We live on a hill too. A very steep one, but we never ever water the lawn. Whatever survives survives, and what doesn’t goes away. No way we are going to risk running our well dry to water the lawn or the garden either.
Of course, what other people do also affects the water table, so all those people that do water their lawn, reduce the whole level including ours.
We watered the perennials and orchard and nut trees last year and let everything else just burn up.
Last year we even used kinda clean shower water to water plants, and all the water from the water bath canner, and water used to rinse dishes etc etc.
If it weren’t for hurricanes and TS’s, I wouldn’t water either, we have to pay for our water and it’s not cheap. We have several erosion walls along the hillside that help, but we are having to raise them higher. Raised one last weekend, got several more to go as I can afford.