Hello altogether,
I wanted to link WEAP with MODFLOW and I do have an existing Groundwater Model in "Processing MODFLOW". Is it also possible to use this software instead of MODFLOW 2000 and just concerning the following parameters that can be used by WEAP:
BAS6 (Process Basic), BCF6 (Block-Centered Flow),
CHD (Constant-Head), DIS (Discretization), DRN (Drain), HUF2 (Hydrogeologic Unit
Flow), LPF (Layer Property Flow), OC (Output Control), RCH (Recharge), RIV (River),
WEL (Well)."

I am very thankful for any advice and support.
Thanks, Janine

Good question! Although I have not worked with "Processing MODFLOW"
(PM), as far as I know it is one of many graphical user interfaces for
MODFLOW and other groundwater flow or quality models. As such, PM will
read and write standard MODFLOW files, as it uses MODFLOW to do the
actual groundwater flow calculations. Therefore, you should be able to
link the underlying MODFLOW model to WEAP. One question, though, is
what version of MODFLOW does PM work with, e.g., MODFLOW 2000 or MODFLOW
2005? WEAP is designed to work only with MODFLOW 2000. The MODFLOW
packages you list--BAS6, BCF6, CHD, DIS, DRN, HUF2, LPF, OC, RCH, RIV,
WEL--are all compatible with WEAP.

If you send a copy of your PM / MODFLOW model to me
(jack.sieber@sei-us.org), I could take a quick look to verify that WEAP
can indeed work with it.

I should note that the current version of WEAP cannot deal with some
MODFLOW input file options, such as PARAMETERs and OPEN/CLOSE and
EXTERNAL file references. I am working now to enhance WEAP to handle a
wider range of MODFLOW models. If anyone would like to send me their
MODFLOW model (please don't send the huge results files, though), it
would help me in testing this new version of WEAP.

Jack