This year, at least in San Diego and Oceanside, the restrictions have odd numbered addresses watering 3 days a week, and the even numbered addresses watering three other days of the week, with one day -- at least in Oceanside -- where nobody can water.
I suspect that the major reason for this is not for equity (the odd-even scheme gave odd numbered houses more summer days where they could water since both July and August have one more odd numbered day than even numbered days), and certainly was to make it easier to remember. I'm pretty sure the reason is technological.
Twenty or more years ago, automated watering systems were found mostly at large commercial properties, golf courses and other large watering systems. Homes were generally manually controlled -- often just with hoses connected to manual sprinklers. Now, a significant percentage of homes with built in sprinklers (which should be homes in dryer climates -- I only watered the lawn, and only a bit, one of the years I owned and occupied homes in Illinois) have these automated systems. The system at our house, and I presume most systems, can easily be programmed to water on specific days of the week, but not on odd or even days. And making the rule different for manual watering and automated watering would be both unfair and unenforceable (if caught on the wrong day, you could often claim that you had whatever type of system you don't have and get away with it).
And our system is now programmed to water the correct 3 days a week, for 8 minutes. If the lawn starts dying too quickly, I'll bump it back to 10 minutes. After that, if it dies, either I'll let it die, or suggest that the landlord can take over the water bill and pay the fines for extra watering.
