Anonymity, presumably. That said, you'd think there would be no reason that whatever real-world authority is ensuring no one extracts more than their purchased credits allow would already have all the secret information and could just be the clearing house for the transactions.
Farmers are on large plots, and there is only so much watertable. Why do they need to be anonymous?
Sounds like more blockchain hype + the hidden potential for Nestle or whoever to buy up all the water rights discretely. Utilities should not be anonymous.