Blair J.M.,University of Waikato |
Ostrovsky I.,Israel Oceanographic And Limnological Research |
Hicks B.J.,University of Waikato |
Pitkethley R.J.,Eastern Region Fish and Game |
Scholes P.,Bay of Plenty Regional Council
Canadian Journal of Fisheries and Aquatic Sciences | Year: 2013
To predict potential effects of climate and anthropogenic impacts on fish growth, we compared growth rates of rainbow trout (Oncorhynchus mykiss) in nine closely located warm-temperate lakes of contrasting morphometry, stratification and mixing regime, and trophic state. Analyses oflong-term mark-recapture data showed that indeep oligotrophic and mesotrophic lakes, trout growth rates increased with increasing indices of lake productivity. In contrast, in shallow eutrophic lakes, where fish habitat volume is constrained by temperature and dissolved oxygen, trout growth rates declined with increasing productivity. Growth rates were higher in lakes with greater volumes of favourable habitat (i.e., dissolved oxygen > 6.0 mg·L-1 and temperature < 21 °C) and lower in lakes with increased turbidity, chlorophyll a, and nitrogen concentrations. Our findings suggest that increases in lake productivity and temperatures as a result of global climatic change are likely to be more detrimental to salmonid habitat quality in shallower, productive lakes, while salmonids will better endure such changes in deeper, oligotrophic lakes. Fishery managers can use this information to aid future stocking decisions for salmonid fisheries in warm-temperate climates.
Mackay E.B.,UK Center for Ecology and Hydrology |
Maberly S.C.,UK Center for Ecology and Hydrology |
Pan G.,CAS Research Center for Eco Environmental Sciences |
Reitzel K.,University of Southern Denmark |
And 14 more authors.
Inland Waters | Year: 2014
The use of geoengineering techniques for phosphorus management offers the promise of greater and quicker chemical and ecological recovery. It can be attractive when used with other restoration measures but should not be considered a panacea. The range of materials being proposed for use as well as the in-lake processes targeted for manipulation continues to grow. With increasing political imperatives to meet regulatory goals for water quality, we recommend a coordinated approach to the scientific understanding, costs, and integration of geoengineering with other approaches to lake management. © International Society of Limnology 2014.
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.
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.
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.
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.
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.
Tay H.W.,University of Waikato |
Bryan K.R.,University of Waikato |
Pilditch C.A.,University of Waikato |
Park S.,Bay of Plenty Regional Council |
Hamilton D.P.,University of Waikato
Marine and Freshwater Research | Year: 2012
Water-quality observations in estuaries can be highly variable in time and space, making it difficult to quantify nutrient fluxes and to discriminate patterns. We measured nitrate, phosphate and ammonium concentrations in two shallow tidally dominated estuaries in Tauranga Harbour, New Zealand, during four periods (winter, start of spring, end of spring and summer) within 1 year, to determine the source of variability observed in a 19-year monitoring program. These measurements consisted of high-frequency monitoring during one 24-h period (covering a daytime flood-ebb tide and a night-time flood-ebb tide) at each estuary. Concentrations of nitrate and ammonium had distinctive tidal patterns, with rising values during ebb flows. This tidal asymmetry caused a net seaward flux of dissolved inorganic nitrogen (nitrate and ammonium), with higher exports at night. Net fluxes were 34358kgN per tidal cycle for nitrate and 2293kgN per tidal cycle for ammonium. Fluxes were large relative to previously published model-based predictions for the region, particularly during winter. Our results showed that estuarine sampling strategies need to account for tidal variability and the role of episodic runoff events, and highlighted the importance of correctly validated mass fluxes from field measurements for comparisons with nutrient-loading models. © CSIRO 2012.
Abell J.M.,University of Waikato |
Hamilton D.P.,University of Waikato |
Paterson J.,Bay of Plenty Regional Council
Australasian Journal of Environmental Management | Year: 2011
Decades of nutrient pollution have caused water quality to decline in the nationally iconic Te Arawa (Rotorua) lakes in New Zealand. Pastoral agriculture is a major nutrient source, and therefore this degradation represents an external environmental cost to intensive farming. This cost is borne by the wider community, and a major publically funded remediation programme is now under way. This article describes the range of actions being taken to reduce nutrient loads from internal (lake bed sediments) and external (primarily diffuse) sources in the lake catchments. The high economic cost and uncertain efficacy of engineering-based actions to reduce internal nutrient loads is highlighted. Major changes to land management practices to control diffuse nutrient pollution are required throughout New Zealand if the need for costly and lengthy remediation programmes elsewhere is to be avoided. More action to educate farmers and the public about eutrophication issues, development and enforcement of environmental standards, and further consideration of the use of market-based instruments are proposed as ways to correct the current market failure. © 2011 Environment Institute of Australia and New Zealand Inc.
Ross P.M.,University of Waikato |
Fairweather R.M.,University of Waikato |
Culliford D.P.,University of Waikato |
Park S.,Bay of Plenty Regional Council |
And 2 more authors.
New Zealand Journal of Marine and Freshwater Research | Year: 2016
To investigate the uptake and depuration of polycyclic aromatic hydrocarbons associated with the Rena oil spill we sampled the surf clam Paphies subtriangulata at two open coast locations (6 km apart) just prior to oil coming ashore (7 October 2011), then at 1–3 week intervals for the next 4 months. Total polycyclic aromatic hydrocarbons (tPAH) increased at both sites from 1 to 96–124 µg kg−1 (wet weight) by 18 October before declining to low levels (<4 µg kg−1) by February 2012. Ongoing sampling throughout 2012–2014 included three additional sites to the north east (up to 30 km away) and a site 5 km to the south east revealing tPAH levels generally <10 µg kg−1 except in October 2013 where levels ranged between 39–45 µg kg−1 at all sites. A comparison of PAH component profiles with oil-contaminated beach sediment indicated that the high levels observed in surf clams between October–December 2011 were clearly associated with the Rena spill. However, the October 2013 peak had a PAH profile inconsistent with weathered Rena oil, suggesting an alternative source of contamination. Our results highlight the potential for P. subtriangulata as a PAH monitoring tool but recognise more study is needed to better quantify baseline levels and uptake and depuration dynamics. © 2016 The Royal Society of New Zealand.