Lake Rotoroa is the larger of the two large glacial lakes in Nelson Lakes National Park. The lakes were formed when rivers were dammed behind past glaciers’ terminal moraines (ridges of rubble that form at the front of a glacier) (source www.teara.govt.nz). Lake Rotoroa (meaning long lake in maori) is a long deep lake nestled in the montains, near the small town of St Arnaud. The Sabine and D’Urville Rivers flow into the southern end of the lake. It is one of the sources of the Buller River, draining into it via the Gowan River (Te Kauparenui). The lake is surrounded by indigenous beech forest.