Not Available Data Integration (NADI) Tool is planned tool by me to fill the data gaps in timeseries based on the river connections.
This video showcases the first prototype that can extract the river connections for other parts of the program. I've made a QGIS plugin to interface with that part to make a GIS tool.
The river network of tributaries can be downloaded from USGS.
Github Link: https://github.com/Atreyagaurav/nadi