Let's see, software I've never heard of and helping someone who's never designed a tank? Absolutely nothing could go wrong, huh?
Nader, you went from asking questions on another engineer's disaster of a design to now doing this yourself, using software you're not familiar with? You need to have someone who is familar with this help you, step by step. It would be much better if you were to use the Bureau of Reclamation tables, rather than a black box.