Below are some great websites for information on water storage with an explanation as to what they share. I hope you will check them out.
Food and Water in an Emergency(pdf)- This is a publication put out by FEMA. It has a lot of concise to the point information on water storage, as well as information on many other emergency prep items.
Calculator- A great calculator for food storage, I believe it is only doing a two week supply of water.
Basic Guidelines- Some basic guidelines for water storage.
EPA- EPA's FAQ on all things water. You can search it for all sorts of info such as emergency water treatment and sources.
Emergency Essentials- One of many sites that sells commercial water storage equipment. You can find containers that are specifically made for long term water storage.
I will bookmark these in my favorite websites tab for future use. Hopefully you will find some use in them!