Waipa River


The Waipa River is in the Waikato region of the North Island of New Zealand. The headwaters are in the Rangitoto Range east of Te Kuiti. It flows north for, passing through Otorohanga and Pirongia, before flowing into the Waikato River at Ngāruawāhia. It is the Waikato's largest tributary. The Waipa's main tributary is the Puniu River.
In the headwaters upstream of Otorohanga the river can be very clear during low flow conditions. This section of the river flows through rough farmland and patches of native bush. In this clearer part of the river there can be very good fly fishing for trout, but you'll need to ask the land owners permission to access the river.
The Waipa is prone to flooding in its lower reaches as flood flows can be over 100 times——those of dry flows and the river can rise up to.
In 2013 Maniapoto Māori Trust Board and the riparian local councils set up a joint management agreement for the river, following the passing of Nga Wai o Maniapoto Act 2012.

Speed of flow

The table below shows the time water takes to flow the from Te Kuiti to its confluence with the Waikato in times of low flow and high flow -

Power stations

In 2003 Hydro Power Ltd was given consent to build a hydro-electric power station, with weirs in the , upstream from Owen Falls, and penstocks carrying water down the gorge to a station on the west bank below the falls. Work was done in 2006, but, in 2007, Hydro Energy Ltd was fined for unconsented damage to native vegetation in building the penstock. The resource was initially estimated to be able to generate 10 to 20MW. Construction halted, though Renewable Power bought the asset in 2010 and estimates potential at 9MW.
In 2017 Nova Energy were given consent to build a 360MW gas-turbine station on the Ongaruhe Stream, close to its confluence with the Waipa. The mid-merit Waikato Power Plant at 869 Kawhia Rd, Otorohanga is expected to be used for 10 to 15 minutes, 3 or 4 times a day.

Pollution

measures water quality monthly at five sites from Mangaokewa to Whatawhata. The measurements show poor quality along most of the river, with excess nitrogen, silt and phosphorus, though E. coli levels have improved with improved sewage treatment, though generally not enough for safe swimming; recreational rivers should have median E. coli levels below 126 per 100ml, but Waipa's range from 160 to 320. Turbidity levels north of Otorohanga rise to more than double the levels needed to support plant photosynthesis and phosphorus levels also rise above targets in that stretch. Nitrogen levels increased at all five sites between 1993 and 2012 due to intensified land use, now adding 3,075 tonnes a year. By comparison, the total from sewage works and Te Awamutu dairy factory is 66 tonnes.
Ministry for the Environment figures averaged between 1998 and 2007 showed the Waipa at Otorohanga had 280 E.coli per 100ml, 360 faecal coliforms per 100ml, 0.55 mg/litre nitrogen and 0.03 mg/litre phosphorus.
At Pirongia the figures were 390 E.coli per 100ml, 425 faecal coliforms per 100ml, 0.49 mg/litre nitrogen and 0.06 mg/litre phosphorus.
At Whatawhata the figures were 0.92 mg/litre nitrogen and 0.06 mg/litre phosphorus.
In the Mangaokewa stream 0.02 mg/litre phosphorus.
Pollution has been worsening for nitrogen and phosphorus, though turbidity has improved, as shown in this table of important improvements, or deteriorations in relative seasonal Kendall slope estimator trends. in the river at Whatawhata -
TurbidityNitrate-NDissolved reactive P
1993–20172.0-1.2
2008–20175.9-2.0

Soil conservation

Regional Council estimates that is at risk of severe erosion in the Middle Waipa and of stream bank to be prone to erosion. Project Watershed plans for planting on, plus 976 km of stream bank and 1,332 km of fencing, from 2017 to 2026.

Organic farming

In 2018 a scheme was launched by the Waikato River Authority to attract investment in $100 million of hybrid bonds to convert up to 18 dairy farms on, or roughly 5% of the catchment, to organic farms, with the aim of reducing pollution from the worst farms by about 45%.

Bridges

Listed in order from the confluence with the Waikato and moving south they are:-
Over was navigable by waka and Pirongia was busy as the head of steamboat navigation until the railway was built to Te Awamutu in 1880, though some settlers used it as far as Te Kuiti. The steamship Lillie was used on the river from at least 1876 to 1878. From 1902 to 1909 H H Gould ran the 1899 5 hp SS Opuatia from Ngāruawāhia to Whatawhata one day and on to Pirongia next day. A 1915 guidebook still said, "Small steamers ply up and down the river from Huntly". An 1881 article said a journey upriver would normally take 36 hours, but more in dry weather, when shoals at Whatawhata and Te Rore were hard to cross. An 1898 petition complained about wharfage charges at Mercer being a tax on residents along the Waipa. Around 1900 the Freetrader, owned by the Waikato Company, "was withdrawn owing to competition from the Walsh brothers with their launch Victory, which could traverse the winding Waipa much more easily than the cumbersome stern-wheeler."
As late as 1919 Waipa County Council pressed for removal of shingle shoals to permit navigation to Pirongia and got money for improvements from government and the county councils. Evidence given to the Inland Waterways Commission in 1921 said boats carrying 20 tons could reach Pirongia for most of the year and, up to about 30 years before, vessels carried 60 tons to Pirongia and a special fleet of steamers ran to Te Kuiti. Steamers were set back by the sinking of the Opuatia at Whatawhata in 1920. The Waikato Shipping Co had been running a weekly service to Pirongia with the former Waihou River steamer, SS Erin, which seems to have continued until WSC stopped trading in 1922. A Public Works Department report in 1925 said the river was non-navigable above its junction with the Mangapu at Otorohanga.