MIZU MAHOU GURAI SHIKA TORIE GA NAI KEDO GENDAI CHISHIKI GA AREBA JUUBUN DA YO NE?

Frim, a 5-year-old orphan living on the streets in the slum, remembers her past life as a Japanese woman. Her daily life is filled with violence and injustice, and she has no one on her side. All she has is water magic and modern knowledge. Even a roofed place to sleep is a luxury. But by improving her environment with ideas that don't yet exist in this world, and finding ways to use water magic for things other than drinking, Frim gradually makes a name for herself... (Source: ComicWalker, translated) — Description from AniList community (anilist.co).