It rises on the north slopes of the Mamaku Plateau at the southern end of the Kaimai Range and meets the Opuiaki River at the head of Lake McLaren, which discharges to the Wairoa River a short distance downstream from the lake at the confluence with the Mangakarengorengo River.

The river has been modified as part of the Kaimai hydro power scheme.

The 15.6 MW Lloyd Mandeno Power Station is on the left bank of the river and discharges water diverted from other nearby streams.

About 4 kilometres (2.5 mi) below this is a concrete arch dam with the 6.25 MW Lower Mangapapa Power Station.

This article about a river in the Bay of Plenty Region is a stub.