This page has appendix A to the application by the New Zealand and the North Canterbury Fish and Game Councils and the New Zealand Recreational Canoeing Association. The application is for a water conservation order in respect of the Hurunui River.
- When making an application for a Water Conservation Order, section 201(2)(a) of the Act requires that the applicant shall identify the water body to which the application applies.
- The waters that are the subject of this application are:
- The mainstem of the upper Hurunui River and all of its lakes, tributaries and contributing waters (including hydraulically connected groundwaters) from its source in the Main Divide of the Southern Alps down to immediately above its confluence with the Mandamus River (at or about NZMS 260 M33 736238) ("Upper Hurunui Waters”); and:
- The mainstem of the lower Hurunui River from immediately above its confluence with the Mandamus River (at or about NZMS 260 M33 736238) down to the sea ("Lower Hurunui River").
- These waters are described below, beginning with an overview of the catchment, then moving generally from the upper to the lower catchment, from the Main Divide of the Southern Alps to the East Coast.
- The maps and photos referred to below are provided at the conclusion of this Appendix.
Overview of Hurunui River catchment
- An aerial photo of the Hurunui River catchment is provided as Photo 1. The catchment of the Hurunui River is also shown on Infomaps 260 Series L32, L33, L34, M32, M33 N33, 033.
- The Hurunui River is Canterbury’s sixth largest river by volume. It lies between the Waimakariri River to the south and the Waiau River to the north. Its source is the Main Divide of the Southern Alps adjacent to the Waimakariri, Taramakau and Ahaura headwaters, the latter two flowing to the West Coast.
- Snow lies over much of the upper catchment in winter and early spring although there are no permanent snowfields. The headwaters were strongly glaciated during the Pleistocene period and glacial processes dominate the character of the landscape.
- The Hurunui River flows in an easterly direction before entering the sea near Cheviot approximately 200 kilometres from its alpine source. The Hurunui catchment covers approximately 2670 km2. About 1060km2 (40%) of this lies in the upper catchment, which provides around 75% of the river’s total water yield.
- Long term flow records in the Hurunui River are available from the Mandamus recorder, located in the Hawarden Gorge just upstream of the Mandamus confluence. The natural hydrology of the Upper Hurunui Waters has not been modified by abstractions.
- The mean annual flow at the Mandamus recorder is 53 cumecs. The lowest flows are usually during late summer and autumn. However, sustained low flows at the Mandamus recorder site are uncommon because of regular freshes and a lack of abstraction above that point. The mean monthly flow at the recorder ranges from 34 cumecs in March to 77 cumecs in October. The mean monthly 7-day low flow1 ranges from 21 cumecs in March to 48 cumecs in October. The mean annual 7-day low flow is 16.6 cumecs. Floods can occur throughout the year but the largest and most sustained flood events tend to be in winter and spring. The mean annual flood flow is 534 cumecs with a highest recorded flow of 1,140 cumecs. Floods and freshes play a very important part in maintaining the form and character of the river and its associated habitats.
- Water quality in the Upper Hurunui Waters is very high, reflecting the natural state of the upper catchment and the lack of point source discharges to these waters.
- Water quality in three of the Hurunui Lakes, being Lake Sumner, Lake Taylor and Loch Katrine, was reported in MfE (2006). The results of water quality testing undertaken between December 2004 – April 2006 showed that Lake Sumner was microtrophic, indicating pristine water quality while Lake Taylor and Loch Katrine were oligotrophic. A comparison with water quality results from the 1990s suggests Lake Sumner has improved water quality while no change was detected in Lakes Taylor or Loch Katrine.
- In addition, two sites on the Hurunui River mainstem are included in the National Water Quality Network, including the Mandamus confluence (to indicate baseline conditions) and at the State Highway 1 bridge (to reflect ‘impact’ conditions). These records suggest that water quality at the Mandamus confluence is in its natural state, with expected fluctuations depending on flow rate (NIWA, 2007). Higher flows are naturally associated with lower clarity, higher turbidity, and higher nitrate and phosphorous concentrations. E coli levels remain low irrespective of flow. Water quality at the State Highway 1 site has been degraded as a result of land use intensification in the lower catchment.
- The Upper Hurunui Waters, including lakes, tributaries and contributing waters, and the Lower Hurunui River are described in more detail below.
Upper Hurunui Waters
- Maps 1-5 depict the lakes, major tributaries and reach of the Hurunui River mainstem that are included within the definition of the “Upper Hurunui Waters.” Photos 2 – 9 also illustrate some of the Upper Hurunui Waters.
- For the purposes of this application, the Upper Hurunui Waters include all surface waters and hydraulically connected groundwaters in the Hurunui River catchment immediately above the confluence of the mainstem with the Mandamus River. This excludes the Mandamus River and its contributing waters. In other words, the Upper Hurunui Waters include any waters which directly or indirectly contribute flow to the Hurunui River mainstem immediately above its confluence with the Mandamus River.
- At the top of the catchment, the North Branch begins at Harpers Pass and flows for almost 25 kilometres along a glaciated trough before entering Lake Sumner/Hoka Kura. It also has a number of minor tributaries such as Landslip Creek. The valley sides of the North Branch are clad in beech forest, which graduates with increasing altitude into shrubland then alpine tussock on the tops. The valley floor is predominantly grassland and matagouri shrubland, with extensive flats and marshy areas just upstream of Lake Sumner. The North Branch is fast-flowing with a bed of cobbles and coarse gravels until its delta above Lake Sumner, where the gravels become finer.
- Lake Sumner/Hoka Kura covers an area of 1,390 hectares with a maximum depth of 135m. Except for the southwest side which is grazed, it is surrounded largely by forested mountains extending up to 1,900m. The lake plays a vital role in the hydrology of the Hurunui River mainstem by moderating flows.
- In addition to Lake Sumner the other headwater lakes in the upper catchment are; Loch Katrine (83 ha) and Lakes Marion (17 ha), Taylor (214 ha), Sheppard (115 ha) and Mason (53 ha) and the smaller Lake Mary and Raupo Lagoon.
- For the purposes of this application all lakes and lagoons described above are referred to collectively as the “Hurunui Lakes”.
- Loch Katrine drains into neighbouring Lake Sumner by a short navigable channel. Lake Marion flows into Lake Sumner via the Marion Stream. Lakes Taylor and Sheppard lie parallel to each other, separated by a narrow strip of land at their northern ends. Both flow via the Sisters Stream into the Hurunui River approximately 7 kilometres downstream from the Lake Sumner outlet. Lake Mason discharges to the South Branch via Mason Stream. Raupo Lagoon and Lake Mary are shallow tarns formed in depressions in the glacial moraine.
- The mainstem of the Hurunui River winds approximately 40 kilometres from the outlet of Lake Sumner to its confluence with the Mandamus River just above the Amuri Plain. The major tributaries along this reach are the Sisters Stream, South Branch and Seaward Rivers from the true right; and the Jollie Brook, Glenrae and Mandamus Rivers from the true left.
- Between the Lake Sumner outlet and the Seaward River confluence, the bed of the Hurunui River mainstem is generally entrenched within glacial outwash terraces, with a bed of boulders, cobbles and gravel. This section is fast flowing, commonly about 30 metres wide and with frequent rapids and some short rock gorges characterized by deep pools. The lower part of this reach between the South Branch confluence and the Seaward River confluence flows for several kilometres through a steep-sided valley with native beech/hardwood forest and kanuka shrubland. The natural character throughout is very high and the aquatic habitats unmodified by abstraction or surrounding land use. The moderating influence of Lake Sumner stabilises river flows, reducing the extent and duration of low flow periods and smoothing flood peaks.
- Downstream of the Seaward River confluence, the mainstem enters a gorge named Maori Gully, where the surrounding vegetation is also mainly beech forest and mature shrubland. Below Maori Gully the river widens briefly before being confined by terraces and then entering the rocky Hawarden Gorge just upstream of the Glenrae River confluence. The surrounding terraces and hillsides are characterized by native forest, shrubland and broom.
- The South Branch flows roughly parallel to the North Branch before joining the mainstem approximately 13 kilometres below Lake Sumner. Its main tributary is the North Esk River, which joins the South Branch approximately 10 kilometres upstream from its confluence with the North Branch. The upper South Branch catchment contains the ‘Hurunui Mainland Island’, a 12,000 ha area of river flats and beech forest managed intensively by the Department of Conservation for predator control and threatened species protection. The lower South Branch flows through a series of moraines and glacial outwash terraces before joining the main stem. The South Branch carries a significant proportion of flow to the mainstem. As its flows are not moderated by a lake, it contributes flow variability and turbidity to the mainstem when in fresh.
- Lake Sumner Forest Park, administered by the Department of Conservation, encompasses much of the upper catchments of the North and South Branches, and the land surrounding Lakes Sumner and Mason, with marginal strips edging the lakes, major tributaries and the Hurunui River. The tenure of most of the remaining land is Crown Pastoral Lease.
- The water quality, quantity, levels and flow characteristics of all the Upper Hurunui Waters are either pristine or in a highly natural state.
- The only notable allocation of water from the Upper Hurunui Waters is for a salmon farm which is consented to take 425l/s from the Sister's Stream (consent CRC 951163.1). The Applicants believe this salmon farm is not currently operational. However, if this salmon farm were operational it would discharge the full flow back into the river very close to the abstraction site, so that only a very short reach of Sister's Stream would be affected by the take. In addition this discharge is subject to conditions preventing any contamination from cleaning chemicals and setting an upper limit on the concentration of suspended solids. The Applicants consider that this discharge does not degrade receiving waters to the extent that they can no longer be considered to be in their natural state.
- With the exception of land developed for grazing on terraces and valley floors, the surrounding landscapes and riparian areas are also largely in their natural state.
- It is noted that in May 2007, Biosecurity New Zealand confirmed that the invasive algae didymo had been detected in a sample taken from the mainstem of the Hurunui River approximately 7 kilometres below Lake Sumner (near Jollie Brook confluence). This infestation is presently in its early stages and has not progressed to the large algae mats present in other affected waterways. The Applicants consider that it does not presently affect the outstanding and highly natural aquatic habitats, fisheries and recreational experiences afforded by the Upper Hurunui Waters. While there is some uncertainly about the future impact of didymo on the entire Hurunui river system, experience in rivers with more abundant didymo infestations show that large algae mats often disappear for considerable periods of time. The Applicants also note that much research is being done into how didymo may be eradicated or controlled.
Lower Hurunui River
- Photo 10 illustrates the transition point between the upper and lower Hurunui River.
- For the purposes of this application, the “Lower Hurunui River” includes the reach of the mainstem from immediately above its confluence with the Mandamus River to the sea. The tributaries in this reach are excluded. This exclusion extends to the Mandamus River catchment itself.
- Below the confluence with the Mandamus River, the mainstem of the Hurunui River becomes braided across the Amuri Plains before entering a rocky gorge through the Lowry Peaks Range. Once it leaves the Lowry Peaks Gorge at State Highway 1 the river again becomes widely braided, flanked by terraces and high hills. The Hurunui River reaches the Pacific Ocean approximately 80 kilometres north east of Christchurch and just south of Gore Bay. The mouth is contained by sandstone cliffs on the true right, with an extensive lagoon on the true left, flanked by coastal broadleaf forest.
- The Lower Hurunui River has been modified by abstractions, by dairy farm run-off (especially from the Pahau River) and by flood protection works. The surrounding land is used primarily for agriculture and forestry. Despite these influences, the Lower Hurunui River contributes to the outstanding values of the Upper Hurunui Waters, as described in more detail in Appendix B of this application.