diff --git a/grpc4bmi/bmi_client_docker.py b/grpc4bmi/bmi_client_docker.py
index b774be1..47c58e2 100644
--- a/grpc4bmi/bmi_client_docker.py
+++ b/grpc4bmi/bmi_client_docker.py
@@ -23,6 +23,17 @@ class BmiClientDocker(BmiClient):
         output_dir (str): Directory for input files of model
         user (str): Username or UID of Docker container
         remove (bool): Automatically remove the container when it exits
+        extra_volumes (Dict[str,Dict]): Extra volumes to attach to Docker container.
+            The key is either the hosts path or a volume name and the value is a dictionary with the keys:
+
+            - ``bind`` The path to mount the volume inside the container
+            - ``mode`` Either ``rw`` to mount the volume read/write, or ``ro`` to mount it read-only.
+
+            For example:
+
+            .. code-block:: python
+
+                    {'/data/shared/forcings/': {'bind': '/forcings', 'mode': 'ro'}}
 
     """
 
@@ -31,10 +42,13 @@ class BmiClientDocker(BmiClient):
 
     def __init__(self, image, image_port=50051, host=None,
                  input_dir=None, output_dir=None,
-                 user=os.getuid(), remove=True):
+                 user=os.getuid(), remove=True,
+                 extra_volumes=None):
         port = BmiClient.get_unique_port()
         client = docker.from_env()
         volumes = {}
+        if extra_volumes is not None:
+            volumes.update(extra_volumes)
         self.input_dir = None
         if input_dir is not None:
             self.input_dir = os.path.abspath(input_dir)
diff --git a/test/conftest.py b/test/conftest.py
index 09a0b11..e966f30 100644
--- a/test/conftest.py
+++ b/test/conftest.py
@@ -1,7 +1,8 @@
 import pytest
 
-def write_config(p):
-    p.write_text("""data: /data/input/PEQ_Hupsel.dat
+
+def write_config(p, data_fn='/data/input/PEQ_Hupsel.dat'):
+    p.write_text(f"""data: {data_fn}
 parameters:
   cW: 200
   cV: 4
@@ -59,3 +60,17 @@ def walrus_input(tmp_path):
     write_config(cfg)
     write_datafile(tmp_path / 'PEQ_Hupsel.dat')
     return cfg
+
+
+@pytest.fixture()
+def walrus_input_on_extra_volume(tmp_path):
+    # Have config in input dir and forcings data file on extra volume
+    input_dir = tmp_path / 'input'
+    input_dir.mkdir()
+    cfg = input_dir / 'config.yml'
+    write_config(cfg, '/forcings/PEQ_Hupsel.dat')
+    extra_dir = tmp_path / 'forcings'
+    extra_dir.mkdir()
+    write_datafile(extra_dir / 'PEQ_Hupsel.dat')
+    extra_volumes = {extra_dir: {'bind': '/forcings', 'mode': 'ro'}}
+    return input_dir, extra_volumes
diff --git a/test/test_docker.py b/test/test_docker.py
index d776516..b3ed700 100644
--- a/test/test_docker.py
+++ b/test/test_docker.py
@@ -10,6 +10,17 @@ def walrus_model(tmp_path, walrus_input):
     del model
 
 
+@pytest.fixture()
+def walrus_model_with_extra_volume(tmp_path, walrus_input_on_extra_volume):
+    (input_dir, extra_volumes) = walrus_input_on_extra_volume
+    model = BmiClientDocker(image="ewatercycle/walrus-grpc4bmi:v0.2.0",
+                            image_port=55555,
+                            input_dir=str(input_dir),
+                            extra_volumes=extra_volumes)
+    yield model
+    del model
+
+
 class TestBmiClientDocker:
     def test_component_name(self, walrus_model):
         assert walrus_model.get_component_name() == 'WALRUS'
@@ -26,3 +37,9 @@ def test_initialize(self, walrus_input, walrus_model):
     def test_get_value_ref(self, walrus_model):
         with pytest.raises(NotImplementedError):
             walrus_model.get_value_ref('Q')
+
+    def test_extra_volume(self, walrus_model_with_extra_volume):
+        walrus_model_with_extra_volume.initialize('/data/input/config.yml')
+        walrus_model_with_extra_volume.update()
+        # After initialization and update the forcings have been read from the extra volume
+        assert len(walrus_model_with_extra_volume.get_value('Q')) == 1