Post apocalyptic 3 short stories dystopian novel

I read this book a few years ago and its driving me mad trying to remember the name!
I think the book was split into three sections, I can't remember what disaster had occurred - potentially a nuclear bomb of some sort.

The first section involved a family trying to survive in their house, they had a bath filled with water to drink out of and were all getting ill except a little girl who refused to come out from under the dining room table and didnt drink from the bath water, only her own supply which was not infected. I think the dad shot the family's dog or cat or they just left it outside to die as it was crying at the back door. I remember something about them raiding an abandoned supermarket for food.

Another section was set on a farm in the middle of nowhere but I don't remember much about it. I think there was some kind of rape or incest there, I may have mixed that up with another book.

The final section was about a community living in a bunker. They had built up a working system with schools and family units, cant remember how they had the supplies to survive.

If anyone knows which book i'm talking about i'll be very appreciative!! Some of the facts are probably wrong, its hazy! Thanks.

Children of the Dust by Louise Lawrence. My brief note after I read it: A depressing story, but also riveting and a fast read. Additional thought: Don't read if you are squeamish.

As a post script, another multi-generational multi-part story by the same author is The Crowlings. It was pretty good too. Set on another planet, futuristic.
Summary: Young Ben Crowling suddenly becomes leader of his clan. This position enables him to learn how dissatisfied his people are with the clan's ancient traditions. Mikklau wants to go to the city were money is easy to earn, Linni wants to enjoy a comfortable and carefree life. In The Crowlings, the clan comes to realize they must re-adopt the old way of life if they are to survive.

Louise Lawrence has written several science fiction novels but her stories tend to be more 'depressing' and sad than Monica Hughes' books.

Ahh thats it thank you! Always wanted to find the book again since reading it.

The original post also reminded me of The Girl Who Owned a City which is another fun post-apocalyptic read. (A little heavy on the Ayn Rand, but if you can get past politicking in your fiction... )

I'm unsure what you meant in the last sentence... but the original query is definitely Children of the Dust by Louise Lawrence.

Oh, I know the original query was solved, it's just the way she described the book reminded me of Girl Who Owned a City, and so I was recommending it as an additional read - with the warning that there was a lot of moralizing/political opinion in there as well (some people don't like reading stuff like that, so I try to warn if I remember.)

Not trying to confuse the requester, just to offer another read she might enjoy.

I have it wishlisted myself, it sounds good!