Well my understanding is that visa, MasterCard ECT. Are far more efficient in terms of energy and transaction time when compared to Bitcoin and Ether. Visa uses about a quarter of the power per 100,000 transactions.
So I would assume that would mean fewer data center computers to cool and therefore less water used per transaction
https://summerschool.globalbioethics.org/wp-content/uploads/2015/11/Savulescu-2001-Bioethics.pdf