Model too slow when vertical hydraulic conductivity is 0.1* Kx

model is too slow and the time step is also small When I assign vertical hydraulic conductivity 0.1*kx.
details about the model:
since an urban area well was given throughout study area where buildup is there
recharge was given 10% of monthly average rainfall
model is run under the phreatic condition
study area mainly consists of alternate layers of clay and sand. is there any thumb rule like vertical flow should be 0.1*kx?. Since inflow from the first layer to bottom will b high due to gravity, feflow will consider it automatically? because i think the problem for small time steps is due to slow the vertical flow of rainfall

I suppose that by reducing the vertical conductivity the residual conductivity of the potentially dry first layer will be lower by a factor of 10, and recharge may not be able to infiltrate. This leads to a pressure build-up at the surface, with periodic break-throughs once saturation is high enough to increase k to a degree that lets the water drain down. If you are using the default residual water level of 1 mm for the phreatic layer(s), I suggest to increase this reasonably to increase residual saturation, hence residual k in dry layers.

if the average water level from the ground is around 5m, what range of value I can apply from residual water level?

When i gave residual water level 0.2m model run without any error. Thank you so much

You're welcome. You just have to keep in mind that this increases k in the unsat zone in all directions.

When i gave little high value, the head shows some error during the stress period. why is it so?