From cfd9febde4177ffc2370fdf92a1dbf70ccb2333c Mon Sep 17 00:00:00 2001
From: wpbonelli <wbonelli@ucar.edu>
Date: Sat, 18 Jan 2025 15:13:21 -0500
Subject: [PATCH] docs(prt-fmi): clarify only required when post-processing

---
 autotest/test_prt_exg.py | 20 +++++++++++---------
 doc/mf6io/prt/fmi.tex    |  4 ++--
 2 files changed, 13 insertions(+), 11 deletions(-)

diff --git a/autotest/test_prt_exg.py b/autotest/test_prt_exg.py
index 3de7dbe01bd..fef907baf02 100644
--- a/autotest/test_prt_exg.py
+++ b/autotest/test_prt_exg.py
@@ -108,15 +108,17 @@ def build_mf6_sim(idx, test):
         trackcsv_filerecord=[prt_track_csv_file],
     )
 
-    # create a flow model interface
-    # todo Mike Fienen's report (crash when FMI created but not needed)
-    # flopy.mf6.ModflowPrtfmi(
-    #     prt,
-    #     packagedata=[
-    #         ("GWFHEAD", gwf_head_file),
-    #         ("GWFBUDGET", gwf_budget_file),
-    #     ],
-    # )
+    # create a flow model interface. should be ignored.
+    # Mike Fienen reported that an early version of PRT
+    # crashed if FMI is provided when using an exchange.
+    flopy.mf6.ModflowPrtfmi(
+        prt,
+        packagedata=[
+            # garbage paths
+            ("GWFHEAD", "heads.hds"),
+            ("GWFBUDGET", "budget.cbc"),
+        ],
+    )
 
     # create exchange
     gwf_name = get_model_name(idx, "gwf")
diff --git a/doc/mf6io/prt/fmi.tex b/doc/mf6io/prt/fmi.tex
index 08ef20bced1..76ec7ef112d 100644
--- a/doc/mf6io/prt/fmi.tex
+++ b/doc/mf6io/prt/fmi.tex
@@ -1,6 +1,6 @@
-Flow Model Interface (FMI) Package information is read from the file that is specified by ``FMI6'' as the file type.  The FMI Package is required, and only one FMI Package can be specified for a PRT model.
+Flow Model Interface (FMI) Package information is read from the file that is specified by ``FMI6'' as the file type.  The FMI Package file is required only if the PRT Model is running in a separate simulation from a previously run GWF Model. If the PRT Model is coupled to a GWF Model by an exchange, the FMI Package file is not required. Only one FMI Package can be specified for a PRT model.
 
-For most simulations, the PRT Model needs groundwater flows for every cell in the model grid, for all boundary conditions, and for other terms, such as the flow of water in or out of storage.  The FMI Package is the interface between the PRT Model and simulated groundwater flows provided by a corresponding GWF Model that is running concurrently within the simulation or from binary budget files that were created from a previous GWF model run.  The following are several different FMI simulation cases:
+The PRT Model needs groundwater flows for model grid cells, for boundary conditions, and for other terms, such as the flow of water in or out of storage.  The FMI Package is the interface between the PRT Model and simulated groundwater flows provided by a corresponding GWF Model that is running concurrently within the simulation or from binary budget files that were created from a previous GWF model run.  The following are several different FMI simulation cases:
 
 \begin{itemize}