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Waitaki Catchment Water Allocation Regional Plan

1. Introduction

2. Legal framework

3. The natural and physical resources and communities of Waitaki catchment

4. Overview of requirements for water

5. Issues to be addressed

6. Objectives

7. Policies

8. Rules

9. Anticipated environmental results

10. Definitions and abbreviations

Changes to the Regional Plan: Water for Otago

3. The natural and physical resources and communities of Waitaki catchment

Overview

Aoraki/Mt Cook and the mountains of the Southern Alps/Kā Tiritiri o te Moana dominate the Waitaki catchment. Flows of ice, water and eroded rock have formed the glacial lakes and braided rivers of the Mackenzie and Ahuriri basins; carved a gorge through the Benmore, Kirkliston and Hawkdun ranges; and culminate in the extensive braided Lower Waitaki River. The continuing uplifting and weathering of the mountains by rain, snow and ice provide constant flows of water and gravel down the river and its tributaries to the sea. Tributary rivers and streams join the flow from the mountains, providing connections to wetlands, springs and aquifers. The Waitaki River reaches widths of up to one kilometre before meeting the Pacific Ocean north of Oamaru.

The Waitaki catchment, with its extreme variation in topography and climate, provides a diverse range of freshwater habitats and species, and a strong sense of place for people. The catchment is home to a large number of indigenous fish and birds, including the black stilt - one of New Zealand's rarest and most specialised braided riverbed birds.

Just over 5,000 people live in the catchment, with many more returning to visit year after year. The rivers and lakes are popular recreation resources for a range of activities.

Aoraki/Mt Cook and the Waitaki River are the ancestral mountain and river of Ngāi Tahu. The upper catchment and Aoraki/Mt Cook National Park are nationally and internationally recognised nature and tourism locations.

Water in the catchment provides essential supplies to towns and communities, including Oamaru and parts of Waimate District, and is a very important source of electricity and hydro-electricity storage nationally. It also provides for significant irrigation on land both in and out of the catchment.

Natural resources

Climate

Prevailing north-west winds from the Tasman Sea, forced up over the ranges of the main divide, are the predominant source of water for the catchment, dropping an annual average of 8,000 millimetres of rain, snow and sleet in the alpine area, with slightly more precipitation in summer than in winter. This alpine precipitation provides about 80 percent of flow in the catchment.

Rainfall declines rapidly with distance from the mountains. While Aoraki/Mt Cook village averages about 4,000 millimetres of rain each year, at Twizel and Ōmārama (60 kilometres away), annual rainfall is much less than that - just over 500 millimetres. The low rainfall and prevailing north-west wind bring a sub-continental climate of warm summers and cold winters to the Mackenzie and Ahuriri basins. Temperatures in the summer in these basins frequently exceed 30 degrees Celsius and droughts are common, while frosts can occur at any time of year.

For the lower part of the catchment (east of Lake Benmore), the dominant weather patterns are southerly or south-easterly storms with occasional north-east winds from the coast. These patterns do not bring the high rainfall or temperatures associated with weather from the north-west that dominates in the upper catchment. However, easterly storms can generate large floods in the foothills of South Canterbury and North Otago, contributing to high flows in the Lower Waitaki River. Average annual rainfall is low, approximately 500 mm between Waitaki Dam and the east coast.

Drought occurs in most of the catchment because of the low and sporadic rainfall, high rates of evapotranspiration associated with high winds and temperatures, and low soil moisture.

Landform, geology and land cover

The main divide of the Southern Alps/Kā Tiritiri o te Moana (at altitudes over 3,000 metres) forms a steep glaciated boundary to the north-west of the catchment. The bare rock, bluffs and scree on the high slopes provide constant inputs of weathered rock that, combined with glaciers, have formed the moraines and extensive glacial outwashes of the Mackenzie and Ahuriri basins. The Mackenzie and Ahuriri are wide intermountaine basins dominated by extensive tussock grasslands and expansive views to the surrounding mountains.

To the east and south, these basins are bounded by the Rollesby, Dalgety, Grampians, Benmore and Kirkliston ranges - steep, rocky mountains with rolling, rounded summits rising to about 2,000 metres which are some of the driest greywacke mountains in New Zealand. The Waitaki River marks the geological divide between the greywacke of Canterbury and the schists of Otago.

The middle Waitaki valley consists of gorges and valleys cut through the Benmore, Hawkdun and St Mary ranges. On their seaward side, the mountains ease into foothills (600-800 metres) and rolling downlands through to the lower Waitaki alluvial floodplains, which are characterised by flat terraces stepping down to the river.

The catchment land cover (Table 1 below) is varied, reflecting the underlying geology and climatic features of the area and a history of land use modifications.

Table 1: Land cover of the Waitaki catchment

Source - New Zealand Land Cover Database 2 (Snapshot 2001/2)

Water resources

The Waitaki River has the fourth largest flow of all New Zealand rivers, with a mean historical flow (1927-2000) at Waitaki Dam of 359 cubic metres per second (m3/s). It is fed predominantly by water flowing from the main divide mountains through Lakes Ōhau, Pūkaki and Tekapo and the Ahuriri River. The ice- and snow-fed upper catchment has a strong seasonal flow regime with summer peaks produced by heavy rain and snow/glacial melt, and lowest flows in winter (June, July, and August). Inflows to Lakes Pūkaki, Tekapo and Ōhau, the Ahuriri River and, if it was unmodified, the Lower Waitaki River peak in summer and are lowest in winter. Glacial lake inflows vary significantly from year to year - with up to 30 percent less in a dry year.

The glacial lakes of Tekapo, Pūkaki and Ōhau influence flows downstream by dampening flood peaks and modifying flood flows into the lower catchment. This natural storage, together with the control of lake levels by hydro-electricity development further regulates downstream flow.

Four large braided river systems (the Tekapo, Pūkaki, Ōhau and Ahuriri) cross the upper basins. Of these, only the Ahuriri, which contributes around nine percent of catchment inflows, follows its natural water course. The other three rivers have been largely diverted into the canals of the upper Waitaki hydro-electricity system. Other, smaller tributaries (including the Fork Stream, Irishman Creek, Mary Burn, Twizel River, Wairepo Creek, Grays River, Sawdon Stream and Edward Stream) collectively provide five percent of annual inflows into Lake Benmore. The peak flows in these rivers (apart from Fork Stream which has a high proportion of its flow from snow melt) tend to be in winter and spring (May to November) with low flows from February to April.

Downstream of Ōmārama, the four rivers combine to form a single channel carved through steeply sided valleys. This part of the river is dammed in three places, creating Lakes Benmore, Aviemore and Waitaki. Tributaries of these lakes, which contribute five percent to the total catchment inflow, include the Otematata, Awahokomo and Otamatapaio Rivers.

Just below the Waitaki Dam, the river widens to become a large, braided river flanked, in places, by wetlands with a coastal lagoon where it reaches the sea. Along the length of both banks of the Lower Waitaki River, small rivers and streams (including the Hakataramea River, Elephant Hill and Waikakahi Streams, Awakino River, Kurow River, Otiake River, Otekaieke River, Maerewhenua River, Awamoko River, and Welcome Creek/Whakapapa Ariki) flow into the mainstream. Collectively these tributaries, which have peaks flows in winter, provide two percent of the river flow.

Groundwater (which frequently exchanges water with rivers and streams) is found throughout the catchment. Depth to groundwater is variable over the catchment and within specific basins. Wetlands and springs are generally associated with shallow groundwater including those associated with the Grays, Ahuriri, Twizel and Ōhau Rivers; Duntroon Spring; Welcome Creek/Whakapapa Ariki and Waikakahi Stream. Springs and wetlands tend to occur in three general areas in the lower Waitaki valley - at the base of terraces, at locations where gravels become narrower or shallower, and along the riparian margins. The larger groundwater storage areas are found in the Tekapo and Twizel basins and lower Waitaki valley downstream of Black Point. All groundwater in the upper catchment will flow into Lake Benmore. In the lower Waitaki valley, groundwater flow is more complex, with flow from both the aquifer to the river and from the river to the aquifer, and to the sea.

The braided rivers of the Waitaki catchment are formed and maintained by a number of interacting factors, predominantly: flood flow regime; sediment/gravel inputs and throughput; riparian flood protection works; and vegetation encroachment onto the riverbed. The way these factors interact influences the form and character of braided rivers. Each of these factors in the Waitaki catchment has changed historically, or is changing, due to natural processes and human intervention.

Catchment Ecology

The braided river system is a dynamic and diverse ecosystem comprising riparian wetlands, swift water, pools, ephemeral areas, braided channels and gravel islands. It is the combination of these habitat types and the ability of species to move between them, and the ever-changing nature of the river bed and flows, that provides the unique braided river ecosystem.

Important wetlands are found throughout the catchment. Nationally significant wetlands occur at the margins of the glacial lakes, around the smaller rainfed lakes (particularly those on the western side of Lake Tekapo) and at the river mouth.

In the Lower Waitaki River, river terrace and riparian wetlands are particularly important as breeding, spawning, feeding or shelter areas for birds and fish.

The habitats provided by the lakes, rivers and wetlands, and their margins support a huge variety of aquatic plant and animal life. Large areas of the catchment contain unmodified habitats, the significance of which is recognised in the Aoraki/Mt Cook National Park and the South West New Zealand (Te Wāhipounamu) World Heritage Area.

Plants Many vegetation types are present in the Waitaki catchment, reflecting the differences in habitat created by the variations of altitude, temperature, rain and snow as well as historic land use changes. The indigenous vegetation ranges from alpine herb-fields through tussock grasslands to scrub, wetlands, and forest (Table 1). Around 100 indigenous plant species are associated with braided rivers and their wetland margins.

There are 78 recorded species of threatened plants within the catchment, of which approximately half are associated with rivers, lakes and wetlands. The most threatened (nationally critical threat status) wetland plant species (recorded at the Ben Omar Swamp and near the Pūkaki River) is sneezeweed (Centipeda minima). Two species of indigenous broom, Carmichaelia kirkii (nationally endangered) and Carmichaelia vexillata (in serious decline), are the area's most commonly recorded threatened plant species and occur on river terraces. Macrophytes and periphyton form the basis of the food chain and are critical to the functioning of aquatic ecosystems.

Invertebrates The catchment contains a diverse range of terrestrial and aquatic invertebrate species. The composition of aquatic invertebrate communities varies from location to location depending on a variety of interacting environmental factors including flow, substrate type and stability, water quality, climate and biogeography. The indigenous robust grasshopper, which lives on dry river terraces, is nationally endangered and is found only in the Waitaki catchment.

Fish Twenty-four species of indigenous fish, 13 of which are diadromous (complete some part of their life cycle at sea), are known in the catchment. Six threatened indigenous fish species (Canterbury mudfish, lowland and upland long-jawed galaxias, big-nosed galaxias, long-finned eel and lamprey) are present. The most threatened of these fish taxa are the lowland long-jawed galaxias (Galaxias cobitinus - nationally critical), and the Canterbury mudfish (Neochanna burrowsius - nationally endangered) which has been found in only 20 places including the Waikakahi Stream. The lowland long-jawed galaxias is found only in the upper tributaries of Canterbury's braided rivers including the Hakataramea, Twizel, Otamatapaio, Ahuriri and Lower Ōhau Rivers in this catchment.

Brown and rainbow trout occur throughout the catchment, whereas Chinook salmon are found only below the Waitaki Dam.

Birds The upper catchment is used (for breeding or visiting) by 30 species of indigenous birds, ranging from the larger free-flying mountain species (kea), to smaller forest and scrub birds (rifleman/titipounamu) and birds of the broad, open braided riverbeds. Braided rivers provide habitat for more than 80 species of birds, including the wrybill, black stilt, black-billed gull and black-fronted tern, which have evolved on braided rivers and now have specific adaptations for breeding and feeding on them. The braided riverbeds and deltas of the upper catchment are the primary breeding habitat for the black stilt, one of New Zealand's rarest birds (only 100 exist). Another bird found in the catchment and listed as nationally critical with an estimated population of 250 individuals is the southern crested grebe, recorded on Lakes Alexandrina, McGregor, Middleton and Aviemore. The catchment also contains 15 percent of the country's remaining wrybill population and 60 percent of the remaining black-fronted terns. Other threatened birds are the Australasian bittern (wetland species), blue duck (mountain streams), and banded dotterel (braided rivers). A range of game birds is found in ponds and wetlands.

Lizards One of the three gecko species and four of the six skink species recorded in the Waitaki are threatened. Of these lizards, only the jewelled gecko (Nauklinus gemmeus), the green skink (Oligosoma chloronoton) and the long-toed skink (Oligosoma longipes) live in riparian areas, river terraces or river islands. They have been recorded near the Tekapo River and upstream of Lake Ōhau and Lake Pūkaki.

Physical resources (related to water)

Towns and settlements

The majority (65 percent) of the 5,000 residents in the catchment live in towns and settlements of which Twizel is the largest with a population of 1011. Others include the rural service townships of Kurow and Ōmārama, Aoraki/Mt Cook village (which services the management and tourism of the national park), and the settlements of Aviemore, Lake Waitaki, Otematata and Lake Tekapo that were once hydro towns but now exist primarily for tourism and growing holiday home/subdivision needs. Piped water supplies service these and the smaller settlements of Ōhau, Duntroon, and Glenavy with potable water.

Hydro-electricity installations

Since 1935, the water in the Waitaki catchment has been used to generate electricity. Between 1935 and 1985 the three main glacial lakes (Tekapo, Pūkaki and Ōhau) were dammed and the levels raised, the braided rivers of the Mackenzie Basin diverted into canals, and the river in the upper Waitaki was dammed to create the artificial lakes of Benmore, Aviemore and Waitaki. Five power stations were built at the dams. The scheme comprises eight power stations with an installed capacity of 1,723 megawatts and produces approximately 8,000 gigawatt-hours annually.

Depending on inflows, the Waitaki hydro-electricity scheme generates approximately 20-25 percent of New Zealand's electricity annually, with Lakes Tekapo and Pūkaki providing around 65 percent of the nation's hydro-electricity storage capacity. This storage is critically important to the nation's energy system, especially for security of supply in the South Island in dry years. The operational flexibility of hydro-electricity generation compared to other generation types, particularly thermal, means it plays a key role in the ability to match supply to patterns of peak demands.

Water is also used in micro hydro-electricity generation for localised use such as ski fields and high country stations.

Agricultural installations

The agricultural sector consists of mainly dryland grazing in the Mackenzie and Ahuriri basins, with more intensive agriculture in the Hakataramea and lower Waitaki valleys. There is a small area of horticulture in the lower Waitaki valley, including some viticulture.

Water from the catchment is used for stock drinking-water and irrigation. Stock drinking-water is transported via open channel and piped schemes; in the upper catchment the infrastructure is associated with hydro-electricity canals. Rural water supply schemes are fed from the lower Waitaki, Hakataramea and Maerewhenua catchments.

The water irrigates approximately 54,600 hectares of land (about ten percent of New Zealand's irrigated land). About 8,600 hectares are currently irrigated from takes in the upper catchment, supplied mostly through individual or small scheme/collective infrastructure, together with the Upper Waitaki Irrigation Scheme which takes water from upstream of the Waitaki Dam (although the irrigated area is in the lower catchment). Construction has begun on an irrigation scheme to take water from the upper Ōhau River for irrigating a further 4,000 hectares.

Takes in the lower catchment irrigate an estimated 46,000 hectares of land. The two largest irrigation schemes (Lower Waitaki on the south side of the river and Morven-Glenavy-Ikawai on the north bank) provide water to the coastal alluvial plains of the Lower Waitaki River. The command areas for these schemes extend outside the catchment, taking water as far south as Oamaru and beyond the Waihao River to the north. In addition there is one smaller scheme (Maerewhenua) as well as some private irrigation infrastructure in the lower Waitaki valley. Stage 1 of the North Otago Irrigation Company development, due for commissioning in February 2006, will add a further 10,000 hectares.

Parks and reserves

Of the catchment's 12,000 square kilometres, about a quarter is classified as public reserves and protected areas. This land, administered by the Department of Conservation, is mostly upstream of Lakes Tekapo, Pūkaki and Ōhau, or in the Ahuriri catchment, or on the Ben Ōhau, the Hawkdun and the Kirkliston ranges.

Aoraki/Mt Cook National Park covers about six percent of the total catchment area. A third of the park is in permanent snow and ice, and the remainder mostly steep, actively eroding mountain land. The park is internationally recognised for its outstanding natural values and attracts an estimated 250,000 visitors each year. Along with Westland/Tai Poutini and Fiordland National Park, Aoraki/Mt Cook National Park became New Zealand's first world heritage area in 1986 and part of the much larger 2.6 million hectare South West New Zealand (Te Wāhipounamu) World Heritage Area in 1989.

The ongoing process of tenure review of Crown pastoral leases is adding high country land to the conservation estate.

Other infrastructure

The catchment has very little other water-related infrastructure. There is an industrial processing site at Pukeuri, just north of Oamaru, which uses water provided via the Lower Waitaki irrigation scheme infrastructure. Other water uses are for bottled water, snow-making on the Roundhill and Ōhau ski fields, gravel washing and a very small amount for mining in the Maerewhenua catchment. Salmon farms have been established in the hydro canal system.

Social, economic and cultural characteristics

Significance to Ngāi Tahu

Waitaki is the ancestral river of Ngāi Tahu, fed by the sacred waters of Aoraki and the tears of Raki (Sky Father). The life-giving waters flow to the sea passing through the valleys and plains of Papatūānuku (Earth Mother). The river is a symbol of permanence and source of spiritual meaning to tāngata whenua. The creation traditions tell of the interconnection between earth, sky and the natural elements, the source of life or mauri that emerged from the primordial waters, and the realm of the gods who made Te Waipounamu habitable for humans.

Tribal whakapapa links the cosmological world of the gods and present generations, giving rise to a spiritual relationship and respect for the mauri evident in the tribal landscape. The Waitaki River is a central element of the tribal identity and mana, a taonga derived from the gods, which requires a reciprocal duty to protect the Waitaki and the associated natural resources now and for future generations.

Wāhi tapu and wāhi taonga are cultural anchors associated with the Waitaki catchment. These include sites linked to the creation traditions, burial sites and areas where important historical events have occurred.

The relationship with the Waitaki catchment is recalled in traditions, place names, songs and whakapapa. The practice of mahinga kai was a cornerstone of Ngāi Tahu existence and culture, a seasonal food and resource-gathering activity requiring intimate knowledge of the catchment, seasons and methods of procurement. The Waitaki catchment was a prime provider of mahinga kai resources and a means of travel by reed raft (mōkihi).

Kaitiakitanga, a function of manawhenua, involves the observance of kawa and tikanga, traditional rules applied to protect the mauri from harm by human actions, to ensure that the health and spirit of the Waitaki remains intact and the principle of sustainable use of the natural resources observed.

The three Papatipu Rūnanga whose takiwa intersect in the catchment - Te Rūnanga o Arowhenua, Te Rūnanga o Waihao and Te Rūnanga o Moeraki - exercise kaitiakitanga on behalf of their whānau and hapū. Te Rūnanga o Ngāi Tahu is the iwi authority vested with statutory functions to act in the interests of Ngāi Tahu in matters of natural resource management.

Population and communities

The Waitaki River has strong emotional, spiritual, aesthetic, cultural, social and economic value for people who live in, make their livelihood from, holiday in and travel through the catchment. The scenery, setting and its landforms, along with its sparse population mostly concentrated in small towns, provide a distinctive rural lifestyle and holiday destination. In many places the development of the community infrastructure was linked to hydro construction.

The population of the catchment and surrounding districts (about two percent of the national population), is both decreasing and ageing, with relatively fewer younger people and more older people than the national average. The population grows significantly over summer months when, for example, the Twizel population increases from 1,000 to 6,000 people, and over 50,000 people are estimated to camp around the lakes over the summer. There has recently been a significant increase in lifestyle and holiday home development around Lake Tekapo, Twizel, Ōmārama and Otematata.

Most of the catchment area upstream of Waitaki Dam is farmed in high country stations. Historically these stations were Crown leasehold land, but a recent process of tenure review means farmers are negotiating with the Crown for an arrangement that sees some of the land returned to the Crown for conservation and the remainder to the farmer as freehold land. This reorganisation of land holdings can mean that runholders have an increased need to use farmland more intensively. Changes in land use, including the introduction of viticulture and dairying conversion, will influence the community in future.

In 2003, the entire Mackenzie, Waimate and Waitaki Districts had a combined population close to 34,000 people, produced $1.3 billion in output and $0.5 billion of value added (equivalent to Gross Domestic Product). Around 30 percent of the 12,000 local jobs and value added was based on primary production, particularly cropping and livestock farming (including significant input into food processing), and food processing itself. Retail and accommodation accounted for a further 20 percent of the jobs. The utilities sector (predominantly electricity generation and distribution) accounted for about three percent of value added and 0.3 percent of employment, reflecting its capital-intensive nature.

Recreation and tourism

The catchment provides for a wide range of outdoor recreation activities and experiences, some of which are not found elsewhere in New Zealand. The natural and scenic attributes of the catchment, including its rivers and lakes, are defining characteristics of what people want to experience. The lakes and canals are popular for recreation.

Aoraki/Mt Cook National Park is a nationally significant recreation and tourism destination that offers tramping, walking, climbing and sightseeing, but other parts of the catchment are increasingly attracting visitors, especially from within New Zealand. For example, although 70 percent of visitors to Aoraki/Mt Cook National Park are from overseas, New Zealanders are the predominant recreational users (80-85 percent) in other parts of the catchment.

Fishing is a major recreation activity in the catchment. A national survey of anglers (2001/2002) estimated that just over a tenth of days spent fishing across New Zealand were in the Waitaki catchment. About a quarter of those days were spent on Lake Benmore, a further quarter on the Lower Waitaki River and the rest on a mixture of other lakes and rivers. The Tekapo and Ahuriri rivers are regarded as nationally significant trout fisheries and attract proportionally more overseas and out-of-region anglers than other locations.

Fish and Game New Zealand has reported the Lower Waitaki River to be the most intensely fished stretch of river in New Zealand. It attracts anglers from throughout New Zealand and overseas. Special features are the 'big river', the presence of three major fish species (brown and rainbow trout, and salmon) in the same river, the size of the fish, and opportunities for solitude. Fishing for eel, whitebait, kahawai, flounder, mullet, cod and skate occur at the river mouth.

Canoeing, kayaking and rafting of upper catchment rivers occur predominantly during controlled flow releases into the Tekapo and Pūkaki rivers. Kayakers consider the slalom courses used during the controlled releases to be nationally significant. Catchment lakes are popular for boating, camping, rowing (to international standards), swimming, wind-surfing and water-skiing. Lake Aviemore has ideal conditions (considered to be some of the best in the South Island) for wind-surfing. The Lower Waitaki River offers the 'big river' experience for recreationalists, including international jet boating events. The catchment also supports hunting, camping, skiing, cycle touring, climbing (near Duntroon), mountain biking, walking, four-wheel driving, tramping and gliding (Ōmārama).

Commercial fisheries

There are three salmon farms/fisheries on the Mackenzie hydro canals which together contribute about 400 tonnes or five percent of New Zealand's annual salmon production. The Lower Waitaki River supports a commercial eel fishery with a 9.5 tonne annual catch of long finned eels. The only other commercial fishery is for whitebait.