Waihou is literally translated as “new water”. The river is approximately 80 miles long and rises mainly in the Mamaku and Patetere plateaus between Putaruru and Rotorua. For most of its length it flows north-north-westwards along the eastern side of the down-faulted Hauraki depression, finally joining the sea near Thames on the eastern side of the Firth of Thames – the river also being named the Thames by the navigator Captain James Cook.
The absorbent nature of most of the catchment area prevents flash flooding except in the major tributary, the Ohinemuri River, which joins the Waihou at Paeroa and flows from the Coromandel Range to the east. Peak discharges may have exceeded 35,000 cusecs, the bulk of the discharge being from the Ohinemuri River. Minimum discharges have probably been less than 1,000 cusecs. It is navigable for small boats as far as Paeroa, 20 miles from the coast.
by James Cecil Schofield, M.SC., New Zealand Geological Survey, Otahuhu.