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 16005411 | 3394502 page 1 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. 16005411 | 3394502 page 2 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 16005411 | 3394502 page 3 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.