Are the pumping rates interpolated between time periods? I have pump totalizer data on irregular time steps and I am trying to make sure that I am representing them correctly in the pump time series. In the example below I show the date and the totalizer readings in (gals). I convert the total gals to an average gpm computed over the time period since the last reading, then to a ft3/day for input into modflow. Does modflow interpolate the flow between time steps, or does it use a specified flow rate for each time step until another one is specified (stepped pump rate). For example is the pump rate on 3/13/12 in the example below 0.00 ft3/day, or is it 77.33 ft3/day? I want to make sure that I get the mass balance for pumped volume correct.
Date
gals)
(gpm)
(ft3/day)
3/12/12
0.0
0.0
0.0
3/15/12
5,212.0
1.2
-232.3
3/16/12
8,674.0
2.4
-462.8
3/19/12
9,752.0
0.2
-48.0