title: A multifaceted analysis of diurnal streamflow patterns through the application of advanced analytical tools

authors: Sarwar, Muhammad Waqas

subjects: Evapotranspiration

abstract: Understanding the complex dynamics of water flow within a catchment is fundamental to effective water resource management. This understanding involves robust knowledge of the catchment's hydrological and physiographical features. It requires a profound grasp of the spatiotemporal variability in a catchment's climatic and hydrological patterns. Within this context, this thesis started with a comprehensive review of the historical and current literature on diurnal fluctuations in groundwater. The review touched upon several different aspects of the phenomenon, ranging from discussing the mechanisms of the origin of these signals, their role in the catchment's water balance, their link with groundwater and with the transpiration activities of the vegetation, and in the end, the importance of studying these catchments in revealing characteristics of a catchment. 
Potential gaps in the analysis of diurnal fluctuations are identified by exploring the literature., which motivated the compilation of this thesis. Firstly, the relationship between diurnal fluctuation and the potential evapotranspiration of riparian plants is investigated in relation to its effect on catchment reservoir storage. A novel method of estimating evapotranspiration (ET) rates is devised by establishing a relationship between diurnal streamflow changes and the catchment's riparian source area. The method reasonably estimated riparian evapotranspiration (ET) and linked the riparian area's dynamics with the diurnal patterns in stream flow by assuming a linear relationship between saturated riparian reservoirs and outflow. This analysis provided a much-needed understanding of the behaviour of the diurnal signals in a catchment and its relationship with the physical features of the catchment.
Further, this analysis deeply studied the concept of time delay associated with the transpiration activities of riparian plants and catchments' response regarding diurnal fluctuation. Additionally, the seasonal evolution of ET estimates and the time lag revealed the tight coupling between stream response and active vegetation zones, with more significant and rapid fluctuation in colder months than warmer ones. In conclusion, the method provided an elaborate understanding of the complex interplay between riparian zones, groundwater dynamics, and streamflow patterns, contributing to a more profound understanding of catchment hydrology. 
Another significant thesis objective was to develop advanced automated techniques for detecting and analysing diurnal fluctuations to provide fast and reliable observations of diurnal fluctuations from a large dataset. Manually identifying this scarce phenomenon in an extensive multi-year dataset is time-consuming and one of the biggest reasons for minimal, large-sample studies concerning diurnal streamflow fluctuations. This is addressed by forming an automated process of diurnal fluctuation extraction with the application of the wavelet transform. 
The capabilities of both types of wavelet transformation, the discrete wavelet transform (DWT) and continuous wavelet transform (CWT) are tested to reveal time-frequency information of diurnal signals. A detailed workflow is developed to choose the best wavelet for detrending a streamflow series to obtain diurnal fluctuation. The detrending performance of the DWT process is compared against the traditional time-based detrending methods like the moving average. It confirms the superiority of wavelet transform in optimal detrending of observed streamflow data series. The CWT presented many different plots and revealed exciting features in the diurnal patterns in streamflow. The CWT information is then used to develop an algorithm for extracting diurnal episodes from extensive streamflow records. The extraction process captured an adequate number of diurnal episodes, which matched well with the manual identifications. Overall, the automated technique addressed the limitations posed by manual identification and contributed significantly to the advancement of time-frequency dynamics of diurnal fluctuations. 
Finally, with the knowledge of diurnal fluctuation gained in the first research objective and with the capabilities of the wavelet transform, a large sample study is carried out using streamflow records from different New Zealand catchments. Various dataset sources from streamflow records, snow cover maps, and digital elevation rasters are used to calculate different catchment characteristics. The analysis showed that characteristics like catchment shape and size strongly correlate with diurnal amplitude. The diurnal lag also showed patterns of change with the catchment parameters. It is revealed that the correlation between catchment size and diurnal amplitude becomes weaker in larger catchments due to the diverse and heterogeneous nature of environmental processes within these regions.
This research significantly contributes to a deeper understanding of the temporal patterns of streamflow, providing valuable insights for hydrological modeling and water resource management. By integrating field observations, advanced analytical methods, and regional context, this work advances the understanding of diurnal streamflow dynamics.

text: A multifaceted analysis of diurnal streamflow patterns through the application of advanced analytical tools Understanding the complex dynamics of water flow within a catchment is fundamental to effective water resource management. This understanding involves robust knowledge of the catchment's hydrological and physiographical features. It requires a profound grasp of the spatiotemporal variability in a catchment's climatic and hydrological patterns. Within this context, this thesis started with a comprehensive review of the historical and current literature on diurnal fluctuations in groundwater. The review touched upon several different aspects of the phenomenon, ranging from discussing the mechanisms of the origin of these signals, their role in the catchment's water balance, their link with groundwater and with the transpiration activities of the vegetation, and in the end, the importance of studying these catchments in revealing characteristics of a catchment. 
Potential gaps in the analysis of diurnal fluctuations are identified by exploring the literature., which motivated the compilation of this thesis. Firstly, the relationship between diurnal fluctuation and the potential evapotranspiration of riparian plants is investigated in relation to its effect on catchment reservoir storage. A novel method of estimating evapotranspiration (ET) rates is devised by establishing a relationship between diurnal streamflow changes and the catchment's riparian source area. The method reasonably estimated riparian evapotranspiration (ET) and linked the riparian area's dynamics with the diurnal patterns in stream flow by assuming a linear relationship between saturated riparian reservoirs and outflow. This analysis provided a much-needed understanding of the behaviour of the diurnal signals in a catchment and its relationship with the physical features of the catchment.
Further, this analysis deeply studied the concept of time delay associated with the transpiration activities of riparian plants and catchments' response regarding diurnal fluctuation. Additionally, the seasonal evolution of ET estimates and the time lag revealed the tight coupling between stream response and active vegetation zones, with more significant and rapid fluctuation in colder months than warmer ones. In conclusion, the method provided an elaborate understanding of the complex interplay between riparian zones, groundwater dynamics, and streamflow patterns, contributing to a more profound understanding of catchment hydrology. 
Another significant thesis objective was to develop advanced automated techniques for detecting and analysing diurnal fluctuations to provide fast and reliable observations of diurnal fluctuations from a large dataset. Manually identifying this scarce phenomenon in an extensive multi-year dataset is time-consuming and one of the biggest reasons for minimal, large-sample studies concerning diurnal streamflow fluctuations. This is addressed by forming an automated process of diurnal fluctuation extraction with the application of the wavelet transform. 
The capabilities of both types of wavelet transformation, the discrete wavelet transform (DWT) and continuous wavelet transform (CWT) are tested to reveal time-frequency information of diurnal signals. A detailed workflow is developed to choose the best wavelet for detrending a streamflow series to obtain diurnal fluctuation. The detrending performance of the DWT process is compared against the traditional time-based detrending methods like the moving average. It confirms the superiority of wavelet transform in optimal detrending of observed streamflow data series. The CWT presented many different plots and revealed exciting features in the diurnal patterns in streamflow. The CWT information is then used to develop an algorithm for extracting diurnal episodes from extensive streamflow records. The extraction process captured an adequate number of diurnal episodes, which matched well with the manual identifications. Overall, the automated technique addressed the limitations posed by manual identification and contributed significantly to the advancement of time-frequency dynamics of diurnal fluctuations. 
Finally, with the knowledge of diurnal fluctuation gained in the first research objective and with the capabilities of the wavelet transform, a large sample study is carried out using streamflow records from different New Zealand catchments. Various dataset sources from streamflow records, snow cover maps, and digital elevation rasters are used to calculate different catchment characteristics. The analysis showed that characteristics like catchment shape and size strongly correlate with diurnal amplitude. The diurnal lag also showed patterns of change with the catchment parameters. It is revealed that the correlation between catchment size and diurnal amplitude becomes weaker in larger catchments due to the diverse and heterogeneous nature of environmental processes within these regions.
This research significantly contributes to a deeper understanding of the temporal patterns of streamflow, providing valuable insights for hydrological modeling and water resource management. By integrating field observations, advanced analytical methods, and regional context, this work advances the understanding of diurnal streamflow dynamics.

year: 2024

title: Fine-scale cryogenic sampling of planktonic microbial communities: Application to toxic cyanobacterial blooms

authors: Puddick, Jonathan

abstract: A lack of fine-scale methods for sampling planktonic microbial populations hinders advancement in understanding the responses of these communities to environmental conditions. Current methods provide resolution at scales of centimeters to meters, but not at the millimeter-scale required to understand highly stratified communities. To address this we developed two cryogenic sampling tools to collect spatially-precise samples from aquatic environments while simultaneously preserving the microbial communities. The application of these samplers was examined over a 5.5 h period using a cyanobacterial scum (Microcystis) formed in experimental mesocosms. A cryogenic “surface snatcher” collected a discrete layer (ca. 1 mm) of surface water. Compared to conventional surface sampling methods, the surface snatcher samples contained up to 22-times more microcystin, indicating that less underlying water was incorporated into the sample. A cryogenic “cold finger” sampler was used to collect vertical profiles of the upper 40 mm of the water column. This profiler provided new insights into the fine-scale structure of Microcystis scums, demonstrating that more microcystin-producing Microcystis was contained in the surface 5 mm than the 35 mm below. The results also showed that upregulation of microcystin production was highly localized in the top 2.5 mm of the Microcystis scum. Our results demonstrate that extreme changes in cyanobacterial communities can occur over small distances, and indicate that sampling resolution is of great importance for improving knowledge on cyanobacterial blooms and toxin production. While this study focused on microcystin-producing Microcystis, the cryogenic sampling tools described here could be applied to any planktonic microbial community.

text: Fine-scale cryogenic sampling of planktonic microbial communities: Application to toxic cyanobacterial blooms A lack of fine-scale methods for sampling planktonic microbial populations hinders advancement in understanding the responses of these communities to environmental conditions. Current methods provide resolution at scales of centimeters to meters, but not at the millimeter-scale required to understand highly stratified communities. To address this we developed two cryogenic sampling tools to collect spatially-precise samples from aquatic environments while simultaneously preserving the microbial communities. The application of these samplers was examined over a 5.5 h period using a cyanobacterial scum (Microcystis) formed in experimental mesocosms. A cryogenic “surface snatcher” collected a discrete layer (ca. 1 mm) of surface water. Compared to conventional surface sampling methods, the surface snatcher samples contained up to 22-times more microcystin, indicating that less underlying water was incorporated into the sample. A cryogenic “cold finger” sampler was used to collect vertical profiles of the upper 40 mm of the water column. This profiler provided new insights into the fine-scale structure of Microcystis scums, demonstrating that more microcystin-producing Microcystis was contained in the surface 5 mm than the 35 mm below. The results also showed that upregulation of microcystin production was highly localized in the top 2.5 mm of the Microcystis scum. Our results demonstrate that extreme changes in cyanobacterial communities can occur over small distances, and indicate that sampling resolution is of great importance for improving knowledge on cyanobacterial blooms and toxin production. While this study focused on microcystin-producing Microcystis, the cryogenic sampling tools described here could be applied to any planktonic microbial community.

year: 2016

title: Translated application interfaces - issues of engagement

authors: Mato, Paora James

abstract: In New Zealand, English is the language that dominates contemporary technologies. Usability testing was completed on a range of applications, available with a Māori-language interface, to gauge levels of awareness, engagement and perception. Nearly all of the respondents were unaware of the availability of these interfaces but most indicated they would prefer to use the Māori-language versions. In terms of engagement and usability, users initially engaged using Māori but switched to English when they wanted to quickly complete the task at hand. Few remained fully engaged with the Māori-language interfaces. High levels of language switching were reported and some frustration as the participants encountered new and unfamiliar uses of words. At face value the feedback suggests the translated interfaces contained unnecessary complications and that better design and content might have enhanced the user experience. However, there is evidence that extended use would enable users to become more familiar with the interfaces alluding to initial barriers created by a previous competence in another language -- in this case English. With this previous competence in mind it might be more useful to employ design concepts that would alleviate initial difficulties and serve to keep the user engaged in the target language for longer periods of time.

text: Translated application interfaces - issues of engagement In New Zealand, English is the language that dominates contemporary technologies. Usability testing was completed on a range of applications, available with a Māori-language interface, to gauge levels of awareness, engagement and perception. Nearly all of the respondents were unaware of the availability of these interfaces but most indicated they would prefer to use the Māori-language versions. In terms of engagement and usability, users initially engaged using Māori but switched to English when they wanted to quickly complete the task at hand. Few remained fully engaged with the Māori-language interfaces. High levels of language switching were reported and some frustration as the participants encountered new and unfamiliar uses of words. At face value the feedback suggests the translated interfaces contained unnecessary complications and that better design and content might have enhanced the user experience. However, there is evidence that extended use would enable users to become more familiar with the interfaces alluding to initial barriers created by a previous competence in another language -- in this case English. With this previous competence in mind it might be more useful to employ design concepts that would alleviate initial difficulties and serve to keep the user engaged in the target language for longer periods of time.

year: 2015