Please break apart my idea and find as many faults as you can.

[River Song]

Observation - If the money was there, I'd put a camera up a pole and monitor it from your remote
using Point-to-Point 802.11 Links - total cost around £180

Water - I guess that massive collection would look odd but my response might be "you wanna drink or what".

Could investigate underground/covered IBC Tanks

You might also look at this commercial rainwater harvesting offering. It may be far too expensive but it may give some ideas.

http://www.mygroupea.co.uk/themes/mygroup/img/KSW.pdf