Problem

How can I distribute loading to manholes based on areas of different population types (such as wards) that have different consumption per person per area?

Solution

First, use the Thiessen Polygon tool to generate service areas for each manhole. If you want to ensure that service areas associated with a manhole stay within the respective type/ward, select "Polygon Boundary" and select the shapefile that contains the polygons with the different population types (such as the different wards). Attach both shapefiles as a background layer for visualization.

Next, use Load Estimation by Population method in Loadbuilder (Tools > Loadbuilder), with the Thiessen polygon selected as the Service Area Layer.

• For the Population Layer, select the shapefile containing the different population types/wards (the same shapefile you used in background)
• For the Population Density Type Field, select the field in your shapefile that designates the different type of population (for example Ward A, Ward B, etc).
• Next, for the Population Density Field, select the field in your shapefile that contains the population density (pop/area) and respective unit.
• Then, enter the respective load densities in the table at the bottom.

Loadbuilder will distribute loads to manholes according to the area of the respective service area layer along with the population density and load density of the overlapping population layer.

For more instructions/training on this subject, see the Water Fundamentals training workbook (page 314) and at ~29 minutes in this video from our training course: WaterGEMS/WaterCAD Fundamentals Part 19: Building Models from Geospatial Data

See Also

Converting Model Elements to Shapefiles

How do each of the Loadbuilder methods work? 

Import loads from shapefile containing polygons with land use type and total population