title: Measurements and modelling of the tidal salt intrusion along the Waihou River

authors: James, Brooke

subjects: salt intrusion

abstract: Salt intrusions can exist within rivers and are influenced by shape of an estuary and tidal and river flows. Incoming tidal water moves into a region of freshwater influence which can have a strong influence on biological and geochemical properties in the water column. These features constitute a transition zone with spatially and temporally varying dynamics. As such, it is challenging to correctly represent these features in numerical hydrodynamic and sediment transport models. We report field observations of the salt intrusion processes in the Waihou River estuary in New Zealand. Most of the research that has been conducted thus far on the Waihou River has centred around sediment transport, gold mining impacts, water quality and fish populations and there is a lack of systematic collection of vertical water property data. Measurements of water column properties (salinity, temperature and turbidity) were taken at different tidal stages and river flows and used to track the movement and characteristics of the salt intrusion. In-situ water samples were collected and used to form a calibration for suspended sediment concentrations. The salinity intrusion was observed to intrude to 7.2-11.8 km (at 1 PSU) upstream from the mouth of the river. The estuary exhibited both mixed and stratified conditions, with a clear salt wedge shape observed for only one out of five surveys. The salinity intrusion length appeared to be primarily controlled by the by river flow, with a shorter intrusion length and stronger stratification occurring for higher river flows. Greater turbidity was observed within the marine water compared to fluvial waters, and turbidity was greater near the bed implying that the primary delivery mechanism of sediment to the lower reaches of the river is import from the offshore or intertidal marine regions. Numerical hydrodynamic modelling using Delft 3D was undertaken and was compared to the field data. While the model had previously been calibrated for water levels and velocity in two-dimensions, the adapted 3D version of the model did not accurately predict the structure or extent of the salinity intrusion. Model results under-estimated the salinity intrusion, which was attributed to over-mixing of the water column, however, the performance improved when a lower value for horizontal eddy diffusivity was used. This work emphasises the need to obtain vertically resolved data sets to allow for robust calibration of numerical models, which are commonly used in environmental management decisions.

text: Measurements and modelling of the tidal salt intrusion along the Waihou River Salt intrusions can exist within rivers and are influenced by shape of an estuary and tidal and river flows. Incoming tidal water moves into a region of freshwater influence which can have a strong influence on biological and geochemical properties in the water column. These features constitute a transition zone with spatially and temporally varying dynamics. As such, it is challenging to correctly represent these features in numerical hydrodynamic and sediment transport models. We report field observations of the salt intrusion processes in the Waihou River estuary in New Zealand. Most of the research that has been conducted thus far on the Waihou River has centred around sediment transport, gold mining impacts, water quality and fish populations and there is a lack of systematic collection of vertical water property data. Measurements of water column properties (salinity, temperature and turbidity) were taken at different tidal stages and river flows and used to track the movement and characteristics of the salt intrusion. In-situ water samples were collected and used to form a calibration for suspended sediment concentrations. The salinity intrusion was observed to intrude to 7.2-11.8 km (at 1 PSU) upstream from the mouth of the river. The estuary exhibited both mixed and stratified conditions, with a clear salt wedge shape observed for only one out of five surveys. The salinity intrusion length appeared to be primarily controlled by the by river flow, with a shorter intrusion length and stronger stratification occurring for higher river flows. Greater turbidity was observed within the marine water compared to fluvial waters, and turbidity was greater near the bed implying that the primary delivery mechanism of sediment to the lower reaches of the river is import from the offshore or intertidal marine regions. Numerical hydrodynamic modelling using Delft 3D was undertaken and was compared to the field data. While the model had previously been calibrated for water levels and velocity in two-dimensions, the adapted 3D version of the model did not accurately predict the structure or extent of the salinity intrusion. Model results under-estimated the salinity intrusion, which was attributed to over-mixing of the water column, however, the performance improved when a lower value for horizontal eddy diffusivity was used. This work emphasises the need to obtain vertically resolved data sets to allow for robust calibration of numerical models, which are commonly used in environmental management decisions.

year: 2024

title: That 'austere anti-aesthetic angel': James K. Baxter and Puritanism

authors: Moffat, Kirstine

abstract: It is necessary to begin with an apology to James K. Baxter. In my previous musings on the Puritan legacy in New Zealand I have chastised Baxter, along with other writers and critics of his generation, for using Puritanism as a reductive catchphrase to summarise all that they most despise about New Zealand society (Moffat, 'Destruction'). The phrase that I have repeatedly used to epitomise Baxter's perceived antagonism is his description of Pu,itanism as an 'austere anti-aesthetic angel' (Complete Prose 2. 328). Returning to this phrase as I meditate at much greater length on Baxter's relationship with Puritanism, I realise that I am guilty of flattening and simplifying what is a much more complex engagement with Puritanism in his prose writing. Baxter's phrase contains both condemnation and implied praise. He was vehemently opposed to what he regarded as the Puritan suspicion of imagination and sexuality, and throughout his writing castigated all the social and religious forces that sought to curb and quell aestheticism and the natural, instinctual self. Yet, he also refers to Puritanism as 'austere', a quality that much of his writing and his own life choices suggest he regarded as admirable, particularly as it relates to a paring back and relinquishing of the unnecessary paraphernalia of capitalism and materialism. And what to make of 'angel'? Surely this is more than simply alliterative effect. It too undercuts the antagonism of 'anti-aesthetic' to suggest that in Baxter's eyes there is at least a trace of the divine about Puritanism and its legacy.

text: That 'austere anti-aesthetic angel': James K. Baxter and Puritanism It is necessary to begin with an apology to James K. Baxter. In my previous musings on the Puritan legacy in New Zealand I have chastised Baxter, along with other writers and critics of his generation, for using Puritanism as a reductive catchphrase to summarise all that they most despise about New Zealand society (Moffat, 'Destruction'). The phrase that I have repeatedly used to epitomise Baxter's perceived antagonism is his description of Pu,itanism as an 'austere anti-aesthetic angel' (Complete Prose 2. 328). Returning to this phrase as I meditate at much greater length on Baxter's relationship with Puritanism, I realise that I am guilty of flattening and simplifying what is a much more complex engagement with Puritanism in his prose writing. Baxter's phrase contains both condemnation and implied praise. He was vehemently opposed to what he regarded as the Puritan suspicion of imagination and sexuality, and throughout his writing castigated all the social and religious forces that sought to curb and quell aestheticism and the natural, instinctual self. Yet, he also refers to Puritanism as 'austere', a quality that much of his writing and his own life choices suggest he regarded as admirable, particularly as it relates to a paring back and relinquishing of the unnecessary paraphernalia of capitalism and materialism. And what to make of 'angel'? Surely this is more than simply alliterative effect. It too undercuts the antagonism of 'anti-aesthetic' to suggest that in Baxter's eyes there is at least a trace of the divine about Puritanism and its legacy.

year: 2017

title: New Zealand’s Performance Based Research Funding (PBRF) model undermines Maori research

authors: Roa, Tom

subjects: Performance Based Research Funding

abstract: The Performance Based Research Funding (PBRF) model was instigated in 2002 to increase “the quality of research through peer assessment and performance indicators” in New Zealand (Ministry of Education 2002: 17). It is used to allocate funding between universities, departments and researchers according to the putative quality and quantity of their research outputs over the preceding 6 years. PBRF is expected to incentivise improved research excellence and efficiency, and allow government to invest research funds where greatest returns will result. This is potentially a huge gain for Māori. However, “by changing the conditions of knowledge production, research assessment exercises may also alter the shape and direction of disciplines by diverting and channelling researchers’ intellectual attention and political engagement, influencing what they study, how they do it, and how they report and write” (Middleton 2009: 194). Indeed, universities repeatedly encourage researchers to focus on activities that will improve their PBRF rankings. We believe that an unintended consequence of PBRF is the creation of significant barriers to increasing the volume, scope and quality of environmental research for Māori.

text: New Zealand’s Performance Based Research Funding (PBRF) model undermines Maori research The Performance Based Research Funding (PBRF) model was instigated in 2002 to increase “the quality of research through peer assessment and performance indicators” in New Zealand (Ministry of Education 2002: 17). It is used to allocate funding between universities, departments and researchers according to the putative quality and quantity of their research outputs over the preceding 6 years. PBRF is expected to incentivise improved research excellence and efficiency, and allow government to invest research funds where greatest returns will result. This is potentially a huge gain for Māori. However, “by changing the conditions of knowledge production, research assessment exercises may also alter the shape and direction of disciplines by diverting and channelling researchers’ intellectual attention and political engagement, influencing what they study, how they do it, and how they report and write” (Middleton 2009: 194). Indeed, universities repeatedly encourage researchers to focus on activities that will improve their PBRF rankings. We believe that an unintended consequence of PBRF is the creation of significant barriers to increasing the volume, scope and quality of environmental research for Māori.

year: 2009