The Inhini River's watershed covers 135 km2 (52 sq mi),[6] and its mean annual discharge is an estimated 12.4 m3/s (440 cu ft/s).

[6] The mouth of the Inhini River is located about 57 km (35 mi) east-northeast of Wrangell, Alaska, about 130 km (81 mi) northwest of Stewart, British Columbia, and about 135 km (84 mi) south of Telegraph Creek, British Columbia.

[11] The Inhini River originates in two forks near the border of Alaska.

The longer eastern fork flows from the glacial meltwaters of Mount Rastus[12] and Simma Mountain,[13] close to the source of Simma Creek,[14] a tributary of the Craig River.

This fork flows for about 7 km (4.3 mi) before being joined by the west fork, which flows from the glacial meltwaters of Mount Fawcett,[15] an Alaska–British Columbia boundary peak.