New Mexico, Monday, May 21, from 9:30 – 11:00 am.

Tacoma Water is a public utility that serves the Tacoma, Washington, metropolitan area, a direct service population of 97,000, in addition to multiple water agencies in the southern Puget Sound area. Tacoma’s water supply comes from two primary sources, groundwater wells and the upper portion of the Green River watershed. Howard Hanson Dam impounds a multipurpose storage reservoir on the Green River that is partially available for municipal supply on a seasonal basis.

Tacoma Water expects to enter long-term water supply agreements in the near future. An analysis of yield and associated uncertainties was required in order to maximize the commitment of water in these future agreements, specifically for Green River diversions, Howard Hanson reservoir storage, and South Tacoma wellfields.

To meet this need, CH2M HILL developed a Voyage™ Water Resources Decision Support Model that can simulate the behavior of the portfolio supply system for decision-making. The combined supply system includes pumped groundwater, storage and run-of-river conditions that can vary from day to day. A dynamic, object-oriented system model was built to evaluate yield and simulate daily operations during the municipal storage season. Complex water rights and allocation rules were included in the operations model. Multiple climate scenarios, corresponding to varied projected carbon emissions, were also included to facilitate long-term planning.

As a result of this work, the risk-adjusted average summertime yield increased 19% over previous, more conventional analyses that did not evaluate daily operations or explicitly address reliability. This result also improved reliability for decision-making with robust statistical support. The operational model is currently being enhanced to provide seasonal decision support for multiparty adaptive management of reservoir storage and continued investigation of current and future supply portfolio and treatment operations under varied climate conditions.

Find out more about the model, decision-making process, and results during my World Environmental and Water Resources Congress presentation on May 21.

Mr. Anderson is a senior technologist and project manager based in Portland, Oregon. He has more than 12 years of experience in urban infrastructure systems planning, design and construction and has performed a variety of engineering and project management roles for public and private clients. He is the Global Technology Leader for Resource Systems Analysis.