The source of the 29.4-kilometre Karigasjoki River is located on Oađátmohčohka fell in the northern part of Muotkatunturi Wilderness Reserve. After first heading into a northeasterly direction, it turns northwest and meets the Cuohkatanája, a tributary flowing from the north. The River Karigasjoki winds its way westwards in a flat, peaty valley. It is joined by the Luomusjoki from the north, which is considerably longer than the main channel, and the Vudnjosjohka, Vuorgočearjohka and Buoidatjohka from the south. The lower reaches of the river flow faster, and after the Buoidatjohka confluence, it runs in an almost constant series of rapids until it joins the Anárjohka (River Inarijoki) south of Old-Karigasniemi village. The easiest way of reaching the River Karigasjoki for paddlers is following a quad trail that starts at the end of the forest road along the Luomusjoki River for around 2.5 km.