I am working in a project of glacier mass balance. For my project I want to integrate the area of the drainage basin in a glaciological system model (GSM). As the drainage area changes with time due to topographic evolution (ice accumulation or melt), I need to be able to integrate some code which calculates this area in the GSM. Would anybody know where I could find some code to compute the drainage area of a region?
Sue Greenlee's original code - that Esri's and many other watershed codes are based on - was published in FORTRAN in 1988. I'd go looking for that - don't see it on the web - but you could always email her! Kind of surprised it's not in GitHub, it's pretty neat code.
Jenson S. K. and J. O. Domingue. 1988. Extracting Topographic Structure from Digital Elevation Data for Geographic Information System Analysis. Photogrammetric Engineering and Remote Sensing 54 (11): 1593-1600.