Every state/district/ ,or perticularly water resource department, having their rain gauge stations,either automatic or manual in river basin as per their need ,u can also try any dam project site in your basin,on this location rain gauge station might be installed.
The conventional rain gauge observations in many parts of the world such as Upper Blue Nile basin are sparse and unevenly distributed. An alternative to traditional rain gauge observations could be satellite-based rainfall estimates. Satellite rainfall estimates could be used as a sole product (e.g., in areas with no (or poor) ground observations) or through integrating with rain gauge measurements.
In the following study ( cited below), the potential of a newly available Climate Hazards Group Infrared Precipitation with Stations (CHIRPS) rainfall product has been evaluated in comparison to rain gauge data over the Upper Blue Nile basin in Ethiopia for the period of 2000 to 2015. ( hoping it is useful)
Getachew Tesfaye Ayehu, Tsegaye Tadesse, Berhan Gessesse, and Tufa Dinku " Validation of new satellite rainfall products over the Upper Blue Nile Basin, Ethiopia" Atmos. Meas. Tech., 11, 1921–1936, 2018 (https://www.atmos-meas-tech.net/11/1921/2018/amt-11-1921-2018.pdf )
You can see all the stations and their start of operations here (some have been running for decades, many stations will offer the data for the years you are looking for - note that the NMA has over 1000 stations collecting data):
http://www.ethiomet.gov.et/stations/information
Data requests have to be made directly to the NMA, and they charge per data point. In theory, you can request data online here:
However, in my experience you need to go to the NMA directly, or have someone go on your behalf. However, before going, determine which stations you are looking for. Once you are in the office, the process is relatively straight forward.