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Whakatane, New Zealand

Burnell J.,Institute of Geological & Nuclear Sciences | Campen B.V.,University of Auckland | Kortright N.,Environmental Management Services Ltd | Lawless J.,Lawless Geo Consulting | And 3 more authors.
Geothermics | Year: 2015

Worldwide, the second-longest well-documented history of large-scale use of magmatic-related geothermal systems is in the Taupo Volcanic Zone in New Zealand. Since 1991, geothermal energy usage and its effects have been controlled by a single piece of legislation. This integration of resource allocation and effects management under a single Act, with sustainable management a cornerstone, differs from the approach taken in many countries. The overall objectives are further detailed at a regional level in policies and plans with a focus on resource management. This paper reviews this approach after almost 60 years of development, with the focus on achieving long-term (>100 years) usage including a description of three brief case studies. © 2015 Elsevier Ltd.

Scott B.J.,Institute of Geological & Nuclear Sciences | Mroczek E.K.,Institute of Geological & Nuclear Sciences | Burnell J.G.,Institute of Geological & Nuclear Sciences | Zarrouk S.J.,University of Auckland | And 3 more authors.
Geothermics | Year: 2016

The Rotorua Geothermal Field (RGF) is a unique example of a geothermal system that has been managed intensively to both obtain energy in a sustainable manner and to preserve the surface features and their intrinsic value. The field underwent an extensive bore closure programme in the 1980s. Exploitation today is characterised by a reduced number of shallow bores (140 consented bores and an additional 42 with down hole heat exchanges) with limits set on use by a management plan designed and monitored by the Bay of Plenty Regional Council. The RGF has a wide range of uses, values and differing significance to the Rotorua community, including cultural values, economic benefits, energy source and a tourism driver.A collection of research and monitoring activities are presented in this paper. We summarise the current management regime, surface feature trends and results of chemical research, repeated heat flow surveys at Whakarewarewa and representative temperature-contour maps of the geothermal resource. These data and results show that the composition of the primary deep fluids have changed little over time, while marked physical changes have occurred at surface features; a mix of positive recovery signs, along with many complex exceptions to those trends are seen. The use of modern numerical modelling methodology, using bore temperature records, geology and chemical data allow for improved modelling of the system. © 2015 Elsevier Ltd.

Taylor M.D.,Waikato Regional Council | Kim N.D.,Massey University | Briggs R.M.,University of Waikato | Taylor A.,Waikato Regional Council | Guinto D.F.,Bay of Plenty Regional Council
Applied Clay Science | Year: 2012

Dealumination is a term used to describe an increase in the concentration of acid extractable Al as a result of accelerated weathering or chemical attack of primary crystalline and short-range order aluminosilicates. Two specific mechanisms have been proposed: (1) partial dissolution of clay minerals by local areas of high acidity associated with fertiliser granules; (2) surface complexation and extraction by the fluoride and residual hydrofluoric acid present in phosphate fertilisers. This process has been observed in State of the Environment data from the Waikato region, New Zealand, for farmed soils (which receive substantial inputs of phosphate fertilisers) but not for background soils (which are unfertilised). Additional data, including results from XRF analysis for total Al on the original Waikato region samples, acid extractable Al from two neighbouring regions, Auckland and Bay of Plenty, and trends in the data at sites resampled 5. years apart are reported in this work. Retrospective analysis of the Waikato samples by XRF for total Al showed that there was no significant difference between farmed and background soils (whereas the increase in acid extractable Al was significant, p < 0.0001), indicating total Al concentrations were not increasing in farmed soils but the form of it was changing. In farmed soils, proportionately more Al is becoming acid-extractable over time. Acid extractable Al results were consistent with dealumination occurring in all 3 regions (p < 0.015 to < 0.0001) and significant (p < 0.0001) increases were seen in farmed soils compared to background ones over 5. years, with a mean increase in acid extractable Al of about 1000. mg/kg/year. The actual mechanisms of dealumination and associated soil processes need to be verified, and the relative importance of possible causative factors delineated (two possible causes are high localised acidity around fertiliser granules, and high annual loadings of F). Whatever the causes, the effects of this process on soil properties and implications to soil management need to be ascertained. © 2012 Elsevier B.V.

Pearson S.C.P.,Institute of Geological & Nuclear Sciences | Alcaraz S.A.,Institute of Geological & Nuclear Sciences | Barber J.,Bay of Plenty Regional Council
Hydrogeology Journal | Year: 2014

Tauranga low-temperature geothermal system (New Zealand) has been used for the last 40 years for direct uses including space heating, bathing and greenhouses. Warm-water springs in the area are between 22 and 39 °C, with well temperatures up to 67 °C at 750 m depth. A heat and fluid flow model of the system is used to determine reservoir properties and assess thermal potential. The model covers 130 km by 70 km to 2 km depth, and was calibrated against temperatures measured in 17 wells. Modelling shows that to maintain the observed primarily conductive heat flow regime, bulk permeability is ≤2.5×10-14m2 in sedimentary cover and ≤1×10-16 m2 in the underlying volcanic rocks. The preferred model (R2 =0.9) corresponds to thermal conductivities of 1.25 and 1.8 W/m2 for sedimentary and volcanic rocks, respectively, and maximum heat flux of 350 mW/m2. The total surface heat flow is 258 MW over 2,200 km2. Heat flux is highest under Tauranga City, which may be related to inferred geology. Model simulations give insights into rock properties and the dynamics of heatflow in this low-temperature geothermal system, and provide a basis to estimate the effects of extracting hotfluid. © Springer-Verlag Berlin Heidelberg 2013.

Boothway D.,Bay of Plenty Regional Council
Hydrology and Water Resources Symposium 2014, HWRS 2014 - Conference Proceedings | Year: 2014

Room for the River, New Zealand perspective, case studies, and lessons learnt. New Zealand is a young country, geologically speaking, which means we have ever changing catchments sculptured by earth movements and active energetic rivers. Human settlement has tried to tame the land for economic gain. New Zealand has successfully created a food basket for itself and the world. However, the taming of the rivers has come at a cost. This paper looks at how well we have "tamed our rivers" in different parts of the country, the lessons we have learnt and how we can improve our soft and hard engineering projects to create an even better future for our country. Through the use of case studies, sharing of information, reviewing projects within cities and large rural catchments, being honest with ourselves on what has and has not worked for the benefit of all, we share real life experiences on how we are currently raising our "room for the river" bar. In so doing we hope to enhance New Zealand's image of pure clean rivers and awe inspiring landscapes.

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