The Clarence/Waiau-toa is one of NZ’s longest and least known rivers. The river begins at Lake Tennyson on the eastern slopes of the Spenser Mountains in the Lewis pass area. The headwaters of all the major top-of-the- south rivers originate in these mountains, the Waiau-toa (Clarence), Waiau, Kawatiri (Buller) and the Wairau. The Clarence and the Waiau flow parallel on either side of the St James range until the Clarence turns at the Hanmer range and flows NE between the Kaikoura ranges. It continues in this direction until rounding the northern end of the Seaward Kaikoura Mountains and then flowing south into the Pacific Ocean near the settlement of Clarence, 40 km north of Kaikoura.