The Koshin River's watershed covers 437 km2 (169 sq mi),[5] and its mean annual discharge is 4.89 m3/s (173 cu ft/s).[5] The mouth of the Koshin River is located about 165 km (103 mi) northeast of Juneau, Alaska and about 115 km (71 mi) north of Telegraph Creek, British Columbia. The Koshin River's watershed's land cover is classified as 43.0% conifer forest, 36.3% shrubland, 8.8% mixed forest, 5.4% barren, 2.5% wetland, and small amounts of other cover.[5]
The Koshin River originates on the north side of Level Mountain on the Nahlin Plateau. From its source the river flows generally north for about 58 km (36 mi).[4] From its source it first flows northwest to Hatin Lake,[11] just west of Callison Ranch.[12] This headwater reach of the Koshin River lies just north of Matsatu Creek.[13] From Hatin Lake the Koshin River flows north along a meandering course with many wetlands. Lost Creek joins the Koshin, flowing northwest from Level Mountain.[14] A few kilometres downriver Kaha Creek joins the Koshin, also flowing northwest from Level Mountain.[15] Continuing north the Koshin River passes by a number of lakes, including Tedideech Lake,[16] before emptying into the Nahlin River at Nahlin Crossing.[17][13]
The historic Yukon Telegraph Trail follows much of the Koshin River, passing through Callison Ranch and running north along the river to Nahlin Crossing.[18][13]
^ abcLength measured using Google Maps path tool, BCGNIS coordinates, topographic maps, and TopoQuest
^ abcde"Northwest Water Tool". BC Water Tool. GeoBC, Integrated Land Management Bureau, Ministry of Agriculture and Lands, Government of British Columbia. Retrieved 12 August 2021.