Frozen ground is an important consideration in cold regions hydrology because pore ice can impede the ability of water to infiltrate into and migrate within soils, thereby altering water flow paths and increasing surface runoff. High latitude regions are particularly susceptible to changes in climate, where increases in temperature and changing precipitation trends can alter soil freeze/thaw dynamics. However, there has been limited research on infiltration processes in subarctic alpine environments due to sparse historic data and difficulties with gathering direct measurements. In addition, few hydrological models consider the complexity of frozen soils in such environments. The objectives of this thesis are to assess the ability of the GeoStudio finite element modelling suite to simulate observed soil temperature and moisture data and to evaluate the sensitivity of the models to changing climate scenarios. GeoStudio’s Multiphysics model integrates several models that allow it to simulate concurrent water flow and temperature dynamics in variably saturated environments experiencing soil freezing and thawing. Field data for this study are obtained from Wolf Creek Research Basin (WCRB) in southern Yukon, Canada. Data for quantifying snowmelt, soil moisture, soil temperature, and soil composition were collected at three sites in WCRB from April 2015 to August 2016, adding to the available historical data. Results of the GeoStudio models illustrate the dominance of snow in controlling freeze/thaw dynamics and simulate the study environment to reasonable accuracy with some discrepancies in timing and variability. In addition, GeoStudio is particularly sensitive to surface conditions affecting both coupled heat and water flow processes compared to independent changes of air temperature and precipitation, suggesting future climatic scenarios may have a notable impact on frozen soils. This research helps elucidate the complex heat transfer and water movement processes that control infiltration in northern environments and provides a quantitative assessment of their sensitivity to future climate warming. / Thesis / Master of Science (MSc)

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Consideration of almost any geomorphology textbook will show the fundamental argument that in cold environments mechanical weathering processes, usually freeze-thaw, will predominate and that chemical weathering will be temperature-limited, often to the point of non occurrence. These basic concepts have underpinned geomorphology for over a century and are the basis for the development of many landforms in periglacial regions. With the introduction of data loggers so field data became more readily available but, sadly, those data were not of a quality to other than justify the existent assumptions and thus did little more than reinforce, rather than test, the nature of our understanding of cold region weathering. Factors such as rock properties were dealt with to a limited extent but rock moisture was all but ignored, despite its centrality to most weathering processes. Here the results of field studies into weathering in cold regions, coupled with laboratory experiments based on the field data, are presented. An attempt is made to overcome the shortcomings of earlier studies. Temperature, moisture and rock properties have all been considered. Processes were not assumed but rather the data were used to evaluate what processes were operative. The results, both in terms of weathering process understanding per se and of its application to landform development, significantly challenge our longheld perceptions. Information is presented that shows that it is not temperature, but rather water, that is the limiting factor in cold region weathering. Indeed, in the absence of water, many cold environments have attributes akin to a hot desert. The relevance of this is that weathering processes other than freeze-thaw may play a significant role and that in the presence of water chemical weathering can play a far greater role than hitherto thought. Overall, the whole concept of zonality with respect to weathering is questioned. Finally, the attributes of weathering are put within the context of landform development and questions raised regarding the origin of some forms and of their palaeoenvironmental significance. Attributes of periglacial, glacial and zoogeomorphic processes and landforms in present and past cold environments are also presented. / Thesis (Ph.D.)-University of Natal, Pietermaritzburg, 2003.

Icings are common hydrological phenomena in arctic and subarctic regions. Their bodies are made up of the accumulation of ice layers formed by the freezing of overflow water during the winter season. Icing formation is a process involving a complex system of thermodynamics and hydrodynamics. In this thesis, the formation mechanics of river icings and ground icings are studied in terms of both thermal and hydrological processes. / The energy exchange systems during icing layer formation involve two ice water interfaces and some intra-layer water flow. Using energy balance analysis, this research finds that the outgoing energy components can be ranked according to their importance, with sensible heat being the most important component, radiation heat loss being of secondary importance, and latent heat loss being the least important factor. Further, this research illustrates that the heat conduction between the underlying ice and a newly formed icing layer is time dependent. For example, during the first half cycle of icing layer formation, heat is conducted into the underlying ice, but during the second half of the cycle the heat is conducted in an opposite direction. / During icing layer formation, the energy input is supplied mainly by water and incoming solar radiation. Intra-layer running water provides a significant amount of energy when air temperatures are milder, but its significance decreases when air temperatures become colder. Solar radiation during the day may also play an important role in the energy supply regime. / River icing formation involves several hydrological processes. The location of a river icing is basically controlled by the channel slope. The damming effect of icing mass plays a significant role in the extension of the icing body, especially in the upstream direction. River icings grow slowly, and generally experience three stages of development, namely the 'freeze-up' stage, 'obstruction' stage and 'overflow' stage, the third stage dominating icing growth. The formation of each icing layer is virtually a small-scale reproduction of these three stages. The model simulation shows that the thickness of icing accumulation increases with an increase in the initial water depth in the channel, but simulation also shows that there is a limiting threshold. The thickness of icing accumulation decreases when the initial channel water depth exceeds this threshold. / The growth of an icing is an event-dominated discontinuous process. Even during one icing layer formation, simultaneous growth occurs only within a very limited distance. At a specific location, icing growth is related temporally only over a short period of time. As a discontinuous process, icing spreading and thickening during an overflow event depends entirely on the climatic and topographical conditions. / Even though icing layering is influenced by many variables, under small discharge rates, as in the case of ground icing growth, statistical analyses show that the mean spreading length of an overflow event can be described efficiently by five variables: discharge, the temperature of the water, the product of air temperature and wind speed, air temperature and the icing surface slope previous to overflow. The maximum spreading length, however, may only be controlled by four variables: discharge, water temperature, air temperature and the product of air temperature and wind speed. Under field conditions, when wind speed is not measured, this wind related variable may be dropped with only a small decrease in confidence level.

The existence of anchor ice in supercooled water can have a profound impact on the management of water resource infrastructures in cold regions. For example, it can raise a tailrace water level and cause significant losses in generation revenue. So far, there have been limited studies on anchor ice, therefore, many problems still exist and much more study is needed. In the present research, experimental and mathematical studies of anchor ice were carried out. Experiments were conducted in a counter-rotating flume, located in a cold room at the University of Manitoba. The experiments were mainly focused on anchor ice evolution around rocks and on gravel beds under different hydro-meteorological conditions. The results are compared to a mathematical model developed herein and some important parameters such as anchor ice porosity and frazil ice deposition coefficient are examined. The growth process of anchor ice was monitored by two CCD cameras. A digital processing program was developed to analyze anchor ice images and determine the growth rate of anchor ice. In addition, anchor ice density, an important factor when studying anchor ice, was estimated and the effect of air temperature, Froude number and Reynolds number is explored. By analyzing torque load signals from the counter-rotating flume, the variation of bed roughness with the growth of anchor ice is elucidated. The deposition coefficient of anchor ice growth was also determined from the experiments. A mathematical model was developed based on a two-stage method to simulate the process of frazil ice transportation and deposition. Both frazil ice attachment and heat transfer between the supercooled water and ice crystals are considered in the model. Four governing equations related to the distribution of velocity and frazil ice transportation and deposition inside and outside the roughness layers were built. A fourth-order Runge- Kutta numerical method was used and programmed in Matlab to solve the governing equations. The growth rate of anchor ice under different hydro-meteorological conditions can be simulated by this numerical model. The proposed experimental and mathematical studies of anchor ice are presented intuitively in this paper and the results from this study contribute to a better understanding of the anchor ice growth mechanism. This study will help to develop better management strategies to mitigate ice related complications associated with hydroelectric generating stations and other hydraulic structures in cold regions.

The existence of anchor ice in supercooled water can have a profound impact on the management of water resource infrastructures in cold regions. For example, it can raise a tailrace water level and cause significant losses in generation revenue. So far, there have been limited studies on anchor ice, therefore, many problems still exist and much more study is needed. In the present research, experimental and mathematical studies of anchor ice were carried out. Experiments were conducted in a counter-rotating flume, located in a cold room at the University of Manitoba. The experiments were mainly focused on anchor ice evolution around rocks and on gravel beds under different hydro-meteorological conditions. The results are compared to a mathematical model developed herein and some important parameters such as anchor ice porosity and frazil ice deposition coefficient are examined. The growth process of anchor ice was monitored by two CCD cameras. A digital processing program was developed to analyze anchor ice images and determine the growth rate of anchor ice. In addition, anchor ice density, an important factor when studying anchor ice, was estimated and the effect of air temperature, Froude number and Reynolds number is explored. By analyzing torque load signals from the counter-rotating flume, the variation of bed roughness with the growth of anchor ice is elucidated. The deposition coefficient of anchor ice growth was also determined from the experiments. A mathematical model was developed based on a two-stage method to simulate the process of frazil ice transportation and deposition. Both frazil ice attachment and heat transfer between the supercooled water and ice crystals are considered in the model. Four governing equations related to the distribution of velocity and frazil ice transportation and deposition inside and outside the roughness layers were built. A fourth-order Runge- Kutta numerical method was used and programmed in Matlab to solve the governing equations. The growth rate of anchor ice under different hydro-meteorological conditions can be simulated by this numerical model. The proposed experimental and mathematical studies of anchor ice are presented intuitively in this paper and the results from this study contribute to a better understanding of the anchor ice growth mechanism. This study will help to develop better management strategies to mitigate ice related complications associated with hydroelectric generating stations and other hydraulic structures in cold regions.

Hydrological models have been developed to estimate snow accumulation, snowmelt and snowmelt runoff on the Canadian Prairies; however, their proper scale of application is unknown in the Prairie environment. The first objective of this thesis is to examine the proper scale for pre-melt snow accumulation as snow water equivalent (SWE) and snowmelt in a Prairie first order basin. Spatially distributed and spatially aggregated approaches were used to calculate SWE and snowmelt at St. Denis National Wildlife Area (SDNWA). Both approaches used models with similar physics, but differed in the model scale at which calculations were carried out. The simulated pre-melt SWE, cumulative seasonal SWE, and daily snowmelt from the two modelling approaches were compared to field observations of pre-melt SWE, cumulative seasonal SWE, and daily snowmelt; comparisons of areal cumulative seasonal SWE, areal snowmelt, snowmelt duration, and snow-covered area were also conducted between two modelling approaches. Results from these comparisons showed that both approaches had reasonable and similar accuracy in estimation of SWE and snowmelt. The spatially aggregated approach was more computationally efficient and was selected as a modelling scale for small-sized prairie basins. <p>Another objective of this thesis is to derive a snow hydrology model for the Canadian Prairies. Physically-based hydrological models were assembled in the Cold Regions Hydrological Model Platform (CRHM) using the aggregated approach. Tests of pre-melt SWE and surface snowmelt runoff were conducted at two basins in Saskatchewan Creighton Tributary of Bad Lake and Wetland 109, St. Denis. Results showed that the snow hydrology model had a reasonable capability to simulate SWE and snowmelt runoff to the stream and wetland. <p>Droughts are natural hazards that develop frequently on the Canadian Prairies. Analyzing the impact of drought on hydrological processes and water supply is another objective of this thesis. Synthetic drought scenarios were proposed for the Creighton Tributary of Bad Lake and the corresponding impacts on the snowmelt runoff-related processes were examined. Results indicated that wind redistribution of snow was very sensitive to drought conditions, sublimation of blowing snow and snow-covered period were sensitive to drought, but winter evaporation and infiltration did not show strong trend. The results also showed that drought conditions had magnified effects on the snowmelt runoff and could cause cessation of streamflow. Also, the impacts of the recent 1999-2005 drought on the snowmelt hydrology were investigated at St. Denis. Results illustrated that three-years (1999-2002) of severe winter drought were followed by a normal year (2002-03) and then a two-year (2003-05) recovery period, and then returning to normal (2005-06). Results showed that both snowfall and rainfall during hydrological winter were consistently low for severe drought and surface snowmelt runoff was very much lower during severe drought, about 45-65 mm less compared to that in the normal periods.

Hydrological models have been developed to estimate snow accumulation, snowmelt and snowmelt runoff on the Canadian Prairies; however, their proper scale of application is unknown in the Prairie environment. The first objective of this thesis is to examine the proper scale for pre-melt snow accumulation as snow water equivalent (SWE) and snowmelt in a Prairie first order basin. Spatially distributed and spatially aggregated approaches were used to calculate SWE and snowmelt at St. Denis National Wildlife Area (SDNWA). Both approaches used models with similar physics, but differed in the model scale at which calculations were carried out. The simulated pre-melt SWE, cumulative seasonal SWE, and daily snowmelt from the two modelling approaches were compared to field observations of pre-melt SWE, cumulative seasonal SWE, and daily snowmelt; comparisons of areal cumulative seasonal SWE, areal snowmelt, snowmelt duration, and snow-covered area were also conducted between two modelling approaches. Results from these comparisons showed that both approaches had reasonable and similar accuracy in estimation of SWE and snowmelt. The spatially aggregated approach was more computationally efficient and was selected as a modelling scale for small-sized prairie basins. <p>Another objective of this thesis is to derive a snow hydrology model for the Canadian Prairies. Physically-based hydrological models were assembled in the Cold Regions Hydrological Model Platform (CRHM) using the aggregated approach. Tests of pre-melt SWE and surface snowmelt runoff were conducted at two basins in Saskatchewan Creighton Tributary of Bad Lake and Wetland 109, St. Denis. Results showed that the snow hydrology model had a reasonable capability to simulate SWE and snowmelt runoff to the stream and wetland. <p>Droughts are natural hazards that develop frequently on the Canadian Prairies. Analyzing the impact of drought on hydrological processes and water supply is another objective of this thesis. Synthetic drought scenarios were proposed for the Creighton Tributary of Bad Lake and the corresponding impacts on the snowmelt runoff-related processes were examined. Results indicated that wind redistribution of snow was very sensitive to drought conditions, sublimation of blowing snow and snow-covered period were sensitive to drought, but winter evaporation and infiltration did not show strong trend. The results also showed that drought conditions had magnified effects on the snowmelt runoff and could cause cessation of streamflow. Also, the impacts of the recent 1999-2005 drought on the snowmelt hydrology were investigated at St. Denis. Results illustrated that three-years (1999-2002) of severe winter drought were followed by a normal year (2002-03) and then a two-year (2003-05) recovery period, and then returning to normal (2005-06). Results showed that both snowfall and rainfall during hydrological winter were consistently low for severe drought and surface snowmelt runoff was very much lower during severe drought, about 45-65 mm less compared to that in the normal periods.

Precipitation phase is fundamental to a catchment’s hydrological response to precipitation events in cold regions and is especially variable over time and space in complex topography. Phase is controlled by the microphysics of the falling hydrometeor, but microphysical calculations require detailed atmospheric information that is often unavailable and lacking from hydrological analyses. In hydrology, there have been many methods developed to estimate phase, but most are regionally calibrated and many depend on air temperature (Ta) and use daily time steps. Phase is not only related to Ta, but to other meteorological variables such as humidity. In addition, precipitation events are dynamic, adding uncertainties to the use of daily indices to estimate phase. To better predict precipitation phase with respect to meteorological conditions, the combined mass and energy balance of a falling hydrometeor was calculated and used to develop a model to estimate precipitation phase. Precipitation phase and meteorological data were observed at multiple elevations in a small Canadian Rockies catchment, Marmot Creek Research Basin, at 15-minute intervals over several years to develop and test the model. The mass and energy balance model was compared to other methods over varying time scales, seasons, elevations and topographic exposures. The results indicate that the psychrometric energy balance model performs much better than Ta methods and that this improvement increases as the calculation time interval decreases. The uncertainty that differing phase methods introduce to hydrological process estimation was assessed with the Cold Regions Hydrological Model (CRHM). The rainfall/total precipitation ratio, runoff, discharge and snowpack accumulation were calculated using a single and a double Ta threshold method and the proposed physically based mass and energy balance model. Intercomparison of the hydrological responses of the methods highlighted differences between Ta based and psychrometric approaches. Uncertainty of hydrological processes, as established by simulating a wide range of Ta methods, reached up to 20% for rain ratio, 1.5 mm for mean daily runoff, 0.4 mm for mean daily discharge and 160 mm of peak snow water equivalent. The range of Ta methods showed that snowcover duration, snow free date and peak discharge date could vary by up to 36, 26 and 10 days respectively. The greatest hydrological uncertainty due to precipitation phase methods was found at sub-alpine and sub-arctic headwater basins and the least uncertainty was found at a small prairie basin.

The thesis presents a systematic experimental and numerical study on the interactions among porous fence, airflow, and windblown snowdrifts, a knowledge that will contribute to optimize the performance of porous wind shielding system in Cold Regions. A comprehensive review of the concepts, theories, techniques, and key findings associated with the research work has been undertaken. The key technical parameters influencing fence performance have been systematically studied by means of wind tunnel experimental investigations and Computational Fluid Dynamics (CFD) simulations. The study has found that porosity is the most influential structural parameter affecting the performance of porous fences in many aspects. Fence height stands a significant positive position in terms of its performance. It was found that fence performance is not sensitive to the changes of approaching atmospheric airflow velocity. Nevertheless, a bottom gap can improve snow fence trap efficiency. All of those findings agree with most of the findings of other researchers, which affirms that the research methodology adopted in this research is sound. Physical experimental work was performed to assess the reliability and credibility of the numerical models. Those models have been intentionally simplified, which made them easier to construct and quicker to obtain numerical solutions at a lower computational cost. Furthermore, the numerical models demonstrate the level of competence acquired through this research that is implemented in the optimisation of fence design. Special attention has been paid to the issues where elaborate research work has not been systematically reached in the open literature, this includes areas such as the effects of arrangement of porous holes, fence surface shear, and directions of wind load with respect to the fence, etc. Correlation between the reattachment length, the shelter distance, and the creation and distribution of fence surface shear is reported, to the author's knowledge, for the first time in the open literature. General guidelines for the design of shelters based on porous fences have been established through this study. For example, the desirable size of hole range should be identified beforehand, and porous holes with sharp angular corners should usually be avoided in the fence design. It is recommended to place the fence within an angle of 30° to the wind load, where the effective shelter distance can be estimated in a linearized equation, and the normal drag coefficient can be described as a function of cos2θ. Optimal design of the arrangement of porous holes will maximize the fence performance, especially when the close fence environment is of concern. Although the definition of fence effective zone is still vague in the research field, the key factors influencing the fence effective zone have been investigated by evaluating the reduction of wind velocity leeward of the fence in this thesis. It is found that the fence effective zone is not sensitive to the change of approaching airflow velocity, and that increasing fence height will increase the physical size of the fence effective zone, but not in a proportional manner. It is also concluded that fence effective zone will be significantly reduced when the non-normal wind load is inclined at an angle greater than 30° to the fence. The effective zone increases effectively when the fence porosity is optimal. In contrast to the majority of published research work, the transient snow transport model presented in this work considers the snow transport rate as a whole without distinguishing the rate in saltation and suspension layer. The numerical study indicated that the position of the snow crest is mainly determined by the fence height, while porosity and bottom gap mainly affect the downwind deposition length. The optimal porosity for snow fences is in the range of 0.4 to 0.5, which is greater than the one for wind fences, which lies in the range from 0.25 to 0.35. Two snow crests have been observed leeward the fence at the onset of snow deposition, when the fence was placed without a bottom gap to the snow ground. This finding has not been encountered in any of the reported research work. Wind tunnel simulations of snowdrift around the fences have marginally under-predicted the sizes of snow deposition. The numerical predictions were quantitatively and qualitatively in good agreement with the field observations. This incompetence of wind tunnel experiments on porous fences implies that numerical modelling can play a more important role in snow fence research.