Summary:

This is a tool for ArcGIS pro.
Built with ArcGIS pro 2.8.0
Python version 3.4.3
This is a hydrology tool to calculate, for each cell in a raster, the area of upstream cells that drain water to it. It takes a input elevation raster (DEM) and outputs a raster showing drainage area value for each cell.
The (underlying) steps involved are:

1. Fill Potential Sinks in the DEM
2. Calculate Flow direction
3. Calculate Flow accumulation
4. Calculate Drainage Area

  D = F_ac*Cellsize
   where,
   D = Drainage Area
   F_ac = Flow accumulation
   Cellsize = Area of single pixel of input raster

This tool is used to compute the total area of upstream that contribute drain water any given location.