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There is a great deal of good documentation in the Help documentation on this subject. You can find this documentation by goint to Help > Search for Loadbuilder. You will find some good information there. Additionally, below is a brief summary of the different Loadbuilder Methods and how they work.
Billing Meter Aggregation: The service area is typically generated using the Thiessen polygon tool. Whatever billing meter points fall within the service area will be added as a demand to that service area’s corresponding junction.
Billing Meter Aggregation Example Files
Nearest Node/Pipe: Only need point or polygon shapefile. For polygon, it will use the centroid to calculate proximity. The demand will be added to the junction that is closest to that point shapefile/centroid or to the junction adjacent to the pipe, if using nearest pipe.
Note: If you choose to use All Pipes and All Nodes for the layers, this will include inactive elements. If you do not want inactive elements, create a selection set and use this for Pipe Layer and/or Node Layer.
Unit Line: Not GIS based. Uses k factors. It can account for unknown demands (leakage/unmetered.) See more here:
How does the Unit Line Loadbuilder method work?
Equal Flow Distribution: Uses polygons with single demand values. The model nodes that fall within the polygon will get an equally distributed portion of the demand. For example, if the polygon represents 100gpm and two junctions fall within it, they’ll get 50gpm each.
Equal Flow Distribution Example files
Proportional Distribution by area: Uses a service area layer (typically generated using the Thiessen polygon tool) which represents the service area of each junction, along with billing meter polygons with a single demand value. The demand assigned to the junction is based on how much of the flow polygon is overlapping it’s service area. For example, if 25% of the 100gpm demand polygon falls within a junction’s thiessen polygon, then that junction will get 25gpm:
Proportional Distribution by Area Example
Proportional Distribution by population: Requires Thiessen polygon (Service Area Layer), lump-sum demand polygon (Flow Boundary Layer) and population polygon. This method divides the lump-sum flow among the service polygons based upon one of two attributes of the service polygons: the area or the population. The greater the percentage of the lump-sum area or population that a service polygon contains, the greater the percentage of total flow assigned to that service polygon. Note: The flow boundary layer should be a polygon shapefile that is divided into areas or zones (zone A, zone B, etc..) and will include a flow field that has the overall flow for that particular zone. For this method it helps to think of the Service Area Polygons layer as a cookie cutter that is going to be pressed through the population layer and the flow boundary layer. It’s a combination of the weighting of the population layer and zone flow layer data that will determine the loads that are assigned to your service area polygon layers.
Proportional Distribution by Population Example
Projection by Land use/Load Estimation by Land Use: Uses a Thiessen polygon (service area layer) and layer of polygons that represent billing meter areas and their associated land use type. The user enters a guess of how much demand per acre is associated with each land use type and based on each polygon’s size, it will then have a specific demand value. This is distributed to the junctions in the same way as with Proportional Distribution By area. In the image below the portions of the purple land use areas that intersect the red thiessen polygon service areas would determine the value of the demand that is applied to the nodes (junction, manholes, catchbasins, etc...).
Projection by Land Use Example
Projection by Population/Load Estimation by Population: Just like above, except the user is making a guess at how much demand he thinks there is per capita, for each land use type. There is a field in the shapefile for population density, so based on the guess, each polygon will have a resulting demand value, which is distributed to the junctions in the same way as with Proportional Distribution By area.
Projection by Population Example