Yes / The process of capturing and storing carbon dioxide (CCS) was previously considered a crucial and time-sensitive approach for diminishing CO2 emissions originating from coal, oil, and gas sectors. Its implementation was seen necessary to address the detrimental effects of CO2 on the atmosphere and the ecosystem. This recognition was achieved by previous substantial study efforts. The carbon capture and storage (CCS) cycle concludes with the final stage of CO2 storage. This stage involves primarily the adsorption of CO2 in the ocean and the injection of CO2 into subsurface reservoir formations. Additionally, the process of CO2 reactivity with minerals in the reservoir formations leads to the formation of limestone through injectivities. Carbon capture and storage (CCS) is the final phase in the CCS cycle, mostly achieved by the use of marine and underground geological sequestration methods, along with mineral carbonation techniques. The introduction of supercritical CO2 into geological formations has the potential to alter the prevailing physical and chemical characteristics of the subsurface environment. This process can lead to modifications in the pore fluid pressure, temperature conditions, chemical reactivity, and stress distribution within the reservoir rock. The objective of this study is to enhance our existing understanding of CO2 injection and storage systems, with a specific focus on CO2 storage techniques and the associated issues faced during their implementation. Additionally, this research examines strategies for mitigating important uncertainties in carbon capture and storage (CCS) practises. Carbon capture and storage (CCS) facilities can be considered as integrated systems. However, in scientific research, these storage systems are often divided based on the physical and spatial scales relevant to the investigations. Utilising the chosen system as a boundary condition is a highly effective method for segregating the physics in a diverse range of physical applications. Regrettably, the used separation technique fails to effectively depict the behaviour of the broader significant system in the context of water and gas movement within porous media. The limited efficacy of the technique in capturing the behaviour of the broader relevant system can be attributed to the intricate nature of geological subsurface systems. As a result, various carbon capture and storage (CCS) technologies have emerged, each with distinct applications, associated prices, and social and environmental implications. The results of this study have the potential to enhance comprehension regarding the selection of an appropriate carbon capture and storage (CCS) application method. Moreover, these findings can contribute to the optimisation of greenhouse gas emissions and their associated environmental consequences. By promoting process sustainability, this research can address critical challenges related to global climate change, which are currently of utmost importance to humanity. Despite the significant advancements in this technology over the past decade, various concerns and ambiguities have been highlighted. Considerable emphasis was placed on the fundamental discoveries made in practical programmes related to the storage of CO2 thus far. The study has provided evidence that despite the extensive research and implementation of several CCS technologies thus far, the process of selecting an appropriate and widely accepted CCS technology remains challenging due to considerations related to its technological feasibility, economic viability, and societal and environmental acceptance.

Yes / Capturing and storing CO2 (CCS) was once regarded as a significant, urgent, and necessary option for reducing the emissions of CO2 from coal and oil and gas industries and mitigating the serious impacts of CO2 on the atmosphere and the environment. This recognition came about as a result of extensive research conducted in the past. The CCS cycle comes to a close with the last phase of CO2 storage, which is accomplished primarily by the adsorption of CO2 in the ocean and injection of CO2 subsurface reservoir formation, in addition to the formation of limestone via the process of CO2 reactivity with reservoir formation minerals through injectivities. CCS is the last stage in the carbon capture and storage (CCS) cycle and is accomplished chiefly via oceanic and subterranean geological sequestration, as well as mineral carbonation. The injection of supercritical CO2 into geological formations disrupts the sub-surface’s existing physical and chemical conditions; changes can occur in the pore fluid pressure, temperature state, chemical reactivity, and stress distribution of the reservoir rock. This paper aims at advancing our current knowledge in CO2 injection and storage systems, particularly CO2 storage methods and the challenges encountered during the implementation of each method and analyses on how key uncertainties in CCS can be reduced. CCS sites are essentially unified systems; yet, given the scientific context, these storage systems are typically split during scientific investigations based on the physics and spatial scales involved. Separating the physics by using the chosen system as a boundary condition is a strategy that works effectively for a wide variety of physical applications. Unfortunately, the separation technique does not accurately capture the behaviour of the larger important system in the case of water and gas flow in porous media. This is due to the complexity of geological subsurface systems, which prevents the approach from being able to effectively capture the behaviour of the larger relevant system. This consequently gives rise to different CCS technology with different applications, costs and social and environmental impacts. The findings of this study can help improve the ability to select a suitable CCS application method and can further improve the efficiency of greenhouse gas emissions and their environmental impact, promoting the process sustainability and helping to tackle some of the most important issues that human being is currently accounting global climate change. Though this technology has already had large-scale development for the last decade, some issues and uncertainties are identified. Special attention was focused on the basic findings achieved in CO2 storage operational projects to date. The study has demonstrated that though a number of CCS technologies have been researched and implemented to date, choosing a suitable and acceptable CCS technology is still daunting in terms of its technological application, cost effectiveness and socio-environmental acceptance.

<div>With increasing focus on large scale planning and allocation of resources for protection against future flood risk, it is necessary to analyze and improve the deficiencies in the conventional flood modeling approach through a better understanding of the interactions between river hydrodynamics and subsurface processes. Recent studies have shown that it is possible to improve the flood inundation modeling and mapping using physically-based integrated models that incorporate observable data through assimilation and simulate hydrologic fluxes using the fundamental laws of conservation of mass at multiple spatiotemporal scales. However, despite the significance of integrated modeling in hydrology, it has received relatively less attention within the context of flood hazard. The overall aim of this dissertation is to study the heterogeneity in complex physical processes that govern the watershed response during flooding and incorporate these effects in integrated models across large scales for improved flood risk estimation. Specifically, this dissertation addresses the following questions: (1) Can physical process incorporation using integrated models improve the characterization of antecedent conditions and increase the accuracy of the watershed response to flood events? (2) What factors need to be considered for characterizing scale-dependent physical processes in integrated models across large watersheds? (3) How can the computational efficiency and process representation be improved for modeling flood events at large scales? (4) Can the applicability of integrated models be improved for capturing the hydrodynamics of unprecedented flood events in complex urban systems?</div><div><br></div><div>To understand the combined effect of surface-subsurface hydrology and hydrodynamics on streamflow generation and subsequent inundation during floods, the first objective incorporates an integrated surface water-groundwater (SW-GW) modeling approach for simulating flood conditions. The results suggest that an integrated model provides a more realistic simulation of flood hydrodynamics for different antecedent soil conditions. Overall, the findings suggest that the current practice of simulating floods which assumes an impervious surface may not be providing realistic estimates of flood inundation, and that an integrated approach incorporating all the hydrologic and hydraulic processes in the river system must be adopted.</div><div><br></div><div>The second objective focuses on providing solutions to better characterize scale-dependent processes in integrated models by comparing two model structures across two spatial scales and analyzing the changes in flood responses. The results indicate that since the characteristic length scales of GW processes are larger than SW processes, the intrinsic scale (or resolution) of GW in integrated models should be coarser when compared to SW. The results also highlight the degradation of streamflow prediction using a single channel roughness when the stream length scales are increased. A distributed channel roughness variable along the stream length improves the modeled basin response. Further, the results highlight the ability of a dimensionless parameter 𝜂1, representing the ratio of the reach length in the study region to maximum length of the single stream draining at that point, for identifying which streams may require a distributed channel roughness.</div><div><br></div><div>The third objective presents a hybrid flood modeling approach that incorporates the advantages of both loosely-coupled (‘downward’) and integrated (‘upward’) modeling approaches by coupling empirically-based and physically-based approaches within a watershed. The computational efficiency and accuracy of the proposed hybrid modeling approach is tested across three watersheds in Indiana using multiple flood events and comparing the results with fully- integrated models. Overall, the hybrid modeling approach results in a performance comparable to a fully-integrated approach but at a much higher computational efficiency, while at the same time, providing objective-oriented flexibility to the modeler.</div><div><br></div><div>The fourth objective presents a physically-based but computationally-efficient approach for modeling unprecedented flood events at large scales in complex urban systems. The application of the proposed approach results in accurate simulation of large scale flood hydrodynamics which is shown using Hurricane Harvey as the test case. The results also suggest that the ability to control the mesh development using the proposed flexible model structure for incorporating important physical and hydraulic features is as important as integration of distributed hydrology and hydrodynamics.</div>