The one major problem with storage solutions such as those is that they rely on the rain cycle very heavily. Not saying any of them are "bad" ideas but definately not long term solutions regardless of the size of the water storage. Once again the only sure way to guarantee yourself a steady water supply is to have a nearby stream or large natural formation lake as these generally are fed from hundreds of square miles of run off and not from 2 roofs that after a particular amount of time may become damaged and require repair.
I know many people think of wells as solutions but they can have issues aswell, the same as lakes actually. They can become contaminated, a well with an accidentally left unsealed port can attract mice and birds that can fall into the well and then you will have dead animals and all their bacteria in your water source, also if you plan on having a garden to grow food or need water to supply livestock 10000 gallons is not more than a months worth of water during a drought if that.
All city solutions are going to be short term unfortunately unless you just happen to be a suburbanite within walking distance of a nice well flowing creek that stays wet all year round you might consider your in your prepping that will NEED to move at some point.