Only very young people, pensioners, unemployed and other welfare beneficiaries will be able to satisfy new requirements and every now and then shift workers.
People who leave home 5am every day, will have to forget the garden or use more sophisticated watering systems like water tank, bore water, grey water.
Possibly some unemployed could provide watering services, if they don’t have to hold the hose to water at their place.
Of course emigration could be encouraged and immigration restricted as well as regulation of births imposed.
After all, every human being is more than 70% of water.
And obviously somebody slept at the stern when big-dry issues were coming.