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Water Distribution System Hydraulic Model Calibration and System Evaluation Report Chapter 4 – Water Demand Allocation December 2019 P05049-2019-000 Page 11 CHAPTER 4 WATER DEMAND ALLOCATION A crucial element of water distribution modeling is determining accurate, representative water demands and the spatial distribution of these demands throughout the water distribution system because water demand is the driving force behind the hydraulic dynamics of a water distribution system. Water demand allocation is the process of accurately distributing these water demands to the correct points of consumption within the model. 4.1 Base Demand Determination of the demands of a water system is not as straightforward of a process as collecting the physical data of the system. For the Arden Hills water distribution hydraulic model, data from approximately 2,767 meter billing records were analyzed over the months of January 2018 through December 2018 to determine the base demand for the water distribution system. The monthly usage data was converted to average consumption rate in gallons per minute (gpm). The consumption rates were then spatially distributed as water demands in the system using the software InfoWater Demand Allocator®. This software uses GIS technology to assign geocoded consumption data to their designated location within the water distribution system. For each water meter record, advanced search algorithms in the demand allocation software were used to distribute the water demands to the closest pipe. The water demands were then allocated to the nearest node at the end of the pipe. For each node within the model, all of the contributing water demands were summed to represent the total demand imposed on that particular node. When comparing the total demand within the system from the meter billing record data to the meter records from the 3 bulk connections to Roseville, and taking into account the change in storage within the distribution system, there were still minor disagreements between the data records that needed to be resolved. These disagreements are partially due to unaccounted for water (UFW) loss. The most common UFW losses include leakage, errors in measurements, and unmetered usage. In order to resolve inconsistency between water production records and computed customer usage, a top-down determination of the water production and a bottom-up demand determination from the meter billing records was performed. The goal of these analyses is to balance water production and demands at the nodes within the model, and thereby create a mass balance of the water production, storage, and demands within the model of the distribution system.