OpenFlow CONNECT - Pressure needed for a junction: Is it HGL at the junction or pressure at the junction?

Question

Hi everybody 
 I am a little bit confused and hope you can help me in this regard. 
 I have 2 questions: 
 1- In WaterGEMS, for example, when I want to check there is enough pressure for a junction demand at that junction, should I check the pressure at the junction or the HGL at the junction? 
 2- In connection with WaterGEMS, when we measure pressure at a junction in real world with a barometer, does it show the pressure or the HGL ? 
 Thanks for your help in advance. 
 Br, 
 Hasan

Ankit Kulkarni · Accepted Answer

Hello Hasan, 
 Kindly go through the following and see if the answer satisfies your question - 
 Answer 1 - 
 Basically, In WaterGEMS, junctions are those nodes that do not store water (non-storage nodes), water at the junction leaves the network to satisfy the demand of consumers or enters the network as an inflow. Junctions do not directly relate to real-world distribution components but the main role of the junction is to provide a location to withdraw water demanded from the system. So, we put 'demands' as input to all the junctions in the network using the Demand center tool and we measure Pressure Head at the junction point, not HGL. The HGL reduces as the water flows through the pipe and the reason is friction. you can develop a small model as below- can try inputting different values. 
 For example - Say the reservoir R-1 is at 50 m elevation and Junction J-1 and J-2 are at 30 at 20 m elevation respectively. Demands are 20 L/s and 15 L/s at both J-1 and J-2. pipes P-1 and P-2 are having default values. If you compute you will get the following results. 
 
 The pressure head at J-1 is 19.67 m of H2O to satisfy the demand of 20 L/s at a time step. 
 You can try inputting different values to understand the changes happening in both Pressure Head and HGL. 
 Answer 2 - The barometer gives the reading of pressure at that point.

Scott Kampa · Answer

Hello Hasan, 
 To add to Ankit's reply, this link has information may may be useful related to elevations and how hydraulic grade and pressures are calculated in WaterGEMS and WaterCAD: What does node elevation represent in WaterCAD, WaterGEMS and HAMMER? 
 Regards, 
 Scott.

OpenFlow CONNECT - Pressure needed for a junction: Is it HGL at the junction or pressure at the junction?

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