The Rees River is a headwater tributary of the Clutha River / Mata-Au that drains eastward of the main divide of the Southern Alps / Kā Tiritiri o te Moana in New Zealand. The river runs 41 km, drains an area of 406 km², and discharges into the head of Lake Wakatipu at Glenorchy. Bound by the Richardson Mountains to the east and the Forbes Mountains to th…The Rees River is a headwater tributary of the Clutha River / Mata-Au that drains eastward of the main divide of the Southern Alps / Kā Tiritiri o te Moana in New Zealand. The river runs 41 km, drains an area of 406 km², and discharges into the head of Lake Wakatipu at Glenorchy. Bound by the Richardson Mountains to the east and the Forbes Mountains to the west, its snow-covered headwaters rise above 2000 m.