title: Hydrodynamic and water quality modelling of the lower kaituna river and maketu estuary

authors: Goodhue, Nigel David

subjects: numerical

abstract: The Maketu Estuary is a shallow intertidal estuary (2.3 km2) located in the Bay of Plenty, North Island, New Zealand. The Kaituna River contributes the largest freshwater flow into the estuary through control gates. Lake Rotoiti and indirectly Lake Rotorua supply the base flow to the Kaituna River, with tributaries along the 50 km reach also significantly contributing to the flow. Water quality within the river is affected by elevated nutrients, faecal coliforms, high oxygen demand and algae concentrations derived from the lakes as well as contributions from tributaries and industrial and urban discharge. Through the use of a coupled hydrodynamic-biogeochemical numerical model ELCOM-CAEDYM, this study aims to examine the nutrient, phytoplankton and hydrodynamics of the Maketu Estuary and lower Kaituna River. 

Water quality and hydrodynamic measurements were sourced from Environment Bay of Plenty's data archives as well as a number of instrument deployments to collect water velocity, tidal elevation and salinity and temperature measurements during the course of this study. Included in the field work was a survey of the lower river and estuary bathymetry.

Model simulations predicted that the maximum residence time in the Maketu Estuary is 1.5 days, occurring in the inner western region.  Residence time in the lower river (mouth to 8.5 km upstream) is in the order of hours although some variations were predicted near the river mouth. Growth rates of four phytoplankton groups where assessed over a 15 day period in January 2004. In the Kaituna River ELCOM-CAEDYM predicted that the community growth rates were small with the exception of a slight increase in biomass of the two freshwater groups in a semi-detached river bend. The increase in the loop was correlated with an increase of residence time. In the estuary, marine diatoms showed the highest growth rates in the western region which is expected to relate to retention time and available nutrients. Dinoflagellates showed the smallest variation in predicted growth rates, most likely due to their broad salinity tolerance. The two freshwater species showed a reduction in abundance when mixed with marine water. A principle limiting factor to phytoplankton growth in both the river and estuary is the low residence time.

A number of scenarios were simulated in the river and estuary by altering the forcing conditions in the model. A simulation of the increased nutrient load associated with the Rotoiti diversion wall revealed that phytoplankton growth in the river and estuary will not be significantly affected. Because of the close proximity of the control gates to the river mouth, a proportion of water drawn through the structure can be marine. By opening the old river channel, model simulations predicted that a reduction in salinity would be possible, however the outcome of complete freshwater is probably not achievable. Increasing the discharge volume from the river into the estuary was also simulated. The results indicated that increasing the freshwater inflow at Fords Cut would reduce the salinity in the estuary while increasing the net (residual) flow towards the estuary mouth. Increasing the flow would also result in a greater range of salinity in regions of the estuary. Changing the inflow location to the historic Papahikahawai Channel also affected the salinity in the estuary. The most significant effect of an inflow at this location was a reduction of the residual currents in the western region of the estuary.

text: Hydrodynamic and water quality modelling of the lower kaituna river and maketu estuary The Maketu Estuary is a shallow intertidal estuary (2.3 km2) located in the Bay of Plenty, North Island, New Zealand. The Kaituna River contributes the largest freshwater flow into the estuary through control gates. Lake Rotoiti and indirectly Lake Rotorua supply the base flow to the Kaituna River, with tributaries along the 50 km reach also significantly contributing to the flow. Water quality within the river is affected by elevated nutrients, faecal coliforms, high oxygen demand and algae concentrations derived from the lakes as well as contributions from tributaries and industrial and urban discharge. Through the use of a coupled hydrodynamic-biogeochemical numerical model ELCOM-CAEDYM, this study aims to examine the nutrient, phytoplankton and hydrodynamics of the Maketu Estuary and lower Kaituna River. 

Water quality and hydrodynamic measurements were sourced from Environment Bay of Plenty's data archives as well as a number of instrument deployments to collect water velocity, tidal elevation and salinity and temperature measurements during the course of this study. Included in the field work was a survey of the lower river and estuary bathymetry.

Model simulations predicted that the maximum residence time in the Maketu Estuary is 1.5 days, occurring in the inner western region.  Residence time in the lower river (mouth to 8.5 km upstream) is in the order of hours although some variations were predicted near the river mouth. Growth rates of four phytoplankton groups where assessed over a 15 day period in January 2004. In the Kaituna River ELCOM-CAEDYM predicted that the community growth rates were small with the exception of a slight increase in biomass of the two freshwater groups in a semi-detached river bend. The increase in the loop was correlated with an increase of residence time. In the estuary, marine diatoms showed the highest growth rates in the western region which is expected to relate to retention time and available nutrients. Dinoflagellates showed the smallest variation in predicted growth rates, most likely due to their broad salinity tolerance. The two freshwater species showed a reduction in abundance when mixed with marine water. A principle limiting factor to phytoplankton growth in both the river and estuary is the low residence time.

A number of scenarios were simulated in the river and estuary by altering the forcing conditions in the model. A simulation of the increased nutrient load associated with the Rotoiti diversion wall revealed that phytoplankton growth in the river and estuary will not be significantly affected. Because of the close proximity of the control gates to the river mouth, a proportion of water drawn through the structure can be marine. By opening the old river channel, model simulations predicted that a reduction in salinity would be possible, however the outcome of complete freshwater is probably not achievable. Increasing the discharge volume from the river into the estuary was also simulated. The results indicated that increasing the freshwater inflow at Fords Cut would reduce the salinity in the estuary while increasing the net (residual) flow towards the estuary mouth. Increasing the flow would also result in a greater range of salinity in regions of the estuary. Changing the inflow location to the historic Papahikahawai Channel also affected the salinity in the estuary. The most significant effect of an inflow at this location was a reduction of the residual currents in the western region of the estuary.

year: 2007

title: Symmetry operators and separation of variables for spin-wave equations in oblate spheroidal coordinates

authors: Kalnins, Ernie G.

subjects: Mathematics

abstract: A family of second-order differential operators that characterize the solution of the massless spin s field equations, obtained via separation of variables in oblate spheroidal coordinates and using a null tetrad is found. The first two members of the family also characterize the separable solutions in the Kerr space-time. It is also shown that these operators are symmetry operators of the field equations in empty space-times whenever the space-time admits a second-order Killing–Yano tensor.

text: Symmetry operators and separation of variables for spin-wave equations in oblate spheroidal coordinates A family of second-order differential operators that characterize the solution of the massless spin s field equations, obtained via separation of variables in oblate spheroidal coordinates and using a null tetrad is found. The first two members of the family also characterize the separable solutions in the Kerr space-time. It is also shown that these operators are symmetry operators of the field equations in empty space-times whenever the space-time admits a second-order Killing–Yano tensor.

year: 1990-07

title: Māori in the Faculty of Arts and Social Sciences: An analysis of the Faculty of Arts and Social Science data records from 1997-2002

authors: Ashwell, Allanah

subjects: Maori students

abstract: The Ministry of Education has compiled annual reports on the participation of Maori in
tertiary education. The 2002 report presented a comprehensive description of Maori
participation across all tertiary institutions within New Zealand in that year. The figures
show that Maori are markedly under-represented in tertiary institutions, particularly
universities.
The barriers encountered by Maori students can either directly or indirectly impact on
Maori participation, retention and success. The more disturbing outcome is that of
withdrawal or dropping out of higher education, is more likely when a Maori student
experiences and has to confront multiple rather than single barriers.
With this in mind, the aim of this study was to examine and identify trends apparent in
data records of Maori students enrolled in courses offered by the Faculty of Arts and
Social Sciences at the University of Waikato between 1997 and 2002 and to make
recommendations to the Faculty about how negative trends might be addressed. Specific
areas for analysis are detailed in the report.

text: Māori in the Faculty of Arts and Social Sciences: An analysis of the Faculty of Arts and Social Science data records from 1997-2002 The Ministry of Education has compiled annual reports on the participation of Maori in
tertiary education. The 2002 report presented a comprehensive description of Maori
participation across all tertiary institutions within New Zealand in that year. The figures
show that Maori are markedly under-represented in tertiary institutions, particularly
universities.
The barriers encountered by Maori students can either directly or indirectly impact on
Maori participation, retention and success. The more disturbing outcome is that of
withdrawal or dropping out of higher education, is more likely when a Maori student
experiences and has to confront multiple rather than single barriers.
With this in mind, the aim of this study was to examine and identify trends apparent in
data records of Maori students enrolled in courses offered by the Faculty of Arts and
Social Sciences at the University of Waikato between 1997 and 2002 and to make
recommendations to the Faculty about how negative trends might be addressed. Specific
areas for analysis are detailed in the report.

year: 2003-06