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Saltwater intrusion, which can be facilitated by natural conditions, human activities and climate change, is a big threat to mankind from social-economic, environmental and ecological perspective. Agriculture, the largest consumer of water, is identified as both contributor and most vulnerable sector to saltwater intrusion, especially in coastal low-lying areas, with the increasing demands and competition of water owing to economic bloom, population growth and climate fluctuations. Sustainable water resource management is urgently needed owing to its essential in solving this issue. Hence this study is to deliver the understanding of linkage between saltwater ingress and agriculture and seek appropriate water resource management strategies in coastal low-lying areas to address saltwater intrusion and reduce its impacts on agriculture.   This study conducts a comparative case study between Texel, the Netherlands and Shouguang, China to specify the linkages between saltwater intrusion and agriculture with local features. The reasons, impacts and associated mitigations and/or adaptations of the issue, together with the legislation of each region have been investigated and compared.   The results show that for combating the saltwater intrusion and reducing the losses from agriculture, both study areas have adapted specific approaches. Among them similar approaches, despite different legislations and policies, such as developing alternative water resource (treated wastewater and rainwater) and saline agriculture are implemented by both of the regions. Through the comparison, each can learn the lessons from the other. The integrated water legislation together with its effective implementation, the strong involvements of different stakeholders and ecological approach to post-treat effluent of Texel can no doubt inspire Shouguang. While the highlights of counteract measures taken by Shouguang such separating rainwater from wastewater during collection and treatment, water diversion and development of special market to achieve high profit for saline products can obviously inspire Texel as well.   The analysis and comparison between these two case studies can reflect the general problems regarding to water management on saltwater intrusion and agriculture in all the regions that suffer from this problem. Hence, it is concluded that 1) integrated water legislation and management (with climate change considered and integrated as well) are the foundations, while water conservation should be core idea that always kept in mind; 2) strong involvements of different stakeholders and necessary supervision systems can guarantee the effectiveness of implementation; 3) all actions should be based on both technical knowledge and local-cultural knowledge; 4) self-sufficient approaches should be promoted at micro level to reduce the dependency on external water intrusion; 5) economic means should be carefully combined with environmental and ecological ways as well to achieve the goal of development of sustainability; 6) monitoring systems are of great significance.

<p>Approximately 30% of Canadians and 50% of Americans rely on groundwater for their domestic water supplies. A significant portion of this groundwater originates from fractured rock aquifers, as they are ubiquitous throughout North America. In comparison to unconsolidated porous media aquifers, relatively little is understood about biocolloid transport in fractures. A mechanistic understanding of the transport and retention of biocolloids in fractures is important towards determining the risk of biocolloid contamination to these sources, which can have a significant impact on human health. It has been well documented in the interfacial science literature that micro-scale hydrodynamics play a significant role in the transport of particles greater than approximately one micron in diameter, but do not significantly affect the transport of smaller particles. This phenomenon, however, has never been investigated in fractures,where the larger-scale hydrodynamics are complex, and must also be considered. To bridge this knowledge gap, this research was conducted to elucidate the effects of hydrodynamics on the transport and retention of <em>E. coli </em>RS2GFP and carboxylate modified yellow-green polystyrene (CMP) microspheres (0.05 μm diameter) in single, saturated, fractures at the laboratory scale.</p> <p>To achieve this goal, dolomitic limestone samples were acquired from a quarry in Guelph, Ontario, and were fractured under a uniaxial force. The hydrologic properties of each fracture sample were characterized using hydraulic and solute tracer tests. Using a factorial design approach, a known number of either <em>E. coli </em>RS2-GFP or CMP microspheres was released into the fracture under a range of specific discharges (30, 10 and 5 m/day). The resulting effluent concentration profiles were compared to isolate the effects of hydrodynamics on particle transport.</p> <p>Comparing and contrasting the effluent concentration profiles from these experiments revealed that hydrodynamic forces strongly influence the retention of particles larger than 1 μm in diameter in saturated, fractured media. Additionally, the mechanisms that dominate transport and retention are dependent on, and therefore vary with both specific discharge and particle size.</p> / Master of Applied Science (MASc)

Water scarcity is a prevalent issue all over the world. Growing water abstractions combined with uncertain effects of climate increase competition for scarce water resources worldwide, especially in arid and semiarid regions. It is crucial to assess and manage available water resources to ensure its sustainability. There is a need for integrated water management at a watershed scale. Watershed models are a useful tool to support sustainable water management and investigate effects of hydrologic responses at various scales under climate change conditions and to simulate effects of the management decisions. This study aims to assess the sustainability of water resources in the Tuul River Basin in Mongolia using SWAT (Soil Water Assessment Tool) model to understand ecohydrological processes in the basin. The model is used to analyze the trends in water usage on a watershed and subwatershed basis. The water supply and demand dynamics at each sub watershed levels are analyzed to develop a sustainability index based on specific criteria of water sustainability. Sustainability index was used for better water management by targeting areas of the watershed. Using the analysis, strategies for water demand management for the Tuul River basin area were developed. I expect the results of the study with transform water resource situation in the region through better information on the dynamics of the system and will help in alleviating water issues in similar regions of the country and of the world. The model can be a useful tool to support decision makers and to simulate and analyze the effects of water management practices.

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