Mangatangi River

The Mangatangi River, or Mangatangi Stream, originates on the eastern slopes of the Hunua Ranges in New Zealand and flows roughly southwards until it is joined by the Ruaotehuia Stream just north of State Highway 2 between Mangatāwhiri and Maramarua, where it becomes the Maramarua River. Mangatangi can be translated as manga tangi to stream of weeping,[1] or as rippling stream, or babbling brook.[2]

Not to be confused with Mangatangi Streams near Waverley, near Shannon, or flowing into Lake Taharoa.

Mangatangi River
Mangatangi River is located in New Zealand
Mangatangi River
Location
CountryNew Zealand
Physical characteristics
Source 
 • locationHunua Ranges
 • elevation688 m (2,257 ft)
Mouth 
 • location
Maramarua River
 • elevation
15 m (49 ft)
Lengthapprox. 35 km (22 mi)
Basin size196 km2 (76 sq mi)
Discharge 
 • locationSH 2 bridge
 • minimum0.127 cubic metres per second (28 imperial gallons per second)
 • maximum183 m3/s (40,254 impgal/s)

River or stream?

The dictionary defines a river as a large natural stream. The Mangatangi is called a stream by some sources and a river by others. The New Zealand Geographic Board hasn't given it an official name.[3]

The 1:50,000 map shows it as a Stream,[4] but LAWA calls it a River,[5] as does Regional Council in documents on swimming[6] and flow,[7] but a Stream in its catchment management plan.[8] Other references to River are 1894[9] and 1895[10] requests for a bridge, a Ratification Information Booklet and on Te Awa,[11] RNZ,[12] District Council,[13] National Library and local historical group websites.

Geology

The river starts as several small streams on the eastern slopes of the Hunua Ranges. Greywacke and argillite[14] of the Waipapa Group[15] form the High Hunua Horst and underlie the river in the Hunua Ranges.[14] The south-eastern boundary of the horst is the Mangatangi Fault, which runs along the north-west side of the mid section of the river.[16] The upper stream is typically shallow, fast flowing, with cobble and gravel substrate.[14]

Human use

As well as being a water and recreation resource, the river was historically a transport link. It also provided shingle to metal local roads[17] and that use continues.[18] A flax industry also existed as late as 1930.[19]

Mangatangi Dam

The earth-fill dam (2,140,000 m3 (76,000,000 cu ft), with stone facing, was built between 1972 and 1977, on a foundation drainage filled with greywacke,[20] with a 67 m (220 ft) high bellmouth spillway.[21] It is 340 m (1,120 ft) wide, 78 m (256 ft) high and can hold 39,000,000 m3 (8.6×109 imp gal) of water covering 169 ha (420 acres).[20]

Bridges

In 1897 Whangamarino Road Board built a girder bridge across the river.[22] By 1914 it was in disrepair.[23] A flood swept a temporary bridge away, whilst a replacement was being built in 1922.[24]

Further upstream, Stubbs Bridge was also built in 1922, swept away in 1966 and replaced in 1967.[13]

In 1921 Franklin County Council rejected a tender for a bridge with concrete piers, a main span of 64 ft (20 m) and two 20 ft (6.1 m) side spans.[25] Stubbs Bridge was opened on 22 December 1924 by Minister of Public Works, Gordon Coates.[26]

Ecology

Species

Introduced species include rainbow and brown trout. Koi carp[27] and mosquitofish, have become major pests.

Trout were introduced in 1885.[28]

Water quality is high in the regional park, but degrades downstream with increasing agricultural land use, so that by the Watercare Services flow gauging weir, given consent in 2001, only eels and Crans bully (Gobiomorphus basalis) were recorded. Galaxiids are largely absent upstream of the weir. Longfinned and shortfinned eels, and Crans bully are common.[14] Attempts were made in the past to trap eels, in the belief that they damaged fisheries.[29]

Grey teal, brown teal and grey duck have been seen on the reservoir.[30]

Environmental issues

Pollution measurements near the mouth of the river show that it is among the worst 25% of waterways in the country for a majority of pollutants.[27] The catchment is mostly fertile farmland, so intensive agriculture is present and significant agricultural pollution is leached into groundwater and contained in the runoff.

The removal of the native vegetation throughout the catchment to accommodate the increasing demand for farmland has contributed to the silting of the river with loose soils from eroded farmland. That would have been exacerbated by floating the felled logs down the stream, which was licensed under the Timber Floating Act 1873 till at least 1911.[31]

References
  1. "1000 Māori place names - Te Wiki o Te Reo Māori - Māori Language Week | NZHistory, New Zealand history online". nzhistory.govt.nz. Retrieved 20 December 2017.
  2. "North Eastern Waikato Community Plan 2011" (PDF). Waikato District Council.
  3. "New Zealand Gazetteer: Search for Place Names". Land Information New Zealand (LINZ). Retrieved 24 November 2017.
  4. "Mangatangi Stream, Waikato". NZ Topo Map. Retrieved 5 December 2017.
  5. "Land, Air, Water Aotearoa (LAWA) - Mangatangi River at SH2 Maramarua". www.lawa.org.nz. Retrieved 5 December 2017.
  6. "Mangatangi River at Maramarua". Waikato Regional Council. Retrieved 5 December 2017.
  7. "River Level Primary at Mangatangi". riverlevelsmap.waikatoregion.govt.nz. Retrieved 5 December 2017.
  8. "Lake Waikare and Whangamarino Wetland Catchment Management Plan" (PDF). Waikato Regional Council. 2017.
  9. "ROAD BOARD MEETINGS. (New Zealand Herald, 1894-12-12)". paperspast.natlib.govt.nz. Retrieved 24 November 2017.
  10. "COUNTRY NEWS. (New Zealand Herald, 1895-12-25)". paperspast.natlib.govt.nz. Retrieved 24 November 2017.
  11. Taonga, New Zealand Ministry for Culture and Heritage Te Manatu. "Mangatangi dam". teara.govt.nz. Retrieved 5 December 2017.
  12. "Mangatangi Marae says mine adds insult to injury". Radio New Zealand. 17 October 2013. Retrieved 5 December 2017.
  13. "Stubbs Bridge - Mangatangi River" (PDF). Waikato District Council.
  14. Barnes, Grant E (June 2004). "Barriers to fish passage in the Hunua Ranges and Waharau Regional Parks" (PDF). Auckland Regional Council.
  15. "1:250 000 Geological Map of New Zealand (QMAP) / Auckland - GNS Science". www.gns.cri.nz. Retrieved 20 December 2017.
  16. "The Geology of the Tuakau-Mercer Area". Royal Society of New Zealand. 1948. Retrieved 19 December 2017.
  17. "THE MOTOR WORLD (New Zealand Herald, 1924-12-06)". paperspast.natlib.govt.nz. Retrieved 25 November 2017.
  18. "Our Products". Mangatangi River Rock Ltd. Retrieved 19 December 2017.
  19. "EXCHANGE ON LONDON. (New Zealand Herald, 1930-02-18)". paperspast.natlib.govt.nz. Retrieved 19 January 2018.
  20. "Engineering Heritage". www.ipenz.org.nz. Retrieved 24 November 2017.
  21. "Slaking the Big Thirst". New Zealand Geographic. Retrieved 24 November 2017.
  22. "SATURDAY, MARCH 6, 1897. (Waikato Argus, 1897-03-06)". paperspast.natlib.govt.nz. Retrieved 25 November 2017.
  23. "WORK IN THE COUNTY. (Pukekohe & Waiuku Times, 1914-07-10)". paperspast.natlib.govt.nz. Retrieved 25 November 2017.
  24. "TUESDAY, JANUARY 31, 1922. LOCAL AND GENERAL. (Pukekohe & Waiuku Times, 1922-01-31)". paperspast.natlib.govt.nz. Retrieved 25 November 2017.
  25. "ROAD WORKS IN FRANKLIN. (Pukekohe & Waiuku Times, 1921-02-08)". paperspast.natlib.govt.nz. Retrieved 18 January 2018.
  26. "POSTAL PROGRESS. (Pukekohe & Waiuku Times, 1924-12-24)". paperspast.natlib.govt.nz. Retrieved 18 January 2018.
  27. "Land, Air, Water Aotearoa - Mangatangi River at SH2 Maramarua". www.lawa.org.nz. Retrieved 24 November 2017.
  28. "SUMMARY GOLD RETURNS. (Thames Advertiser, 1885-01-31)". paperspast.natlib.govt.nz. Retrieved 5 December 2017.
  29. "CLEARING RIVER OF EELS (New Zealand Herald, 1938-09-14)". paperspast.natlib.govt.nz. Retrieved 25 November 2017.
  30. "ducks on Mangatangi dam Hunua". www.birdingnz.net. Retrieved 24 November 2017.
  31. "AUCKLAND LAND BOARD. (Auckland Star, 1911-07-27)". paperspast.natlib.govt.nz. Retrieved 25 November 2017.

37.224363°S 175.174833°E / -37.224363; 175.174833

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