This thesis develops a methodology for mesoscale model verification and validation that is founded on the rigorous constraint imposed by the need to conserve both water mass and isotopes simultaneously. The isoWATFLOOD model simulates δⁱ⁸O in streamflow, which effectively reduces and constrains errors associated with equifinality in streamflow generation by improving internal parameterizations. The WATFLOOD model is a conceptually-based distributed hydrological model used for simulating streamflow on mesoscale watersheds. Given the model’s intended application to mesoscale hydrology, it remains crucial to ensure conceptualizations are physically representative of the hydrologic cycle and the natural environment. Stable water isotopes because of their natural abundance and systematic fractionation have the ability to preserve information on water cycling across large domains. Several coordinated research projects have recently focused on integrating stable water isotopes into global and regional circulation models, which now provides the opportunity to isotopically force land-surface and hydrological models. Where traditionally streamflows are the primary validation criteria in hydrological modelling, problems arise in remote and ungauged basins, or large watersheds where streamflows may not be well monitored. By streamflow validation alone, no insight is obtained on the internal apportioning and physical representation of sub-processes contributing to streamflow. The primary goal of this research is to develop alternative measures to parameterize mesoscale hydrological models in a physically-based manner, and to validate such models over large domains. This research develops improved model parameterizations that facilitate realistic runoff generation process contributions. The examination of runoff generation processes and the subsequent δⁱ⁸O of these processes are performed for two mesoscale watersheds: Fort Simpson, NWT and the Grand River Basin, ON. The isoWATFLOOD model is shown to reliably predict streamflow and δⁱ⁸O of streamflow, and simulates mesoscale isotopic fractionation associated with evaporation. In doing so, a more physically meaningful, robust modelling tool is developed that is practical for operational use. This research also contributes the first continuous record of δⁱ⁸O in streamflow that enables the visualization of spatial and temporal variability and dominant hydrologic controls within mesoscale watersheds.

This thesis develops a methodology for mesoscale model verification and validation that is founded on the rigorous constraint imposed by the need to conserve both water mass and isotopes simultaneously. The isoWATFLOOD model simulates δⁱ⁸O in streamflow, which effectively reduces and constrains errors associated with equifinality in streamflow generation by improving internal parameterizations. The WATFLOOD model is a conceptually-based distributed hydrological model used for simulating streamflow on mesoscale watersheds. Given the model’s intended application to mesoscale hydrology, it remains crucial to ensure conceptualizations are physically representative of the hydrologic cycle and the natural environment. Stable water isotopes because of their natural abundance and systematic fractionation have the ability to preserve information on water cycling across large domains. Several coordinated research projects have recently focused on integrating stable water isotopes into global and regional circulation models, which now provides the opportunity to isotopically force land-surface and hydrological models. Where traditionally streamflows are the primary validation criteria in hydrological modelling, problems arise in remote and ungauged basins, or large watersheds where streamflows may not be well monitored. By streamflow validation alone, no insight is obtained on the internal apportioning and physical representation of sub-processes contributing to streamflow. The primary goal of this research is to develop alternative measures to parameterize mesoscale hydrological models in a physically-based manner, and to validate such models over large domains. This research develops improved model parameterizations that facilitate realistic runoff generation process contributions. The examination of runoff generation processes and the subsequent δⁱ⁸O of these processes are performed for two mesoscale watersheds: Fort Simpson, NWT and the Grand River Basin, ON. The isoWATFLOOD model is shown to reliably predict streamflow and δⁱ⁸O of streamflow, and simulates mesoscale isotopic fractionation associated with evaporation. In doing so, a more physically meaningful, robust modelling tool is developed that is practical for operational use. This research also contributes the first continuous record of δⁱ⁸O in streamflow that enables the visualization of spatial and temporal variability and dominant hydrologic controls within mesoscale watersheds.

Delineating spatial patterns of precipitation isotopes (“isoscapes”) is important for studies including the hydrology of terrestrial systems, present and past interpretations of climate, and tracer-aided hydrological modelling, among others. However, the extent to which precipitation isoscapes can be predicted across Canada has not been fully articulated. This thesis combines isotopes in precipitation (δ18Oppt) observations from two regional and one global network to create long term and time series precipitation isoscapes for Canada and the northern United States. Multi-linear regressions of a small suite of geographic and climate variables generate the best performing long-term and seasonal models of δ18Oppt. These models are used to develop long term isoscapes for Canada, which capture the general spatial and seasonal trends in δ18Oppt, showing an improvement upon results from previous studies using global models. Building upon long-term δ18Oppt prediction, δ18Oppt observations alongside climatological and geographic predictors are used to create empirical time series prediction models. Five regionalization approaches are used to separate the study domain into isotope zones to explore the effect of spatial grouping on simulations. Generally, the models capture the timing and magnitude of intra-annual (seasonal) δ18Oppt cycles across the study domain while simulating moderate inter-annual variation; however often fail to capture the anomalies in observed δ18Oppt. Uncertainty in predictions is quantified spatially and temporally, and the Köppen-Geiger (Kpn) regionalization is selected as the preferred regionalization scheme for future applications due to adequate model performance and lack of border issues at regional boundaries. Finally, estimates of monthly δ18Oppt from Kpn models, long term annual averages, and daily REMOiso output are used to force an isotope-enabled hydrological model, isoWATFLOOD, in the Fort Simpson Basin, NWT, Canada. Results show streamflow simulations are not significantly impacted by choice of δ18Oppt input; however, oxygen-18 in streamflow and the internal apportionment of water (and model parameterizations) are impacted, particularly during large precipitation and snowmelt events. This work shows how isoWATFLOOD can be used in regions with limited δ18Oppt observations, and that the model can be of value in such regions. This study reinforces that a tracer-aided modelling approach works towards diagnosing issues surrounding model equifinality. / February 2017

Oxygen and hydrogen isotopes (δ18O, δD) are increasingly powerful tools for reconstructing past hydroclimate variability. The utility of δ18O- and δD-based paleoclimate records, however, depends on our understanding of how well these tracers reflect past climate conditions. The dynamics controlling the relationship between climate and water isotope variability are highly complex and often poorly constrained, especially in the tropics, where many key high-resolution paleoclimate records rely on past rainfall isotopes as proxies for hydroclimate. In this dissertation, I use multi-year timeseries of daily rainfall and biweekly dripwater δ18O from northern Borneo – a site for stalagmite δ18O-based paleoclimate reconstruction in the heart of the West Pacific Warm Pool – to track the cloud-to-calcite transformation of δ18O and its relationship to large-scale climate variability. Chapter 2 investigates the variability of rainfall δ18O variability from northern Borneo on diurnal to interannual timescales and its relationship with local and regional climate. Chapter 3 investigates the rainfall-to-dripwater transformation of climate-related isotopic signals following water transit through the Borneo cave system. Overall, this dissertation provides empirical support for the interpretation of northern Borneo stalagmite δ18O as a robust indicator of regional-scale hydroclimate variability, where higher δ18O reflects regional drying. More generally, this research provides a roadmap for obtaining more nuanced interpretations of speleothem δ18O records from multi-year, high-resolution, paired timeseries of rainfall and dripwater δ18O.

This study quantifies spatial and temporal patterns in snow water equivalent (SWE), chemistry, and water isotopes associated with snowpack shading due to aspect and vegetation in the Valles Caldera National Preserve, New Mexico. Depth, density, stratigraphy, temperature, and snow chemistry, isotope, and biogeochemical nutrient samples were collected and analyzed from five snowpit locations on approximate monthly intervals between January-April 2007. SWE showed little variability between sites in January (~10mm) but differences expanded to 84mm (30%) by max accumulation in open sites and 153mm (45%) between all sites. Sulfate varied by 22% (10.6-13.5 microeq/L), Cl- by 35% (17.4-26.9 microeq/L), and d18O by 17% (-16.3 to -13.5), with SWE exhibiting inverse correlations with d18O (r2=0.96), SO42- (r2=0.75), and Cl- (r2=0.60) at max accumulation. Regression relationships suggest variability in SWE and solutes/water isotopes are primarily driven by sublimation. Mass balance techniques estimate sublimation ranges from 1-16% between topographically- and non-shaded open sites.

A Deep Geologic Repository is proposed for a site on the eastern margin of the Michigan Basin at a depth of 680 metres in the Cobourg Formation. A study of the paleo-hydrogeolgical conditions for the area was conducted using numerical simulation of the distribution of natural tracers and the observed hydraulic head. To conduct the study, simulations of the groundwater flow systems were developed for hydraulic head generated from glacial loading cycles to study its effects on advective solute transport. The hydro-mechanical loading during the glacial cycles is assessed using numerical analysis of coupled stress and porewater pressure. The effect of density-dependent flow was assessed in a second study to estimate the degree of penetration of glacially-derived water driven into the basin during periods of glacial loading. Numerical simulations were used to explore the potential freshwater invasion pathways under a variety of conditions. Finally, profiles of 18O and 2H measured in porewater were combined with our understanding of the paleo-hydrogeological conditions derived from the studies above to test the hypothesis that solute transport was diffusion-dominated in this setting. A series of pure diffusion and advection-diffusion models were developed and the results were compared with profiles of natural water isotopes obtained from the study area. The results of the hydro-mechanical study of glacial impact show the development of significant underpressure during the interstadial periods, especially in the lowest permeability formations. The results also show that the formations have not reached hydrostatic conditions at the present time. These results were verified by comparison to measured environmental heads obtained from the study site. The density-dependent modeling showed that freshwater is capable of reaching the location of the study site through several permeable features. The transport simulations showed that the evolution time starting from a uniform initial condition, and using boundary conditions that are defined by freshwater invasion at several depths agrees with the hydro-geological history of this part of the Basin. The results also show the importance of advection on solute transport from the upper and lower boundaries even in rock of extremely low permeability. / Thesis (Ph.D, Civil Engineering) -- Queen's University, 2014-05-30 10:18:01.286

Ice formed by water vapour deposition has been identified in different terrestrial environments: 1) in the atmosphere; 2) at the ground’s surface; 3) in caves; 4) in seasonally frozen ground; and 5) in perennially frozen ground (permafrost). Thus far, ground ice formed by diffusion and deposition of vapour in soils (types 4 and 5) has rarely been studied in a natural setting and remains one of the most poorly described ice types on Earth. This thesis focuses on the dynamics of deposition and sublimation of atmospheric water vapour into permafrost and the isotopic signature (D/H and 18O/16O) of the emplaced ground ice under different experimental conditions. Ground ice was produced in sediments with different thermo-physical characteristics (glass beads, JSC Mars-1 simulant). After a two-month growth period, the higher porosity sediments (JSC) had more than 7x the gravimetric water content than the lower porosity soil. Ground ice profiles had a distinct concave downwards shape due to the decrease in saturation vapour pressure with depth. Results also indicate that vapour deposited ground ice has a distinct δD-δ18O composition that plots near regression slope value of 8. Pore water isotopes plot below the global meteoric water line (GMWL) when the source of moisture is directly on top of the sediments. If an air gap is introduced between the source of moisture and the sediments, the pore water isotopes shift above the GMWL due to re-sublimation at the ground surface. Overall, this thesis addressed some fundamental knowledge gaps required to better understand the growth and isotopic evolution of ground ice emplaced by vapour deposition.

This thesis presents the development of a dual-isotope simulation in a hydrological model, and its application to the lower Nelson River basin. The purpose of this study is to find if the simulation of stable water isotopes aids in hydrological simulation, and if a dual-isotope simulation is an improvement over a single-isotope simulation. The isoWATFLOOD model was enhanced to include δ2H and improve physical representativeness. The model was calibrated using various isotope and flow simulation error functions. Internal hydrologic storages and fluxes were verified by comparing simulated isotope values to observed isotope data. Adding isotope error to the calibration resulted in small but consistent improvements to the physical basis of calibrated parameter values. Isotope simulation error was found to be the best predictor of streamflow simulation performance beyond the calibration period. The dual-isotope simulation identified a number of model limitations and potential improvements from the verification of internal hydrologic storages. / October 2016

The use of stable water isotopes as 18O and 2H are widely used in the last 50 years as tracer in climatic and hydrological studies. Stable water isotopes have slightly different physical properties and require different latent energy for phase changes, so the concentration of water isotopes varies during water phase changes, which is known as fractionation. Specifically in the tropics, the stable water isotopes have a very particular behavior unlike other regions, by the influence of large rainfalls amount, temperature and relative humidity. Cuba is an inland in the middle of the Caribe Sea, where studies about isotopic characterization of precipitations have never been made. In order to understand and explain some issues related to the isotopic behavior of precipitation in this inland, the research work was developed making use of data from that area. The general objective of this research proposal is to characterize the isotopic composition of rainfall in west of Cuba, including the demonstration of the vegetation influence in rainfall isotopic composition, and to determine mathematical models that describe the relationship between rainfall amount, intensity and isotopic composition for future paleoclimatic studies there. Data from the Global Network of Isotopes in Precipitation (GNIP) of the International Atomic Energy Agency (IAEA) were used. Thus, the thesis was developed in three chapters of contents. The first topic addressed was in relation to demonstrate the isotopic fractionation resulting from transpiration by a green canopy. As results, it was shown that transpiration is a fractional process with respect to water isotopes. The magnitude of this fractionation is determined by environmental factors, such as soil water content, rainfall amount, temperature, and the relative humidity. The environmental factors influence the behavior of such important variables as stomatal aperture, the different diffusion resistances, and the kinetic fractionation. Then were proposed eight mathematical models that describes the relationship between rainfall isotopic composition, amount and erosivity for paleoclimatic studies. The trend founded in this research is that months with highest rainfall erosivity were less heavy isotopically. ?2H and ?18O were negatively correlated with erosivity and with the rainfall amount. The rainfall amounts were the higher negative correlation with the isotopic composition for this tropical region. In the third chapter, finally, it was evaluated if even Cuba being an island could be seen the classic effects of the isotopic hydrology as, continentality, rainfall amount and seasonality. As results, rainfalls in western Cuba are in general isotopically enriched in ?18O and ?2H in comparison with other regions at higher latitudes. The annual mean values for ?18O vary between (1 to -8) ? and for ?2H between (15 to -40) ?. Nevertheless, there is marked seasonal behavior, being the rainfalls heavier in winter and more depleted in summer, showing the established patterns for tropical region. The influence of the air masses movement on the rainfall isotopic behavior could be affirming the presence of the continental effect / Isótopos estáveis da água como 18O e 2H foram amplamente utilizados nos últimos 50 anos como traçadores em estudos climáticos e hidrológicos. Os isótopos estáveis da água têm propriedades físicas ligeiramente diferentes, incluindo uma energia latente diferente para as mudanças de fase, de modo que a concentração de isótopos da água se altera em mudanças da fase aquosa, fenômeno conhecido como fracionamento isotópico. Especificamente nos trópicos, os isótopos estáveis da água têm um comportamento muito particular, contrário ao nas regiões temperadas, pela influência dos grandes acumulados da chuva, altas temperaturas e umidade relativa. Cuba é uma ilha no meio do mar Caribe, onde estudos sobre a caracterização isotópica das precipitações nunca foram feitos. Para entender e explicar algumas questões relacionadas ao comportamento isotópico da precipitação nesta ilha, o trabalho de pesquisa foi desenvolvido fazendo uso de dados da área. O objetivo geral desta proposta de pesquisa é caracterizar a composição isotópica das chuvas no oeste de Cuba, incluindo a demonstração da influência da vegetação na composição isotópica da precipitação e determinar modelos matemáticos que descrevem a relação entre a quantidade e intensidade da chuva com a composição isotópica para futuros estudos paleoclimáticos. Para isto foram utilizados dados da Rede Global de Isótopos em Precipitação (GNIP) da Agência Internacional de Energia Atômica (AIEA). Assim, essa tese se apresenta em três capítulos. O primeiro capítulo trata da demonstração do fracionamento isotópico resultante da transpiração através da folha de árvores. A magnitude desse fracionamento é determinada por fatores ambientais, como o teor da água no solo, a quantidade da precipitação, a temperatura e a umidade relativa do ar. Os fatores ambientais influenciam o comportamento de variáveis tão importantes como a abertura estomática, as diferentes resistências de difusão e o fracionamento cinético. No segundo capítulo propõem-se oito modelos matemáticos que descrevem a relação entre a composição isotópica da precipitação, sua quantidade e erosividade, úteis para estudos paleoclimáticos. A tendência encontrada nesta pesquisa é que meses com chuvas mais erosivas foram menos pesadas isotopicamente. Os valores de ?2H e ?18O foram negativamente correlacionados com a erosividade e com os acumulados de precipitação, sendo que os acumulados de precipitação foram os de maior correlação negativa com a composição isotópica nesta região tropical. No terceiro capítulo foi avaliado se em Cuba, uma ilha, podiam ser detectados os efeitos clássicos da hidrologia isotópica. Os valores médios anuais para ?18O variam entre 1 e -8? e para ?2H entre 15 e -40?. No entanto, há um comportamento sazonal marcado, sendo as chuvas isotopicamente mais pesadas no inverno e mais leves no verão, mostrando os padrões estabelecidos para a região tropical. A influência do movimento das massas do ar sobre o comportamento isotópico da chuva pode afirmar a presença do efeito de continentalidade

The use of stable water isotopes as 18O and 2H are widely used in the last 50 years as tracer in climatic and hydrological studies. Stable water isotopes have slightly different physical properties and require different latent energy for phase changes, so the concentration of water isotopes varies during water phase changes, which is known as fractionation. Specifically in the tropics, the stable water isotopes have a very particular behavior unlike other regions, by the influence of large rainfalls amount, temperature and relative humidity. Cuba is an inland in the middle of the Caribe Sea, where studies about isotopic characterization of precipitations have never been made. In order to understand and explain some issues related to the isotopic behavior of precipitation in this inland, the research work was developed making use of data from that area. The general objective of this research proposal is to characterize the isotopic composition of rainfall in west of Cuba, including the demonstration of the vegetation influence in rainfall isotopic composition, and to determine mathematical models that describe the relationship between rainfall amount, intensity and isotopic composition for future paleoclimatic studies there. Data from the Global Network of Isotopes in Precipitation (GNIP) of the International Atomic Energy Agency (IAEA) were used. Thus, the thesis was developed in three chapters of contents. The first topic addressed was in relation to demonstrate the isotopic fractionation resulting from transpiration by a green canopy. As results, it was shown that transpiration is a fractional process with respect to water isotopes. The magnitude of this fractionation is determined by environmental factors, such as soil water content, rainfall amount, temperature, and the relative humidity. The environmental factors influence the behavior of such important variables as stomatal aperture, the different diffusion resistances, and the kinetic fractionation. Then were proposed eight mathematical models that describes the relationship between rainfall isotopic composition, amount and erosivity for paleoclimatic studies. The trend founded in this research is that months with highest rainfall erosivity were less heavy isotopically. ?2H and ?18O were negatively correlated with erosivity and with the rainfall amount. The rainfall amounts were the higher negative correlation with the isotopic composition for this tropical region. In the third chapter, finally, it was evaluated if even Cuba being an island could be seen the classic effects of the isotopic hydrology as, continentality, rainfall amount and seasonality. As results, rainfalls in western Cuba are in general isotopically enriched in ?18O and ?2H in comparison with other regions at higher latitudes. The annual mean values for ?18O vary between (1 to -8) ? and for ?2H between (15 to -40) ?. Nevertheless, there is marked seasonal behavior, being the rainfalls heavier in winter and more depleted in summer, showing the established patterns for tropical region. The influence of the air masses movement on the rainfall isotopic behavior could be affirming the presence of the continental effect / Isótopos estáveis da água como 18O e 2H foram amplamente utilizados nos últimos 50 anos como traçadores em estudos climáticos e hidrológicos. Os isótopos estáveis da água têm propriedades físicas ligeiramente diferentes, incluindo uma energia latente diferente para as mudanças de fase, de modo que a concentração de isótopos da água se altera em mudanças da fase aquosa, fenômeno conhecido como fracionamento isotópico. Especificamente nos trópicos, os isótopos estáveis da água têm um comportamento muito particular, contrário ao nas regiões temperadas, pela influência dos grandes acumulados da chuva, altas temperaturas e umidade relativa. Cuba é uma ilha no meio do mar Caribe, onde estudos sobre a caracterização isotópica das precipitações nunca foram feitos. Para entender e explicar algumas questões relacionadas ao comportamento isotópico da precipitação nesta ilha, o trabalho de pesquisa foi desenvolvido fazendo uso de dados da área. O objetivo geral desta proposta de pesquisa é caracterizar a composição isotópica das chuvas no oeste de Cuba, incluindo a demonstração da influência da vegetação na composição isotópica da precipitação e determinar modelos matemáticos que descrevem a relação entre a quantidade e intensidade da chuva com a composição isotópica para futuros estudos paleoclimáticos. Para isto foram utilizados dados da Rede Global de Isótopos em Precipitação (GNIP) da Agência Internacional de Energia Atômica (AIEA). Assim, essa tese se apresenta em três capítulos. O primeiro capítulo trata da demonstração do fracionamento isotópico resultante da transpiração através da folha de árvores. A magnitude desse fracionamento é determinada por fatores ambientais, como o teor da água no solo, a quantidade da precipitação, a temperatura e a umidade relativa do ar. Os fatores ambientais influenciam o comportamento de variáveis tão importantes como a abertura estomática, as diferentes resistências de difusão e o fracionamento cinético. No segundo capítulo propõem-se oito modelos matemáticos que descrevem a relação entre a composição isotópica da precipitação, sua quantidade e erosividade, úteis para estudos paleoclimáticos. A tendência encontrada nesta pesquisa é que meses com chuvas mais erosivas foram menos pesadas isotopicamente. Os valores de ?2H e ?18O foram negativamente correlacionados com a erosividade e com os acumulados de precipitação, sendo que os acumulados de precipitação foram os de maior correlação negativa com a composição isotópica nesta região tropical. No terceiro capítulo foi avaliado se em Cuba, uma ilha, podiam ser detectados os efeitos clássicos da hidrologia isotópica. Os valores médios anuais para ?18O variam entre 1 e -8? e para ?2H entre 15 e -40?. No entanto, há um comportamento sazonal marcado, sendo as chuvas isotopicamente mais pesadas no inverno e mais leves no verão, mostrando os padrões estabelecidos para a região tropical. A influência do movimento das massas do ar sobre o comportamento isotópico da chuva pode afirmar a presença do efeito de continentalidade