The Demand Parcels Creator and the Water Demands Libraries Manager

The Urban Water Consumption estimation is usually performed from the national and municipal water demand values as well as from other regulations and studies related to the subject.

The Water Demand calculation is one of the most important tasks in the design of water distribution and sanitary sewer networks because it is the starting point to define the design flows from which several components of these networks will be dimensioned.

As a way to offer informatics tools that facilitate the design and analysis of urban hydraulic works, we have included in our CLOACAS (SEWERS) and AQUEDUCTOS software a water demand calculation tool named the Demand Parcels Creator, which allows you to define the demand for a “Typical” Urban Parcel or Lot based on its associated land use. This tool uses a series of water demands libraries in order to ease the Water Consumption definition of that parcel.

Here we will give the characteristics of these tools in detail.

The Demand Parcels Creator

The following figure shows the Demand Parcels Creator dialog:


In it are three zones numbered in the above image and detailed below:

1 Add, Delete, and Save Buttons

With these buttons, it is possible to:

  • Create a new Water Demand Parcel. When clicking this button, you must specify a unique name and a description for it in the respective text boxes, as well as indicate its assigned water consumptions or uses, taken from the current Water Demands Library.
  • Remove the current Water Demand Parcel. With a parcel selected on the “Current Parcel” list, pressing the delete button will remove it from the project permanently. Any drawn object associated with the deleted parcel will also be removed.
  • Save changes to the current Water Demand Parcel. When a new demand parcel is created and its properties introduced, you must press this button to ensure that the information is stored before leaving or moving to create a new one. Similarly, when modifications are made, this option should be used.

2 Water Demands Libraries and Associated Water Demand Consumptions

In one Water Demands Library, you will find reference to Water Demand values grouped by Uses or Consumption Types, i.e., there are different consumptions for single and multifamily houses and for shops and restaurants, among others uses. In fact, as we´ll see later, using the Libraries Manager dialog, it is possible to add your own Consumptions Types, based on your preferences as well on your country’s regulations.


When you select a Water Demands Library from the list, you will see below, in the Water Consumptions table, the associated demands. For example, for multifamily housing (apartment buildings):


These Water Consumptions types within each water demand library can be assigned to any Demand Parcel.

3 Water Demand Parcel Data

To define a Demand Parcel, it is strictly necessary to assign it a unique name and at least one water consumption type with the respective quantity. The description, although recommended, is optional.

Having defined its name and description, select the desired group from the Libraries’ list and, from the water consumptions list, select the one which applies, taking into account the characteristics of the typical parcel created.

For example, in the case of a 325 m2 area lot to be used for a single family house, we would have the sequence shown in the following image to create the associated Water Demand Parcel as well as to determine its total water consumption:


1. Click on the button to create a new water demand parcel, and enter its name and description.

2. Select the single family home water demands library and, from the table, select (by clicking on it) the consumption type that suits the characteristics of the lot or parcel (in this case, being the lot area 325 m2, use the third row: extension between 301 and 400 m2).

3. Click on the Add Consumption button in order to assign this water demand to the current Demand Parcel.

4. Enter the water consumption’s associated quantity. In this case, being that its assigned unit is “l/d/Unit,” enter 1 (one house per lot or parcel).

5. Save the changes by clicking the save button.

In this case, the parcel water demand is 1900 l/d (liters per day), as can be appreciated in the right bottom of the dialog.

A more complex example would be the Water Demand Parcel used to model a lot where one hotel with the following characteristics exists:

  • 250 bedrooms
  • 250 m2 of restaurant area
  • Swimming pool with 375 m2 of area
  • 150 m2 green areas

In the following image, we schematize the Water Demands Libraries and the required water consumptions types used to determine this Demand Parcel’s Total Demand:


As you may see, the total Water Demand for the hotel parcel is 141.550,00 l/d.

The Water Demands Libraries Manager

With this dialog, it is possible to modify the water demands values (quantity and unit) as well as to create new water demands libraries tailored to applicable preferences or regulations.

It is accessed by clicking on the button at the bottom left of the Water Demand Parcels Creator:


By default, the water demand libraries included here are based on the provisions defined in Venezuela’s current standards (Gaceta Oficial No. 4,044), but the user can modify them and even create the libraries considered necessary to adapt to any specific regulation.

For a better understanding of using this Libraries manager, we’ll show, with an example, the steps to create a new water demand library containing various uses or consumptions types:

1. Click on the New button and enter a name for the new water demands library. We´ll use: W.D. #1. Now Click on Save Library button.


2. To add water consumptions, click the button New Water Consumption:


In the case shown in the above image, we have set that the water demand consumption for public offices depends on the horizontal area used as such in any building. Therefore, the unit that suits this best is liters per day per square meter.

Other uses to include in our Water Demands Library could be cinemas, theaters, and the like, in which the water consumption is based on a per seat basis. In this case, we would have:


As shown, the Water Demands Libraries Manager is quite versatile to suit any kind of water demand consumption type.

3. Save the changes and you´ll see the new library in the list of available ones:


The Demand Parcels Creator will assume, for the total water consumption calculation of a particular parcel, that the quantity indicated by the user for any water consumption is consistent with the unit specified in the libraries manager.

If, for example, units are l/d/seat, it is expected that the user enters the number of seats in the corresponding quantity field, in order to obtain l/d as the water demand.