Deal users!
please help me!
i have a Reservoir but i do not have any report about loss to groundwater of it. now i want to do expression builder to calculate the amount of loss to groundwater ( the figure = 1.5% of total capacity of reservoir each month)
I do not know, I have to use what structure.
How I can do it?

If you want 1.5% of the current storage of the reservoir to be lost to groundwater each month, here is the expression you would use for the "Loss to Groundwater" variable for the reservoir:

PrevTSValue(Storage Volume[Million m^3]) * 1.5%

This will take the storage volume from the end of the previous timestep (which is the storage at the beginning of the current timestep) and multiply it by 1.5%.

Jack