Demand allocation in WaterGEMS

If you had the demand data in the form of shapefiles for the zones, then you could use the tool called Loadbuilder. See the below information on that.

http://communities.bentley.com/products/hydraulics___hydrology/w/hydraulics_and_hydrology__wiki/10862.how-do-each-of-the-loadbuilder-methods-work

With the demands in the excel sheet, you should have demands distributed to all the nodes. And then import them using Modelbilder.

http://communities.bentley.com/products/hydraulics___hydrology/w/hydraulics_and_hydrology__wiki/3100.importing-demands-from-a-spreadsheet-tn  

Here is another relevant article in our wiki:

Distributing a lump sum demand over a large area

As Sushma said, there are many ways to spatially allocate demands - it depends on what data you have and your needs. You mentioned that you have demands per sub-zone in a spreadsheet, but how exactly does that look like? Does a "subzone" in your spreadsheet represents a total demand for a polygon area that encompasses multiple demand nodes? How is that polygon represented in the spreadsheet? Do you have a polygon shapefile of these zones, to go along with it?

Regarding service areas - you can certainly manually draw polygons, but they'll need to have a field in the metadata (database) that defines the ElementID of the respective node (this is the ID seen in junction properties, for example). The easiest method is to use the Thiessen Polygon tool in WaterGEMS to generate the service area polygons for you, and assign them to the respective node's ElementID.