The
Grey River / Mawheranui is located in the northwest of the
South Island of New Zealand. It rises in
Lake Christabel, one of numerous small lakes on the western side of the
Southern Alps,12 kilometres southwest of the
Lewis Pass, and runs westward for 120 kilometres before draining into the
Tasman Sea at
Greymouth. The river was named by explorer
Thomas Brunner in honour of New Zealand politician
Sir George Grey. The official name of the river was changed to Grey River / Mawheranui in 1998 by way of the
Ngai Tahu Claims Settlement Act 1998. The
Maori name for the river system and surrounding area is
Mawhera, with Mawheranui being distinguished from the northern branch Little Grey River / Mawheraiti.