A month after the earthquake, tap-water in Tokyo shows much radioactive materials level than that of drinkable water suggested by WHO.
Unfortunately I could not find bottled water today in the shops. After earthquake I could purchase only one 2-litter bottled-water. It is not easy to find bottled-water which is seemed to free from radioactive things. As I don't want to drink tap water, I have been purchasing small amount bottoed-water, which is about 3 times higher price than gas. I could not even find it today.
By the way, I have heard that one of the reason of this water shortage is, bottled water packs are sending to refuges. it is priority of course. some area don't have tap water still now, one month after the earthquake.
Secondly, the earthquake destroyed many plants, besides shortage of electric power, many plants can not run as usual. Especially one maker of lid part of plastic bottle has been affected badly. That become a literally bottle neck.