Viability of using One-Time-Pad + HMAC in low-volume IoT communications
Two points adding to Raoul's answer are:-


To generate a HMAC you need a key, and this key will have to be stored within the meter.  If there's a key, traditional encryption can be used if you can somehow generate IVs.  Or don't generate them and accept that repeat readings will be transmitted as repeat cipher text.  This probably isn't a particularly serious issue for water consumption. Although, a static reading suggests the occupants are on holiday and the house is unoccupied. So this is an example of information leakage.
You compare OTP distribution to traditional key distribution.  That might be true but have you considered the office end?  This application of a OTP is about the worst possible kind.  OTPs do not perform well in many to one transmissions.  There will have to be a huge one time pad at the receiving station to decode readings from (100k+) meters. And how will you decode the reading if the meter ID is encrypted?  If you use an IP address as an identifier, that can be intercepted so what's the point of encrypting the meter ID?  And what happens if you roll out more meters?  More OTP material has to be stored, interwoven with existing OTP material and subsequently tracked at the base office.


In summary, this is not the most appropriate scenario for a OTP. But, it you only had one meter (for lets say a home automation system), OTP is perfect as it eliminates all the cryptographic code /testing issues.  Assuming of course that you can estimate the required pad size as Raoul suggests.