title: Measurements and modelling of eutrophication processes in Lake Rotoiti, New Zealand

authors: von Westernhagen, Nina

subjects: 3D modelling

abstract: Deterioration of water quality is a common problem for aquatic systems globally, which is accelerated by factors such as urban settlement, farming, forestry and recreation. Spatial variability of water quality in these systems hinders a more advanced understanding of their dynamics, to better enable strategies to be developed to combat their deterioration. Understanding the drivers for spatial variability is fundamentally important for predicting how lake ecosystems will respond to management scenarios and which management actions are most likely to be successful to improve lake health. Through a field study in a morphologically diverse lake in New Zealand, and the application of a lake ecosystem model, this study examined the spatial and temporal variability of phytoplankton biomass and made a detailed consideration of the performance of three-dimensional lake ecosystem models. To gain insight in the spatial variability in phytoplankton productivity, surface phytoplankton productivity measurements were carried out at three stations in morphologically complex Lake Rotoiti, North Island, New Zealand, with the objective of defining variations between sites and seasons, and the dominant environmental drivers of these variations. There was no overarching statistical relationship between measured environmental variables and primary productivity or specific production. Inorganic nutrient concentrations at the surface of the shallow station were low throughout the whole year but at the other two stations they showed a typical pattern for monomictic lakes of higher levels during winter mixing and declining concentrations during thermal stratification. The high variability between the three sites indicates that it is important to account for local differences in productivity in morphologically diverse lakes, and that whole-lake productivity estimates may vary greatly depending on the location and depth at which measurements are made. To gain understanding of the spatial variability, a higher resolution three-dimensional (3D) model, ELCOM-CAEDYM, was used to simulate the time-varying horizontal and vertical variations in water quality over one year (May 2004-May 2005). The main inflow to Lake Rotoiti arises via the Ohau Channel from adjacent eutrophic Lake Rotorua. Highly spatially resolved field data were collected monthly to validate the model performance for simulations of temperature, dissolved oxygen and chlorophyll a. The model was configured to simulate a geothermal heat source in the deepest part of the main lake basin. Model simulations of temperature, dissolved oxygen and chlorophyll a were highly correlated with measurements of these variables but simulations of spatial variations in nutrient concentration showed relatively low correlation coefficient values, in particular at a station located in a shallow embayment. An examination of the behaviour of a conservative tracer introduced into the major inflow of Lake Rotoiti, the Ohau Channel, confirmed previous findings that this inflow could enter the lake as a surface inflow, interflow or underflow, depending on temperature gradients between the inflow and the lake water column. The results showed that ELCOM-CAEDYM is capable of reproducing highly spatially resolved field data in a complex, geothermally-influenced lake, and can provide important insights into the fate of heat and constituents in major inflows. A wall to divert Ohau Channel water directly towards the outflow of Lake Rotoiti was implemented in August 2008. Based on parameter values calibrated for the time period before the inflow diversion (May 2004-May 2005), ELCOM-CAEDYM was applied to the post-diversion wall period of August 2008-August 2009. The model showed good fit with observed data for temperature, dissolved oxygen and chlorophyll a, but the model showed a poor fit when simulations were compared with in situ nutrient concentrations at all stations. Simulations with ELCOM-CAEDYM suggest that model accuracy may be improved when a simplified dynamic sediment diagenesis model is available. This could provide for less sensitivity to sediment nutrient release rates of the model and better model fit to in situ data. Ecosystem modelling is likely to play an increasingly important role in lake management and scientific understanding of lake processes as computer speed increases and models undergo further refinements. The model development is in a phase of relative maturity in which water quality simulations provide an efficient and rational tool to compare water quality outcomes and cost effectiveness of lake improvement techniques, to provide for preservation and improvement in water quality in the future.

text: Measurements and modelling of eutrophication processes in Lake Rotoiti, New Zealand Deterioration of water quality is a common problem for aquatic systems globally, which is accelerated by factors such as urban settlement, farming, forestry and recreation. Spatial variability of water quality in these systems hinders a more advanced understanding of their dynamics, to better enable strategies to be developed to combat their deterioration. Understanding the drivers for spatial variability is fundamentally important for predicting how lake ecosystems will respond to management scenarios and which management actions are most likely to be successful to improve lake health. Through a field study in a morphologically diverse lake in New Zealand, and the application of a lake ecosystem model, this study examined the spatial and temporal variability of phytoplankton biomass and made a detailed consideration of the performance of three-dimensional lake ecosystem models. To gain insight in the spatial variability in phytoplankton productivity, surface phytoplankton productivity measurements were carried out at three stations in morphologically complex Lake Rotoiti, North Island, New Zealand, with the objective of defining variations between sites and seasons, and the dominant environmental drivers of these variations. There was no overarching statistical relationship between measured environmental variables and primary productivity or specific production. Inorganic nutrient concentrations at the surface of the shallow station were low throughout the whole year but at the other two stations they showed a typical pattern for monomictic lakes of higher levels during winter mixing and declining concentrations during thermal stratification. The high variability between the three sites indicates that it is important to account for local differences in productivity in morphologically diverse lakes, and that whole-lake productivity estimates may vary greatly depending on the location and depth at which measurements are made. To gain understanding of the spatial variability, a higher resolution three-dimensional (3D) model, ELCOM-CAEDYM, was used to simulate the time-varying horizontal and vertical variations in water quality over one year (May 2004-May 2005). The main inflow to Lake Rotoiti arises via the Ohau Channel from adjacent eutrophic Lake Rotorua. Highly spatially resolved field data were collected monthly to validate the model performance for simulations of temperature, dissolved oxygen and chlorophyll a. The model was configured to simulate a geothermal heat source in the deepest part of the main lake basin. Model simulations of temperature, dissolved oxygen and chlorophyll a were highly correlated with measurements of these variables but simulations of spatial variations in nutrient concentration showed relatively low correlation coefficient values, in particular at a station located in a shallow embayment. An examination of the behaviour of a conservative tracer introduced into the major inflow of Lake Rotoiti, the Ohau Channel, confirmed previous findings that this inflow could enter the lake as a surface inflow, interflow or underflow, depending on temperature gradients between the inflow and the lake water column. The results showed that ELCOM-CAEDYM is capable of reproducing highly spatially resolved field data in a complex, geothermally-influenced lake, and can provide important insights into the fate of heat and constituents in major inflows. A wall to divert Ohau Channel water directly towards the outflow of Lake Rotoiti was implemented in August 2008. Based on parameter values calibrated for the time period before the inflow diversion (May 2004-May 2005), ELCOM-CAEDYM was applied to the post-diversion wall period of August 2008-August 2009. The model showed good fit with observed data for temperature, dissolved oxygen and chlorophyll a, but the model showed a poor fit when simulations were compared with in situ nutrient concentrations at all stations. Simulations with ELCOM-CAEDYM suggest that model accuracy may be improved when a simplified dynamic sediment diagenesis model is available. This could provide for less sensitivity to sediment nutrient release rates of the model and better model fit to in situ data. Ecosystem modelling is likely to play an increasingly important role in lake management and scientific understanding of lake processes as computer speed increases and models undergo further refinements. The model development is in a phase of relative maturity in which water quality simulations provide an efficient and rational tool to compare water quality outcomes and cost effectiveness of lake improvement techniques, to provide for preservation and improvement in water quality in the future.

year: 2010

title: William Sharman Crawford (Billy) Nicholl, the prospector who discovered the Martha lode at Waihi: his life, told largely in his own words

authors: Hart, Philip

abstract: Billy Nicholl was that rare miner, one who recorded his life. Born in Ireland, when still a boy he arrived in New Zealand in 1862. After his father died at an early age, he acquired a step-father, whom he disliked, with good reason; and in her later years his mother’s mind would fade.
From 1868, when he was probably aged 14, until shortly before his death, he was a prospector and miner. Excited by the early Thames mining days, he learnt the skills needed to be a successful prospector, and during the 1870s worked with several mates on the Coromandel field, with some success. After briefly participating in the Te Aroha rush of 1880, he saw from the summit of that mountain the outcrops of the Waihi reefs, and turned his attention to that largely unexplored area. Although there was considerable claim and counter-claim about who first explored the area and who first found gold, Nicholl was the first to discover a payable lode, the famous Martha. 
After telling his mates of his discovery, they marked out the line of reef and started to develop several claims. For a time Nicholl was in charge of developing his find, and took a leading part in attempting for form a company to work the ground, succeeding on the third attempt. For a while he operated the first battery. But in time he lost control over his discovery and, far from profiting, lost a large amount of money. After leaving Waihi for Karangahake, he would be forced into bankruptcy in 1884.
His first experience of overseas prospecting was in Fiji, where he found traces of gold but nothing payable. Returning to Waihi, he struggled to earn a living for his young family, taking contracts and owning a small farm to supplement his mining endeavours, notably at Maratoto in the 1890s. During that decade his wife abandoned him and their children, and to make his fortune – and because of the lure of another gold rush – he went to Klondike, where he had many exciting experiences but, being unable to mine there, returned poorer than before.
In Nicholl’s last years he did some farming but his main interest continued to be prospecting, and he explored the Waitekauri area into his eighties until declining health forced him to desist. In his later years he recorded details of his life, notably several versions of the discovery of the Martha lode, to the great benefit of posterity.

text: William Sharman Crawford (Billy) Nicholl, the prospector who discovered the Martha lode at Waihi: his life, told largely in his own words Billy Nicholl was that rare miner, one who recorded his life. Born in Ireland, when still a boy he arrived in New Zealand in 1862. After his father died at an early age, he acquired a step-father, whom he disliked, with good reason; and in her later years his mother’s mind would fade.
From 1868, when he was probably aged 14, until shortly before his death, he was a prospector and miner. Excited by the early Thames mining days, he learnt the skills needed to be a successful prospector, and during the 1870s worked with several mates on the Coromandel field, with some success. After briefly participating in the Te Aroha rush of 1880, he saw from the summit of that mountain the outcrops of the Waihi reefs, and turned his attention to that largely unexplored area. Although there was considerable claim and counter-claim about who first explored the area and who first found gold, Nicholl was the first to discover a payable lode, the famous Martha. 
After telling his mates of his discovery, they marked out the line of reef and started to develop several claims. For a time Nicholl was in charge of developing his find, and took a leading part in attempting for form a company to work the ground, succeeding on the third attempt. For a while he operated the first battery. But in time he lost control over his discovery and, far from profiting, lost a large amount of money. After leaving Waihi for Karangahake, he would be forced into bankruptcy in 1884.
His first experience of overseas prospecting was in Fiji, where he found traces of gold but nothing payable. Returning to Waihi, he struggled to earn a living for his young family, taking contracts and owning a small farm to supplement his mining endeavours, notably at Maratoto in the 1890s. During that decade his wife abandoned him and their children, and to make his fortune – and because of the lure of another gold rush – he went to Klondike, where he had many exciting experiences but, being unable to mine there, returned poorer than before.
In Nicholl’s last years he did some farming but his main interest continued to be prospecting, and he explored the Waitekauri area into his eighties until declining health forced him to desist. In his later years he recorded details of his life, notably several versions of the discovery of the Martha lode, to the great benefit of posterity.

year: 2016

title: Bicultural perspectives on Māori legal research

authors: Mackinnon, Jacquelin

subjects: Māori

abstract: Increasingly, legal research projects undertaken at law school or in practice will involve Māori custom law and/or tikanga Māori.' The role of both Māori custom law and tikanga Māori is most evident in the work of the Māori Land Court in the interpretation and application of legislation relating to Māori land. Increasingly, general statutes incorporate Māori principles and values, such as those to be found in the Resource Management Act 1991, or make explicit reference to the principles of the Treaty of Waitangi. The statutory interpretation function of the Courts in relation to these, and less obvious examples, requires knowledge of tikanga Māori and/or Māori custom law. For any analysis of the work of the Courts or of the legislature, knowledge of tikanga Māori and/or custom law is required. Both Māori custom law and tikanga Māori are preserved by and accessed through the oral tradition. In addition to its role in the Courts and in relation to legislation, the most significant role played by the oral tradition is in the work of the Waitangi Tribunal. The oral tradition also plays an increasingly important part in other areas requiring research. What follows is an introduction to the oral tradition and its role in the legal system of Aotearoa/New Zealand. An understanding of the oral tradition is essential to the construction of a research path that is both ethical and effective.

text: Bicultural perspectives on Māori legal research Increasingly, legal research projects undertaken at law school or in practice will involve Māori custom law and/or tikanga Māori.' The role of both Māori custom law and tikanga Māori is most evident in the work of the Māori Land Court in the interpretation and application of legislation relating to Māori land. Increasingly, general statutes incorporate Māori principles and values, such as those to be found in the Resource Management Act 1991, or make explicit reference to the principles of the Treaty of Waitangi. The statutory interpretation function of the Courts in relation to these, and less obvious examples, requires knowledge of tikanga Māori and/or Māori custom law. For any analysis of the work of the Courts or of the legislature, knowledge of tikanga Māori and/or custom law is required. Both Māori custom law and tikanga Māori are preserved by and accessed through the oral tradition. In addition to its role in the Courts and in relation to legislation, the most significant role played by the oral tradition is in the work of the Waitangi Tribunal. The oral tradition also plays an increasingly important part in other areas requiring research. What follows is an introduction to the oral tradition and its role in the legal system of Aotearoa/New Zealand. An understanding of the oral tradition is essential to the construction of a research path that is both ethical and effective.

year: 2007