Best or beneficial management practices (BMPs) are often relied upon as a mitigation strategy for nitrate contamination throughout Canada. At a regional scale, reducing the quantity of nutrients applied to agricultural land is one BMP approach that has been implemented internationally. While these BMP strategies have been proven to successfully reduce the environmental impact of agriculture on water systems, the time interval between BMP implementation and a noticeable improvement in groundwater quality can be quite extensive. This lag time has been observed at the agriculturally impacted Thornton Well Field in Oxford County. Despite seven years of significant reductions in fertilizer application within the capture zone of this municipal well field, declining nitrate concentrations have yet to be observed in the production water wells. In order to accelerate nitrate reductions at the Thornton Well Field, an integrated approach, combining BMPs with a stimulated in situ denitrification strategy, was implemented. This research focused on the use of a cross-injection scheme to stimulate in situ denitrification within the production aquifer units, up-gradient of the Thornton Well Field. Briefly, this strategy involves injecting a carbon source and electron donor into a high flux aquifer zone using an injection and extraction system positioned perpendicular to the regional flow field. Through altering the geochemical conditions, the injections stimulate indigenous bacteria to reduce harmful nitrate to innocuous dinitrogen gas. The main objectives of this research included: characterizing the hydrogeologic and geochemical properties of the target aquifer; pilot scale testing of the proposed in situ denitrification system; and suggesting an approach for up-scaling to a full-scale treatment scheme capable of remediating the elevated nitrate concentrations at the Thornton Well Field. Core logging, electrical resistivity studies, several methods of hydraulic characterization, tracer testing, and three-dimensional groundwater modelling were used to quantify the physical properties of the target aquifer and to develop a hydrogeologic conceptual model of the site. The aquifer unit was found to be unconfined in the experiment vicinity, consisting of a complex system of six main hydrostratigraphic layers of sand and gravel featuring variable hydraulic conductivity (K) values. Despite the hydrogeologic complexity, the geochemical properties of the aquifer were relatively uniform with depth. Anion, cation, alkalinity, pH, dissolved oxygen, and nitrous oxide data all contributed to this conjecture. Of particular interest, however, were the elevated dissolved oxygen concentrations, which rivalled atmospheric saturation throughout the entire aquifer sequence. The background physical and chemical characterization identified two main challenges that would potentially influence the performance of the in situ denitrification process: stimulating uniform denitrification in the fast flowing, complex aquifer system and overcoming the elevated oxygen concentrations to achieve the necessary anaerobic conditions. Following the initial site characterization phase, several preliminary cross-injection experiments were designed and performed. These experiments featured an injection-extraction circulation cycle which spanned five metres and was operated normal to groundwater flow. Acetate was selected as the electron donor and carbon substrate. The first test involved a single acetate injection followed by an extensive period of groundwater sampling. Unfortunately, this initial test provided no indication of stimulated in situ denitrification. All anion, cation, and nitrous oxide concentration and isotope data collected during and following this injection remained within the range of background estimates. Following the first injection experiment, a subsequent test involving multiple, repetitive acetate injections was implemented to overcome the highly aerobic nature of the aquifer and support the growth and reproduction of denitrifying bacterial populations. The second injection phase included 19 individual injections that were operated at intervals of every day to every other day over a total period of 26 days. These injections successfully lowered the dissolved oxygen concentrations within the target aquifer to an average range of 0 to 4 mg/L. The least conductive layers featured the lowest oxygen concentrations, while the higher K layers maintained elevated oxygen concentrations. The nitrite, nitrate, and enriched NO3-15N and NO3-18O isotope data suggested a high degree of stimulated denitrification in the least conductive layers and a limited degree in the high-K layers. The lower-K units corresponding to multi-level well ports ML7-2, ML7-5, and ML7-6 achieved a 46 percent reduction in nitrate, while the layer represented by ML7-1 attained a 100 percent reduction in nitrate. Alternatively, due to the constant influx of dissolved oxygen and limited residence times, very little denitrification was observed in the fast flowing layers corresponding to ports ML7-3, ML7-4, and ML7-7. Overall, a percent reduction, in terms of nitrate mass crossing the 5-m wide treatment lens, of only eleven percent was calculated. These results clearly demonstrate that the K-profile had a significant impact on stimulating in situ bioremediation. Two major system challenges were observed, including an inability to successfully stimulate denitrification within the highly permeable layers and the generation of harmful nitrite at nearly all aquifer depths. Based on these significant challenges, it was concluded that additional experimentation is required before this remediation technique can be expanded to a full-scale in situ treatment scheme. The most significant recommendation requested the development and execution of a third injection phase, consisting of multiple, consecutive substrate injections designed to systematically test various pulsing intervals, injection concentrations, and electron donors. Despite the current limitations, this approach has great potential. It is believed that with additional research, the in situ stimulation of denitrification could be used to successfully reduce the elevated nitrate concentrations at the Thornton Well Field.

Thesis (Ph. D.)--University of Queensland, 2002. / Includes bibliographical references.

Warren County, Kentucky is located south of the southern boundary of the Rough Creek Graben marked by the Pennyrile fault system. The Pennyrile fault system is a regional southwest-northeast trending fault system that extends into Kentucky from the Reelfoot rift zone. The Rough Creek fault system bounds the northern arm of the Rough Creek Graben and trends northwest-southeast also extending from the Reelfoot rift zone. The Rough Creek fault system is related to the Shawneetown fault system in southeastern Illinois and occupies the southern end of the Illinois Basin. The East Continent Rift Basin intersects the Rough Creek Graben near its Eastern terminus and is parallel and west of the Grenville front. The structure under investigation in this paper was discovered west of the town of Woodburn, Kentucky. In 1992, West Bay Exploration Company of Michigan conducted a seismic survey of the Woodburn area and produced a series of two-dimensional profiles of the subsurface extending down to the Precambrian basement. Analysis of these profiles revealed a number of 'pop-ups' or possible wrench-related structures that can be traced upward through faulting from the Precambrian basement through the Knox Group and into the Mississippian section. Recent analysis of well log, seismic, and Radar images indicate extensive faulting in the Woodburn area indicative of wrench-fault related activity. A convincing surface expression of the deeper structure can be discerned from Radar imaging, aeromagnetic, and topographic maps of the region. An anomalous concentration of sinkholes is also visible from topographic maps and is aligned parallel to the curvature of the wrench structure on its western, southern, and eastern flanks. Wrench faults and associated structures are known to be productive traps for petroleum. West Bay Exploration Company of Traverse City Michigan drilled the subject structure in 1993 but the borehole test proved negative. Nonetheless, a detailed analysis of the subsurface using GIS and related software should aid in developing a prospecting tool for exploration geologists and aid in understanding the characteristic geologic sections of the Rough Creek Graben.

Soil moisture is a measure of the water content in a soil that is dependent upon precipitation, evapotranspiration, runoff, drainage, and irrigation. Nebraska is one of the few states that measures soil moisture in an extensive network that records weather variables on a daily basis. Daily soil moisture observations are collected from depths of 10, 25, 50, and 100 centimeters and analyzed in this research. Data from these stations are evaluated on the spatial and temporal scales using spatial interpolations, time-series analysis, and cross-correlations to better understand the variations of soil moisture in the Northern Great Plains. Spatial interpolation grids were created for May through October of 2005, after the data were grouped into datasets of weekly, biweekly, and monthly observations. These datasets were imported into a Geographic Information System (GIS) and the Ordinary Kriging method was applied for spatial interpolation. The interpolation parameters were set to create output surfaces of 4x4, 16x16, 32x32, and 64x64 kilometer grids for analysis of their variations. As expected, it is found that soil moisture content is higher in southeastern Nebraska and lower in the northwest. Changes in the grid size render small scale variations, however, the general pattern of estimated soil moisture distribution does not change. The temporal analysis concluded that the soil's physical properties have a much greater effect on soil moisture than a station's location within the east-west moisture gradient. Sandy soils were consistently drier, while silt and clay soils retained water for a longer duration. The topmost layer of soil experiences the greatest variation due to interactions with the surface boundary layer. The highest water content values for silty soils were observed in the summer months, while the highest values for sandy soils were observed in the spring and fall months. The most soil moisture variation occurs in the summer and fall, while the least amount of variation occurs in spring and winter. Cross-correlations, measuring the time-lag relationship, demonstrated the impact of soil physical properties on soil moisture by depth, the influence of precipitation on 10 and 25 cm depth soil moisture, and the impact of near-surface soil moisture on maximum surface temperature. A stronger relationship was observed between soil moisture and maximum surface temperatures than with precipitation and soil moisture at various depths.

Despite the fact that asymmetries in hurricanes, such as spiral rainbands, polygonal eyewalls and mesovortices, have long been observed in radar imagery, many aspects of their dynamics still remain unsolved, particularly in the formation of the secondary eyewall. To fill this gap, a simple 2D barotropic "dry" model and the high-resolution PSU-NCAR non-hydrostatic mesoscale model (MM5) are used to study hurricane asymmetries. The Empirical Normal Mode (ENM) and the newly developed Space-Time Empirical Normal Mode (ST-ENM) techniques, together with Eliassen-Palm (EP) flux calculations, are used to extract wave modes from the model generated datasets to investigate their impact on the changes in the structure and intensity of the simulated hurricanes. From the ENM diagnostics of the 2D simulations, it is shown how an incipient storm described by a vortex monopole intensifies by "inviscid damping" of a "discrete-like" vortex Rossby wave (VRW) or quasimode. The critical radius, the structure, and the propagating properties of the quasimode are found to be consistent with predictions of the linear eigenmode analysis of small perturbations. The fastest growing wavenumber-4 unstable VRW modes of a vortex ring reminiscent of a mature hurricane are extracted and their relation with the polygonal eyewalls, mesovortices, and the asymmetric eyewall contraction established. When asymmetric disturbances are placed outside a strong vortex ring with a large vorticity skirt they relax to form concentric rings of enhanced vorticity that contain a secondary wind maximum. The role of internal dynamics on Concentric Eyewall Genesis (CEG) is further evaluated using the full physics MM5 / La présence d'asymétries dans les ouragans est un phénomène connu et observé depuis plusieurs années. Par exemple, les bandes de pluie spirales, les murs de l'oeil polygonaux et les méso-vortexes ont été observés à maintes reprises à l'aide d'imagerie radar. Par contre, plusieurs aspects de leur dynamique restent incompris. En particulier, nous nous intéressons à l'apparition de yeux secondaires. A fin d'étudier ce phénomène, un simple modèle barotrope 2D "sec" ainsi que le modèle PSU-NCAR méso-échelle nonhydrostatique (MM5) sont utilisés pour étudier les asymétries des ouragans. Lors de l'analyse des données du modèle, la technique de Modes Normaux Empiriques (MNE) et, celle plus récente, de Modes Normaux Empiriques Espace-Temps (MNE-ET) sont utilisées conjointement avec le calcul de flux Eliassen-Palm (EP) afin d'isoler les modes d'ondes et étudier leur impact sur le changement de structure et d'intensité des ouragans simulés. L'analyse MNE des simulations 2D a montré qu'un orage naissant décrit par un tourbillon monopole s'intensifie grâce au "freinage inviscide" d'une onde de Rossby sur un tourbillon (ORT) "quasi-discret" ou quasimode. Le rayon critique, la structure, ainsi que les propriétés de propagation du quasimode sont consistants avec les prédictions de l'analyse linéaire des modes propres pour de petites perturbations. Le mode instable avec le nombre d'onde 4 à plus forte croissance a été identifié. Il correspond aux modes ORT instables d'un anneau de tourbillon réminiscent d'un ouragan mature. Les liens entre ces modes et le mur de l'oeil polygonal, le méso-vortex, ainsi que la contraction asymétrique du mur de$

Crop production in Brazil has changed significantly over the last decade. New crops are being cultivated to satisfy the world's growing demand for Brazilian export products —a demand that has caused substantial changes in land use and cover, mainly characterized by the increase in large-scale mechanization of agriculture, deforestation, and intensification of agricultural land use. Brazil currently provides crop production information at the municipality level. This information was analyzed using Geographic Information Systems (GIS) to examine changes in the spatial distribution of the production of various crops and livestock in Brazil for 1990-2006. In addition, to better understand the relationship between agricultural expansion and deforestation, spatial data on agricultural expansion and deforestation over the Legal Amazon were statistically analyzed for 2000-2006. The results indicate that changes in the spatial patterns of crops have indeed taken place in central and northeastern Brazil as well as in the southern Amazon region. The areas to crops such as soybean and sugarcane expanded, surpassing the total area planted to domestic food crops, which, in turn, recorded a significant decrease in area. This crop expansion has exerted pressure on other crops and livestock, pushing them further into the Amazon forest region during 1990-2006. In the same period, pasture was the predominant land use in the Legal Amazon; however, results indicate that the area planted to soybean increased whereas the area under pasture decreased. Statistical analyses revealed that, in those areas with over 50% forest, deforestation was strongly related to agricultural expansion. Defore / La production agricole du Brésil a changé significativement durant la dernière décennie. De nouvelles cultures ont été adoptées afin de répondre à la croissance de la demande mondiale pour des produits d'exportation brésiliens – une demande qui a occasionné des changements substantiels au niveau de l'utilisation et de la couverture du sol, principalement caractérisés par l'accroissement à large échelle de la mécanisation de l'agriculture, de la déforestation et de l'intensification de l'agriculture. Le Brésil met à disposition de l'information concernant la production agricole au niveau municipal. Cette information a été analysée par le biais d'un Système d'Information Géographique (SIG) afin d'étudier les changements dans la distribution spatiale de la production de différentes cultures et d'élevage au Brésil de 1990 à 2006. De plus, afin de mieux comprendre la relation entre l'expansion agricole et la déforestation, des données spatiales ont été analysée statistiquement pour l'Amazone Légale pour une période allant de 2000 à 2006. Les résultats indiquent que des changements dans les patrons spatiaux ont en effet pris place au centre et au nord-est du Brésil ainsi qu'au sud de la région amazonienne. Les zones prévues pour cultiver le soja et la canne-à-sucre ont augmenté, surpassant même les surfaces semées pour des cultures vivrières qui ont par ailleurs enregistrées une diminution significative. L'extension de ces cultures a exercé une pression sur les autres cultures et sur les élevages bovins, les poussant à l'intérieur de la forêt amazonienne durant la période 1990-2006. Au cours de la même période, alors q

Little is known about clouds during drought. In 1999-2005 the Canadian Prairies experienced one of the most severe and prolonged droughts in its climatological record. The objective of this study is to characterize and better understand clouds and their associated radiative properties during drought in the Canadian Prairie Provinces with a particular focus on this recent drought. Drought severity was determined using the Standardized Precipitation Index. Cloud properties from NASA/GEWEX's Surface Radiation Budget data base were used to examine overall cloud amount, optical thickness, and top-of-the-atmosphere albedo. It was found that, although cloud amounts differ slightly from dry to wet conditions (approximately a 10% increase in cloud cover fraction from 63% when severely dry to 73% when severely wet), the correlation with precipitation is weak. The occurrence of thin clouds increased as drought severity increased, whereas medium thickness clouds and thick clouds decreased. Similar trends were found to pertain at smaller scales. / Très peu est connu a propos des nuages durant une sècheresse. Entre 1999 et 2005, les Prairies canadiennes ont vécu une des sècheresses les plus sévères et les plus longues dans ses registres climatologiques. L'objectif de cette étude est de caractériser et de mieux comprendre les nuages et leurs propriétés radiatives durant les sècheresses dans les provinces des Prairies canadiennes. Une attention particulière a été donnée à cette récente sècheresse. La sévérité de la sècheresse a été déterminée avec l'index standardise de précipitations. Les propriétés des nuages obtenues de la base de données du Budget Radiatif de Surface de NASA/GEWEX ont été utilisées pour examiner l'ensemble de la quantité de nuage, l'épaisseur optique et l'albédo du haut de l'atmosphère. Les résultats ont démontré que malgré une légère différence dans la quantité de nuage entre des périodes sèches et humide (une augmentation d'environ 10% dans la couverture nuageuse de 63% durant des conditions extrêmement sèches a 73% pendant des périodes extrêmement humide), la corrélation avec la précipitation est faible. Les nuages minces augmentent lorsque la sévérité de la sècheresse augmente, alors que les nuages d'épaisseur moyenne ou épaisse diminuent. Les résultats ont aussi démontré que des tendances similaires se rapportent à plus petite échelle.

While significant attention has been given to understanding the initiation mechanisms of convective storms over mountainous terrain, far less has been given to the factors controlling their subsequent evolution. Here we perform an observational and numerical investigation of the evolution of convective storms initiated by the Black Hills mountains of South Dakota. These Hills are preferentially located within the United States to access moist, unstable air, and are thus a local hot-spot for convection initiation. Applying a convective-celltracking algorithm to 53 observed events initiated by the Black Hills revealed three types of storm evolution: short-lived, short-track cells; long-lived, short-trackcells; and long-lived, long-track cells. Analysis of the background wind profiles during each event revealed modest differences amongst the storm types, which were tested using quasi-idealized, convection-permitting numerical simulations. The track-lengths and durations of convective cells produced in these simulations were consistent with those in our observed events, demonstrating that these modest differences in background wind profile could indeed largely explain a convective storm's evolution. / Bien que beaucoup d'attention a été accordée à la compréhension des mécanismes d'initiation des tempêtes convectives sur un terrain montagneux, beaucoup moins a été mis sur les facteurs qui contrôlent leur évolution ultérieure. Ici, nous effectuons une enquête observationelle et numérique des tempêtes initiées par les montagnes Black Hills du South Dakota. Ces montagnes initient beaucoup de convection grace à leur accès à l'air humide et instable. L'application d'un algorithme suivant les pistes de 53 tempêtes initiés par les Black Hills a révélé trois types d'évolution: tempête de courte-piste, courte-durée; tempête de courte-piste, longue-durée; et tempête de longue-piste, longue-durée. Un analysis des profils de vents pendant chaque événement a révélé de légères differences entre les types de tempêtes, qui ont été testés par des simulations numériques. Les longueurs de piste et les durées des tempêtes produites dans ces simulations étaient similaires à celles des événements observés, ce qui démontre que ces légères différences dans les profils de vent pourraient en effet expliquer l'évolution de chaque type de tempête.

Located in southern Quebec, at the northeastern extremity of Lake Champlain, the Missisquoi Bay is subject to eutrophication arising from excess nutrients, predominantly phosphorus (P), contributed by agricultural runoff. Land use patterns, agronomic practices, soil properties, and geomorphology have an impact on soil P. Studies have used hydrologic models [e.g., the Soil and Water Assessment Tool (SWAT)] to characterize P loadings from the region's agricultural watersheds. The lack of a proper understanding of the impact of spatial variability and heterogeneity of soil properties on the prediction of runoff, sediment and nutrient movement has proven a major challenge. In order to overcome this, field surveys, spatial variability characterization of P through geostatistics, heterogeneity quantification and hydrologic modeling using SWAT were undertaken. An extensive geostatistic study of soil properties was followed by the use of SWAT to predict runoff, sediment and total phosphorus (TP). Soil surveys carried out in the summers of 2011 and 2012 measured soils physical and chemical properties. Variogram analysis characterized the spatial variability of soil test phosphorus (STP). Ordinary kriging (OK) was used to estimate STP values at unsampled locations. Due to OK's smoothing effect, some high value areas were underestimated, while some low areas were overestimated. Compared to OK, sequential Gaussian simulation (SGS) helped characterize the uncertainty and provides better estimates at non-sampled locations. Areas above the STP threshold at which P has the potential to move to freshwater after precipitation events, combined with topographic factors, were identified. The uncertainty in variogram parameters (sill, nugget and range) was characterized using a Bayesian Hierarchical framework, aiding in understanding the complexity and heterogeneity in the STP dataset attributable to land use patterns. The Posterior mean and 95% credible confidence intervals of the variogram parameters and STP values were developed. An Independent Component Analysis (ICA) technique, which overcame the problem of matrix inversion in co-simulation, served in the decomposition of spatially-correlated geochemical variables. This implementation was tested on three correlated variables: magnesium, calcium and iron. The measured soil properties required by SWAT were regionalized and clustered using a Regionalization with Constrained Clustering and Partitioning (REDCAP) algorithm. Five maps were created based on 5, 10, 15, 20 and 24 part partitioning. Each of these maps had different measures of heterogeneity and each was used as inputs for five different configurations of SWAT. Mean monthly flow, sediment and total P load from April 2001 to December 2002 were used to assess model performance before and after calibration. Overall, there was no significant difference in runoff simulation between any of the five map configurations, which might be due to the impacts of the SCS-CN (soil conservation service-curve number) method in simulating runoff. In the study watershed, using a higher resolution (number of regions) of soil data did not improve predictions of monthly streamflow, sediment or TP. / Situé dans le sud du Québec, à l'extrémité nord-est du Lac Champlain, la Baie Missisquoi est sujette à une eutrophisation attribuable à un excès d'éléments nutritifs, principalement le phosphore (P), provenant du ruissellement agricole. L'utilisation des terres, les pratiques agronomiques, les propriétés du sol et la géomorphologie influencent la teneur en P du sol. Employant des modèles hydrologiques tel le Soil and Water Assessment Tool (SWAT), une série d'études ont déjà servi à caractériser les charges en P provenant des bassins versants agricoles de la région. Une compréhension inadéquate de l'impact de la variabilité spatiale et de l'hétérogénéité des propriétés du sol sur la prédiction du ruissellement et du déplacement des sédiments et éléments nutritifs, rend la tâche difficile. Afin de surmonter cette difficulté, des relevés sur le terrain, une caractérisation de la variabilité spatiale du P par géostatistique, une quantification de son hétérogénéité, et une modélisation hydrologique avec SWAT furent entrepris. Une étude géostatistique approfondie des propriétés du sol fut suivie par l'utilisation de SWAT pour prédire le ruissellement, et les charges en sédiment et phosphore total (TP). Des relevés pédologiques entrepris durant les étés de 2011 et 2012 permirent de mesurer les propriétés physiques et chimiques des sols. Une analyse par variogramme caractérisa la variabilité spatiale de la teneur en P du sol (TSP). Le krigeage ordinaire (OK) servit à l'estimation de la TSP à des sites non-échantillonnés. Etant donné l'effet de lissage de l'OK, certaines valeurs élevées furent sous-estimées, tandis que certaines petites valeurs furent surestimées. Comparé au OK, la simulation séquentielle gaussienne (SSS) permit d'évaluer l'incertitude et fournit de meilleures estimations pour les sites non-échantillonnées. Les régions en deçà du seuil auquel le P a le potentiel de se déplacer jusqu'au cours d'eau après une pluie, et les facteurs topographiques qui y sont liés furent identifiés. L'incertitude des paramètres de variogramme (palier, pépite et portée) fut évaluée dans un cadre hiérarchique bayésien, permettant une analyse plus approfondie de la complexité et de l'hétérogénéité des données de TSP pouvant être attribués à l'utilisation des terres. Des moyennes a posteriori, avec intervalle de crédibilité de 95%, furent générées pour les paramètres de variogramme et les valeurs de TSP. Une technique d'analyse en composantes indépendantes (ICA), surmonta le problème d'inverser une matrice lors de la co-simulation, et servit à la décomposition de variables géochimiques corrélées dans l'espace. Cette méthode fut éprouvée pour trois variables corrélées, soit le magnésium, le calcium et le fer. Les propriétés du sol mesurées et requises par SWAT furent régionalisées et groupe en utilisant un algorithme de régionalisation avec groupement et partitionnement sous contraintes (REDCAP). Cinq cartes furent crées selon que le territoire fut partitionné en 5, 10, 15, 20 ou 24 parties. Chacune de ces cartes différa en son hétérogénéité, et chacune servit comme donnée d'entrée à une configuration particulière de SWAT. Les débits moyens mensuels et les charges en sédiment et phosphore totales mesurés entre avril 2001 et décembre 2002 servirent à évaluer la performance du modèle avant et après son étalonnage. Le fait qu'aucune des cinq configurations (partitions de la carte d'entrée) du modèle ne se démarqua, s'explique par le fait que la méthode des numéros de courbe du Soil Conservation Service, servant à simuler le ruissellement, ne permet pas de retenir de petites mais importantes différences des propriétés physiques des sols. Dans le bassin versant étudié, l'utilisation d'une résolution (nombre de régions) plus élevée avec le modèle SWAT n'améliora ni la prédiction des débits moyens mensuels, ni celle des charges en sédiment et phosphore total.

As climate change continues to drive glacier retreat in the Cordillera Blanca, Peru, the fraction of dry season runoff derived from groundwater baseflow is increasing. Therefore, it is necessary to improve our understanding of proglacial hydrogeology to forecast how groundwater can offset decreasing meltwater resources. Unfortunately, little is known about high-elevation groundwater, the physical hydrogeological properties of aquifers, or contributions to stream flows in the Cordillera Blanca, Peru. This thesis addresses these knowledge gaps and presents the results from a groundwater investigation of two glaciated watersheds in the Cordillera Blanca during the July 2012 dry season. Investigative techniques include drilling with a portable drill, slug tests to measure permeability, and hydrochemical mixing model analysis. In the Llanganuco Pampa, glaciofluvial outwash and glacial till aquifers were identified with hydraulic conductivities of 10-4 and 10-5 m/s and groundwater flow velocities of 0.62 and 0.09 m/day, respectively. In the Quilcayhuanca Pampa, a buried talus aquifer was identified with an average hydraulic conductivity of 10-5 m/s and an average groundwater flow velocity of 0.10 m/day. The buried talus aquifer extended across the valley and was hydraulically connected to recent talus slope deposits along the valley side. Talus slopes are ubiquitous features in the Cordillera Blanca and the results presented here show that they are a significant pathway for groundwater recharge of valley aquifers and springs. Tracers from surface water and groundwater samples were used in a binary mixing model to estimate tributary and groundwater contributions to stream flow. Groundwater contributions to stream flow were 18% in the Llanganuco Upper Pampa and 21% in the Quilcayhuanca Pampa. These results suggest that discharge from the studied valley aquifers are a crucial component of dry season stream flow in the Cordillera Blanca. Further research is still needed to identify and quantify the sources of groundwater recharge (i.e. precipitation, glacial meltwater, and/or bedrock fracture flow) to better understand the ability of groundwater to buffer dry season flows in the context of melting glaciers. / Pendant que le retrait des glaciers de la Cordillera Blanca, Pérou, se poursuit à cause des changements climatiques, la part des eaux de ruissèlement provenant du débit de base des eaux souterraines augmente durant la saison sèche. Par conséquent, il est nécessaire d'améliorer nos connaissances en hydrogéologie périglaciaire afin de prévoir comment les eaux souterraines peuvent compenser la diminution des ressources en eaux de fontes. Malheureusement, les propriétés physico-hydrogéologiques des eaux souterraines de hautes altitudes, ainsi que leur contribution à l'écoulement des cours d'eau de la Cordillera Blanca, Pérou, sont très largement incomprises. Cette thèse présente les résultats de l'étude des eaux souterraines dans deux bassins versants de la Cordillera Blanca, menée en juillet 2012 durant la saison sèche. Pour se faire, les techniques d'investigation incluent des forages à la foreuse portative, des essais de perméabilité et des analyses de modèles hydrogéochimiques de mélange. Dans la Pampa Llanganuco, Il a été évalué que les aquifères d'épandages fluvio-glaciaires et de tills glaciaires atteignent respectivement des conductivités hydrauliques de 10-4 et 10-5 m/s et des vitesses d'écoulement d'eaux souterraines de 0.62 et 0.09 m/jour. Dans la Pampa Quilcayhuanca, le système aquifère de talus a été identifié avec, en moyenne, une conductivité hydraulique de 10-5 m\s et une vitesse d'écoulement d'eaux souterraines de 0.10 m/jour. Ce système s'étend à travers la vallée tout en étant hydrauliquement relié aux récents dépôts de débris rocheux le long des flancs. Les résultats présentés ici montrent l'omniprésence des dépôts de débris rocheux dans la Cordillera Blanca ainsi que leur importance dans la recharge des aquifères et des sources de la vallée. Les traceurs dans les échantillons d'eaux de surface et d'eaux souterraines ont été utilisés dans un modèle mixte à deux composantes pour estimer la contribution des affluents et des eaux souterraines dans l'écoulement du cours d'eau principal. La contribution des eaux souterraines à l'écoulement du cours d'eau était de 18% dans la Pampa Llanganuco et 21% dans la Pampa Quilcayhuanca. Ces résultats suggèrent que les eaux souterraines, provenant des aquifères des vallées, représentent une part importante de l'écoulement des cours d'eau durant la saison sèche dans la Cordillera Blanca. De plus amples recherches sont cependant nécessaires pour identifier et quantifier les sources de recharge en eaux souterraines (précipitations, eaux de fontes glaciaires et/ou écoulement dans les fractures du substrat rocheux) afin de mieux comprendre la capacité des eaux souterraines à entretenir l'écoulement des cours d'eau durant la saison sèche dans le contexte de la fonte des glaciers.