The Ōpārau River is a river of the Waikato Region of New Zealand's North Island in the area occupied by Ngāti Hikairo.^[1] It flows southwest from its sources in the Pirongia Forest Park, the highest being The Cone, and flows into the Kawhia Harbour, 5 kilometres (3 mi) east of Kawhia.^[2] The river has about 171 km (106 mi) of tributaries.^[3]

The New Zealand Ministry for Culture and Heritage gives translations of "place of many fortified villages" or "place of falsehood" for Ōpārau.^[4] The official name was confirmed by Gazette as Ōpārau River on 21 June 2019.^[5]

The river is naturally turbid and had low to moderate levels of phosphorus and nitrogen,^[6] though it is among the poorer rivers for ammoniacal nitrogen, black disc and e coli measurements.^[7]

Tiritiri Matangi peninsula, in the river's estuary,^[8] is a protected area of international ecological significance, as it is an important stop for migratory seabirds.^[9] Redfin bully and kōaro are common fish in the river.^[10] Fragrant fern^[11] and Pānakenake grow in the valley.^[12]

Walking tracks around the upper catchment of the river are the Ōpārau Route, Bells Track and Hihikiwi Track (part of Te Araroa long distance trail).^[13]

In 1885 the road crossing the river was only 6 ft (2 m) wide at Ōpārau.^[14] From about 1900 a coach ran for passengers between Kawhia and Te Awamutu,^[15] with a launch between Kawhia and Ōpārau.^[16] Ōpārau Ferry Bridge opened in 1913.^[17] In 1924 a 52 ft (16 m) concrete bridge was built over the Ōpārau to carry what is now SH31.^[18] Metalling of the road was completed in 1926.^[19]

In 1938 the Hamilton mayor, John Fow, and Chamber of Commerce were reviewing plans for a new link to Kawhia. A route through the valley, via Kaniwhaniwha^[20] and Karamu was suggested and, by 1945, there was much backing for a 10 mi (16 km) long road on that route, which would have reduced the distance between Hamilton and Kawhia by about 20 mi (32 km).^[21]

From 1923 Ōpārau was served by hydroelectric power, generated for the dairy^[22] by a 33 hp (25 kW) turbine at Mangapapa Falls,^[23] about 2 km (1 mi) upstream from the village.^[24] A 1922 Order in Council allowed up to 10 cu ft (283 L) per second of water to be taken.^[25] The dairy opened in 1904.^[26]

Ōpārau village had a school from 1902^[27] until it closed in 2006.^[28]

• List of rivers of New Zealand

"Place name detail: Oparau River". New Zealand Gazetteer. Land Information New Zealand. Retrieved 12 July 2009.

Photos -

• Landing shed and boat
• Bridge, store and probably dairy factory about 1912
• Bridge and landing shed about 1915
• Remains of hydroelectric dam in 1984
• Mangapapa Falls

38°03′S 174°55′E / 38.050°S 174.917°E / -38.050; 174.917