Where in Sichuan is 虾 pronunced ha1 (xa⁵⁵)? 《现代汉语方言音库 • 成都话音档》has two listings for 虾 one that says:


  xa⁵⁵ 又ɕia⁵⁵


xa⁵⁵ can pretty much be pinyinized as ha1 - for simplification here.

And there is of course a second entry that says:


  ɕia⁵⁵ 又xa⁵⁵


Now of course it looks like I've answered my own question - seeing as the name of the book is 成都话音档. But, ha1 is not a pronunciation I've heard before for 虾 in Sichuanese and most people don't believe that it even exists. I'm curious as to where this pronunciation is still maintained in Sichuan.

It's certainly part of the vestiges of 湖广填川.
It does not exist any more in Chengdu dialect (my mother's tongue), but I think if you regard Chongqing dialect as a part of Sichuanese, there must be somewhere.

The only usage of 'ha' in Chengdu dialect is in 蛤蟆 but it is ha2, and it does not seem to be a native word in Sichuanese but imported from Standard Chinese. We traditionally use 赖克宝 instead.

The dialects in some place in Chongqing sometimes pronounce 解决 as gai3 jio2. And I believe that this is because they mostly keep the original dialect inherited from Hubei/Hunan dialect. So 虾 must be pronounced as ha1 there.