diff --git a/.github/workflows/remove-obsolete-cache.yml b/.github/workflows/remove-obsolete-cache.yml
new file mode 100644
index 00000000..fdbabca6
--- /dev/null
+++ b/.github/workflows/remove-obsolete-cache.yml
@@ -0,0 +1,35 @@
+# Example taken from https://docs.github.com/en/actions/using-workflows/caching-dependencies-to-speed-up-workflows#managing-caches
+name: Cleanup Caches on PR Merge
+
+on:
+  pull_request:
+    types:
+      - closed
+
+jobs:
+  cleanup:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Check out code
+        uses: actions/checkout@v3
+
+      - name: Cleanup
+        run: |
+          gh extension install actions/gh-actions-cache
+
+          REPO=${{ github.repository }}
+          BRANCH="refs/pull/${{ github.event.pull_request.number }}/merge"
+
+          echo "Fetching list of cache key"
+          cacheKeysForPR=$(gh actions-cache list -R $REPO -B $BRANCH -L 100 | cut -f 1 )
+
+          ## Setting this to not fail the workflow while deleting cache keys.
+          set +e
+          echo "Deleting caches..."
+          for cacheKey in $cacheKeysForPR
+          do
+              gh actions-cache delete $cacheKey -R $REPO -B $BRANCH --confirm
+          done
+          echo "Done"
+        env:
+          GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
diff --git a/HISTORY.rst b/HISTORY.rst
index 38fbc33b..2edbe13a 100644
--- a/HISTORY.rst
+++ b/HISTORY.rst
@@ -10,6 +10,7 @@ History
 -------------------
 * `RavenPy` now uses `platformdirs` to write `raven_testing` to the user's cache directory. Dynamic paths are now used to cache data dependent on the user's operating system. Developers can now safely delete the `.raven_testing_data` folder in their home directory without affecting the functionality of `RavenPy`.
 * Updated `raven-hydro` to v0.2.4 to address CMake build issues.
+* Added a workflow to remove obsolete GitHub Workflow cache files.
 
 0.12.2 (2023-07-04)
 -------------------
diff --git a/environment.yml b/environment.yml
index ec11f7d8..1e032c61 100644
--- a/environment.yml
+++ b/environment.yml
@@ -5,6 +5,7 @@ channels:
 dependencies:
   - python >=3.8,<3.12
   - raven-hydro ==0.2.4
+  - libgcc  # for mixing raven-hydro from PyPI with conda environments
   - affine
   - cftime
   - cf_xarray