I dunno, I’ve maintained lawns for 20 years and I’ve never watered any of them—none are brown. The trick is to not have a monoculture lawn; get some clover and mix it in. I haven’t spent a dime on seed or fertilizer, and I mow weekly. For weeds, I just pull what looks gross. I’m in zone 5b near the Great Lakes, USA.
@Oren
Australia is hot; sometimes we have low rainfall, regularly hitting 97°F.
Kill the lawn and switch to buffalo grass. Super low maintenance and drought-tolerant; plus, it looks great.
You could plant some nice native plants along the curb to reduce the amount of grass you need to water. Xeriscape.