Demand Allocation for the Gwinnett County, GA, Hydraulic and Water Quality Model Setup

This paper presents the methodology used for demand allocation to be used for setting up a hydraulic and water quality model for the water network system of a major metropolitan area in Georgia. The Gwinnett County Department of Water Resources (GCDWR) provides potable water to a population in excess of 650,000. The GCDWR operates approximately 3000 miles of water lines, 11 distribution storage tanks and two water treatment plants — the 150 MGD Lanier Water Filtration Plant and the new 75 MGD Shoal Creek Filter Plant. The new filter plant is currently supplying potable water to the Lanier Filter Plant's clear well. In 2005–06 Envirosoft-Engineering & Science Inc. (now Halcrow Inc.) developed a hydraulic and water quality model that can simulate the operation of the Gwinnett water supply system. This model can be used to assist the GCDWR in predicting hydraulic performance, disinfection needs, and the impacts of future major system expansions. The water demand assigned to the model was based on the GCDWR water billing records for July 2005. To allocate the demand, the project team used the georeferenced water meter data that relates each user account to a physical location. The GCDWR has georeferenced more than 98 percent of its customers in this way. An incremental demand of 16 percent was added to each node in the model to account for physical losses and for customers whose meters are not georeferenced.