The Tauwharenīkau River flows from Mount Hector in the Tararua ranges down to Lake Wairarapa, draining the area of the Tararua ranges between the Waiohine River and the Hutt River. It is described as the smallest of the three rivers in this part of the range. As the river exits the mountains, it passes through a notable gorge, which is a defining feature of the paddling experience.

The primary documented paddling route runs from Cone Hut to Bucks Road, rated Class II at normal flows and rising to Class III at high water. This trip can be completed as a day trip or stretched into a two-day outing, and is accessible as either an out-and-back or a through trip. The river is flow-dependent and requires a reasonable amount of rainfall to be in paddleable condition — it is described as needing "a little rain," which is an important planning consideration. Paddlers should monitor flow levels before committing to a trip, particularly during drier periods.

The gorge section is considered visually striking, and the overall character of the river is shaped by its mountain origins and the confined canyon it cuts through as it leaves the ranges. Given its location in the Wellington region of New Zealand's North Island, the river is accessible for day trips from the wider Wellington area.