To account for boundary effects it is advised to create a buffer around the aquifer of our study area.
1. In the main menu go to Vector | Geoprocessing Tools | Buffer...
2. In the Buffer dialogue choose the Malawi_GIS_data Shire Valley Alluvial Aquifer as Input layer. Set the Distance to 10 kilometers. Keep the other settings as default and save the layer to the Malawi_GIS_data.gpkg with the layer name Shire buffer 10km.
3. Click Run. Click Close to close the dialogue after processing.
Now the Shire buffer 10km layer is visible in the map canvas.
Because we're only considering the aquifer that covers Malawi, we're going to clip the Shire buffer 10km layer to the country boundary in the next subsection.