It seems to me you want to read the water meter remotely but without interfering with it.
The simplest way would be have the camera send you the picture then type the reading in by hand.
Telephone bills were done that way once. A photograph would be taken of a whole bank of meters, and the numbers would then by entered into bills. The photo was kept as a record in case there was an error or dispute.
..., you're serious... well that could explain a few things.
As far as reading the meter without breaking it out into something electronic for the arduino to use. I realize this is the arduino forum, but a friend of mine was working on a similar image processing project with a Raspberry PI and a webcam. (I'll get the full details and see if i can't get him in touch with you later if you'd like) But he was going to have it look at a bunch of meters in his house (I recall fuel gauge, a watt meter, 2 water meters, a few thermometers, and some other stuff), read off what they have on them, and on 1 hand, put it all into a spreadsheet. And in the case of things like his fuel meter (his house is heated with diesel fuel) if it got too low, it'd send him an email telling him to get more fuel. Or if the water meter was showing a constant usage for like 30-40 minutes in 1 part of his house, it'd spam his daughters facebook telling her to stop taking such long showers and wasting all the hot water (don't know if that was an actual thing, we just chuckled about things he could make it do over lunch a couple weeks ago)
(I'll note though, He already had this system in place done with arduino and then having more conventional methods like digital flow meters, an electric level gauge, and other things get the readings, rather then looking at the meters in place for the info. With the email fuel need alerts and stuff. He had told me he was doing this new project cause he was bored and wanted an excuse to build one of the RPi's he bought into something.)