Deltares · Manangka · Jan 24, 2024 · Jan 23, 2024 · Jan 24, 2024 · Jan 24, 2024
diff --git a/docs/api/changelog.rst b/docs/api/changelog.rst
@@ -25,6 +25,11 @@ Changed
   advice doing development installations with pixi from now on. `See the
   documentation. <https://deltares.github.io/imod-python/installation.html>`_
 
+Added
+~~~~~
+- Added support for coupling a GroundwaterFlowModel and Transport Model i.c.w.
+  the 6.4.3 release of MODFLOW. Using an older version of iMOD Python
+  with this version of MODFLOW will result in an error.
 
 [0.15.1] - 2023-12-22
 ---------------------

diff --git a/imod/mf6/__init__.py b/imod/mf6/__init__.py
@@ -13,6 +13,7 @@
 from imod.mf6.evt import Evapotranspiration
 from imod.mf6.ghb import GeneralHeadBoundary
 from imod.mf6.gwfgwf import GWFGWF
+from imod.mf6.gwfgwt import GWFGWT
 from imod.mf6.hfb import (
     HorizontalFlowBarrierBase,
     HorizontalFlowBarrierHydraulicCharacteristic,

diff --git a/imod/mf6/exchangebase.py b/imod/mf6/exchangebase.py
@@ -0,0 +1,42 @@
+from typing import Dict, Tuple
+
+from imod.mf6.package import Package
+
+_pkg_id_to_type = {"gwfgwf": "GWF6-GWF6", "gwfgwt": "GWF6-GWT6"}
+
+
+class ExchangeBase(Package):
+    """
+    Base class for all the exchanges.
+    This class enables writing the exchanges to file in a uniform way.
+    """
+
+    _keyword_map: Dict[str, str] = {}
+
+    @property
+    def model_name1(self) -> str:
+        if "model_name_1" not in self.dataset:
+            raise ValueError("model_name_1 not present in dataset")
+        return self.dataset["model_name_1"].values[()].take(0)
+
+    @property
+    def model_name2(self) -> str:
+        if "model_name_2" not in self.dataset:
+            raise ValueError("model_name_2 not present in dataset")
+        return self.dataset["model_name_2"].values[()].take(0)
+
+    def package_name(self) -> str:
+        return f"{self.model_name1}_{self.model_name2}"
+
+    def get_specification(self) -> Tuple[str, str, str, str]:
+        """
+        Returns a tuple containing the exchange type, the exchange file name, and the model names. This can be used
+        to write the exchange information in the simulation .nam input file
+        """
+        filename = f"{self.package_name()}.{self._pkg_id}"
+        return (
+            _pkg_id_to_type[self._pkg_id],
+            filename,
+            self.model_name1,
+            self.model_name2,
+        )
diff --git a/imod/mf6/gwfgwf.py b/imod/mf6/gwfgwf.py
@@ -1,22 +1,22 @@
-from typing import Dict, Optional, Tuple
+from typing import Optional
 
 import cftime
 import numpy as np
 import xarray as xr
 
 from imod.mf6.auxiliary_variables import add_periodic_auxiliary_variable
+from imod.mf6.exchangebase import ExchangeBase
 from imod.mf6.package import Package
 from imod.typing import GridDataArray
 
 
-class GWFGWF(Package):
+class GWFGWF(ExchangeBase):
     """
     This package is for writing an exchange file, used for splitting up a model
     into different submodels (that can be solved in parallel). It (usually)
     is not instantiated by users, but created by the "split" method of the
     simulation class."""
 
-    _keyword_map: Dict[str, str] = {}
     _auxiliary_data = {"auxiliary_data": "variable"}
     _pkg_id = "gwfgwf"
     _template = Package._initialize_template(_pkg_id)
@@ -72,24 +72,6 @@ def set_options(
         self.dataset["xt3d"] = xt3d
         self.dataset["newton"] = newton
 
-    def filename(self) -> str:
-        return f"{self.packagename()}.{self._pkg_id}"
-
-    def packagename(self) -> str:
-        return f"{self.dataset['model_name_1'].values[()]}_{self.dataset['model_name_2'].values[()]}"
-
-    def get_specification(self) -> Tuple[str, str, str, str]:
-        """
-        Returns a tuple containing the exchange type, the exchange file name, and the model names. This can be used
-        to write the exchange information in the simulation .nam input file
-        """
-        return (
-            "GWF6-GWF6",
-            self.filename(),
-            self.dataset["model_name_1"].values[()].take(0),
-            self.dataset["model_name_2"].values[()].take(0),
-        )
-
     def clip_box(
         self,
         time_min: Optional[cftime.datetime | np.datetime64 | str] = None,

diff --git a/imod/mf6/gwfgwt.py b/imod/mf6/gwfgwt.py
@@ -0,0 +1,38 @@
+from copy import deepcopy
+from typing import Optional
+
+import cftime
+import numpy as np
+
+from imod.mf6.exchangebase import ExchangeBase
+from imod.mf6.package import Package
+from imod.typing import GridDataArray
+
+
+class GWFGWT(ExchangeBase):
+    _pkg_id = "gwfgwt"
+    _template = Package._initialize_template(_pkg_id)
+
+    def __init__(self, model_id1: str, model_id2: str):
+        super().__init__(locals())
+        self.dataset["model_name_1"] = model_id1
+        self.dataset["model_name_2"] = model_id2
+
+    def clip_box(
+        self,
+        time_min: Optional[cftime.datetime | np.datetime64 | str] = None,
+        time_max: Optional[cftime.datetime | np.datetime64 | str] = None,
+        layer_min: Optional[int] = None,
+        layer_max: Optional[int] = None,
+        x_min: Optional[float] = None,
+        x_max: Optional[float] = None,
+        y_min: Optional[float] = None,
+        y_max: Optional[float] = None,
+        top: Optional[GridDataArray] = None,
+        bottom: Optional[GridDataArray] = None,
+        state_for_boundary: Optional[GridDataArray] = None,
+    ) -> Package:
+        """
+        The GWF-GWT exchange does not have any spatial coordinates that can be clipped.
+        """
+        return deepcopy(self)
diff --git a/imod/mf6/pkgbase.py b/imod/mf6/pkgbase.py
@@ -10,7 +10,7 @@
 from imod.mf6.interfaces.ipackagebase import IPackageBase
 
 TRANSPORT_PACKAGES = ("adv", "dsp", "ssm", "mst", "ist", "src")
-EXCHANGE_PACKAGES = "gwfgwf"
+EXCHANGE_PACKAGES = ("gwfgwf", "gwfgwt")
 
 
 class PackageBase(IPackageBase, abc.ABC):

diff --git a/imod/mf6/simulation.py b/imod/mf6/simulation.py
@@ -17,7 +17,10 @@
 import xugrid as xu
 
 import imod
+import imod.logging
+import imod.mf6.exchangebase
 from imod.mf6.gwfgwf import GWFGWF
+from imod.mf6.gwfgwt import GWFGWT
 from imod.mf6.model import Modflow6Model
 from imod.mf6.model_gwf import GroundwaterFlowModel
 from imod.mf6.model_gwt import GroundwaterTransportModel
@@ -236,6 +239,10 @@ def write(
             if isinstance(model, Modflow6Model):
                 model._model_checks(key)
 
+        # Generate GWF-GWT exchanges
+        if gwfgwt_exchanges := self._generate_gwfgwt_exchanges():
+            self["gwtgwf_exchanges"] = gwfgwt_exchanges
+
         directory = pathlib.Path(directory)
         directory.mkdir(exist_ok=True, parents=True)
 
@@ -273,9 +280,9 @@ def write(
                     value.write(key, globaltimes, ims_write_context)
             elif isinstance(value, list):
                 for exchange in value:
-                    if isinstance(exchange, imod.mf6.GWFGWF):
+                    if isinstance(exchange, imod.mf6.exchangebase.ExchangeBase):
                         exchange.write(
-                            exchange.packagename(), globaltimes, write_context
+                            exchange.package_name(), globaltimes, write_context
                         )
 
         if status_info.has_errors():
@@ -791,16 +798,10 @@ def from_file(toml_path):
 
     def get_exchange_relationships(self):
         result = []
-        flowmodels = self.get_models_of_type("gwf6")
-        transportmodels = self.get_models_of_type("gwt6")
-        # exchange for flow and transport
-        if len(flowmodels) == 1 and len(transportmodels) > 0:
-            exchange_type = "GWF6-GWT6"
-            modelname_a = list(flowmodels.keys())[0]
-            for counter, key in enumerate(transportmodels.keys()):
-                filename = f"simulation{counter}.exg"
-                modelname_b = key
-                result.append((exchange_type, filename, modelname_a, modelname_b))
+
+        if "gwtgwf_exchanges" in self:
+            for exchange in self["gwtgwf_exchanges"]:
+                result.append(exchange.get_specification())
 
         # exchange for splitting models
         if is_split(self):
@@ -1044,3 +1045,16 @@ def __repr__(self) -> str:
         else:
             content = attrs + ["){}"]
         return "\n".join(content)
+
+    def _generate_gwfgwt_exchanges(self):
+        flow_models = self.get_models_of_type("gwf6")
+        transport_models = self.get_models_of_type("gwt6")
+
+        # exchange for flow and transport
+        exchanges = []
+        if len(flow_models) == 1 and len(transport_models) > 0:
+            flow_model_name = list(flow_models.keys())[0]
+            for transport_model_name in transport_models.keys():
+                exchanges.append(GWFGWT(flow_model_name, transport_model_name))
+
+        return exchanges
diff --git a/imod/templates/mf6/exg-gwfgwt.j2 b/imod/templates/mf6/exg-gwfgwt.j2
diff --git a/imod/tests/fixtures/package_instance_creation.py b/imod/tests/fixtures/package_instance_creation.py
@@ -299,6 +299,7 @@ def create_instance_boundary_condition_packages(is_unstructured):
             },
         ),
     ),
+    imod.mf6.GWFGWT("model_name1", "model_name2"),
 ]
 
 

diff --git a/imod/tests/test_mf6/test_exchangebase.py b/imod/tests/test_mf6/test_exchangebase.py
@@ -0,0 +1,71 @@
+from contextlib import nullcontext as does_not_raise
+
+import pytest
+
+from imod.mf6.exchangebase import ExchangeBase, _pkg_id_to_type
+
+
+class DummyExchange(ExchangeBase):
+    _pkg_id = "gwfgwt"
+
+    def __init__(self, model_id1: str = None, model_id2: str = None):
+        super().__init__()
+        if model_id1:
+            self.dataset["model_name_1"] = model_id1
+        if model_id2:
+            self.dataset["model_name_2"] = model_id2
+
+
+def test_package_name_construct_name():
+    # Arrange.
+    model_name1 = "testmodel1"
+    model_name2 = "testmodel2"
+    exchange = DummyExchange(model_name1, model_name2)
+
+    # Act.
+    package_name = exchange.package_name()
+
+    # Assert.
+    assert model_name1 in package_name
+    assert model_name2 in package_name
+
+
+@pytest.mark.parametrize(
+    ("model_name1", "model_name2", "expectation"),
+    (
+        [None, None, pytest.raises(ValueError)],
+        ["testmodel1", None, pytest.raises(ValueError)],
+        [None, "testmodel2", pytest.raises(ValueError)],
+        ["testmodel1", "testmodel2", does_not_raise()],
+    ),
+)
+def test_package_name_missing_name(model_name1, model_name2, expectation):
+    # Arrange
+    exchange = DummyExchange(model_name1, model_name2)
+
+    # Act/Assert
+    with expectation:
+        exchange.package_name()
+
+
+def test_get_specification():
+    # Arrange.
+    model_name1 = "testmodel1"
+    model_name2 = "testmodel2"
+    exchange = DummyExchange(model_name1, model_name2)
+
+    # Act.
+    (
+        spec_exchange_type,
+        spec_filename,
+        spec_model_name1,
+        spec_model_name2,
+    ) = exchange.get_specification()
+
+    # Assert
+    assert spec_exchange_type is _pkg_id_to_type[DummyExchange._pkg_id]
+    assert model_name1 in spec_filename
+    assert model_name2 in spec_filename
+    assert DummyExchange._pkg_id in spec_filename
+    assert spec_model_name1 == model_name1
+    assert spec_model_name2 == model_name2
diff --git a/imod/tests/test_mf6/test_mf6_gwfgwf.py b/imod/tests/test_mf6/test_mf6_gwfgwf.py
@@ -169,7 +169,7 @@ def test_option_xt3d_propagated(circle_model, xt3d_option, tmp_path):
     label_array = get_label_array(circle_model, 3)
     split_simulation = circle_model.split(label_array)
 
-    # check that the created exchagnes have the same newton option
+    # check that the created exchanges have the same newton option
     for exchange in split_simulation["split_exchanges"]:
         assert exchange.dataset["xt3d"].values[()] == xt3d_option
         textrep = exchange.render(tmp_path, "gwfgwf", [], False)
@@ -185,7 +185,7 @@ def test_option_variablecv_propagated(circle_model, variablecv_option: bool, tmp
     label_array = get_label_array(circle_model, 3)
     split_simulation = circle_model.split(label_array)
 
-    # check that the created exchagnes have the same variablecv option
+    # check that the created exchanges have the same variablecv option
     for exchange in split_simulation["split_exchanges"]:
         assert exchange.dataset["variablecv"].values[()] == variablecv_option
         textrep = exchange.render(tmp_path, "gwfgwf", [], False)
@@ -202,7 +202,7 @@ def test_option_dewatered_propagated(circle_model, dewatered_option: bool, tmp_p
     label_array = get_label_array(circle_model, 3)
     split_simulation = circle_model.split(label_array)
 
-    # check that the created exchagnes have the same dewatered option
+    # check that the created exchanges have the same dewatered option
     for exchange in split_simulation["split_exchanges"]:
         assert exchange.dataset["dewatered"].values[()] == dewatered_option
         textrep = exchange.render(tmp_path, "gwfgwf", [], False)
@@ -219,7 +219,7 @@ def test_save_flows_propagated(circle_model, budget_option: bool, tmp_path):
     label_array = get_label_array(circle_model, 3)
     split_simulation = circle_model.split(label_array)
 
-    # check that the created exchagnes have the same dewatered option
+    # check that the created exchanges have the same dewatered option
     for exchange in split_simulation["split_exchanges"]:
         assert exchange.dataset["save_flows"].values[()] == budget_option
         textrep = exchange.render(tmp_path, "gwfgwf", [], False)

diff --git a/imod/tests/test_mf6/test_mf6_simulation.py b/imod/tests/test_mf6/test_mf6_simulation.py
@@ -448,7 +448,8 @@ def test_write_exchanges(
         transient_twri_model.write(tmp_path, True, True, True)
 
         # Assert
-        assert Path.exists(tmp_path / sample_gwfgwf_structured.filename())
+        _, filename, _, _ = sample_gwfgwf_structured.get_specification()
+        assert Path.exists(tmp_path / filename)
 
     @pytest.mark.usefixtures("split_transient_twri_model")
     def test_prevent_split_after_split(
-Original file line number
+Diff line change
@@ Expand Up @@
                 },
             ),
         ),
+        imod.mf6.GWFGWT("model_name1", "model_name2"),
     ]
@@ Expand Down @@