Greetings,
I am modeling a primary irrigation network in WaterGEMS, whereby a limited number of nodes supplying green areas are open for one hour, then closed and a further group of nodes of around the same total demand is open for the same period and so on, for a total irrigation schedule of 10 hours per day.
The project site consists of a hilly area in its middle, with the level difference at the top being around 10-12 meters higher than the surrounding low areas. The pumping station supplying the entire system is at the lower level of the site where the supply line is located. The pump used to supply the model is a VSP with a constant target HGL.
While the pressure variations throughout the network are acceptable and do not pose much concern, it is at the top of the hill that I am getting problems: The minimum required pressure to operate irrigation emitters (sprinklers, bubblers, etc) taking into account headlosses is around 4- 4.2 bars, so I have set my pump head at 6 bars to attain this pressure. This is happening, but when the time comes to activate the nodes demand at the high area, I am getting a sharp drop in the pressure at the time the node is active, with the drop exceeding 4 bars. This is obviously getting below the pressure required for proper irrigation supply.
I have tried and checked everything to make sure there was no choking point such as very small diameters somewhere, but it doesn't look there was any.
I would appreciate any help to resolve this matter. I am including as an attachment, the pressure graph of a node in the hilly area that shows the pressure drop.
Thanks and best regards,
Amine Salameh
Amine, is the network unbalanced at this timestep? Check the Calculation Summary. If so, see the guidance here: Troubleshooting the Network Unbalanced or Cannot solve network hydraulic equations user notification
If the network is not unbalanced, check the tabs at the bottom of the Calculation Summary after selecting the 5.0 hour timestep, for clues. If you are using controls, there could be a conflict or multiple controls "fighting". See this: Troubleshooting Controls in WaterCAD and WaterGEMS
You can also try creating a profile of the hydraulic grade back to the source, to try to pinpoint any large headlosses or other clues at that timestep.
Regards,
Jesse DringoliTechnical Support Manager, OpenFlowsBentley Communities Site AdministratorBentley Systems, Inc.