The spatial distribution and properties of rainfed orchards in semi-arid environments result from complex interactions between man and the physical and economical environment. This thesis investigates a number of these interactions in the context of the mechanisation of management practices since the 1950's. It is shown how the practice of clean sweeping (i.e. frequent shallow tillage) influences the orchard water balance and how the removal of traditional soil and water conservation structures affects the connectivity of overland flow to the river system. Although clean sweeping prevents transpiration and competition by weeds, it also constrains the root growth in the plough layer, so that the trees cannot access the water from small rain events. In addition, clean sweeping promotes accelerated soil erosion. It appears that the practice of clean sweeping limits the water availability in orchards on loamy soils with an annual rainfall in the order of 300 mm. It is demonstrated that the presence and properties of rainfed orchards are related to spatial patterns of soil characteristics and climate. The observed decline in conservation structures like terraces and check-dams leads to an increase in the connectivity of water and sediment to the river system. An alternative for these traditional techniques to retain the water and the soil is the application of cover crops. The advantage of cover crops is that they do not limit the field size. A drawback in dry areas is the competition for water and nutrients between the cover crop and the trees. Field evidence and water balance simulations suggest that cover crops are feasible in areas with an annual precipitation of 500 mm or more.

The spatial distribution and properties of rainfed orchards in semi-arid environments result from complex interactions between man and the physical and economical environment. This thesis investigates a number of these interactions in the context of the mechanisation of management practices since the 1950's. It is shown how the practice of clean sweeping (i.e. frequent shallow tillage) influences the orchard water balance and how the removal of traditional soil and water conservation structures affects the connectivity of overland flow to the river system. Although clean sweeping prevents transpiration and competition by weeds, it also constrains the root growth in the plough layer, so that the trees cannot access the water from small rain events. In addition, clean sweeping promotes accelerated soil erosion. It appears that the practice of clean sweeping limits the water availability in orchards on loamy soils with an annual rainfall in the order of 300 mm. It is demonstrated that the presence and properties of rainfed orchards are related to spatial patterns of soil characteristics and climate. The observed decline in conservation structures like terraces and check-dams leads to an increase in the connectivity of water and sediment to the river system. An alternative for these traditional techniques to retain the water and the soil is the application of cover crops. The advantage of cover crops is that they do not limit the field size. A drawback in dry areas is the competition for water and nutrients between the cover crop and the trees. Field evidence and water balance simulations suggest that cover crops are feasible in areas with an annual precipitation of 500 mm or more.

Developing critical loads for nitrogen (N) in the Athabasca Oil Sands Region (AOSR) requires an understanding of the hydrological connectivity and potential for N transport among uplands, fens and bogs typical in the wetland-rich Boreal region of northern Alberta. The Cumulative Environmental Management Association’s (CEMA) overarching mandate is to determine a nitrogen critical load specific to the Boreal region of northern Alberta. To this end, nitrogen amendment experiments were initiated at two Boreal wetland sites: an upland – rich fen gradient at Jack Pine High (JPH) and an upland – fen – bog mosaic at Mariana Lakes (ML), 45 km north and 100 km south of Fort McMurray respectively. The objectives of this study are to use geochemical and isotopic tracers to describe baseline hydrogeochemical variability and connectivity between bog, fens and upland areas in the AOSR. Sites were instrumented with piezometer nests and water table wells along transects that cover the targeted landscape units (n = 108 sampling locations). Fieldwork related to this thesis was conducted during the open-water season: in June and August 2011, and in May, July, and September 2012. Field campaigns also included a snow survey (March 2012), and spring melt/freshet sampling (April 2012). The analysis of spatiotemporal variability of water isotopes and geochemistry in the years 2011-2012 yielded: i) a characterization of baseline conditions from which perturbations can be assessed, and ii) evidence of connectivity among landscape units. No evidence for elevated concentrations of nitrogen related to the amendment experiments was found in 2011 or 2012. The baseline characterization and annual monitoring did show increasing concentrations of inorganic ammonium with increasing depth associated with increasing solute concentrations: average concentrations of inorganic ammonium were 23 mg/L at deepest sampling locations (7 m) at ML bog and ML fen landscape units. These ammonium concentrations in porewaters, given a porosity of 0.90 for peatlands, constitute a store of ammonium that may be a significant source of nitrogen if the hydrology is altered due to co-occurring changes in vegetation (due to, for example, elevated nitrogen inputs), climate and/or landuse. Hydrologic connectivity at JPH is likely driven by topography. Hydraulic head in 2011 and 2012 field seasons showed that flow persisted from the upland to the fen. The consistent and distinct geochemical signatures and isotopic labelling of mid-depth and deep groundwater samples of fen and upland landscape units is consistent with such a stable groundwater continuum. Near-surface water samples at JPH fen however varied hydrogeochemically in response to seasonal changes in precipitation inputs, water levels, and biogeochemical productivity. At ML, hydrological connectivity is a function of antecedent moisture conditions (which determines run-off) and low and variable (10-6 to 10-9 m/s) hydrological conductivity of the peatland substrate (which may result in lateral flow where hydraulic head shows potential for vertical re- or discharge). Near-surface samples showed greater temporal than spatial variability as snowmelt inputs, variations in antecedent moisture conditions and seasonal changes in biogeochemical process rates affected nutrient and solute concentrations. In contrast, shallow, mid-depth and deep samples showed greater spatial than temporal variability. The spatial distributions of parameters could be associated to some degree with vegetation, distance along a surficial flowpath, or depth to mineral substrate or distance from the upland/edge transition. / Graduate / 0996 / 0388 / 0425 / cbkusel@yahoo.ca

Developing critical loads for nitrogen (N) in the Athabasca Oil Sands Region (AOSR) requires an understanding of the hydrological connectivity and potential for N transport among uplands, fens and bogs typical in the wetland-rich Boreal region of northern Alberta. The Cumulative Environmental Management Association’s (CEMA) overarching mandate is to determine a nitrogen critical load specific to the Boreal region of northern Alberta. To this end, nitrogen amendment experiments were initiated at two Boreal wetland sites: an upland – rich fen gradient at Jack Pine High (JPH) and an upland – fen – bog mosaic at Mariana Lakes (ML), 45 km north and 100 km south of Fort McMurray respectively. The objectives of this study are to use geochemical and isotopic tracers to describe baseline hydrogeochemical variability and connectivity between bog, fens and upland areas in the AOSR. Sites were instrumented with piezometer nests and water table wells along transects that cover the targeted landscape units (n = 108 sampling locations). Fieldwork related to this thesis was conducted during the open-water season: in June and August 2011, and in May, July, and September 2012. Field campaigns also included a snow survey (March 2012), and spring melt/freshet sampling (April 2012). The analysis of spatiotemporal variability of water isotopes and geochemistry in the years 2011-2012 yielded: i) a characterization of baseline conditions from which perturbations can be assessed, and ii) evidence of connectivity among landscape units. No evidence for elevated concentrations of nitrogen related to the amendment experiments was found in 2011 or 2012. The baseline characterization and annual monitoring did show increasing concentrations of inorganic ammonium with increasing depth associated with increasing solute concentrations: average concentrations of inorganic ammonium were 23 mg/L at deepest sampling locations (7 m) at ML bog and ML fen landscape units. These ammonium concentrations in porewaters, given a porosity of 0.90 for peatlands, constitute a store of ammonium that may be a significant source of nitrogen if the hydrology is altered due to co-occurring changes in vegetation (due to, for example, elevated nitrogen inputs), climate and/or landuse. Hydrologic connectivity at JPH is likely driven by topography. Hydraulic head in 2011 and 2012 field seasons showed that flow persisted from the upland to the fen. The consistent and distinct geochemical signatures and isotopic labelling of mid-depth and deep groundwater samples of fen and upland landscape units is consistent with such a stable groundwater continuum. Near-surface water samples at JPH fen however varied hydrogeochemically in response to seasonal changes in precipitation inputs, water levels, and biogeochemical productivity. At ML, hydrological connectivity is a function of antecedent moisture conditions (which determines run-off) and low and variable (10-6 to 10-9 m/s) hydrological conductivity of the peatland substrate (which may result in lateral flow where hydraulic head shows potential for vertical re- or discharge). Near-surface samples showed greater temporal than spatial variability as snowmelt inputs, variations in antecedent moisture conditions and seasonal changes in biogeochemical process rates affected nutrient and solute concentrations. In contrast, shallow, mid-depth and deep samples showed greater spatial than temporal variability. The spatial distributions of parameters could be associated to some degree with vegetation, distance along a surficial flowpath, or depth to mineral substrate or distance from the upland/edge transition. / Graduate / 0996 / 0388 / 0425 / cbkusel@yahoo.ca

A drainage basins runoff response can be determined by the connectivity of generated runoff to the stream network and the connectivity of the downstream stream network. The connectivity of a drainage basin modulates its ability to produce streamflow and respond to precipitation events and is a function of the complex and variable storage capacities along the drainage network. An improved means to measure and account for the dynamics of hydrological connectivity at the basin scale is needed to improve prediction of basin scale streamflow. The overall goal of this thesis is to improve the understanding of hydrological connectivity at the basin scale by measuring hydrological connectivity at the Baker Creek Research Basin during 2009. To this end, the objectives are to 1) investigate the dynamics of hydrological connectivity during a typical water year, 2) define the relationship between the contributing stream network and contributing area, 3) investigate how hydrological connectivity influences streamflow, and 4) define how hydrological connectivity influences runoff response to rainfall events. At a 150 km2 subarctic Precambrian Shield catchment where the poorly-drained heterogeneous mosaic of lakes, exposed bedrock, and soil filled areas creates variable contributing areas, hydrological connectivity was measured between April and September 2009 in 10 sub-basins with a particular focus on three representative sub-basins. The three sub-basins, although of similar relative size, vary considerably in the dominant typology and topology of their constituent elements. At a 10 m spatial resolution, saturated areas were mapped using both multispectral satellite imagery and in situ measurements of storage according to land cover. To measure basin scale hydrological connectivity, the drainage network was treated as a graph network with stream reaches being the edges that connect sub-catchment nodes. The overall hydrological connectivity of the stream network was described as the ratio of actively flowing relative to potentially flowing stream reaches, and the hydrological connectivity of the stream network to the outlet was described as the ratio of actively flowing stream reaches that were connected to the outlet relative to the potentially flowing stream reaches. Hydrological connectivity was highest during the spring freshet but the stream network began to disintegrate with its passing. In some drainage basins, large gate keepers were able to maintain connectivity of the stream network downstream during dry periods. The length of the longest stream was found to be proportional to contributing area raised to a power of 0.605, similar to that noted in Hacks Law and modified Hacks Law relationships. The length of the contributing stream network was also found to be proportional to contributing area raised to a power of 0.851. In general, higher daily average streamflows were noted for higher states of connectivity to the outlet although preliminary investigations allude to the existence of hysteresis in these relationships. Elevated levels of hydrological connectivity were also found to yield higher basin runoff ratios but the shape of the characteristic curve for each basin was heavily influenced by key traits of its land cover heterogeneity. The implications of these findings are that accurate prediction of streamflow and runoff response in a heterogeneous drainage basin with dynamic connectivity will require both an account of the presence or absence of connections but also a differentiation of connection type and an incorporation of aspects of local function that control the flow through connections themselves. The improved understanding of causal factors for the variable streamflow response to runoff generation in this environment will serve as a first step towards developing improved streamflow prediction methods in formerly glaciated landscapes, especially in small ungauged basins.

A drainage basins runoff response can be determined by the connectivity of generated runoff to the stream network and the connectivity of the downstream stream network. The connectivity of a drainage basin modulates its ability to produce streamflow and respond to precipitation events and is a function of the complex and variable storage capacities along the drainage network. An improved means to measure and account for the dynamics of hydrological connectivity at the basin scale is needed to improve prediction of basin scale streamflow. The overall goal of this thesis is to improve the understanding of hydrological connectivity at the basin scale by measuring hydrological connectivity at the Baker Creek Research Basin during 2009. To this end, the objectives are to 1) investigate the dynamics of hydrological connectivity during a typical water year, 2) define the relationship between the contributing stream network and contributing area, 3) investigate how hydrological connectivity influences streamflow, and 4) define how hydrological connectivity influences runoff response to rainfall events. At a 150 km2 subarctic Precambrian Shield catchment where the poorly-drained heterogeneous mosaic of lakes, exposed bedrock, and soil filled areas creates variable contributing areas, hydrological connectivity was measured between April and September 2009 in 10 sub-basins with a particular focus on three representative sub-basins. The three sub-basins, although of similar relative size, vary considerably in the dominant typology and topology of their constituent elements. At a 10 m spatial resolution, saturated areas were mapped using both multispectral satellite imagery and in situ measurements of storage according to land cover. To measure basin scale hydrological connectivity, the drainage network was treated as a graph network with stream reaches being the edges that connect sub-catchment nodes. The overall hydrological connectivity of the stream network was described as the ratio of actively flowing relative to potentially flowing stream reaches, and the hydrological connectivity of the stream network to the outlet was described as the ratio of actively flowing stream reaches that were connected to the outlet relative to the potentially flowing stream reaches. Hydrological connectivity was highest during the spring freshet but the stream network began to disintegrate with its passing. In some drainage basins, large gate keepers were able to maintain connectivity of the stream network downstream during dry periods. The length of the longest stream was found to be proportional to contributing area raised to a power of 0.605, similar to that noted in Hacks Law and modified Hacks Law relationships. The length of the contributing stream network was also found to be proportional to contributing area raised to a power of 0.851. In general, higher daily average streamflows were noted for higher states of connectivity to the outlet although preliminary investigations allude to the existence of hysteresis in these relationships. Elevated levels of hydrological connectivity were also found to yield higher basin runoff ratios but the shape of the characteristic curve for each basin was heavily influenced by key traits of its land cover heterogeneity. The implications of these findings are that accurate prediction of streamflow and runoff response in a heterogeneous drainage basin with dynamic connectivity will require both an account of the presence or absence of connections but also a differentiation of connection type and an incorporation of aspects of local function that control the flow through connections themselves. The improved understanding of causal factors for the variable streamflow response to runoff generation in this environment will serve as a first step towards developing improved streamflow prediction methods in formerly glaciated landscapes, especially in small ungauged basins.

Linkages between the controls on depressional storage and catchment streamflow response were examined in a wetland dominated basin in the Canadian Prairie Pothole region through a combination of field monitoring and modelling. Snowmelt, surface storage, water table elevation, atmospheric fluxes, and streamflow were monitored during spring snowmelt and summer in a 1 km2 sub-catchment containing a semi-permanent pond complex connected via an intermittent stream. Snow accumulation in the basin in spring of the 2013 study year was the largest in the 24-year record. Rainfall totals in 2013 were close to the long term average, though June was an anomalously wet month. The water budget of the pond complex indicates that there was a significant subsurface contribution to surface storage, in contrast to previous studies in this region. Following snowmelt, subsurface connectivity occurred between uplands and the stream network due to activation of the effective transmission zone in areas where the water table was located near the ground surface, allowing significant lateral movement of water into the stream network. Modelling results suggest there was significant infiltration into upland soils during the study period and that upland ponds are an important consideration for accurately simulating catchment discharge. The flux of groundwater to the wetland complex during periods of subsurface connectivity was also important for maintaining and re-establishing surface connectivity and streamflow. As the observed period of surface and subsurface hydrological connectivity was one of the longest on record in the catchment due to very wet conditions, the results of this study denote observations of the wet extremes of the hydrological regime important for proper understanding, modelling, and prediction of streamflow in the region.

Au cours des deux derniers siècles, le Rhône a connu de fortes modifications de son régime hydrologique et de sa dynamique fluviale, aboutissant à une diminution drastique de la diversité structurelle et fonctionnelle des habitats, à la fois sur le fleuve et ses marges. Un programme de restauration ambitieux du fleuve a ainsi été lancé à la fin des années 1990. Cette thèse s'inscrit dans le suivi des travaux de restauration, entrepris entre 1999 et 2006, sur 18 chenaux latéraux. Elle se fonde sur l'analyse croisée de mesures in situ de la granulométrie du substrat, des épaisseurs de lames d'eau et de sédiments fins dans les chenaux latéraux, de données topographiques et hydrologiques ainsi que d’acquisitions photographiques aéroportées. Nous disposons de données avant travaux pour 12 chenaux latéraux et de 3 à 7 campagnes de mesures post-travaux, couvrant de 5 à 15 années. Afin d'évaluer l'ajustement des conditions hydromorphologiques, la diversité fonctionnelle et la pérennité des chenaux latéraux en tant qu'habitats aquatiques, l'étude s'appuie sur des statistiques et de la modélisation à portée prédictive. Nous démontrons que les patrons granulométriques et les vitesses d'accumulation des alluvions fines peuvent être relativement bien estimés à partir de descripteurs de l'hydrodynamisme des écoulements de crue dans les bras dépendant de leur géométrie (fréquence de connexion amont, contrainte de cisaillement et capacité de reflux). Les relations statistiques empiriques établies indiquent qu'il est possible d'estimer, a priori, l’effet de la modification de la géométrie des bras restaurés sur les patrons granulométriques et la quantité de fines qui s’y déposent. La durée de vie potentielle des bras est également estimée à partir des données acquises et discutée en fonction de différents modèles tendanciels. A l’issue de ces analyses, des outils opérationnels sont ainsi proposés, permettant de guider les futures opérations de restauration de ce type sur le Rhône. / Over the past two centuries, the hydrological regime and the fluvial dynamics of the Rhône River have been highly modified, leading to a drastic decrease in the structural and functional habitat diversity of the main river channel and floodplains. An ambitious restoration project was initiated at the end of the 1990's. This thesis deals with the monitoring of 18 floodplain channels, which were restored between 1999 and 2006. We combined analysis based on grain size of deposits, fine sediment thicknesses, water depth, topographical and hydrological data and airborne imagery. We used pre-restoration data for 12 floodplain channels coupled with between three and seven post-restoration surveys for each channel, ranging from 5 to 15 years after restoration. To assess the adjustment of hydromorphological conditions, the physical functional diversity and the persistence of floodplain channels as aquatic habitats, we used statistical analysis and a modeling approach that allowed us to forecast conditions. Results demonstrate that both (i) grain size patterns and (ii) fine sediment accumulation rates can be predicted using simple hydrologic and/or hydraulic descriptors (upstream overflow frequency, shear stress, back-flowing capacity), which reflect the control exerted by the geometry of floodplain channels on their flooding regime (upstream overflow frequency, shear stress and backflow capacity). Such empirical statistical relationships can be used a priori to estimate the potential effects of different floodplain channel geometries on the propensity to accumulate fine sediment and the grain sizes of this sediment. Estimates of potential ranges of floodplain channel life spans are provided and discussed according to multiple trend models. This research has direct application and provides tools to river managers that will help guide this type of floodplain channel restoration design in the future on the Rhône River.

Submitted by Renata Lopes (renatasil82@gmail.com) on 2016-05-31T15:37:55Z No. of bitstreams: 1 lucianarabelodearaujo.pdf: 3777751 bytes, checksum: f71885f2bbf7188c5613e7ece870e07f (MD5) / Rejected by Adriana Oliveira (adriana.oliveira@ufjf.edu.br), reason: primeira letra de cada palavra chave em maiúsculo on 2016-07-02T12:46:13Z (GMT) / Submitted by Renata Lopes (renatasil82@gmail.com) on 2016-07-04T10:27:45Z No. of bitstreams: 1 lucianarabelodearaujo.pdf: 3777751 bytes, checksum: f71885f2bbf7188c5613e7ece870e07f (MD5) / Approved for entry into archive by Adriana Oliveira (adriana.oliveira@ufjf.edu.br) on 2016-07-13T16:13:25Z (GMT) No. of bitstreams: 1 lucianarabelodearaujo.pdf: 3777751 bytes, checksum: f71885f2bbf7188c5613e7ece870e07f (MD5) / Made available in DSpace on 2016-07-13T16:13:25Z (GMT). No. of bitstreams: 1 lucianarabelodearaujo.pdf: 3777751 bytes, checksum: f71885f2bbf7188c5613e7ece870e07f (MD5) Previous issue date: 2012-02-27 / Poças adjacentes em ambientes aquáticos costeiros podem servir como refúgio para organismos em condições ambientais desfavoráveis, desde que haja conexão hidrológica entre os sistemas. Neste trabalho, foram avaliados os fatores estruturadores e a importância da hidroconectividade para comunidades zooplanctônicas de 3 lagoas salinas e 15 poças adjacentes localizadas em Quissamã/RJ, e o papel do banco de ovos de resistência na recolonização de uma lagoa costeira. Amostras da comunidade e das variáveis ambientais foram coletadas no período de um ano (Maio 2010 – Fevereiro 2011) e o banco de ovos foi coletado em agosto de 2010 no sistema Garça. Através de uma NMS utilizando o índice de similaridade de Bray-Curtis, as poças mostraram ser mais similares entre si do que com as lagoas, independente do período (seca ou chuva). Uma RDA mostrou que a salinidade e o pH foram os principais fatores estruturadores das comunidades. O cálculo da diversidade beta evidenciou que as poças apresentaram uma menor turnover temporal. No sistema Garça, as poças apresentaram bancos de ovos mais ricos que a lagoa, e 45% das espécies registradas na comunidade ativa da lagoa foram registradas exclusivamente nas poças. Embora as lagoas e suas poças não tenham sido mais similares no período chuvoso, a conectividade parece ter uma grande importância, devido à presença de espécies dulcícolas nas lagoas nos períodos mais chuvosos, encontradas também nas poças. Este fato, além da menor diversidade beta exibida pelas poças sugere que a dispersão não é limitante, possivelmente formando uma metacomunidade. A alta contribuição da comunidade ativa e dormente das poças para a comunidade ativa da lagoa da Garça mostra o potencial destes ambientes na manutenção e recolonização da comunidade zooplanctônica deste sistema. / Small-sized pools next to coastal lakes may serve as refuge for organisms during unfavorable environmental conditions in the lakes, due to sporadic connections between all aquatic systems. We assessed the importance of environmental variables and of the hydrological connectivity for the structure of zooplankton communities in three saline lagoons and 15 adjacent pools from Brazil. We also evaluated the role of the resting egg bank in the recolonization of the zooplankton community in one coastal lagoon. Zooplankton and environmental variables were collected during one year (2010–2011) and the resting egg bank was collected in August 2010 in the Garça system. NMS analyses using a Bray-Curtis index showed that the pools were more similar between each other than between the lagoons, regardless of the season (dry or rainy). A RDA showed that salinity and pH were the main structuring factors of communities in all lagoon systems. The beta-diversity index demonstrated that the lagoons had a higher temporal turnover. In the Garça system, the pools showed richer egg banks than the lagoon and 45% of the species recorded in the lake’s active community were founded in the pools. Although lagoons and pools were not more similar in the rainy season, the connectivity seems to have a major role due to the presence of freshwater species in the lakes, that were also found in the pools. This fact, plus the lower beta diversity showed by pools suggest that dispersal is not limited. The high contribution of the active and dormant communities of the pools for Garça lake’s active community shows the potential of these environments in the maintenance and recolonization of zooplankton community in this system.

Excess nitrogen (N) from terrestrial landscapes poses environmental challenges as it moves via surface runoff and groundwater flows into aquatic ecosystems. Managing and anticipating the environmental challenges associated with these altered N inputs from terrestrial to aquatic ecosystems requires a deep understanding of how N is biogeochemically transformed, retained, and/or transported in streams and rivers. Here, I used long-term data on surface stream and groundwater chemistry as well as discharge to determine the main sources of N and estimate the N mass balance of a 1.4 km boreal stream reach. The goal was to evaluate daily net uptake or production rates of different N forms (ammonium - NH4-N, nitrate NO3-N and dissolved organic N - DON) throughout the seasons, and assess physical and chemical factors that may drive changes in net processing. The mass balances analysis revealed distinct patterns in net uptake among N forms. Notably, there was clear evidence of NH4-N and DON uptake (removal) in the stream, while NO3-N processing patterns showed neither clear uptake nor production. Further, variation in net uptake for NH4-N and DON was positively related to stream DOC, DOC:DIN, and C:N ratios, indicating that carbon rich conditions promoted greater N demand in this ecosystem. By comparison, variations in net NO3-N uptake or production at the reach scale were only weakly correlated with these carbon rich conditions. Finally, I assessed these patterns within the nutrient processing domains (NPDs) framework to characterize the behavior/character of the study reach. Accordingly, during the open water season, the stream reach acted mostly as a consumer for both NH4-N and DON, while on many dates it acted as a weak enhancer for NO3-N. These findings contribute to the broader understanding of N dynamics in boreal stream ecosystems and emphasize the complex interplay among organic and inorganic N forms, carbon dynamics, and nutrient processing in these environments. This knowledge is crucial for effective environmental management and conservation efforts in the region.