Waipā River
The Waipā 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 Ōtorohanga and Pirongia, before flowing into the Waikato River at Ngāruawāhia. It is the Waikato's largest tributary. The Waipā's main tributary is the Puniu River. In the headwaters upstream of Ōtorohanga 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 access to the river may be limited without landowner permission. The Waipā 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 ( Waipā River) Act 2012. On 16 July 2020 the official name was gazetted as Waipā River. 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 (15% of days are slower than this) and high flow (15% of days faster) - Floods. Years with large floods have included 1875, 1892, 1893, 1897, 1907, 1926, 1930, 1946, 1953, 1958, 1986, 1988, 1989, 1991, 1995, 1998, 2002, 2004 and 2012. In August 1893 the river was 3 inches (7.6 cm) higher than it was in during the 1875 flood. Maunder's mill at Whatawhata and bridges on the Whatawhata to Tuhikaramea road were washed away. A minimum flow of /second  was measured in 1946 and a flood flow of over /sec was measured in the May 1953 floods. In 1958 hundreds of houses were flooded in Ōtorohanga and Tu Kuiti. The July 1998 peak flows in the upper Waipā 776 were the highest recorded since 1958 and at Whatawhata flows were /sec, compared to /sec in 1958. In July 2002 flows at Whatawhata were /sec and, in March 2004, /sec. The 2004 flood was comparable to that of 1958. At Ōtorohanga, the Primary School and surrounding houses were flooded, when the river spilled into its old course (see map below ) and filled the area behind the stop banks. There was also flooding in July 2012. Power stations. In 2003 Hydro Power Ltd was given consent to build a hydro-electric power station, with weirs in the Okahukura Stream, 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 ( Waipā) 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 (connected to the Maui Gas Pipeline) on the Ongaruhe Stream, close to its confluence with the Waipā. 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. Waikato Regional Council 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 Waipā'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 Waipā at Otorohanga had 280 E.coli per 100ml (53rd worst out of 154), 360 faecal coliforms per 100ml (83rd of 252), 0.55 mg/litre nitrogen (161th of 342) and 0.03 mg/litre phosphorus (187th of 361). At Pirongia the figures were 390 E.coli per 100ml (35th worst out of 154), 425 faecal coliforms per 100ml (64th of 252), 0.49 mg/litre nitrogen (174th of 342) and 0.06 mg/litre phosphorus (80th of 361). At Whatawhata the figures were 0.92 mg/litre nitrogen (94th of 342) and 0.06  mg/litre phosphorus (69th of 361). In the Mangaokewa stream 0.02 mg/litre phosphorus (237th of 361). Pollution has been worsening for nitrogen and phosphorus, though turbidity has improved, as shown in this table of important (ie slope direction probability over 95% and RSKSE over ±1% pa) improvements, or deteriorations (-) in relative seasonal Kendall slope estimator (RSKSE) trends (% per year). in the river at Whatawhata (monthly records are flow-adjusted using a Lowess curve fit with 30% span.) - Soil conservation. Regional Council estimates that is at risk of severe erosion in the Middle Waipā (Waitomo, Turitea, Pirongia, Karakariki, Puniu, Mangaotama , Mangawhero and Mangapiko catchments) 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:- Steamer services. Over was navigable by waka and Pirongia (Alexandra) 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, though possibly only as far as the confluence of the Mangapu and Mangaokewa streams, about upstream from Ōtorohanga. In 1885 the river was used to carry material for the railway construction as far as Te Kuiti. Mr Gibbons' steamship, Lillie, started in 1876 to 1878. In 1895 Walsh Bros were running "SS Victory". 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 Waipā. 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 Waipā much more easily than the cumbersome stern-wheeler." As late as 1919 Waipā 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 (and sometimes SS Excelsior), 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. Settlements. Settlements near the river include Rangitoto, Otewa, Ōtorohanga, Pokuru, Puketōtara, Pirongia, Te Pahu, Te Rore, Ngāhinapōuri, Whatawhata, Te Kowhai, Ngāruawāhia.