Frequently asked questions on the Battle of Water Networks District Meter Areas (BWNDMA)


Q1: What does "approach this number from the top will be favored" means? Do you mean 15 DMAs is better than 14 and 16?

A1: For the water utility a solution with 16 DMAs will be better than a solution with 17 DMAs because is closer to their objective that is 15 DMAs. Solutions with 14 DMAs or less will not be allowed, a solution will be considered valid only if it has 15 or more DMAs. The problem description was updated considering this on Feb 15th.


Q2: How would you evaluate "similar demand" for the DMAs?

A2: The similarity in the demands will be assessed through the standard deviation of the volume of water that enters a DMA during the week. The problem description was updated considering this on Feb 15th.


Q3: Is it intentional that in the initial model, one of the FCVs (Mamatoco_FCV) is closed and the rest are completely open?

A3: The initial model corresponds to the configuration of the network in 2014, and does not necessarily function correctly for the hydraulic conditions of the network in 2022.


Q4: What can be done with the existing FCVs in the model? Can I modify their initial states? Can I modify their settings?

A4: The initial state and setting can be changed with no additional cost during the rainy season. If there are changes in either of these variables during the dry season, they will be tabulated in in the indicator OpCHnet. The problem description was updated considering this on Feb 15th.


Q5: When substituting one pipe for a new pipe, what changes should be made to the minor loss coefficient? In the new pipe, will the value be null compared with the given coefficient or will the value be equal to the previous pipe?

A5: The value of the loss coefficient for a new pipe should be 0.02 per meter of pipe length. The problem description was updated considering this on Feb 15th.


Q6: Can I install new pipes as a substitution to any part of the model, or can I only substitute pipes whose original diameter is 152 mm?

A6: Only pipes with an original diameter greater than 152 mm can be replaced, the minimum diameter to be installed is 203 mm. Any pipe of the system can be closed to create DMAs but only the ones with higher diameter than 152 mm can be replaced or can be installed a parallel pipe.


Q7: Is it possible to define a DMA without installing a PRV at the entrance, or would it be necessary to define a fictitious PRV with a setting that avoids actual PRV performance?

A7: To define a DMA, a PRV must be installed at the entrance. This may have a setting that ensures no performance at any moment during the simulation. The problem description was updated considering this on Feb 15th.


Q8: Can a DMA contain one (or multiple) of the network's tanks?

A8: A DMA can contain one (or multiple) of the network's tanks.


Q9: Given that some consumers are directly connected to the main lines, is it possible to leave certain consumers isolated outside of the DMAs? How can I compute the effects of these consumers on DMAs and maintain uniform demand?

A9: Some consumers can be isolated from the DMA given their position in the network. These isolated nodes cannot exceed 55 (equivalent to 0.05% of the nodes in the network). These nodes will not be taken into account in the relation of demands or in the distribution of the DMA. The inp model and the problem description was updated considering this on Feb 15th.


Q10: In the DMA configuration criterion, you list the number of DMAs and their uniformity, how are you going to compute these criteria together?

A10: These criteria will be evaluated independently of the number of DMAs and their relation. The relevant equations are listed in the problem description. The problem description was updated considering this on Feb 15th.


Q11: How do you consider pressure restrictions in nodes that stay outside of DMAs?

A11: Maximum pressure restrictions apply only to nodes inside of DMAs. Minimum pressure restrictions apply to all nodes in the network.


Q12: If I encounter nodes whose pressure restrictions are impossible to fulfill, what can I do about these nodes?

A12: At only three nodes, negative pressures are allowed; the pump suction nodes. The inp model was updated considering this on Feb 15th.


Q13: Can controls be defined for any element of the network?

A13: Controls can be defined for any element of the network.


Q14: Can pipes be opened or closed during the simulation? Can I change the installed FCV settings to control tanks? What about PRV? Can I change the speed of the pumps?

A14: During the simulation, pipes cannot be opened or closed, and FCV and PRV settings cannot be changed. Changing of pump motor velocities is also not permitted. These changes are only allowed between the dry and rainy seasons and will be evaluated through the indicator OpCHnet.


Q15: The model has some closed pipes, should they stay closed?

A15: The status of the pipes can be changed with no additional costs for the rainy season. Modifications in status from rainy to dry season will be assessed through OpCHnet index.


Q16: Do all demands nodes must be included in a DMA? Can non-demand nodes be outside of a DMA?

A16: Not all demand nodes must be included in a DMA. The water utility considers that a maximum of 55 demand nodes can be outside of DMAs due to its physical isolation. Non-demand nodes can be outside a DMA.


Q17: There are seven nodes left without any elevation. Is this the correct configuration of the system?

A17: There are only five nodes with zero elevation: three pump suction nodes and two reservoirs that represent the aquifer extraction points. The inp model was updated considering this on Feb 15th.


Q18: In section 4.1.5 - is figure 1 an example or this is you want the network to work? Is this a binding configuration? It says that ". The Figure 1 presents the desired supply configuration regarding the main pipes system of E-Town.". Is "desired" means mandatory?

A18: The figure 1 is not a binding configuration, is just some guidance about the network functioning but if you want to propose another configuration is perfectly valid.


Q19: In section 4.1.1 refers to the 55 demand nodes that can be outside a DMA. Is the 15m pressure constraint apply to these nodes? If you were referring to the nodes connected by pipe 1733 then there are more than 55 demand nodes at this location.

A19: The 15 m pressure constraint apply to all demand nodes (whether they are inside a DMA or not). We are referring to some nodes that are disconnected from other nodes, such as node 6173.


Q20: In section 4.2.1 it says that "... the replacement of pipes is restricted to pipes with diameters larger than 152 mm". Can a parallel pipe be placed to such a pipe? If so, can the old pipe be closed?

A20: No modifications to pipes with a diameter of 152 mm or less are allowed. This because the water utility considers that the disruption and reconstruction of the pavement roads is not worth the modification of the system.


Q21: In 4.1.1 the formulas for Vin and Vout are the same, can you clarify the difference?

A21: The equations are the same but the definition is different. Vin corresponds to the volume that enters to a specific DMA and Vout is output volume that leaves a DMA to supply another DMA.


Q22: In 4.2.2 it states the maximum PRV installed at the entrances to a DMA is 2. What about exit connections to other DMAs (supplying other DMAs)?

A22: Each DMA can have a maximum of two entrances. If one particular DMA has 5 PRVs, only two can correspond to entrances and the other ones would be connections to other DMAs (entrances to the other DMAs).


Q23: Can new pipes be installed in the layout of existing pipes but not be connected to all nodes in the path (option 1 in the figure below) or must they be installed exactly between existing nodes (option 2)?

A23: The pipes must be installed as the option 2.


Q24: What diameter of PRV should I install for pipes in which the inside diameter does not coincide with the diameter from the valve table?

A24: In the case that the exact diameter is not listed, use the next largest diameter available in the table.


Q25: Can I install a PRV in any pipe, independent of its size?

A25: Yes, PRVs can be installed in any pipe regardless of diameter.


Q26: Should I consider the model as-is, or can I include a Check Valve in some elements of the system? In the case that I can add CVs, can they only be added at tanks or can they be added in any part of the network?

A26: Check valves can be added at no additional cost in any pipe within the system.


Q27: When a new PRV is added we will have to add a new junction to connect the PRV to (it will not replace the pipe it is on), right?

A27: Yes, you must add a junction at the end of the pipe and install the PRV.


Q28: Are we allowed to provide/define rules for tank operation throughout the year (e.g. opening/closing pipes connected to tanks during the simulation)?

A28: No, you can open/close pipes between the two season of the year but no during the simulation.


Q29: We would like to disconnect some tanks from network, what can we do?

A29: You can install new bypass pipes in order to disconnect the tanks from the network. In this way, the option 1 of the graph shown in answer 23 is permitted.


Q30:  In the problem description in Table 2, a maximum flow has been defined for Mohan pump station in dry season (206 L/s) while there are two pumps at this station. This 206 L/s is the total sum of both pump capacities or it is the maximum flow for each of them?

A30:  The 206 L/s is the total sum of both pump capacities in Mohan station.