title: Seismic hazard in the Taupo - Reporoa Region

authors: Pyne, Adrian

subjects: Earthquake

abstract: New Zealand lies astride a convergent plate margin, as a result it experiences hundreds of earthquakes a year. This study was commissioned in response to Environment Waikato's contingency planning for such natural disasters.

The Taupo - Reporoa region was identified in a report to Environment Waikato (Waikato Regional Council) as needing to be studied, in order to quantify the level of earthquake hazard. This region lies in the centre of the Taupo Volcanic Zone, and has, over thousands of years built up considerable thicknesses of unconsolidated mainly volcanogenic materials. It is recognised that towns and cities that are sited on these materials are at risk from amplification of seismic waves and will experience greater damage, than if they were on hard rock.

Soils were analysed by the following geotechnical tests: hand penetrometer, Bush penetrometer, shear vane, the standard compression test, and dynamic cyclical loading. Samples were also taken for soil moisture and bulk density. The results from these tests have been used to evaluate the region for seismic hazard, and to semi-quantitatively correlate with reports and claims of damage from earthquakes. A number of parameters were able to be derived from the field tests and the cyclic loading which were used in the final analysis.

The results showed that some soils were substantially weaker than others, which correlated with historical accounts of damage. A seismic microzoning map was constructed on the basis of the difference in soil strengths.

text: Seismic hazard in the Taupo - Reporoa Region New Zealand lies astride a convergent plate margin, as a result it experiences hundreds of earthquakes a year. This study was commissioned in response to Environment Waikato's contingency planning for such natural disasters.

The Taupo - Reporoa region was identified in a report to Environment Waikato (Waikato Regional Council) as needing to be studied, in order to quantify the level of earthquake hazard. This region lies in the centre of the Taupo Volcanic Zone, and has, over thousands of years built up considerable thicknesses of unconsolidated mainly volcanogenic materials. It is recognised that towns and cities that are sited on these materials are at risk from amplification of seismic waves and will experience greater damage, than if they were on hard rock.

Soils were analysed by the following geotechnical tests: hand penetrometer, Bush penetrometer, shear vane, the standard compression test, and dynamic cyclical loading. Samples were also taken for soil moisture and bulk density. The results from these tests have been used to evaluate the region for seismic hazard, and to semi-quantitatively correlate with reports and claims of damage from earthquakes. A number of parameters were able to be derived from the field tests and the cyclic loading which were used in the final analysis.

The results showed that some soils were substantially weaker than others, which correlated with historical accounts of damage. A seismic microzoning map was constructed on the basis of the difference in soil strengths.

year: 1995

title: A supercapacitor technique for efficiency improvement in linear regulators

authors: Kularatna, Nihal

subjects: engineering

abstract: Paper describes a novel supercapacitor based approach to recover the wasted energy in linear regulators. In this US patent pending technique, a single supercapacitor or an array of supercapacitors could be coupled with a linear series or shunt regulator, where the supercapacitors are charged by the input current of the regulator. This supercapacitor technique, by maintaining the dropout voltage limit before a new capacitor is placed in the series path, recovers the energy and does not use the supercapacitors for voltage conversion. Average efficiency of the overall circuit is improved by a significant amount, while maintaining the useful hall marks of a linear regulator. An example of a 12 to 5 volt proof of concept circuit is detailed with an overall efficiency improvement from 42% to over 78%. The technique is versatile, and, can be developed further to compete with the higher efficiency switching power supplies.

text: A supercapacitor technique for efficiency improvement in linear regulators Paper describes a novel supercapacitor based approach to recover the wasted energy in linear regulators. In this US patent pending technique, a single supercapacitor or an array of supercapacitors could be coupled with a linear series or shunt regulator, where the supercapacitors are charged by the input current of the regulator. This supercapacitor technique, by maintaining the dropout voltage limit before a new capacitor is placed in the series path, recovers the energy and does not use the supercapacitors for voltage conversion. Average efficiency of the overall circuit is improved by a significant amount, while maintaining the useful hall marks of a linear regulator. An example of a 12 to 5 volt proof of concept circuit is detailed with an overall efficiency improvement from 42% to over 78%. The technique is versatile, and, can be developed further to compete with the higher efficiency switching power supplies.

year: 2009

title: Lake Rotokakahi water quality modelling

authors: Jones, Hannah Frances Emily

abstract: Lake Rotokakahi is an iwi-owned lake, administered by the Lake Rotokakahi Board of Control. The lake has a surface area of 4.4 km2, a mean depth of 17.5 m, and a catchment of 19.7 km2 of which most is in exotic forest (46.5%), with some pasture (27.8%) and regenerating native forest and scrub (25.7%). Lake Rotokakahi has only one permanent surface inflow and it is assumed that the lake must be predominantly groundwater fed. The lake outflow, Te Wairoa Stream, flows into Lake Tarawera. Monitoring indicates that water quality has recently declined in the lake, with a shift from a mesotrophic state in the 1990's, to currently being classified as eutrophic. Increased algal biomass has reduced water clarity and in May 2011 the first ever recorded algae bloom of a toxic cyanobacterium species resulted in a fish kill in Te Wairoa Stream. With the majority of the catchment in either exotic or native forest, the cause for the decline in water quality is unclear. However there is some concern that forestry harvesting operations may lead to increased surface runoff of sediment and associated phosphorus in ephemeral streams that feed into the lake. The objective of this study was to setup a water quality model for Lake Rotokakahi, which in the future may provide a decisionsupport tool for lake managers.
The model used, DYRESM-CAEDYM, is a one-dimensional (1D) coupled hydrodynamic-water quality model that has been widely used in New Zealand and overseas. Methodology for deriving model forcing data (e.g. meteorological data, inflow volumes and nutrient loads), including the application of catchment and lake water balances, is described in this report. The catchment water balance indicates that groundwater and rainfall account for 37% and 42%, respectively, of the total inflow volume to the lake, with surface and ephemeral inflows contributing a smaller proportion (c. 20% combined). Furthermore, it appears that groundwater contributes a significant proportion (c. 60 - 70%) of the total nutrient loads, although surface and ephemeral inflows also contribute a significant proportion (34%) of the total phosphorus load. It should be noted that the catchment water balance is based on a very limited dataset, and therefore subject to significant uncertainty. 
We simulated the period July 2009 to June 2012 with DYRESM-CAEDYM. Model performance statistics indicated reasonable simulation of water quality for the calibration period, but did not satisfactorily capture the magnitude and dynamics of chlorophyll a and some nutrient species over an independent model validation period. There may be a number of reasons for the poor model performance over the validation period. For example, it may be that zooplankton and/or freshwater mussels (kakahi), which were not included in the model configuration, may exert significant grazing pressure on the phytoplankton populations at certain times. Furthermore, the significant uncertainty in the catchment water and nutrient loads most likely will have affected model performance. Nutrient concentrations are routinely monitored only in the surface inflow. There are no measurements of nutrient and sediment loads in ephemeral streams, and there is very limited data on groundwater nutrient concentrations.
In its current form, the DYRESM-CAEDYM model is not suitable for scenario testing of lake management options. It is recommended that effort is directed at quantification of ephemeral and groundwater inflows and their associated nutrient and (particularly for ephemeral inflows) sediment loads. This may be particularly important for ephemeral inflows located close to the lake that may be influenced by forestry harvesting operations. Recent increases in measured total phosphorus and phosphate concentrations in the surface inflow and in the lake, combined with the degradation of water quality that has already occurred over the last 20 years, provides further impetus for addressing this critical information gap. Were new data to  become available, opportunities exist for improving the performance of the current model and for developing a three-dimensional coupled hydrodynamic-water quality model (e.g. ELCOM-CAEDYM) with representation of kakahi and/or zooplankton, which may be able to resolve questions pertinent to the functioning of the lake, and to lake and catchment management.

text: Lake Rotokakahi water quality modelling Lake Rotokakahi is an iwi-owned lake, administered by the Lake Rotokakahi Board of Control. The lake has a surface area of 4.4 km2, a mean depth of 17.5 m, and a catchment of 19.7 km2 of which most is in exotic forest (46.5%), with some pasture (27.8%) and regenerating native forest and scrub (25.7%). Lake Rotokakahi has only one permanent surface inflow and it is assumed that the lake must be predominantly groundwater fed. The lake outflow, Te Wairoa Stream, flows into Lake Tarawera. Monitoring indicates that water quality has recently declined in the lake, with a shift from a mesotrophic state in the 1990's, to currently being classified as eutrophic. Increased algal biomass has reduced water clarity and in May 2011 the first ever recorded algae bloom of a toxic cyanobacterium species resulted in a fish kill in Te Wairoa Stream. With the majority of the catchment in either exotic or native forest, the cause for the decline in water quality is unclear. However there is some concern that forestry harvesting operations may lead to increased surface runoff of sediment and associated phosphorus in ephemeral streams that feed into the lake. The objective of this study was to setup a water quality model for Lake Rotokakahi, which in the future may provide a decisionsupport tool for lake managers.
The model used, DYRESM-CAEDYM, is a one-dimensional (1D) coupled hydrodynamic-water quality model that has been widely used in New Zealand and overseas. Methodology for deriving model forcing data (e.g. meteorological data, inflow volumes and nutrient loads), including the application of catchment and lake water balances, is described in this report. The catchment water balance indicates that groundwater and rainfall account for 37% and 42%, respectively, of the total inflow volume to the lake, with surface and ephemeral inflows contributing a smaller proportion (c. 20% combined). Furthermore, it appears that groundwater contributes a significant proportion (c. 60 - 70%) of the total nutrient loads, although surface and ephemeral inflows also contribute a significant proportion (34%) of the total phosphorus load. It should be noted that the catchment water balance is based on a very limited dataset, and therefore subject to significant uncertainty. 
We simulated the period July 2009 to June 2012 with DYRESM-CAEDYM. Model performance statistics indicated reasonable simulation of water quality for the calibration period, but did not satisfactorily capture the magnitude and dynamics of chlorophyll a and some nutrient species over an independent model validation period. There may be a number of reasons for the poor model performance over the validation period. For example, it may be that zooplankton and/or freshwater mussels (kakahi), which were not included in the model configuration, may exert significant grazing pressure on the phytoplankton populations at certain times. Furthermore, the significant uncertainty in the catchment water and nutrient loads most likely will have affected model performance. Nutrient concentrations are routinely monitored only in the surface inflow. There are no measurements of nutrient and sediment loads in ephemeral streams, and there is very limited data on groundwater nutrient concentrations.
In its current form, the DYRESM-CAEDYM model is not suitable for scenario testing of lake management options. It is recommended that effort is directed at quantification of ephemeral and groundwater inflows and their associated nutrient and (particularly for ephemeral inflows) sediment loads. This may be particularly important for ephemeral inflows located close to the lake that may be influenced by forestry harvesting operations. Recent increases in measured total phosphorus and phosphate concentrations in the surface inflow and in the lake, combined with the degradation of water quality that has already occurred over the last 20 years, provides further impetus for addressing this critical information gap. Were new data to  become available, opportunities exist for improving the performance of the current model and for developing a three-dimensional coupled hydrodynamic-water quality model (e.g. ELCOM-CAEDYM) with representation of kakahi and/or zooplankton, which may be able to resolve questions pertinent to the functioning of the lake, and to lake and catchment management.

year: 2014