>Magister Scientiae - MSc / The Department of Water and Sanitation (DWS) is considering the implementation of an Aquifer Protection Strategy to protect the country’s critical groundwater resources. This study will assist in filling the knowledge gap in the form of a groundwater protection zoning case study in the Rawsonville area. Understanding how groundwater is being accessed and used is required in determining the level and type of groundwater protection needed. Groundwater access points were identified as being boreholes, springs and rivers. A few potential contamination sources were identified at the site such as leachate from fertilizers and pesticides which may reach the groundwater used by the farmers for domestic water supply as well as irrigation.

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Doctor of Philosophy / Department of Sociology, Anthropology, and Social Work / Gerad D. Middendorf / In the almost 40 years since the passage of the Clean Water Act and 25 years of regulating nonpoint source pollution, and despite countless state and local community projects focused on water quality issues, clean water goals have not been met. To comprehend this failure and understand how water resources are governed and how water quality goals are pursued, I explore how watershed-level governance structures emerged and function in their specific local environment, within the state hierarchy of water governance, and as implementation of state and national policy. To this end, the structure, process, and outcomes of two newly organized and local watershed-level governance structures in Kansas were examined. An actor-oriented political ecology approach informed by environmental governance and watershed management literature was used to guide the study. Attaining water quality goals necessitates recognizing the connections between the political economy of agriculture, the cultural factors acting upon agricultural producers, and the natural, biophysical environment. Thusly, a comparative case study strategy was employed for the overall research design. Documents and interview transcripts were analyzed employing a grounded theory approach for differences and similarities; they were also sorted into topical categories and coded for common themes. The research questions focused on the agency and capacity of local watershed structures to determine the relations regarding water resource use in their watershed. Central questions addressed structure responsiveness to local versus state or national concerns; the underlying interests reflected by community member participation; and the effectiveness of local water-governance in protecting water resources. Governance models that began with holistic, alternative, participatory strategies are evolving into targeted, problem-solution strategies, and what began as watershed management is becoming problem shed management.

Les réseaux multi-terminaux à courant continu sont une solution efficace pour intégrer l’énergie électrique produite en grande quantité par de grands parcs éoliens offshore. Bien que le recours à la technologie HVDC soit maitrisé pour des applications point-à-point, des verrous technologiques sont encore à lever pour permettre une exploitation sûre d’un réseau à courant continu. La protection est le principal domaine technique pour lequel des progrès sont encore attendu. Des stratégies de protection fiables et assurant le meilleur ratio technico-économique sont à l’étude. Ces travaux de thèse ont pour objectif la mise en œuvre d’une philosophie de protection à sélectivité totale, identique à celle utilisée dans les réseaux de transport traditionnels. Cette étude considère l’utilisation de liaison par câbles uniquement, de convertisseurs VSC-MMC composées de sous-modules en demi-pont et de disjoncteurs hybrides à courant continu. Une association de deux algorithmes de détection de défaut a été proposée. Une étude du temps disponible pour l’élimination du défaut a été menée. Enfin, des simulations numériques avec le logiciel EMTP ont permis d’évaluer la fiabilité de la stratégie de protection. / In a near future, multi-terminal High Voltage Direct Current grids (MT-HVDC grids) appear to be a suitable solution for the integration of power electricity produced by remote offshore windfarms into the AC transmission system. Though the recourse to HVDC point-to-point links is well-known, challenges still remain for a safe operation of HVDC grids. Protection is the main technical field still under study and reliable protection strategies ensuring the best technological and economic ratio are investigated. This thesis focused on a full selective protection philosophy similar to the one applied to AC transmission systems. The consideration of cable links, Half-Bridge VSC-MMC converters and hybrid DC circuit breakers defines the frame of the study. An association of two algorithms for the identification of faults is suggested. The time available for the fault clearing process has been investigated. Simulations performed with EMTP software have been used to evaluate the reliability of the suggested strategy.

於歷史事件中我們知道電力網路中些許的傷害會導致大停電事件的發生，而電力網路的安全是學者們一直以來關心的議題，複雜網路發展至今，已有不少研究人員利用複雜網路的方法來分析電力網路，本論文即利用複雜網路的分析方法，分析台灣電力網路脆弱性，並提出一新穎的保護策略。 文章中引用三種分析方法分析台灣電力網路的脆弱性，第一為根據網路效率(efficiency of complex network)，第二為根據靜態負載的連鎖性失效(static load cascading failure)，第三為根據動態負載的連鎖性失效(dynamic load cascading failure)，三種脆弱性分析的方法得到結果的交集處，在文中被認為是電力網路中最具風險的變電站。根據靜態負載的連鎖性失效的結果，我們在不改變網路結構和整體網路的負載量之下，提出一新穎的安全策略，試圖降低靜態負載時連鎖性失效帶來的傷害，並分析此安全策應用至ER隨機網路(ER random network)、BA無尺度網路(BA scale-free network)和台灣電力網路，且量化其結果。 三種脆弱分析的結果皆有共通的部份，表示台灣電力網路在拓樸分析下並不堅固，其結果顯示此安全策略是有效的。本篇論文分析的網路均是無權重也無方向性的網路，如此，未來在網路脆弱性與安全策略的研究還有進一步的研究空間。 / From blackout events in history, we know the damage of a few substations or transmission lines can lead to a big blackout, and the robustness of power grids are always a great concern. Recently the topological analyses of power grid network have developed rapidly and its achievements have become a center of attention. This thesis aims to investigate the vulnerability of Taiwan’s power grid through topological analyses and propose a novel protection strategy. This thesis introduces three methods to investigate the vulnerability of Taiwan’s power grid. The first method is based on efficiency of complex network. The second method is based on static load cascading failure. The third method is based on dynamic load cascading failure. The common results of the three results are considered the high risks in Taiwan’s power grid. According to the static load cascading failure, we propose a protection strategy against cascading failure without changing the structure of network and the whole load of the network, and then demonstrate the effectiveness of this strategy on an ER random network, a BA scale-free network and Taiwan’s power grid numerically. The three methods having the common results, one may say Taiwan’s power grid isn’t robust under the topological analyses, and our protection strategy may be useful for decreasing the damage after cascading failure.