Great project! I am the technical lead on a non-profit dam monitoring project and will be implimenting a similar solution both upstream and down. Might also add a servo control of the flow control gate.
I think I can get away with a long range wifi (enGenius ENG-EOC2611P) for my access to the internet. I have power, so at least that is one technical hurdle that I dont have to worry about.
What I am most interested in is your sketches for the Aurdino board. Seems like you had a little trial and error with the moving tide and signals bouncing off the pier causing inconsistent results in the early stages of your development. I'm sure I will have the same issue. Would like to benefit from your lessons learned in that area. From what I can tell, your compensation algs are built into the Aurdino chipset correct?
I would be happy to share all my results and data with you as well as any improvements that I come up with.
Erik