The Nelgese is the longest tributary of the Adycha. It begins between two high ranges of the Verkhoyansk Range, running approximately from north to south to the west of the Khunkhadin Range. It heads roughly north across the Yana Plateau in a wide, swampy area dotted with ancient lakes. Then it turns northeast at the feet of the northwestern side of the Nelgesin Range, flowing through a narrow valley before it joins the Adycha 78 km downstream from the mouth of the Derbeke and 13 km upstream from the mouth of the Charky.