Figuring out my water bill

Here in my area of Toronto, water rates are rising 9%/year. To quickly figure out how long it will take for my bill to double, I look to the rule of 72.

Therefore it will take 72/9 or approximately 8 years to double.

What a scam! The area I am in does not have 100 year old pipes like some older downtown areas. So why am I paying these insane doubling rates? Where is this money going? Are they spending all of it?