View the akflow.m matlab script. It will do what you need...
This analysis looks at 100 Alaskan rivers and creates a graphic based on their hydrographs. The comments in the matlab script document the methods and the data used. Enjoy!
Want to order a shirt?
Men's version is here
Women's version is here
At both of those links, you can change size, you can select a different 'product' (shirt style - look for the no minimum ones). It's a bit fiddly, but I'm sure you can work it out.
Or, steal the .png or the .jpg graphics in this repository and do whatever you like with them.