Understanding Demand Allocation

Step-by-step:

Demand Allocation in InfoWater Pro allows users to calculate, distribute, and manage demands in a network model. The evolution of geographical information systems has led to the availability of comprehensive data sets, including land use, water meter locations, and demand area polygons. These data, when properly processed, can be effectively used to create system demands throughout a hydraulic network model.

As a pre-allocation task, GIS data sets are imported, such as all meter records or polygon layers. Each meter in the model needs a spatial location. Use geocoding sources to get this data and join it to a billing systems database to allocate demands. Customer or meter billing data, with distinct X and Y coordinates, provide an accurate measure of localized demands imposed on the water distribution system.

Demands are allocated using the Demand Allocation Manager. There are several distinct allocation methodologies that can be used for the allocation process:

1. Polygon Intersection: uses spatial intersection of a demand class categorization polygon with demand area polygon coverage to determine the nodal demand allocation. The InfoWater Pro Allocator considers the demand area polygons as the Primary polygon coverage, while the classes/classifications layer is represented as a Secondary polygon definition. During the allocation process, the program intersects polygons of the Primary layer with those of the Secondary layer. Before using the Allocator tool, all polygons must be registered as their respective layers.
2. Polygon Extraction: used when a polygon coverage has already been intersected with a land base or other classification polygon boundary and has been imported into InfoWater Pro and registered as an InfoWater Pro Allocator layer. With this method, the total demand at each junction node is calculated by summing all the individually assigned demand categorization polygons into a single demand field.
3. Meter Summation: used when customer billing data is available. This allocation method uses a primary layer that represents the demand (or service) area polygon coverage and a meter layer to represent meter data.
4. Closest Junction: used when customer/meter billing data is available. For this method, the meter layer needs to be configured so the Demand Field and, optionally, the Usage Type Field contain demand and water duty data at each of the meters. This method provides a means to assign demands to the junctions closest to the water meter. For each of the junction nodes, the demands are then summed up to establish localized demands imposed on each of the nodes.
5. Closest Pipe: works with customer billing data and also requires meter configuration. The Demand Field and optional Usage Type Field contain demand and water duty data at each of the meters. A Spatial Join or Local Search option is also available. For each of the meters, the closest pipe is first located. The meter demands are then assigned to either the closest upstream or downstream nodes for each of the selected pipes. The demands routed to the nearest junction may be assigned in full, or they may be split in a weighted fashion between the two nodes connecting the pipe. For each of the nodes, all contributing meters are summed to represent the total demand imposed on that node.
6. Meter-Junction: similar to the closest junction method, but meters are allocated to junction nodes. In other words, it is a user-defined version of the closest junction method, which generates meter demands automatically. For the meter-junction method to be employed, the user must specify which fields possess or will possess the junction IDs.
7. Meter-Pipe Allocation: similar to the closest pipe method, but meters are allocated to pipes. It is a user-defined version of the closest pipe method. User must specify which fields possess or will possess the pipe IDs.

Depending on the allocation method used, relevant settings are available in the Demand Allocation Manager.

The Usage Data tab of the Demand Allocation Manager allows for usage or land use data to apply demands to different demand categories. Users can alter customized water duty factors to allocate demands to a specific pattern or field.

Once the demand allocation is performed, the results can be viewed in the Allocation Report & Water Duty Calculator. In this report, users can compare the allocation results with usage or land use data.

At this point, the Meter Assignment tool is used to view which meters are currently assigned to certain pipes or junctions, and to assign them. In the map, review where meters are assigned, indicated by red lines. If any meters do need to be reassigned, they can be reallocated using the Meter-Junction or Meter-Pipe methods with the adjusted data.