The main goal of this research is to contribute to the understanding of nutrient transport and transformations in soil and its impact on groundwater on a large scale. This thesis specifically integrates the physical, chemical and biochemical nitrogen transport processes with a spatial and temporal Land Surface Scheme (LSS). Since the nitrogen biotransformation kinetics highly depends on soil moisture and soil temperature, a vertical soil nitrogen transport and transformations model was coupled with SABAE-HW. The model provides an improved interface for groundwater modeling to simulate soil moisture and soil temperature for a wide range of soil and vegetation. It is assumed that the main source of organic N is from animal manure. A-single-pool nitrogen transformation is designed to simulate nitrogen dynamics. Thus, the complete mathematical model (SABAE-HWS) is able to investigate the effects of nitrogen biochemical reactions in all seasons. This thesis reports the first field comparison of SABAE-HW using an extensive ten-year data set from BOREAS/BERMS project located in Saskatchewan, Canada. The performance of SABAE-HWS is calibrated and verified using 3 years (2002-2004) data from Carberry site in Canada, Manitoba. The effects of three rates of hog manure application, 2500, 5000, and 7500 gal/acre, was investigated to study the distribution of soil ammonium and soil nitrate within the 120 cm of soil profile. The results clearly showed that there is a good agreement between observed and simulated soil ammonium and nitrate for all treatment at the first two years of study. However, it was found a significant difference between observations and simulations at lower depths for 7500 gal/acre by the end of growing season of 2004. Also, 10 years climate data from OJP site was used to evaluate the effect of manure rates on the distribution of soil nitrate at Carberry site. The results indicated that to minimize the risk of nitrate leaching, the rate of manure application, accumulated soil nitrogen from earlier applications and the atmospheric conditions should be all taken into account at the same time. Comparing the results of SABAE-HWS and SHAW model also showed the importance of the crop growth model in simulating soil NH4-N and NO3-N.

The main goal of this research is to contribute to the understanding of nutrient transport and transformations in soil and its impact on groundwater on a large scale. This thesis specifically integrates the physical, chemical and biochemical nitrogen transport processes with a spatial and temporal Land Surface Scheme (LSS). Since the nitrogen biotransformation kinetics highly depends on soil moisture and soil temperature, a vertical soil nitrogen transport and transformations model was coupled with SABAE-HW. The model provides an improved interface for groundwater modeling to simulate soil moisture and soil temperature for a wide range of soil and vegetation. It is assumed that the main source of organic N is from animal manure. A-single-pool nitrogen transformation is designed to simulate nitrogen dynamics. Thus, the complete mathematical model (SABAE-HWS) is able to investigate the effects of nitrogen biochemical reactions in all seasons. This thesis reports the first field comparison of SABAE-HW using an extensive ten-year data set from BOREAS/BERMS project located in Saskatchewan, Canada. The performance of SABAE-HWS is calibrated and verified using 3 years (2002-2004) data from Carberry site in Canada, Manitoba. The effects of three rates of hog manure application, 2500, 5000, and 7500 gal/acre, was investigated to study the distribution of soil ammonium and soil nitrate within the 120 cm of soil profile. The results clearly showed that there is a good agreement between observed and simulated soil ammonium and nitrate for all treatment at the first two years of study. However, it was found a significant difference between observations and simulations at lower depths for 7500 gal/acre by the end of growing season of 2004. Also, 10 years climate data from OJP site was used to evaluate the effect of manure rates on the distribution of soil nitrate at Carberry site. The results indicated that to minimize the risk of nitrate leaching, the rate of manure application, accumulated soil nitrogen from earlier applications and the atmospheric conditions should be all taken into account at the same time. Comparing the results of SABAE-HWS and SHAW model also showed the importance of the crop growth model in simulating soil NH4-N and NO3-N.

Wind transport and sublimation of snow particles are common phenomena across high altitude and latitude cold regions and play important roles in hydrological and atmospheric water and energy budgets. In spite of this, blowing snow processes have not been incorporated in many mesoscale hydrological models and land surface schemes. A physically based blowing snow model, the Prairie Blowing Snow Model (PBSM), initially developed for prairie environments was used to model snow redistribution and sublimation by wind over two sites representative of mountainous regions in Canada: Fisera Ridge in the Rocky Mountain Front Ranges in Alberta, and Granger Basin in the Yukon Territory. Two models were used to run PBSM: the object-oriented hydrological model, Cold Regions Hydrological Modelling Platform (CRHM) and Environment Canadas hydrological-land surface scheme, Modélisation Environmentale Communautaire Surface and Hydrology (MESH). PBSM was coupled with the snowcover energy and mass-balance model (SNOBAL) within CRHM. Blowing snow algorithms were also incorporated into MESH to create MESH-PBSM. CRHM, MESH and MESH-PBSM were used to simulate the evolution of snowcover in hydrological response units (HRUs) over both Fisera Ridge and Granger Basin.<p> To test the models of blowing snow redistribution and ablation over a relatively simple sequence of mountain topography, simulations were run from north to south over a linear ridge in the Canadian Rocky Mountains. Fisera Ridge snowcover simulations with CRHM were performed over two winters using two sets of wind speed forcing: (1) station observed wind speed, and (2) modelled wind speed from a widely applied empirical, terrain-based windflow model. Best results were obtained when using the site meteorological station wind speed data. The windflow model performed poorly when comparing the magnitude of modelled and observed wind speeds. Blowing snow sublimation, snowmelt and snowpack sublimation quantities were considerably overestimated when using the modelled wind speeds. As a result, end-of-winter snow accumulation was considerably underestimated on windswept HRUs. MESH and MESH-PBSM were also used to simulate snow accumulation and redistribution over these same HRUs. MESH-PBSM adequately simulated snow accumulation in the HRUs up until the spring snowmelt period. MESH without PBSM performed less well and overestimated accumulation on windward slopes and the ridge top whilst underestimating accumulation on lee slopes. Simulations in spring were degraded by a large overestimation of melt by MESH. The early and overestimated melt warrants a detailed examination that is outside the scope of this thesis.<p> To parameterize snow redistribution in a mountain alpine basin, snow redistribution and sublimation by wind were calculated for three winters over Granger Basin using CRHM. Snow transport fluxes were distributed amongst HRUs using inter-HRU snow redistribution allocation factors. Three snow redistribution schemes of varying complexity were evaluated. CRHM model results showed that end-of-winter snow accumulation can be most accurately simulated when the inter-HRU snow redistribution schemes take into account wind direction and speed and HRU aerodynamic characteristics, along with the spatial arrangement of HRUs in the catchment. As snow transport scales approximately with the fourth power of wind speed (u4), inter-HRU snow redistribution allocation factors can be established according to the predominant u4 direction over a simulation period or can change at each time step according to an input measured wind direction. MESH and MESH-PBSM were used to simulate snow accumulation and ablation over these same HRUs. MESH-PBSM provided markedly better results than MESH without blowing snow algorithms.<p> That snow redistribution by wind can be adequately simulated in computationally efficient HRUs over mountainous terrain has important implications for representing snow transport in large-scale hydrology models and land surface schemes. Snow redistribution by wind caused mountain snow accumulation to vary from 10% to 161% of seasonal snowfall within a headwater catchment in the Canadian Rocky Mountains, and blowing snow sublimation losses ranged from 10 to 37% of seasonal snowfall.

Wind transport and sublimation of snow particles are common phenomena across high altitude and latitude cold regions and play important roles in hydrological and atmospheric water and energy budgets. In spite of this, blowing snow processes have not been incorporated in many mesoscale hydrological models and land surface schemes. A physically based blowing snow model, the Prairie Blowing Snow Model (PBSM), initially developed for prairie environments was used to model snow redistribution and sublimation by wind over two sites representative of mountainous regions in Canada: Fisera Ridge in the Rocky Mountain Front Ranges in Alberta, and Granger Basin in the Yukon Territory. Two models were used to run PBSM: the object-oriented hydrological model, Cold Regions Hydrological Modelling Platform (CRHM) and Environment Canadas hydrological-land surface scheme, Modélisation Environmentale Communautaire Surface and Hydrology (MESH). PBSM was coupled with the snowcover energy and mass-balance model (SNOBAL) within CRHM. Blowing snow algorithms were also incorporated into MESH to create MESH-PBSM. CRHM, MESH and MESH-PBSM were used to simulate the evolution of snowcover in hydrological response units (HRUs) over both Fisera Ridge and Granger Basin.<p> To test the models of blowing snow redistribution and ablation over a relatively simple sequence of mountain topography, simulations were run from north to south over a linear ridge in the Canadian Rocky Mountains. Fisera Ridge snowcover simulations with CRHM were performed over two winters using two sets of wind speed forcing: (1) station observed wind speed, and (2) modelled wind speed from a widely applied empirical, terrain-based windflow model. Best results were obtained when using the site meteorological station wind speed data. The windflow model performed poorly when comparing the magnitude of modelled and observed wind speeds. Blowing snow sublimation, snowmelt and snowpack sublimation quantities were considerably overestimated when using the modelled wind speeds. As a result, end-of-winter snow accumulation was considerably underestimated on windswept HRUs. MESH and MESH-PBSM were also used to simulate snow accumulation and redistribution over these same HRUs. MESH-PBSM adequately simulated snow accumulation in the HRUs up until the spring snowmelt period. MESH without PBSM performed less well and overestimated accumulation on windward slopes and the ridge top whilst underestimating accumulation on lee slopes. Simulations in spring were degraded by a large overestimation of melt by MESH. The early and overestimated melt warrants a detailed examination that is outside the scope of this thesis.<p> To parameterize snow redistribution in a mountain alpine basin, snow redistribution and sublimation by wind were calculated for three winters over Granger Basin using CRHM. Snow transport fluxes were distributed amongst HRUs using inter-HRU snow redistribution allocation factors. Three snow redistribution schemes of varying complexity were evaluated. CRHM model results showed that end-of-winter snow accumulation can be most accurately simulated when the inter-HRU snow redistribution schemes take into account wind direction and speed and HRU aerodynamic characteristics, along with the spatial arrangement of HRUs in the catchment. As snow transport scales approximately with the fourth power of wind speed (u4), inter-HRU snow redistribution allocation factors can be established according to the predominant u4 direction over a simulation period or can change at each time step according to an input measured wind direction. MESH and MESH-PBSM were used to simulate snow accumulation and ablation over these same HRUs. MESH-PBSM provided markedly better results than MESH without blowing snow algorithms.<p> That snow redistribution by wind can be adequately simulated in computationally efficient HRUs over mountainous terrain has important implications for representing snow transport in large-scale hydrology models and land surface schemes. Snow redistribution by wind caused mountain snow accumulation to vary from 10% to 161% of seasonal snowfall within a headwater catchment in the Canadian Rocky Mountains, and blowing snow sublimation losses ranged from 10 to 37% of seasonal snowfall.

The South Saskatchewan River Basin (SSRB) is amongst the largest watersheds in Canada. It is an ecologically diverse region, containing Montane Cordillera, Boreal Plains and Prairie ecozones. The SSRB is subject to chinooks, which bring strong winds, high temperatures and humidity deficits that alter the storage of water during winter. Approximately 40% of winter days experience chinooks. Ablation during chinooks has not been quantified; it is not known how much water evaporates, infiltrates or runs off. The aim of this thesis is to characterise the spatial variability of surface water fluxes as affected by chinooks over SSRB subbasins and ecozones. The objectives are addressed using detailed field observations and physically based land surface modelling. Eddy covariance was deployed at three prairie sites. During winter chinooks, energy for large evaporative fluxes were provided by downward sensible heat fluxes. There was no evidence of infiltration until March. The Canadian Land Surface Scheme (CLASS) coupled to the Prairie Blowing Snow Model (PBSM) was used as the modelling platform. A multi-physics version of CLASSPBSM was developed, consisting of two parameterisation options each for sixteen processes. Field observations were used to evaluate each of the configurations. Three parameterisations provide both best snow and best soil water simulations: iterative energy balance solution, air temperature and wind speed based fresh snow density and de Vries’ soil thermal conductivity. The model evaluation highlighted difficulties simulating evaporation and uncertainty in simulating infiltration into frozen soils at large scales. A single model configuration is selected for modelling the SSRB. Modelling showed that the SSRB generally experiences no net soil water storage change until March, confirming field observations. Chinooks generally reduce net terrestrial water storage, largely due to snowmelt and subsequent evaporation and runoff. The Prairie ecozone is that which is most strongly affected by chinooks. The Montane Cordillera ecozone is affected differently by chinooks; blowing snow transport increases during winter and runoff increases during spring. The Lower South Saskatchewan is the subbasin most affected by chinooks. The Red Deer is the subbasin least affected by chinooks.

L'objectif de la thèse est de développer un albédo de surface journalier pronostique dans les modèles météorologiques et d’évaluer son impact pour le bilan d'énergie et l'hydrologie dans la plate-forme de modélisation SURFEX sur le domaine France. En premier lieu, un albédo climatologique est à ce jour considéré dans SURFEX. Il est analysé dans cette étude par rapport aux albédos quotidiens de SEVIRI et MODIS dont ce dernier est obtenu à partir d'une méthode originale que l'on valide. Ensuite, une méthode est développée pour obtenir des albédos du sol et de la végétation de façon séparée à la fois statiquement, donc sur une base climatologique, puis dynamiquement en s'appuyant sur plusieurs années de données du satellite MODIS. Une fois réglé l'albédo du sol journalier, il est recherché une calibration avec l'humidité du sol nu à l'aide des données du réseau de stations sol SMOSMANIA du sud-ouest de la France. Il est montré que l'on peut prédire l'évolution de l'albédo de surface, par comparaison avec les observations spatiales avec l'humidité seule dans la limite d'une végétation faiblement couvrante. Cet albédo simulé est complété par celui de la végétation seule à partir d'une paramétrisation simplifiée du code de transfert radiatif PROSAIL. L'approche théorique est validée avec les données du site de Majadas pour lequel on montre que l'on sait simuler le cycle d'évolution de l'albédo total avec prise en compte de la chlorophylle au niveau de la feuille. En dernier lieu, il a été réalisé une étude d'impact du nouveau albédo évolutif sur le bilan d'énergie et l'hydrologie dans SURFEX sur la France. Il est aussi mis en place une assimilation de l'albédo conjointement avec l'indice foliaire et l'humidité superficielle, ce qui a des effets positifs pour le cas des végétations qui ne sont pas trop denses. / The main objective of the thesis is to develop a prognostic surface albedo of the visible spectrum and near infrared and assess its impact on the energy balance and hydrology in the modelling platform of SURFEX. First, a statistical approach has generated a global climate albedo product at 0.05 ° for bare soil and vegetation using multiple years 8 -day MODIS onboard TERRA and AQUA satellites heliosynchronous data. Then, an original method has been developed to reduce temporal resolution of MODIS 500m albedo to daily. The result is validated against in situ measurements as well as daily albedo from geostationary satellite MSG / SEVIRI Land SAF project after projection of MODIS. Then a method of separating albedo of bare soil and vegetation is applied to the datasets of the two satellite systems. Using a threshold of vegetation cover, a calibration of the albedo bare soil with measured soil moisture is derived from 2007 to 2010 for 12 SMOSMANIA stations over southwestern France. We derived a parameterization of the albedo of bare soil with moisture to make the climate changing albedo. The albedo and simulated happens to be very well correlated with observations from space, which helps to explain the albedo variations at very short notice. To change seasonally albedo, a simple parameterization of canopy albedo derived from detailed radiative transfer code PROSAIL is used. The variables are the albedo of the sheet, canopy geometry and chlorophyll content. In order to be sensitive to chlorophyll, the study is based on an albedo at 560 nm. The theoretical approach is validated with MODIS satellite data for the site Majadas (Spain). The next step is to conduct an impact study of this new predictive albedo on the energy balance and hydrology within SURFEX over France and highlighting effects on temperature. More preliminary restricted to a SMOSMANIA station, an assimilation scheme is developed for surface albedo together with the leaf area index LAI and surface moisture. This effects an improvement in the prescribed LAI at the beginning of crop growth.

La partie centrale de la chaîne himalayenne présente d’importantes hétérogénéités, en particulier en termes de topographie et de climatologie. La caractérisation des processus hydro-climatiques dans cette région est limitée par le manque de descriptif des milieux. La variabilité locale est alors difficilement représentée par les modélisations mises en œuvre à une échelle régionale.L’approche proposée dans ce travail est de caractériser les systèmes hydro-climatiques à l’échelle locale pour réduire les incertitudes liées à l’hétérogénéité du milieu. L’intégration de données localement précises est testée pour la modélisation de bassins versants peu instrumentés et fortement hétérogènes.Deux sous-bassins du bassin de la Dudh Koshi (Népal) sont utilisés comme échantillons représentatifs des milieux de haute et moyenne montagne, hors contribution glaciaire. Le schéma de surface ISBA est appliqué à la simulation des réponses hydrologiques des types de surface décrits à partir d’observations de terrain. Des mesures de propriétés physiques des sols sont intégrées pour préciser la paramétrisation des surfaces dans le modèle. Les données climatiques nécessaires sont interpolées à partir des observations in situ disponibles. Une approche non déterministe est appliquée pour quantifier les incertitudes liées à l’influence de la topographie sur les précipitations, ainsi que leur propagation aux variables simulées. Enfin, les incertitudes liées à la structure des modèles sont évaluées à l’échelle locale à travers la comparaison des paramétrisations et des résultats de simulation obtenus d'une part avec le schéma de surface ISBA, couplé à un module de routage à réservoir et d'autre part avec le modèle hydrologique J2000. / The central part of the Hindukush-Himalaya region presents tremendous heterogeneity, in particular in terms of topography and climatology. The representation of hydro-climatic processes for Himalayan catchments is limited due to a lack of knowledge regarding their hydrological behavior. Local variability is thus difficult to characterize based on modeling studies done at a regional scale. The proposed approach is to characterize hydro-climatic systems at the local scale to reduce uncertainties associated with environmental heterogeneity.The integration of locally reliable data is tested to model sparsely instrumented, highly heterogeneous catchments. Two sub-catchments of the Dudh Koshi River basin (Nepal) are used as representative samples of high and mid-mountain environments, with no glacier contribution. The ISBA surface scheme is applied to simulate hydrological responses of the surfaces that are described based on in-situ observations. Measurements of physical properties of soils are integrated to precise surface parametrization in the model. Necessary climatic data is interpolated based on available in-situ measurements. A non deterministic approach is applied to quantify uncertainties associated with the effect of topography on precipitation and their propagation through the modeling chain. Finally, uncertainties associated with model structure are estimated at the local scale by comparing simulation methods and results obtained on the one hand with the ISBA model, coupled with a reservoir routing module, and on the other hand, with the J2000 hydrological model.