Running wild / Lucy Jane Bledsoe.

Enhanced descriptions from Syndetics:

Since their mother died five years ago, Willa, her younger brothers, and her father have lived in the wilderness, in a log cabin they built. They survive on food they grow and animals they hunt. Every year they have struggled a little bit more to survive. Now, with winter approaching and her father becoming more reckless, Willa wonders if they will live to see spring. She also knows her father will never agree to leave.
When her father goes on a hunting expedition by himself, Willa convinces her brothers that they must make the four-day journey down the Yukon River to Fort Yukon to get help. But first, they'll need to survive the treacherous trip...and all the while, their father is on their trail.
Perfect for middle grade readers looking for adventure stories with strong female protagonists, Lucy Jane Bledsoe's Running Wild is a page-turner that hooks you from the beginning and doesn't let go.