| Ahaura River | |
| Source1 Location: | Tūtaekurī River and Waiheke River |
| Mouth Location: | Ahaura River |
| Subdivision Type1: | Country |
| Subdivision Name1: | New Zealand |
| Length: | 65km (40miles) |
| Source1 Elevation: | 270m (890feet) |
| Mouth Elevation: | 40m (130feet) |
The Ahaura River is in the South Island of New Zealand. This river drains the western flanks of the Southern Alps and flows into the Grey River.
The Ahaura and its many tributaries rise in the Lake Sumner State Forest park and enters the Grey River at the small settlement of Ahaura approximately 30 km upstream from Greymouth. It drains a huge area of land and in its lower reaches below the Haupiri confluence can have a tea-colour stain for much of the year. The reaches above the junction with the Haupiri tend to have very clear water however for much of the year.[1]
Other rivers in the catchment are the Nancy, Trent, Tutaekuri and Waiheke Rivers. They can all be kayaked, except in late summer and they are the most used rivers on the West Coast. The lower gorge has remnants of Chinese miners' gold diggings. Pack-tracks to Canterbury used to go through Amuri Pass into the Doubtful River Valley and by the Tūtaekurī to the Hope River. The Ahaura in the gorge is a wide, fast, shallow, braided river, with extensive grassy flats, surrounded by beech forest. Earthquake Rapid, is the largest rapid on the river. A 1981 survey described the scenic and recreational values of the gorge as exceptional.[2]
The river is only bridged by the Stillwater–Ngākawau Line and SH7.[3] A punt operated across the river from 1871[4] to 1879, when it was replaced by a bridge.[5] The first railway bridge opened in 1890.[6]
At the gorge the Ahaura's 7-day mean annual low flow is 26.45m2 per second, the mean flow 99.77m2 and the maximum recorded flow 3972.06m2.[7] On 26 December 1957 the flood gauge at the SH7 bridge reached 7.35m (24.11feet). The river's catchment is 870km2.[8]
Gold digging started about 1865[9] and a small settlement of shanties had been built at Ahauru by January 1866.[10] 3,300 were reported to be at work in the area by March 1866[11] and a bridle path had been formed.[12]
The Ahaura Terraces and Nancys Clearing Ecological Areas were declared in 1997 to protect kahikatea and red beech (tawhai raunui) forests on the river's terraces, including kākāriki parakeets.[13]