Question on the formulation to calculate the groundwater reservoir flux

[RY4GIT]

I have a question on the formulation to calculate the groundwater reservoir flux.

Current behavior

The README document says the groundwater module is identical to the NWM formulation. However, there is a little difference in the formulation. Essentially, the NWM uses exp(z), and the CFE uses exp(z)-1 to calculate outflux from the groundwater reservoir. Then, in CFE, the parameter expon is less important and the parameter Coeff (a.k.a. Kgw) is more important in determining groundwater flux than NWM.

I wonder if:

1. there is a reason for the change
2. if there is anyone calculated parameter range suited for the exp(z)-1 formulation

In my view, both formulations make sense: the CFE exp(x)-1 formulation will result in 0 flux from the groundwater reservoir when groundwater storage is zero. On the other hand, since flux becomes equal to the groundwater reservoir is small, exp(x)-1 is not necessary, and the exp(x) NWM model also makes sense.

the NWM formulation (according to WRF-Hydro technical description)

the CFE formulation