Pumping rate input is not equal to simulated output

Hello

I want to find out an answer about pumping rate input and simulated output (4 well BC) of FeFlow simulation on "Phreatic" aquifer type setting. There are several aquifers have been set as "Phreatic" (As the conceputal model needs). We have a reasonable calibration, however, the input pumping volume (pumping rate) is not always equal the simulated output, there is offset for each year. for example, 1st year observed (input) pumping value is 4Gl, Model simulated is 4.2 or 3.7Gl.

After several testing, I am wondering if that is water balance bugs? Any suggestion to deal with that offset? Is the model able to produce the exact (100%) same input and output value? As for the dewatering prediction model, those offset is an issue.

Cheers

In transient pumping, depending on how you set it up, the pumping rate may get averaged from one time to the next.  Use a step function (curve type "step") if you don't want this to happen.  In Phreatic, if a node dries out (minimal water level in the associated element), the model may behave oddly (not sure this would affect the pumping rate though, maybe just the simulated heads).