Waaaaater. Yeah, water's everywhere in this book. But don't worry—no one drowns.
For the most part, water in this novel is seen as something clean and pure, so whenever it's referenced, it's pretty much a good thing. Dinah even says Rachel smelled like water: "Rachel smelled like water. Really! Whenever my aunt walked, there was the scent of fresh water. It was an impossible smell, green and delightful and in those dusty hills the smell of life and wealth" (1.1.16).
How does someone smell like water? Well, as Dinah says, "it was an impossible smell," so really, Dinah's sort of making this up. But not entirely. Since Rachel smells like water, that indicates her symbolic purity. She might not have actually smelled like fresh water, but Dinah means there was something about Rachel, some kind of metaphorical scent, that emanated "life and wealth" from her auntie.
Dinah herself has pretty close ties to water. In her dreams, she's visited by Taweret, a river goddess. As Inna tells her, "You are a child of water. Your spirit answered the spirit of the river. You must live by a river someday, Dinah. Only by a river will you be happy" (2.3.37).
Yeah, water in this novel is also kind of a lady thing. Just as the tides are influenced by the movements of the moon, so are women's periods, or their time in the red tent. Being in touch with water also means that characters like Dinah are in touch with their femininity. Which is a good thing to be in touch with if you're, you know, a midwife.