The Buller/Kawatiri is the largest FMU in the Tasman District and incorporates the upper parts of the Buller/Kawatiri River and its tributaries, and Lakes Rotoiti and Rotoroa. Unusually, a significant lower proportion of the FMU (the Lower Buller and upper Maruia) is within the jurisdiction of the West Coast Regional Council (WCRC).
Kawatiri means deep and swift. The Buller/Kawatiri River’s catchment is very large; the river has the 5th highest average flow and the highest recorded flood flows of any river in New Zealand. A Water Conservation Order protects the wild and scenic and recreational values of the Kawatiri and most of its tributaries.
Water quality is generally good across the FMU. This can be attributed to the dominance of native forest. However, some rivers and streams within farming and urban catchments show high levels of contamination, and there are degrading trends for Nitrate-N and E.-coli, including in the Buller/Kawatiri. The Matakitaki River has issues with clarity.
Water use in the Buller FMU is low and there are currently no water allocation concerns.
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By 2100, all waterbodies and freshwater ecosystems are healthy, connected and resilient, where indigenous ecosystems and biodiversity have healthy mauri and where numerous indigenous fish migrate freely. There is abundant mahinga kai, food and resource gathering, and fishing opportunities. All waterbodies and their margins have high natural character and have room to move and adapt.
In progressing towards these goals, Ngā Iwi o Te Tauihu, Ngāti Waewae and communities are enabled to exercise kaitiakitanga and guardianship. A ki uta ki tai integrated land and water management system protects, maintains and restores the ecosystem health, natural character, biodiversity and mauri of our aquifers, rivers and their braids, lakes, springs, wairepo and wetlands. People respect and take responsibility for freshwater health and value the taonga being protected. Through collaboration and innovation we adapt to new ways of doing things. Our land and freshwater management provide for community, social and cultural wellbeing. We restore, protect and maintain freshwater habitats and the quality and quantity of freshwater, enabling sustainable use and appreciation for generations to come. Freshwater bodies and ecosystems located within Department of Conservation lands are maintained in their natural state.
This long-term vision will be achieved by stepping through the milestones below.
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Compulsory National Values |
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Other National Values |
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Other Community Values |
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The Buller–Kawatiri region is facing a range of environmental and land use challenges that affect its rivers, wetlands, and the species dependant on freshwater habitats.
Key concerns include declining water quality from farming runoff, gold mining, sedimentation, riverside rubbish and waste discharges. Habitat loss due to stream modification, wetland development, clearance of native riparian vegetation, and invasive pest plant species are also concerns.
Ngā iwi and the community desire high water clarity and protection for their scenic lakes and rivers while enabling a range of uses including swimming, fishing, kayaking, rafting, access to gravel and water takes for irrigation.
For a list of all community and iwi identified challenges and issues view the Buller–Kawatiri Issues and Challenges Set – October 2025. (pdf 47 KB)
The current state of water quality at the river sites in the Buller/Kawatiri FMU has been evaluated using the National Objectives Framework of the National Policy Statement – Freshwater Management. Under this framework, key attributes to assess water quality are Total Ammonia, Nitrate-N, Dissolved Reactive Phosphorus, Water Clarity, E. coli, and Macroinvertebrate Index (MCI). Each water quality attribute is ranked from A through D (or A through E for the E. coli attribute) with the D (or E) band representing poor water quality at each river site. Trends over 5 and 15 years are also assigned based on five classes from very likely improving to very likely degrading.
Water quality across the FMU is generally high, helped by the dominance of native forest. Most monitored sites are in the A band for most attributes. There are however some areas for concern in relation to water quality, particularly smaller streams.
On the Buller/Kawatiri River at Longford, Total Ammonia, E.coli and Nitrate-N are all in the A band but these attributes are all showing degrading trends. The Buller/Kawatiri is very popular for kayaking and rafting in many places, and popular for swimming particularly at Murchison. Monitoring has shown that the river is not suitable for contact recreation approximately 5% of the time, mostly associated with high rainfall events. The Macro-Invertebrate Community Index (MCI) is in the C Band with a 5 year median to 2022 of 106 MCI units. MCI is very likely to be degrading.
The Matakitaki River and Murchison/Neds Creek (both sites at SH6 in Murchison) have been identified as having high priority trend results needing further investigation. For the Matakitaki, water clarity is in Band D and very likely degrading, and likely to be largely caused by large on-going slips in the Glenroy River which deliver a considerable load of sediment to the Matakitaki River. The Macro-Invertebrate Community Index (MCI) is in the B Band with a 5 year median to 2022 of 116 MCI units.
Murchison/Neds Creek has a number of poor water quality results. Total Ammonia is showing a degrading trend and is in Band B. The measure for E. coli is in Band E and was recorded at the highest level of any long-term river water quality monitoring site in Tasman District. However, monitoring data shows this is very likely to be an improving trend over the past 5 years. Microbial source tracking shows ruminant animal and wildfowl faecal matter as the main contributors to the faecal contaminant load in the stream. It is also in the C band for Nitrate-N and Dissolved Reactive Phosphorus and showing a likely degrading trend over the past 5 years. The Macro-Invertebrate Community Index (MCI) is in the C Band with a 5 year median to 2022 of 95 MCI units and seems to be improving.
While the Mangles River, is in Band A, there are degrading trends for Nitrate-N and Dissolved Reactive Phosphorus. The measure for E. coli is within Band B, which is generally considered still healthy.
Based on data prior to 2016, very good water quality has been found for the lower reaches of Black Valley Stream which flows through St Arnaud township and into Lake Rotoiti. The macroinvertebrate community was “excellent” or close to “excellent” (MCI over 120) over this period, but is showing signs of declining, possibly due to increasing urbanisation.
The water quality of Lakes Rotoiti and Rotoroa is good (oligotrophic, Trophic Level Index: 2.4). However, there is a possibility that total nitrogen concentrations are increasing. Geochemical analysis of bottom sediments shows minimal human impact. The water quality of Lake Matiri is similarly of good quality.
The main demand for water is mostly from irrigation which accounts for over 90% of water take consents. There are two community water supply reservations located in the “Upper Buller”. One is for St Arnaud and there is also a groundwater community water supply reservation for the Murchison township.
There is non-consumptive use through hydro-electric power generation in the Matiri valley and a small scheme in Watson Creek in the upper Matakitaki catchment.
Generally, water in the FMU is readily available and there are no allocation concerns.
Rainfall is generally high but varies across the FMU from between 1500mm and 3500mm mean annual rainfall per year with the Upper Matiri receiving up to 4000mm per annum. The highest rainfall occurs in the spring period (Sept - Nov). Median annual temperatures of below 4°C occur at high elevations along the Ella, Travers, and St Arnaud Ranges. Murchison observes considerable variation in average daily temperature range over the course of the year, and generally has the hottest temperatures in the region. The FMU experiences the lowest sunshine hours in the region.
The FMU is rugged, with various mountain ranges over 1,500 metres elevation and many peaks over 2000m. Mt Franklin in Nelson Lakes National Park is the tallest mountain in Tasman District at 2340m. Lake Rotoiti and Lake Rotoroa are flooded depressions carved by past glaciers. Lake Rotoiti is the source of the Buller/Kawatiri River and Lake Rotoroa feeds into the Buller/Kawatiri River via the Gowan River. Both Lakes are located within the Nelson Lakes National Park. North of the Buller/Kawatiri River and Murchison there are huge marble and limestone outcrops in an earthquake-shattered landscape.The Matiri Range has two spectacular plateaus 800 metres above the surrounding valley floors – a rare New Zealand landscape.
The upper reaches of the Buller/Kawatiri River are largely sedimentary, with Graywacke and shistose sandstone and mudstone dominating in the area east of the Alpine Fault including the upper Matakitaki, D’Urville, Sabine and Travers Valleys. A band of Separation Point Granite runs north-south down the Lookout Range with its southern limit just south of Mt Murchison and patches further south to Mole Stream and the upper Glenroy catchment. To the west of this granite lies younger sandstone and mudstone in a band from west of Mt Owen through Murchison to Maruia. Localised limestone or marble exist particular around Mt Owen.
Much of the alluvial flat land around Murchison and St Arnaud has reasonably low versatility soils largely due to climatic conditions.
The Buller/Kawatiri River has the fifth highest average water flow and the highest flood flows in New Zealand, the record being 12,700 m3/s in 1926. Its catchment is very large at 6,500km2. The Buller/Kawatiri cuts through granite to form two major gorges and flows for 177km from Lake Rotoiti to the coast near Westport. A Water Conservation Order protects the wild and scenic characteristics, wildlife and fisheries values, and recreational and scientific values of the Buller and most of its tributaries. The water conservation order restricts damming of specified waters. It also restricts the extent of alteration of river flows and form on various rivers within the FMU. These are administered by Council by management of water permits and allocations.
The three main tributaries of the Buller are the:
Other tributaries include:
Many of these rivers are used for fishing, rafting, kayaking and other recreational uses.
There are smaller, spring fed creeks in the FMU. These include Murchison/Neds Creek which drains farmland and residential areas to the south and east of Murchison and Hinehaka Creek which drains farmland in the Hinehaka Plains and into the Buller just upstream of Doughboy Creek.
Other major rivers include the Sabine, D’Urville, and the Travers – these flow into either Lake Rotoiti or Rotorua.
Several larger lakes include Rotoiti, Rotoroa, and Matiri. There are also many alpine lakes including Rotomairewhenua/Blue Lake in the Lake Rotoroa catchment that is one of the clearest lakes in the world with visibility typically ranging from 70-80m.
Around the Buller/Kawatiri, south of Murchison and a little way up the Maruia, bog forests and pakihi are typical. Swamps, kahikatea swamp forest and wetlands associated with old watercourses typify the Maruia wetlands. The largest remaining wetlands in this FMU are pakihi wetlands on elevated terraces in the Deepdale catchment to the south of the Buller River downstream of the Maruia confluence as well as just to the north of the Buller River from the Deepdale. It is estimated that about 80% of valley-floor wetlands have been lost. Black Valley Swamp (60 ha) near St Arnaud is one of the largest remaining wetlands on the valley floor.
In 2005 the invasive algae Didymo was discovered in the Buller/Kawatiri River and is very dominant in reaches downstream of lake outlets.
The FMU retains much of its historic land use - native forest in mountainous wilderness with efforts underway to eradicate pests. River valleys are cultivated predominantly for dairy farms and some forestry. Murchison and St. Arnaud are the largest settlements in the FMU and these are located at the convergence of five major valleys—Maruia, Mangles, Matiri, Buller, and Matakitaki.
Some 19 of New Zealand's 51 native freshwater fish are present in the area, including the northern flathead galaxiid. The longfin eels in Nelson Lakes National Park constitute an important breeding stock. The upper Maruia River holds two rare and unusual fish species normally recorded only to the east of the main divide; Long-jawed Galaxias and Alpine Galaxias. The lake outlets of Rotoiti and Rotoroa provide flow and habitat conditions suitable for trout. Trout abundance has increased in recent years, after a decline in 2014. Kakahi/freshwater mussel (Echyridella menzieii) are found in reasonable numbers in Lakes Rotoiti and Rotoroa.
The globally threatened Blue Duck is common in many upper tributaries of the Buller/Kawatiri. The FMU also contains the majority (about 35 km) of braided river in the district which are mainly in the Buller from Teetotal Flat to Kawatiri Junction, lower Howard River, and Matakitaki River from Nardoo Creek to Mammoth Flat. This braided habitat is used by threatened birds including Black-billed gull, Banded dotterel, Oystercatchers, and Black-fronted tern. The main braided sections face habitat degradation from pest plant invasion (mainly willow).
The national park areas provide large continuous tracts of native forest for wide-ranging and vulnerable birds. Honeydew beech forest communities are present and support many bird species, including nationally vulnerable kaka, falcon, and blue duck. Lake side forests are filled with red and silver beech trees with a range of shrubs while mountain beech dominates more mountainous areas.
Significant amounts of groundwater exist in the aquifers within all of the alluvial valleys of the rivers within the FMU. The aquifer is generally thin ranging from 8 – 15 m thickness. The main recharge to the aquifers are the adjacent rivers and rainfall. The aquifers from limited flow testing show high yields. Recent conversion of a dairy farm to hops has resulted in a move away from surface water take for irrigation to groundwater as groundwater quality is more stable and not subject to sediment etc that get entrained in river water after rain.
The township of Murchison water supply is from groundwater – the groundwater is generally of high quality with low dissolved minerals with nitrate levels being less than 50 % of the Maximum Acceptable Value (MAV) for drinking water.
