Model budget vs. analitical budget

[matevz]

Hi,

does anyone knoe why there is so much difference between model computation and a calculation via some empirical equations?

For example, i calculated the amount of water that has to be pumped out of several wells in a raster (using the 3,6 drawdown and k=6*10-3m/s) with this formula :

Q=k*(H^2-h^2)/(0.733*log(R/re))

where

re - is the ekvivalent radius of the area where water needs to be lowered

R - is radious of influence

H - 15m

h - 11.4

The result with this equation is Q = 357 L/s

When I use same numbers in model i get Q = 1.4 m^3/s (1400 L/s)?

I know the model uses more parameters and the numbers shouldnt be the same completely but this is more that 300% increase!

Does anyone has any idea?

Thanky, matevz