I am trying to create a potential erosion map of my basin for which I require a rainfall distribution map. I have 3 stations' rainfall data for the year 2007- 2015.
How do I create a rainfall map in GRASS GIS?
The question can be separated in two parts:
What is a potential erosion map and how is it made based on rainfall station data?
How can I interpolate a surface based on 3 points using GRASS GIS?
For question 1, I suspect you will need to get a yearly average per station (e.g. Station A: 900 mm/ year rainfall. Station B: 150 mm/year rainfall. Station C: 2200 mm/year rainfall). Your case might be different depending on the method you are using - only you know this answer. Once this is solved, you can go to question 2.
For question 2, Google "GRASS Interpolation". You will find tutorials in webpages and videos on YouTube. Try them, and if you have specific questions after you have tried them, you can ask them here.
See if the below link is any help.
Somewhere in there it tells you how to interpolate. You can try following the tutorial and later experiment with other options in interpolation.