Before a Special Tribunal

Under the Resource Management Act 1991

In the matter of Application for a Water Conservation Order in respect of Te Waikoropupu springs and associated water bodies (including the aquifers, Takaka River, and tributaries)

Statement of Evidence of Paul Williams on behalf of Ngāti Tama Ki Te Waipounamu Trust and Andrew Yuill 28 March 2018

Applicant's solicitors: Maree Baker-Galloway | Rosie Hill Anderson Lloyd Level 2, 13 Camp Street, Queenstown 9300 PO Box 201, Queenstown 9348 DX Box ZP95010 Queenstown p + 64 3 450 0700 | f + 64 3 450 0799 [email protected] | [email protected]

Introduction

1 My full name is Paul Worthing Williams

2 I have studied the groundwater system and karst of the Takaka region since the early 1970s and have published several scientific papers and book chapters on aspects of its groundwater hydrology and karst. I have also studied karst and karst hydrology overseas and therefore have acquired a first-hand international perspective on the significance of the Te Waikoropupu Springs and its groundwater system. As a result, I have long been aware of the unique nature and importance of Te Waikoropupu Springs and so was pleased to agree to present evidence in support of their conservation when approached to do so by the Friends of Golden Bay.

Qualifications and Experience

3 I have the following qualifications and experience:

(a) PhD (Cambridge 1965) (b) ScD (Cambridge 1991) (c) Senior Fellow, International Association of Geomorphologists (2009) (d) Professor and now Emeritus Professor, School of Environment, University of Auckland (since 1972) (e) Member of Geoscience Society of NZ, NZ Geographical Society, NZ Hydrological Society, NZ Speleological Society, International Association of Hydrogeologists, International Association of Geomorphologists, International Union of Speleology. (f) Member since 2001 of the International Union for the Conservation of Nature (IUCN) World Commission for Protected Areas, and since 2013 councillor of the Geoheritage Specialist Group. (g) UNESCO/IUCN consultant since 2002 on the evaluation of natural World Heritage. (h) Co-author with Prof D. Ford of the major international research text, ‘Karst Hydrogeology and Geomorphology’, Wiley (editions 1989 and 2007 and a Chinese translation published 2015). (i) Author of book on the geomorphology of New Zealand, ‘New Zealand Landscape: Behind the Scene’, Elsevier 2017.

4 While this is not a hearing before the Environment Court, I confirm that I have read the code of conduct for expert witnesses contained in the Environment Court Consolidated Practice Note (2014). I have complied with it when preparing my written statement of evidence and I agree to comply with it when presenting evidence. I confirm that the evidence and the opinions I have expressed in my

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evidence are within my area of expertise. I have not omitted to consider material facts known to me that might alter or detract from the opinions that I express.

Scope of Evidence

5 The evidence presented here is a technical explanation of the origin, nature and workings of the groundwater system sustaining Te Waikoropupu Springs. This shows why Te Waikoropupu Springs and the aquifer that feeds them are nationally and internationally significant. Management implications are also identified.

Executive Summary

Scientific Significance of Te Waikoropupu Springs and the Arthur Marble Aquifer

6 Te Waikoropupu Springs are of national and international significance. They are listed on the New Zealand Geopreservation Inventory [www.geomarine.org.nz/NZGI/] as a class A site (international importance). They also feature on the World Karst Aquifer Map at 1: 40M (BGR et al. 2017). The map was constructed using the best available knowledge of an international team under the auspices of UNESCO International Hydrological Programme (UNESCO IHP) and the International Association of Hydrogeologists. The full database is available at www.whymap.org/whymap-viewer.

7 The groundwater system sustaining the springs is known as the Arthur Marble Aquifer and is the largest karst aquifer in New Zealand, having a storage volume of approximately 2.8 cubic kilometres (Table 1). It is located in the Takaka River basin in northwest Nelson (Figure 1). The springs are the principal point of discharge from the aquifer, the outflow supporting the largest spring in New Zealand and Australia. Te Waikoropupu Springs also rank amongst the very largest karst springs of the Southern Hemisphere.

8 The spring water is amongst the optically clearest ever measured, a direct reflection of the exceptional quality of the aquifer and the system that sustains it.

9 The groundwater system is unusual in its complexity: the springs being of large volume, artesian, tidal, having a sea water component, and a broad age spectrum. This is known nowhere else in the Southern Hemisphere.

10 The combination of exceptional quality on a world scale and very unusual features places Te Waikoropupu Springs amongst the world’s scientifically most important springs.

11 If these outstanding international characteristics are to be preserved, then particular attention must be given to environmental management in the recharge zone that contributes water to the marble aquifer.

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Karst

Definition of Karst

12 Te Waikoropupu Springs are fed by a karst system. The term ‘karst’ refers to landscapes and associated hydrological systems developed in particularly soluble rocks such as limestone or, in its metamorphic form, marble. These rocks are composed chemically of calcium carbonate, which is readily dissolved in rainwater. The process that transforms limestone and marble rocks into karst terrain with caves is known as ‘karstification’. Around 10-15% of the Earth’s continental area is composed of karst, but it covers only about 2% of New Zealand.

Marble Karst in NW Nelson

13 7.2.1 Arthur Marble of Upper Ordovician age (450 million years old) is exposed in a 90 km discontinuous belt stretching from Mt Owen through Mt Arthur to Takaka Hill and Golden Bay. The outcrop is variable in width, but in places up to 7 km wide. It also varies in stratigraphic thickness from about 500 m to 1500 m depending on location. It is often steeply dipping and is frequently faulted. Near the headwaters of the Takaka River, marble is found to 1778 m on Mt Arthur and in Takaka Valley it descends well below sea level. Geological details are available in Grindley (1971, 1980) and in Rattenbury et al. (1998).

14 7.2.3 The marble of NW Nelson is well karstified with some caves more than 1 km deep and some with more than 70 km of passages. The flooded zone at the bottom of a cave in Mt Arthur has been dived to a depth of 229 m below the water table level with passages seen still descending. These long and deep caves are old with ancient stream gravels in one of them (Bulmer Cavern on Mt Owen) having been dated to 2.9 million years (Holden 2017). The initiation of the present phase of karstification on Takaka Hill would have been at a similar time to that on Mts Owen and Arthur, although the karst has continued to develop ever since. The caves were developing as the Southern Alps were growing. A still older phase of karstification may have occurred during the original planation of the upland erosion surface prior to its faulting and uplift over the last 6 million years or so.

15 7.2.4 Takaka Valley was formed when compressional forces associated with the building of the Southern Alps affected NW Nelson. About 3 million years ago in the Pliocene to early Pleistocene, the Pikikiruna Fault developed, a north-south reverse fault now expressed in the landscape as the Takaka escarpment. It ruptured a broad erosion surface, part of which was across karstified marble. Relative movement along the fault was upwards on the eastern side and downwards on the west. This displacement split the karst surface and formed Takaka Valley, which is a wedged-shaped fault-angle depression about 9 km

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wide at the coast that tapers inland for 26 km. The downthrow on the western side drove karstified marble well below sea level. The compression also folded Tertiary sediments (Paleogene to early Neogene, 60-30 million years old) in the valley, producing asymmetric synclinal structures that locally took Coal Measures to 185 m depth.

Groundwater Systems

Aquifers

16 Water bearing rocks and gravels from which economic quantities of water can be extracted are known as aquifers. If such rocks are exposed to the atmosphere, then rainwater falling on them infiltrates and descends freely under gravity until it finds its own level. The surface of the water-saturated zone within such rocks (identified by the level of standing water in wells) is known as the water table (or piezometric surface). Beneath the water table, all interconnected pores and fissures are full of water, and this continues downwards until lithostatic pressure closes the pores or fissures, or until an underlying impervious layer is reached. Water in such aquifers is recharged by infiltrating rainwater and occasionally also by water loss along the bed of stream channels. Groundwater moves from the recharge zone to the discharge or outflow zone, where seepage sustains the flow of springs and rivers. Its movement is driven by the hydraulic gradient which, in unconfined aquifers, is expressed as the slope of the water table. In porous aquifers, groundwater movement is very slow (laminar) and obeys Darcy’s Law (1856).

17 Groundwater that moves under an impervious caprock may be confined under pressure. In such circumstances, when a bore is drilled through the caprock into the underlying water-bearing layer groundwater may rise up the bore hole to a distance that depends on the confining pressure. This is referred to as an artesian well. The water levels attained in a series of neighbouring artesian wells defines the potentiometric surface of the confined aquifer.

Karst Groundwater Systems

18 Karst aquifers contrast markedly with standard porous aquifers found in sands and gravels. This is because, instead of granular porosity, karstified rocks have a triple porosity in pores, fissures and caves that enhances over time by rock dissolution as water moves through them. In most rocks porosity does not change with time, but in karst it does. Furthermore, water movement through caves (or conduits) in karst rocks is often rapid and turbulent rather than slow and laminar, which is the normal case in other aquifers. Thus the normal approach to groundwater management applicable to standard porous aquifers (where Darcy’s Law applies) is inappropriate in karstic aquifers.

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19 The nature of porosity in karst is unusual. Limestone and marble rocks that host karst may have interstitial primary porosity but it is often small, and in marble is negligible. Karst rocks have fissures of several types, including joints, faults, and bedding planes, and most importantly for the functioning of karst systems some of these become locally enlarged by dissolution into caves. Solutionally widened fissures are referred to as secondary porosity, and caves are considered to be tertiary (or conduit) porosity. Most of the groundwater flows through them.

20 Recharge by rain that falls directly onto the karst surface is known as autogenic recharge. But recharge that occurs indirectly from rain falling onto neighbouring impervious rocks that then drain onto the karst, where streams then sink underground, is referred to as allogenic recharge. Conduits (caves) through the karst direct groundwater flow to springs where it is discharged. Although more than 90% of water storage in karst is in the primary and secondary matrix of pores and fissures, almost all the groundwater flow to springs takes place through conduits. Because water movement through widened fissures and conduits is often fast and turbulent, groundwater flow through karst usually does not obey Darcy’s Law, which assumes laminar flow. This adds another level of complexity to water management that is particular to karst

Arthur Marble Groundwater System

21 Te Waikoropupu Springs are the principal outflow site for a large groundwater system in marble rock within the Takaka River basin (Figure 1). This groundwater system is located in a metamorphic carbonate rock called Arthur Marble; so it is referred to by Tasman District Council as the Arthur Marble Aquifer (AMA).

22 The large average volume emerging at the springs, about 13 m3/second (Table 1), results in their being recognized as the largest springs in New Zealand and Australia. Springs discharging larger volumes are suspected in Papua New Guinea, but are not shown on the world map because of lack of accurate hydrological data. A karst spring with similar discharge is known in South America. So in terms of the Southern Hemisphere, Te Waikoropupu Springs rank amongst the very largest karst springs known.

23 Being sustained by recharge sourced mainly from surrounding uplands, the emerging waters are cool with an almost unvarying temperature of 11.7°C.

24 The groundwater reservoir is large, with a water volume of estimated as 2.8 km3, and the average transit time (or residence time) of water emerging at the Main Spring is long, about 7.9 years (Table 1), but some of the water in the mix is many decades old. Aquifers in New Zealand with comparable or longer flow- through times include the Canterbury Plains gravels, typically up to 40 years old but sometimes considerably older, and those in ignimbrite rocks of the central North Island volcanic plateau, where Hamurana and other cold water springs

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from volcanic rocks discharge water with estimated residence times of a several decades. Further details of other groundwaters in New Zealand are available in Rosen and White (2001).

25 The clarity of water emerging at the springs is exceptional. The long residence time underground permits organic matter to decompose (and accounts for oxygen levels in water being below saturation when it emerges), and the slow water movement within the aquifer enables the settling out of finely suspended particulate matter, although the recharge waters are also generally clear. These factors plus the filtering effects on organic matter of groundwater biota (stygofauna) result in emerging waters that are exceptionally clear. Davies-Colley and Smith (1995) measured the optical properties of the springs, obtaining an average black-body visibility of 63 m, “the highest yet reported for any fresh water” and close to the theoretical maximum for optically pure water. Thus Te Waikoropupu Springs rank amongst the very clearest in the world.

26 The Arthur Marble Aquifer has a groundwater system that is typical of karsts in pure, dense, crystalline carbonate rocks. It has a triple porosity involving pores, fissures and conduits (cave passages). Most groundwater storage is in solutionally widened fissures (mm scale) and interconnected pores (sub-mm). Although individual conduits may be large (dm-m scale), total conduit porosity in water-filled cave passages occupies a small percentage of the rock mass and so contains relatively little water volume, yet it is through these conduits that almost all of the water is conveyed.

27 Since conduit porosity in the marble is unlikely to exceed a few percent of total aquifer volume, the aquifer can be envisaged to contain a few large but widely spaced conduits (functioning as main drains) that traverse through a water- saturated fissure matrix comprising mm to sub-mm cracks and occasional interconnected pores. Because the main drains are widely spaced, water in some parts of the fissure matrix is remote (km away) from them and so poorly connected to the conduit system.

28 Recharge from rain and floodwater generates a pulse of incoming water that passes through the groundwater system, and like a piston it displaces some of the water already there. Thus new water pushes out old water, but does not itself finally resurge at the springs until some years later.

29 Floodwater pulses are transmitted through conduits under pressure. In the process some water is forced into lateral fissures as the flood peak passes, but later returns back to the conduit as the pressure declines. This natural pumping encourages the exchange of water in underground stores, especially in the fissure matrix. Extended periods of gradually reducing pressure head permits

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water in distant fissures to drain towards conduits and so be expelled from the system.

30 Groundwater storage occurs within and close to active conduits and also remote from them, where it occupies a three-dimensional fissure system that extends laterally several kilometres and vertically several hundred metres. This storage can be remote from drains in both time and distance. Most is laterally remote, but some is deep in the aquifer, including in tectonically depressed caves. The most obvious indicator of water sourced from depth is the chloride (Cl) that must have come from the underlying sea water wedge. Old water, like that found in Ball’s bore, may also come from a relative shallow but hydraulically remote (from conduits) site. Old water with a long transit time is usually an indicator of a laterally remote source rather than an indicator of a deep water source, though it may sometimes be, because of the three-dimensional nature of the aquifer.

31 The Arthur Marble Aquifer is best conceptualized as an extensive fissure matrix pierced by occasional large conduit drains, their development having been driven by dissolution stemming from point recharge sourced mainly from the upper Takaka River over the course of the Quaternary. The groundwater head of about 30 m at the artesian boundary is in itself insufficient to drive deeply circulating flow paths, but when water is confined beneath descending impervious caprock then it will be forced downwards before it can escape upwards. This appears to be the situation in the middle valley near East Takaka below the Motupipi Syncline, where Coal Measures descend to about 185 m below sea level (Ravens 1990, Mueller 1991), although most groundwater will skirt around the nose of the syncline towards the western side of the valley.

32 The active conduit system may intersect an old fissure system and conduits associated with karst formed in the early Cenozoic that was pushed down by the reverse faulting that formed the Takaka fault-angle depression. Very deep cavities will store water, but are unlikely to participate much in contemporary groundwater circulation. Fissuring in the rock matrix will also diminish with depth because the rock is subjected to considerable lithostatic pressure.

33 Te Waikoropupu Springs are the site of emerging waters of different age. This is to be expected in large springs that draw their waters from a wide area. The Main Spring expels a large volume of relatively old waters (average transit time of 7.9 yrs), whereas the Fish Creek Springs pass younger waters (3.5 yrs). Thus it seems that Fish Creek is partly supplied by a closer source, because there is no obvious reason why a much greater transit velocity should occur. About 50% of the water emerging at Fish Creek has a relatively negative stable isotopic signature. It might come from the upper Takaka River, but is more likely derived from leakage of the Waingaro River, which is much closer, has an alpine origin,

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and limited sampling shows to have a δ18O signature almost as negative as the upper Takaka River.

34 From the main loss zone of the upper Takaka River near Lindsays Bridge, the sea is 18 km directly down valley to the north, whereas Te Waikoropupu Springs is 16 km to the NNW. The most likely reason for this northwest deflection is the impervious barrier seawards of Gorge Ck presented by the asymmetric downfold of Tertiary sediments that forces karst ground waters around the western flanks of the structure. Further downstream near the coast, the emergence of outcrops of Onekaka Schist near Waitapu and a possible diorite intrusion at depth may direct groundwaters towards the submarine spring near Rangihaeata Head. The location of Te Waikoropupu Springs is a result of the Waikoropupu River incising its valley through the Coal Measures, in the process exposing a window of underlying marble along the stream bed through which waters under pressure could escape.

35 The area contributing flow to the Arthur Marble Aquifer and hence to Te Waikoropupu Springs is delimited by the main surface watershed of the Takaka River basin (Figure 1) in the unconfined part of the catchment. On the western side of the Takaka valley, this area includes its tributary the Waingaro River, but not the neighbouring Anatoki catchment which, unless there is unrecognized groundwater flow through marble from the Parapara Range, does not contribute water to the Arthur Marble Aquifer. On the eastern side of Takaka valley, the catchment area draining to the Springs is delimited by the principal watershed around Takaka Hill and northwards along the Pikikiruna Range to about Dry River. But there is no clear evidence to show whether water sinking into marble in the area from Rameka Creek to Dry River drains to Te Waikoropupu Springs or just to off-shore springs. Consequently, in Figure 1 the watershed in that region is shown as a dashed line to convey uncertainty about its location.

36 By contrast, beneath the artesian caprock in the confined part of the basin, it is difficult to determine and depict with any precision the location of the groundwater divide. This is for two reasons: (i) because a map is two-dimensional whereas the groundwater system is three-dimensional, and (ii) because there is a divergence of groundwater flow beneath the caprock that takes some water to Te Waikoropupu Springs while the rest goes northwards towards off-shore springs. The boundaries depicted in the confined aquifer area on Figure 1, therefore, need to be interpreted with care. They are dotted to signify uncertainty with respect to location. On the western side, the dotted line would follow the subsurface western limit of marble. On the northeastern side, where the dashed surface divide near Dry River is continued as a dotted line towards the Springs, the dotted line depicts the approximate down-valley limit of the zone that contributes water to the Springs. Thus this section of dotted line should not be interpreted as a

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groundwater divide, because any water that does not go towards the Springs crosses it en route to off-shore springs.

Recharge of Aquifers in the Takaka Valley

37 Recharge refers to the waters that contribute to the groundwater resource. Contributing waters are derived from runoff and infiltration occurring on surrounding highlands and from rain falling in the upper valley. The most important area to contribute recharge to the Arthur Marble Aquifer is the uplands of the Canaan plateau in and around the Abel Tasman National Park, and the main single source of recharge from river water is water loss in the bed of the upper Takaka River.

38 In the Takaka Valley economically usable groundwater resources are found in three rock formations: (1) in alluvial sands and gravels of Quaternary age that cover floodplains and river terraces; (2) in karstified Takaka Limestone of Oligocene age; and (3) in karstified Arthur Marble of Ordovician age. Detail concerning the nature of these rocks, their thickness and distribution is available in Grindley (1971, 1980) and Rattenbury et al (1998) and in references cited therein. In summary, the Quaternary gravels are known to a thickness of at least 59 m but are generally thinner: 5-12 m in East Takaka and 30-50 m thick in Takaka township. Takaka Limestone varies in thickness laterally from about 4 m to 62 m (Mueller 1991). Near Takaka township, this limestone is overlain by Tarakohe Mudstone and in turn rests conformably on Motupipi Coal Measures, but the coal measures thin laterally and, in the upper valley from Lindsay’s Bridge to Upper Takaka, limestones rest directly on marble because the coal measures have wedged out. Arthur Marble underlies most of the valley, its thickness being uncertain but probably in excess of 500 m.

39 When the recharge of the Arthur Marble Aquifer is considered, three issues are important: (i) the areas where recharge occurs; (ii) the volumes contributed; and (iii) the water quality involved. These issues have been investigated by Michaelis (1976), Williams (1977, 1992, 2004), Stewart and Williams (1981), Mueller 1991, Stewart and Thomas (2008) and other authors cited therein, and are elaborated in reports by the Tasman District Council.

40 The principal area where allogenic waters from non-karst rocks contribute to the recharge of the marble aquifer is along an 8.6 km reach of the Takaka River downstream of its confluence with the Waitui Stream in Upper Takaka. River flow at this site is derived from the Tasman Mountains and averages about 14.3 m3/second. Water loss into the river bed is especially evident in the 4.5 km stretch downstream of Lindsays Bridge. The channel is formed in sands and gravels that bridge works showed to be at least 15 m deep, although drilling further downstream near the Craigieburn confluence revealed a gravel thickness

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of 59 m. These river gravels overlie marble that is seen exposed beside the river along the steep eastern side of the valley formed by the fault-line escarpment. At one point, where the escarpment comes close to the channel, water during high stages can be seen to flow directly into a swallow hole in marble. This site, located about 300 m northeast of the confluence of Craigieburn, is informally referred to as Takaka Main Sink. It is unusual in that, under certain high water conditions, sinking flow of the order of several cumecs is seen to reverse on a timescale of minutes. At such times, water level rises and reverse flow also of several cumecs lasts for a few seconds (R. Davies, pers. com.), i.e. the swallow hole temporarily becomes a spring. Reversing stream-sinks/springs in karst are called estavelles. They are well known internationally, but this is the only one recognised in New Zealand. The phenomenon probably arises from convergence of sinking water from the Takaka River and subterranean outflow from Canaan; both recharging the Arthur Marble Aquifer.

41 Recharge of the marble aquifer by water loss along the channel of the upper Takaka River varies in volume, being at a maximum when groundwater levels are low and river discharge high. Under such circumstances perhaps up to 20 m3/second can be absorbed underground, although the average loss is usually much less, estimated as being the order of 8 m3/s. When flow of the upper Takaka River drops to 11 m3/second or less, a state that occurs for about 100 days per year, the river bed becomes dry in the middle valley where it crosses marble. Under such conditions flow in the river channel only resumes again near the confluence of the Waingaro River.

42 Variations in river flow produced by human activity in the Takaka catchment also affect recharge. Releases of water associated with hydroelectric generation at the Cobb Dam produce surges of water that travel as attenuating waves down the Takaka River. These provide pulses of recharge into the marble aquifer as they soak into the river bed. Such surges of flow measured at the Harwoods gauging station in Upper Takaka are recorded some 18 km away at Te Waikoropupu Springs about 10 to 23 hours later, the time varying inversely with the size of the water release from the dam. Such effects are only observable when the Takaka River has run dry in its middle reaches, because otherwise the pulse just runs down the river channel.

43 Closing the penstocks at the dam has the opposite effect, and is similar to abstraction of water from the river. Takaka River flow drops and sends a negative pulse through the system that reduces outflow at the springs, this being particularly noticeable when the middle Takaka River is dry.

44 Another site where recharge occurs through water loss in a river channel is along a stretch of the Waingaro River where it crosses marble, which underlies the river

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for about 4 km upstream of Hamama. Mean river flow is about 17.8 m3/second and losses of 1-2 m3/second can occur.

45 Other smaller areas that contribute allogenic recharge to the Arthur Marble Aquifer include where small streams along the western side of the valley drain from hills in Onekaka Schist and flow onto marble (Go Ahead Ck, Stony Ck, Craigieburn and Sam Ck), and also a line of swallow holes on the eastern side of the valley, where streams from the Pikikiruna Range/ Mt Evans drain from granite onto the marble plateau crossed by Canaan Road.

46 Autogenic recharge is contributed in areas where rain falls directly onto karst. In such places water infiltrates the surface and percolates underground freely under gravity. This occurs either where marble is exposed or where it is mantled by a permeable cover of sands and gravels. The main area contributing autogenic recharge is the marble upland to the east of Takaka Valley crossed by the Canaan Road, although smaller karst upland areas also contribute recharge along the western side of the valley where there are hilly outcrops of marble between Sam Creek and Go Ahead Creek. These upland areas of marble together cover about 100 km2. The fate of waters that sink north of the Anatoki River, along 8 km of steeply dipping marble ranges between Walker Ridge and Parapara Ridge, is unknown, but subterranean drainage along the strike towards or beneath the Anatoki River is conceivable.

47 Where fluvial sands and gravels directly overlie marble in the middle valley near Hamama and further up-valley towards the Craigieburn confluence and beyond, autogenic recharge occurs as rainwater seeps through the sediment veneer, this zone covering about 35 km2. But in the middle valley some sinkholes in gravel may puncture a layer of Motupipi Coal Measures before entering marble, in which case any recharge through the sinkholes would be considered allogenic (and have a different chemical signature). Tasman District Council report that over 200 potential sinkholes have been identified. Some may be associated with Takaka Limestone, but most appear to be collapses into marble. So point recharge into the marble aquifer via sinkholes is likely to be widespread.

48 Outcrops of Takaka Limestone in the middle and lower Takaka Valley are underlain by Coal Measures, and thus although receiving recharge from rain are sealed from contact with the marble. But the Coal Measures thin up-valley, so near Upper Takaka and into the Waitui valley groundwater from Takaka Limestone may drain into underlying marble. But limestone outcrops in this area amount to only a few square kilometres so the quantities of such recharge to the marble are small.

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Artesian conditions

49 An important feature of the transmission zone through the Arthur Marble Aquifer is that upstream from a line across the valley from approximately Hamama to East Takaka the aquifer is unconfined. Thus upstream of the line contributing waters can drain freely into the aquifer from the surface, but downstream there can be no infiltration because the aquifer is confined by a capping of impervious Motupipi Coal Measures. The Arthur Marble occurs over about 80 km2 of the valley floor, with 70 km2 being south of Te Waikoropupu Springs. Around 45 km2 are confined by impervious capock.

50 The caprock over the marble results in the transmission of groundwater in the downstream component of the system being under pressure. The hydraulic head upstream of the artesian boundary provides the energy to drive the groundwater through the system. Thus the surging outflow of water at Te Waikoropupu Springs has an artesian boil as pressure is released, and the level of water rises in bores drilled through the caprock into the confined marble aquifer beneath. The hydraulic head is measured by the difference in elevation of water between the artesian boundary and Te Waikoropupu Springs. This is of the order of 25-30 m over a distance of about 8 km, but it varies with recharge conditions.

51 The position of the artesian boundary is determined by the up-valley edge of the caprock cover, in this case the limit of impermeable Motupipi Coal Measures over the marble. In practice it is difficult to determine the precise edge of the caprock, because the boundary is buried beneath a thick veneer of Quaternary gravels. Thus its position can only be inferred from occasional data derived from outcrops and bores, and from geophysics. Although the artesian boundary in general extends northwest-southeast across the valley between Hamama and East Takaka, its trace is likely to be irregular, especially because there could be a buried course of the Takaka River (formed during one or more glacial low-stands of the sea) that may have locally cut a downstream extending re-entrant into and across the Coal Measures. This is consistent with reports by Stewart and Thomas (2008) and Tasman District Council that drilling upstream of East Takaka revealed a gravel thickness of 59 m; these gravels probably occupying a buried river channel. A seismic profile across the valley from East Takaka to Hamama is interpreted to show, near East Takaka, a minimum of 128 m of mudstones overlying limestones and coal measures, but a thinning of these sediments to the northwest near Hamama where thick Quaternary gravels rest directly on marble (Ravens 1990). Furthermore, the up-valley parts of the artesian caprock gradually thin and in places are punctured by collapse sinkholes that are a result of surface materials falling into underlying karst voids. Thus in the area where the caprock is thin, groundwater is not confined, because drainage can enter via sinkholes. When groundwater levels are high, the floors of some sinkholes may flood (surface runoff also contributes), but when groundwater levels recede any

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sinkhole pondwater drains underground. The artesian boundary, therefore, is best considered to be a zone rather than a sharp edge.

52 Water elevations along the artesian boundary zone vary. The Takaka River channel provides the threshold level for overflow, and near East Takaka this is at about 40 m. Just 3 km to the west at Hamama, where the ground surface elevation is around 60 m, measured water level in Savages bore varies from 51- 21 m (so some sinkholes deeper than 10 m could be flooded by rising groundwater). About 6 km further upstream in the unconfined part of the aquifer, water in Sowman’s bore, which penetrates marble and is located close to the river channel on its western side, varies in level from 48.7 – 19.1 m, averaging around 38 m. A few kilometres west in Brewery Cave, that runs roughly parallel to the river but on the western side of the valley, groundwater is encountered at a similar level (Rob Davies, pers. com.). Thus we see that groundwater levels in bores into the marble in this part of the middle valley can fluctuate in elevation by about 30 m vertically.

53 The variability in groundwater levels in the Arthur Marble Aquifer near the artesian boundary indicates that the head difference to Te Waikoropupu Springs can be as little as 6 m (ca. 20 - 14.3 m) in drought conditions, but can reach around 32 m (ca. 49 - 17.5 m) when the aquifer system is full. It is likely that, when head is at a maximum, the discharge from off-shore springs will also peak, but when head inland is at a minimum the submarine springs cease to flow, because the hydrostatic head of the denser sea water cannot be overcome.

Water Storage in the Arthur Marble Aquifer

54 The Main Spring (including Dancing Sands) has an average discharge approaching 10 m3/second and the water has an average transit time (or residence time) of 7.9 years. So in a period of that duration a total volume of about 2461*106 m3 (2.6 km3) would flow from the spring. In addition, Fish Creek Springs yield an average of 3.3 m3/second and the average residence time is 3.5 years; so the total volume discharged in that interval is 364*106 m3 (0.36 km3). Consequently, the total volume of water stored in the Arthur Marble Aquifer is about 2.8 km3.

55 The area of marble, both exposed and unexposed, in the Takaka catchment is about 180 km2. Approximately 80 km2 lies beneath the Takaka Valley floor, and 45 km2 of that are covered by Tertiary sediments. Upstream of Te Waikoropupu Springs there is about 70 km2 of marble beneath the valley floor plus around 100 km2 comprising the surrounding marble uplands.

56 The stratigraphic thickness of the Arthur Marble varies between about 500 m and 1000 m depending on location, but the geological structure of folded and tilted beds can make the effective thickness for water movement still greater; thus

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explored caves on Mt Arthur reach depths of 1174 m. The karst uplands around Canaan are at about 750 m, but the underlying marble may extend down to about 250 m below sea level. Down-faulted and tilted marble in Takaka Valley probably extends still deeper, conceivably in places to 500 m or more below sea level, but hard data are lacking.

57 Water storage capacity in the marble is in interconnected pores, fractures and conduits. Ford and Williams (2007) present data from mature carbonate rocks of Silurian to Carboniferous age in North America, where matrix porosity ranges from 2.4 - 6.6%, fracture porosity 0.02 - 0.03% and conduit porosity 0.003 - 0.06%. Although these same rocks have 96.4 - 99.7% of their storage in the matrix, the proportion of groundwater flow that passes through the matrix is minimal, with most of it (97 - 99.7%) passing through the conduit network, despite it storing only 0.05 – 2.4 % of the water. A similar situation is to be expected in the Arthur Marble Aquifer.

58 Because marble is a metamorphic rock recrystallized at depth under heat and pressure, most of the primary porosity is excluded and interconnected pores will be few. Yet boreholes into marble in the Takaka Valley show that water is stored within matrix and/or fracture porosity. Bedding is thick and joints relatively widely spaced, so fracture porosity is relatively low. Although unmeasured, a combination of pore and fissure porosity exists in the Arthur Marble but is unlikely to exceed 2%. Conduit porosity is also unmeasured, but in the Carboniferous Limestones containing Mammoth Cave, the longest cave system in the world (590 km), it is estimated as 0.06%. So although the longest and deepest caves in New Zealand are found in Arthur Marble (Bulmer Cavern 71.9 km, Nettlebed- Stormy Pot 38.3 km, Greenlink-Middle Earth on Takaka Hill 33.9 km), conduit porosity of the bulk rock is unlikely to exceed a few percent at most. Taken together, all forms of porosity in the Arthur Marble Aquifer might reach 4-5%, but is likely to be less.

59 Water storage relevant to the flow of Te Waikoropupu Springs occurs across the entire marble outcrop, not just in the marble beneath the valley floor. Thus, for example, the groundwater system associated with Old Cottage Cave beneath Gorge Creek-Harwoods Hole that drains a radial sweep of 8 km directed towards Spittal Spings is part of the contributing area, and is known to contain strongly flowing streams 700 m or so below the surface. Further, not all the storage capacity is below the water table for, as is known from karsts around the world, significant storage is held for months in the epikarst (in about the first 10 m beneath the surface). This is the subcutaneous storage that keeps stalagmites dripping throughout the dry season and sustains the flow of seepages and small springs vital for village water supplies in many countries (Williams 2004b).

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60 Storage of groundwater in the Arthur Marble can be expected to occur across its entire 180 km2 area, including both exposed and unexposed areas, and with saturated zone (phreatic zone) water supplemented by epikarst water from the unsaturated zone. If porosity of all kinds amounts to 3%, then the total volume of water in the aquifer (around 2.9 km3) would require an average saturated zone depth (or thickness) of 530 m (or 800 m at 2% porosity). The aquifer depth needed to store water decreases if total rock porosity exceeds 3% or if significant groundwater storage also occurs in gravel-filled buried channels beneath the valley, some of which certainly occur.

61 Given that reverse faulting pushed a considerable thickness of already karstified marble below the valley floor, then it is to be expected that storage capacity exists well below sea level. After formation of Takaka Valley, the considerable throughput of allogenic waters from the upper Takaka River will have produced (and is still developing) a major enhancement of conduit porosity in marble beneath the valley floor – a second generation conduit porosity.

Discharge of Water from the Arthur Marble Aquifer

62 Groundwater moves downstream through the confined marble aquifer and escapes in various places and amounts according to prevailing pressure conditions. The most well-known outflow area is Te Waikoropupu Springs, a series of cold-water springs situated at 14.3 - 17.5 m above sea level (Figure 2 Plan of Te Waikoropupu Springs). Water temperature is a constant 11.7°C. Average outflow from the entire complex is a little over 13 m3/second (ranging from 14.3 to 5.734 m3/s) of which almost 10 m3/second comes from the combined Main Spring and Dancing Sands Spring, and 3.3 m3/second from Fish Creek Springs, although the latter can run dry during droughts. So the 7-day mean annual low flow of 7.350 m3/s for the combined outflow of the Main and Dancing Sands is, in effect, for the entire springs’ complex; the 10-year low flow being 6.379 m3/s (TDC data).

63 The marble aquifer is confined by coal measures to the coast, but submarine springs are known to emerge through the sandy floor of Golden Bay (located on Oceanographic Chart NZ61) at 1-5 km offshore and at depths of 12-14 m. Although their source is unknown, some of these submarine springs (as near Rangihaeata) are likely to be discharge points for the marble aquifer. If Arthur Marble extends offshore, then it could have been exposed during low-stands of the sea during the Pleistocene, and would then have been a natural outflow point for groundwater. Under such low-stand conditions, the groundwater level in the marble would have been lower than at present and so Te Waikoropupu Springs would probably not have operated. Following postglacial rise of sea level, the lowest karst conduits were back-flooded by sea water, forcing the less dense freshwaters to overflow at a higher level – in this case at Te Waikoropupu

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Springs. Thus the Arthur Marble Aquifer has an underflow-overflow discharge system. The submarine springs are the lowest outflow points, the Main Spring and adjoining Dancing Sands Spring are the first level of overflow, and Fish Creek Springs are the highest level overflow. Under drought conditions the highest level ceases to flow first and the reduced pressure inland may become insufficient to maintain outflow at submarine springs.

64 Evidence that lends support to the connection between the Arthur Marble Aquifer and the sea is the fact that water emerging at Te Waikoropupu Springs is known to be slightly brackish (Michaelis 1974). No rock salt (halite) is known in the local geology, so the most likely source of salinity is the sea. The springs are also tidal (amplitude in the order of mm). The proportion of seawater discharged in the Main Spring varies from about 0.4 – 0.6%, but the proportion is less, 0.2 – 0.4%, in Dancing Sands Spring, and less still in Fish Creek Springs (0.1%). However, as the volume of spring outflow increases, the proportion of salt in the water increases (Williams 1977, Stewart and Thomas 2008). This indicates that stronger groundwater circulation draws in more salt, presumably by inducing more mixing with the underlying saltwater wedge. The mechanism is uncertain, but a venture mixing process may be implicated.

65 The volume of water discharged by submarine springs has not been measured, but estimates have been made by means of water balance calculations. The volume of recharge can be estimated from rainfall. The discharge of Te Waikoropupu Springs is known. Thus if recharge exceeds measured discharge, then the difference could be accounted for by the unmeasured outflow of submarine springs. Stewart and Thomas (2008) discuss various estimates made using this approach and conclude that total submarine outflow could be about 6.45 m3/second, which is equivalent to roughly twice the average outflow of Fish Creek Springs. This seems plausible, although uncertainties could be as great as 20%.

66 The freshwater discharge from Te Waikoropupu Springs is a blend of water from different sources and with different flow through times. The contributions made from individual recharge sources to each spring can be estimated by a mass balance of stable isotope (δ18O) values in which the proportions derived from each recharge source account for the stable isotope (δ18O) value measured at each spring. The outcome was expressed diagrammatically in Williams (1992), and the most recent calculation by Stewart and Thomas (2008) suggests that the karst uplands supply 74% of the flow from the Main Spring with the upper Takaka River contributing 18% and the rest (8%) coming from rainfall recharge in the upper valley. The proportions are different in the Fish Creek Springs with an estimated 50% of flow derived from the upper Takaka River and 25% each from karst uplands and valley rainfall.

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67 The mass balance calculation based on δ18O values indicates that the contribution of upper Takaka River water to the average total outflow of Te Waikoropupu Springs is about 3.45 m3/second. Since the loss of upper Takaka River water into channel gravels near Lindsays Bridge is considerably more than this (estimated as 8 m3/s), it is possible that much of the sinking river water is discharged elsewhere. The volumes involved suggest that it could account for most of the possible submarine discharge of 6.45 m3/second noted in 8.7.4.

Age Spectrum of Water Discharged at Te Waikoropupu Springs

68 Water derived from different recharge areas takes different amounts of time to travel to points of discharge, partly because the lengths of travel vary and also because resistance to flow varies, being slower where pores and fissures are narrow. So the residence time of water in the marble aquifer varies widely. Methods used to determine the age (residence time or flow-through time) and source of groundwaters in New Zealand are discussed by Stewart and Morgenstern (2001).

69 The residence time underground of water discharged at the Main Spring was first estimated in the 1960s by M. Taylor from DSIR using tritium (3H) concentrations in the water, the tritium having come from atmospheric rainout following nuclear explosions. Assuming a piston flow model (where discrete slugs of recharge water move without mixing through a pipe), this yielded transmission times of 3 to 4 years. After further sampling in the 1970s, Stewart and Downs (1982) recalculated residence times comparing piston flow and a one-box models (which assumes a well-mixed reservoir). The one-box model calculations yield longer residence times of 10-12 and up to 20 years, depending on annual mean rainfall prior to sampling.

70 Tritium concentrations in the atmosphere have fallen to close to background since the end of atmospheric nuclear testing, but man-made contamination of the atmosphere by chlorofluorocarbons (CFCs) has increased. CFCs are slightly soluble in water and so can be used to determine the recharge date of groundwaters. The most recent estimates of the residence times of Te Waikoropupu Springs groundwaters employ both tritium and CFCs and comes from the work of Stewart and Thomas (2008). They studied both the Main Spring and Fish Creek Spring and compared three different flow models. But it is recognized that because water emerging at the springs comes from a wide area and is derived from different sources, the waters emerging will have a range of flow-through (or transit) times. As a result, modelling results show peaks of relative young waters but long tails of considerably older water. Stewart and Thomas conclude that the mean residence time for the Main Spring water using tritium data is close to 8 years, with the double dispersion model (DDM) providing the best fit. It shows a mean residence time of 7.9 years, but with 74% of the

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water being 10.2 years old and 26% being 1.2 years old. Results from residence time modelling using CFC concentrations were more variable, but tended to support the tritium DDM model. Application of the same modelling techniques to Fish Creek Spring data shows a residence time (or transit time) of 3.5 years.

71 The range of variability of δ18O values recorded in spring waters can be used to estimate the mean residence time of the youngest component of outflow. This approach provides evidence that youngest component of water emerging at the Main Springs is about 1.2 years and at Fish Creek is about 1.1 years.

72 Water drawn from a 114 m deep artesian bore (Ball’s bore) that penetrates 33 m of Coal Measures before entering marble was found to contain water with a tritium value close to background concentration. This therefore represented water at least 100 years old. When the bore is pumped, the drawdown in the potentiometric surface is reported by Stewart and Thomas (2008) to be quite large, the drop being 3.2 m when the rate of extraction is 10.7 litres/second. This implies low hydraulic conductivity around the bore, which is consistent with a tightly fissured matrix. The evidence therefore shows that at a relatively shallow depth old water can occur in the fissure matrix even though that part of the Arthur Marble Aquifer is close to the discharge zone. The bore site concerned is just 425 m southwest of Te Waikoropupu Springs.

73 At the time of sampling for tritium, the discharge of each spring was not recorded, so the relationship between discharge and mean residence is unknown. However, Stewart and Thomas (2008) note that Cl values at the time of sampling the Main Spring indicate that the 1966 sample was taken during above average flow, the 1972 and 1976 samples during average flows, and the 1999 sample during less than average flow. In terms of the overflow/underflow relationship of the springs, when total outflow is great enough to generate overflow at Fish Creek Springs then the water that emerges is relatively young (3.5 years).

Implications for Management of the Arthur Marble Aquifer

74 Although conditions in the Takaka region are no longer completely natural because of human occupation and land use changes, to ensure conservation of values at Te Waikoropupu Springs that are as close to natural as possible, there are two main considerations: water quality and water quantity.

75 The long residence time of water in the Arthur Marble Aquifer has considerable implications for water quality management. The residence time of groundwater varies with location in the aquifer from about 1.2 years to many decades, but with an average flow-through time of about 8 years. The relatively unvarying composition of stable isotopes shows the water to be well mixed (there is almost no seasonal signal). Thus if unwanted contaminants get into the marble aquifer, they will reside there for a long time and will take a very long time to flush out,

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because of the exponential process of freshwater recharge, mixing and flushing. The implication is that mismanagement by this generation will take at least another generation to rectify.

76 Contaminants enter aquifers in places where recharge of water occurs. In the case of the Arthur Marble Aquifer, these areas are well known. They are of two kinds: areas where water is contributed directly by rainfall (termed autogenic recharge, as where rain falls directly onto marble outcrops and infiltrates diffusely), and areas that receive water from streams that first collected on other rocks and then later flowed across marble where they lose water into their beds (termed allogenic recharge). Autogenic recharge across the entire marble uplands supplies about 74% of the flow from the Main Spring (including Dancing Sands) and valley rainfall another 8%; so the quality of water that infiltrates from the land and from any waste sites (septic tanks etc) is significant for spring water quality. Allogenic streams are significant because they have the potential to carry contaminants long distances downstream to the aquifer recharge zone. The entire Takaka River catchment upstream of the artesian boundary, and including sinkholes in the boundary zone, is in that category. It contributes an average of about 3.45 m3/second to the flow emerging at the Main Spring, i.e. about 18%. The Waingaro River catchment upstream of Hamama also contributes some allogenic water, about 1-2 m3/second, so the quality of this river is also important. Consequently, the implications for management are as clear as the water from the springs: if we are to ensure for posterity water quality at Te Waikoropupu Springs that is as close to natural as possible, then the recharge zones that contribute water to the Arthur Marble Aquifer must receive effective management to guarantee that infiltration to groundwater from both diffuse and point sources is of high quality, and in particular is free of significant animal effluent and agricultural chemical waste.

77 The amount of water emerging at Te Waikoropupu Springs depends on the recharge contributions received from the catchment. When the Arthur Marble Aquifer is full, Te Waikoropupu Springs discharge water at full capacity (>14 m3/second) and any excess water received in the recharge zone overflows down the channel of the Takaka River. When the middle Takaka River is dry, this indicates that the aquifer is not full and so the flow of Te Waikoropupu Springs is made up from on-going recharge plus draw-down of storage in the aquifer. Under such conditions, all contributions of recharge from around the catchment reduce the rate of storage depletion in the aquifer. So water abstraction by human activity from anywhere in the contributing area, including withholding water in the Cobb Reservoir, will increase the rate of depletion of the aquifer and so exacerbate the drop in flow of Te Waikoropupu Springs. Release of water from the Cobb Reservoir will have the opposite effect.

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78 The net annual effect of Cobb Reservoir on Te Waikoropupu Springs is negligible, because it does not influence the amount of water coming down the Takaka River, only its timing. However, it has the potential to influence the springs, because if the reservoir held back water during wet conditions, when the aquifer is full and overflow occurs down the channel, but later released water when the middle Takaka River had become dry, then the release would recharge the aquifer and so reduce its draw-down, hence maintaining spring flow.

79 The implications for water quantity management are that when the middle Takaka River is flowing then water abstractions upstream, including from bores into the confined aquifer, have no material effect on the flow of Te Waikoropupu Springs. But when the channel of the middle Takaka River is dry, then every drop of water taken upstream or from bores into the aquifer depletes the flow of the springs by a similar amount.

80 Water quality and quantity management of bores into Takaka Limestone or into Quaternary gravels downstream of the artesian aquifer boundary, or abstractions from streams in those areas, will have no effect on Te Waikoropupu Springs.

Professor Paul Worthing Williams

28 March 2018

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REFERENCES

BGR, IAH KIT and UNESCO 2017. World Karst Aquifer Map 1: 40 000 000. Berlin, Reading, Karlsruhe and Paris.

Davies-Colley, R.J. and Smith, D.G. 1995. Optically pure waters in Waikoropupu (‘Pupu’) Springs, Nelson, New Zealand. NZ Journal of Marine and Freshwater Research 29, 251-256.

Grindley, G.W. 1971. Sheet S8 Takaka. Geological map of New Zealand. 1: 63 360. Wellington: NZ Department of Scientific and Industrial Research.

Grindley, G.W. 1980. Sheet S13 Cobb. Geological Map of New Zealand 1:63 360. Wellington: N.Z. Department of Scientific and Industrial Research.

Holden, G. 2017. Cosmogenic nuclide dating of the sediments of Bulmer Cavern: implications for the uplift history of southern northwest Nelson, New Zealand. Geoscience Society of NZ, Abstracts of the Auckland Conference.

Meuller, M. 1991. Karst hydrology of the Takaka valley, Golden Bay, northwest Nelson. NZ Journal of Geology & Geophysics 34, 11-16.

Michaelis, F.B. 1976. ‘Physico-chemical features of Pupu Springs.’ NZ Journal of Marine and Freshwater Research 10(4), 613-628.

Rattenbury, M.S., Cooper, R.A., Johnston, M.R. (compilers). 1998. Geology of the Nelson area. Lower Hutt, New Zealand: Institute of Geological & Nuclear Sciences 1:250 000 geological map 9, 67 p.

Ravens, J.M. 1990. Shallow seismic reflection surveys in the Takaka valley, northwest Nelson. NZ Journal of Geology & Geophysics 33, 23-28

Rosen, M.R., and White, P.A. (Editors), 2001. Groundwaters of New Zealand, Wellington, NZ Hydrological Society, 498 p.

Stewart, M.K. and Downes, C.J. 1982. Isotope hydrology of Waikoropupu Springs, New Zealand. In: E.C. Perry and C.W. Montgomery (Editors), Isotope Studies of Hydrologic Processes, Northern Illinois University Press, DeKalb, p 15-23.

Stewart, M.K. and Morgenstern, W. 2001. Age and source of groundwaters from isotope tracers. In: M.R. Rosen and P.A. White (Editors), Groundwaters of New Zealand, Wellington, NZ Hydrological Society, p 161-183.

Stewart, M.K. and Williams, P.W. 1981. ‘Isotope hydrology of the Waikoropupu Springs and Takaka River, northwest Nelson’. NZ Journal of Science 24, 323-337.

Stewart, M.K. and Thomas, J.T. 2008. ‘A conceptual model of flow to theWaikoropupu Springs, NW Nelson, New Zealand, based on hydrometric and tracer (18O, Cl, 3H and CFC) evidence.’ Hydrology and Earth System Sciences 12 (1), 1-19.

Williams, P.W. 1977. ‘Hydrology of the Waikoropupu Springs: a major tidal karst resurgence in northwest Nelson (New Zealand).’ Journal of Hydrology (Netherlands) 35, 73-92.

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Williams, P.W. 1992. ‘Karst Hydrology.’ In: M.P. Mosley (Editor), Waters of New Zealand,. Christchurch: NZ Hydrological Society, p. 187-206.

Williams, P.W. 2004. ‘Karst Systems.’ In: J. Harding et al. (Editors), Freshwaters of New Zealand, Christchurch, NZ Hydrological Society & NZ Limnological Society, p. 31.1-31.20.

Williams, P.W. 2004b. ‘The epikarst: evolution of understanding’. In: W. K. Jones, D.C. Culver, J. S. Hermon (Editors), Epikarst, Karst Waters Institute, Special Publication 9. Charles Town, West Virginia, p. 8-15.

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Figure 1

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Figure 2 Plan of Te Waikoropupu Springs (from Williams 1977)

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Table 1. Te Waikoropupu Springs: discharge values, proportions of flow and residence times

Spring Proportion of Water Age Discharge Alternative Storage vol flow (yrs) (m3/s) (m3/s) (km3)

Fish Creek 1 3.51 3.32 0.364

Main&DS 1 7.91 9.87 2.461

0.743 10.2 7.3 7.4 4

9.2 5 3.05

0.263 1.2 2.57 2.64 0.46

Total TWS 1 13.177 13.38 2.8259

Notes:

1 Stewart & Thomas (2008) Table 6 p.11

2 S&T p. 8

3 S&T p. 13 [74% of flow of Main Spr is 10.2 yrs old]

3 S&T p. 13 [26% of flow of Main Spr is 1.2 yrs old]

4 S&T Table 4 p.8 [74% of flow of Min Sp is from Karst Uplands]

4 S&T Table 4 p. 8 [26% of flow of Main Sp is from Upr Takaka Riv and Valley Rainfall]

5 S&T p. 16-17 [deep system water age is 10.2 yrs, flow is 9200 l/s, so volume = 3 km3

6 S&T p.17 [shallow system storage of 0.4 km3 with age 1.2 yrs requires discharge rate of 10.5 m3/s but 26% of Main Spr discharge is 2.57 m3/s, so with 1.2 yr age storage volume is 0.1 km3.

7 Sum of average flows of Main & Dancing Sands Springs plus Fish Ck Springs

8 S&T p. 1

9 Sum of storage volumes of Main & Dancing Sands Springs plus Fish Ck Springs

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Paul W. Williams

28 March 2018

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