Product(s): Bentley WaterGEMS, Bentley WaterCAD, Bentley HAMMER Version(s): 08.XX.XX.XX Environment: N\A Area: General Subarea: N\A Problem How is the "Flow stored" calculated in the calculation summary? What is the difference between flow supplied, flow demanded and flow stored? What is the difference between Flow(In) vs. Flow(Out) for tanks? Problem ID#: 88470 Solution For each time step in an EPS simulation (or for the single time step in a steady state), WaterCAD/WaterGEMS displays the mass balance of flow supplied, flow demanded, and flow stored. The "Flow Supplied" is the total flow rate out of water sources. This is mainly reservoirs, but also included negative demands (inflows). Reservoirs that are filling will experience negative flow supplied. The "Flow Demanded" is the total demand at that time (flow leaving the system), which could be from fixed demands at nodes, pressure dependent demands, emitter coefficients on hydrants, etc. The "Flow Stored" is the net inflow into tanks at that time. For example, if you have just one tank which has only outflow at that time, the flow stored will be negative, at that amount. If it has only inflow at that time, the flow stored will be positive. Therefore: Flow Stored = Flow Supplied - Flow Demanded In other words, if more flow is coming from reservoir than is demanded, the surplus goes into tank storage. If more flow is demanded than is supplied by reservoirs, the deficit is supplied by tank storage. The Flow(In) or Flow(In Net) is the flow that is being supplied to the tank and is a positive value. The Flow(Out) or Flow (Out Net) is the flow leaving the tank and is a negative value.
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