What is the fine-grained topic of the following text: COMMERCE, Calif. —Thirty students from Keri Wohlford's fifth- and sixth-grade class at Robert Hill Lane Elementary in Monterey Park, Calif., used water conservation practices to revitalize their school garden, while learning and teaching others about water-use efficiency, to take fourth place in the 2019 California Water Service (Cal Water) H2O Challenge. Only return the topic.
Water conservation practices in a school project