Erin Brockovich made her name decades ago as an environmental activist who exposed corporate wrongdoing that polluted drinking water.

So she felt a bit defensive when a television reporter asked how her name landed on a list of water guzzlers during a dire California drought. At one point last year, she received a $1,700 bill for two months of water and fines.

Ms. Brockovich ultimately decided she had to get rid of her lawn, a central part of the backyard oasis she had built over more than two decades living in Agoura Hills, a suburb of large homes with immaculate yards about 40 miles northwest of downtown Los Angeles. She replaced 3,100 square feet of grass with high-tech artificial turf.