The Nelson/Churchill basin is the third largest watershed in North America, with a drainage area of more than 1.4 million square kilometers.

The Nelson River receives water from Lake Winnipeg and flows through northern Manitoba to Hudson Bay.

The Churchill River flows through parts of northern Alberta, Saskatchewan and Manitoba, with a portion of flow being diverted into the Nelson River at Southern Indian Lake, Manitoba and the remaining waters flow through the Churchill River to Hudson Bay.

Nelson River: https://en.wikipedia.org/wiki/Nelson_River
Churchill River: https://en.wikipedia.org/wiki/Churchill_River_(Hudson_Bay)