The aims of this theses were (i) to evaluate trends in spring yields in the Czech Republic (period 1971-2007) and trends in runoff from small forested catchments of the GEOMON network during the period 1994-2011, (ii) evaluate the impact of climate change on streamwater chemistry in acid-sensitive catchment (Lysina), and (iii) estimate the impact of anticipated climate change projected according to different CO2 emission scenarios on flow patterns forested (GEOMON) and alpine headwater (Skalnaté Lake) catchments in the periods 2021-2050 and 2071-2100. Significant negative trends on the annual level were observed at 18% of springs while positive trends at only less than 0.5% of 157 tested objects and 4 of 18 regions revealed significant decreasing trend. To these regions belonged the zones of Carpathian Cretaceous and Paleogene sediments in the southeast and northeast of the Czech Republic, the zones of tertiary and Cretaceous basins in the southeast and Proterozoic and Paleozoic crystalline rocks in the central part of the Czech Republic. Most spring yields were decreasing within the summer months June- August (on average 24%) and least between February and April (on average 15%) (Paper I). There were no general patterns found indicating either significant increases or decreases in runoff on either...

>Magister Scientiae - MSc / Many countries in sub-Sahara African region are characterised by crystalline basement aquifers where groundwater explorations are often described as complex. This is because groundwater availability in such aquifers is largely a consequence of the interaction of several processes related to groundwater process [recharge-flow-discharge process], underlying geological features and fracture connectivity of the aquifer rock matrix. At a local scale, crystalline basement aquifers are heterogeneous and anisotropic due to fractures, geological structures and discontinuities including varying hydraulic characteristics which need to be understood. The lack of detailed investigations of site-specific conditions to assess influence on groundwater recharge process limits implementation of initiatives for groundwater abstraction that supports environment and socio-economic projects. / 2023

Riparian zones are increasingly being adopted as best management practices (BMPs) to control nonpoint source pollution. The effectiveness of these zones in mitigating pollution is a function of the distribution, nature, and rate of water and sediment movement through these zones. The intent of this research was to investigate the influence of site conditions on the hydrologic and sediment transport response of riparian zones/hillslopes. Research investigations were focused in two major areas: field investigations of riparian hillslopes and development of a riparian hillslope model. The objective of the field investigations was to characterize and quantify geomorphic features of riparian slopes that can be used to quantify flow concentration on hillslopes. The riparian hillslope model was used to investigate the dynamics of hydrologic and sediment transport processes. Field investigations revealed that riparian hillslopes were dissected into distinct convergent, divergent, or straight slope segments. In profile, these segments were either concave, straight, or convex. It was hypothesized that the size of such segments reflects the "representative hillslope scale". Probability distributions of catchment area showed that catchment area decreases with slope gradient. Distributions of catchment shape revealed that catchment shape elongates with increasing gradient. Distributions of drainage channel cross-sectional shape data showed a decreasing trend in width to depth ratio with increasing slope gradient. These results indicate that geomorphic features characterizing flow concentration vary with slope gradient and should not be neglected when simulating riparian hillslopes. Model simulations revealed that site conditions such as slope gradient, slope shape, flow concentration, and soil horizon thickness and characteristics play a significant role in shaping the hydrologic and sediment phenomena on these hillslopes. These results underscore the need for evaluation of riparian zones considering specific site conditions. Interflow was the dominant hillslope runoff mechanism. A large fraction of the interflow occurred via macropores. Macropore flow was orders of magnitude quicker than soil matrix flow. Overland flow was found to occur primarily due to saturation excess or return flow. Simulations showed that thinning of soil layers and/or concave-convergent slope shapes provide favorable conditions for generation of saturation excess or return flow. Sediment delivery down the slope increased with increasing flow concentration. / Ph. D.

The rapid expansion of urban systems in both area and population represents the most significant landuse/landcover change occurring in the world today. Urbanization is often accompanied by increasing environmental degradation. This degradation is related to stormwater runoff, air temperatures greater than surrounding rural areas, increased air and water pollution, losses of vegetated lands, and lack of access to sufficient and healthy foods in lower-income areas. Urban agriculture (UA), a practice long established in previous eras but neglected for many decades, can mediate such concerns by providing greenspaces to improve ecosystem services. Successful practice of UA requires recognition of interactions between social and environmental patterns. Neglect of these interactions leads to failure in spatially integrating social and environmental dimensions of the urban landscape, limiting the success of UA. This study investigates siting of UA within Roanoke, Virginia, a compact urban region characterized by social and environmental conditions that can be addressed by effective siting and practice of UA. This research takes a broader perspective than prior studies on UA and urban greenspaces. It proposes innovative applications of geospatial technologies for urban assessment. Studies on UA have typically focused on food insecurity, while studies on greenspaces focus on parks and tree canopy cover, without investigating interactions that promote synergies between these two efforts. Research over the past few years is now recognizing potential contributions for urban agriculture to alleviate environmental issues such as stormwater runoff, soil infertility, and the urban heat island effect. Little of this research has been devoted to the actual siting of urban agriculture to specifically alleviate both socio-economic and environmental issues. This research applies geospatial technologies to evaluate spatial patterns characterizing both environmental and socio-economic disparities within the City of Roanoke, Virginia. This approach has identified specific locations that are open and available for urban agriculture, and has appraised varying levels of socio-economic and environmental parameters. This research identified, at the census block group level, areas with varying levels of degradation. Thus, those locations in which a new urban agriculture greenspace can contribute to both socio-economic and environmental reparation. This research has identified spatial dimensions in which UA will assist in restoring ecosystem services to guide various food production activities. These results can be generalized to other urban locations and contribute to efficient use of urban land and space, improving the three pillars of worldwide sustainability – economic, environment, and social. / Ph. D.

Dissolved organic matter (DOM) is present in all forested catchments and can be important in binding metals, absorbing UV, and the transport of nutrients (C, N, S, P). DOM is extremely heterogeneous in time and space, making it difficult to characterize. New techniques have been developed to determine δ34S and δ18O in DOM. These techniques have been applied to samples from Harp and Plastic Lake catchments (45??23'N, 79?? 08'W, 45??11'N, 78?? 50'W) in order to obtain information about sources and sinks of DOM within forested catchments on the Canadian Shield. In conjunction with sulphate and DOC concentrations, this new data provides valuable insight into sulphur cycling and DOM alteration within these catchments. Data generated for δ34S-DOM and δ18O-DOM appears to be the first data reported in the literature for DOM. The inorganic (δ34S-SO42-) and organic S (δ34S-DOM) differs by environment in both catchments. The range of δ34S-SO42- is between 3. 3‰ and 10. 3‰, and the range of δ34S-DOM is from 3. 4‰ to 8. 7‰. Sulphate in the Harp Lake catchment in most samples is subject to some sort of cycling within the watershed, since δ34S-SO42- differs from precipitation. In the Harp Lake catchment, upland δ34S-SO42- is influenced by historical precipitation. The δ34S-DOM is derived from leaching and microbial activity of DOM from organic horizons in the soil. The δ34S-SO42- and δ34S-DOM of wetland streams is extremely variable, controlled by hydrology. The δ34S-SO42- provides information on oxidation-reduction dynamics in the wetland, and δ34S-DOM provides information about sources of DOS in the wetland. The δ34S-SO42- and δ34S-DOM are possibly related in Harp Lake. Mineralization of DOS as evidenced by δ34S-DOM and DOS concentrations could be a small input of SO42- into Harp Lake. It is possible δ18O-DOM could be an indicator of DOM alteration. The range of δ18O-DOM is between 8. 2‰ and 14. 4‰. The δ18O-DOM in the Harp Lake catchment is highly correlated with relative molecular weight, which has been shown to decrease with increasing alteration. Wetland streams show the largest range in δ18O-DOM, while uplands, groundwater, and Harp Lake are the least varied. The highest δ18O-DOM values are from sources of DOM such as leaf leachates (representative of forest floor litter) and wetlands. The most depleted samples are from groundwater and Harp Lake which typically contain highly altered DOM. The δ34S-DOM and δ18O-DOM can provide valuable information on sources of DOM and DOM alteration within the catchment. The δ18O-DOM could also allow the separation of autochthonous and allochthonous DOM in lakes.

La prévision des crues est un exercice hydrologique complexe : les incertitudes y sont nombreuses, aussi bien dans le processus de modélisation hydrologique, dans la détermination de l'état initial du bassin versant avant le lancement de la prévision, que dans l'évolution des conditions météorologiques futures. Dans le cas des bassins versants non jaugés, où les observations de débits sont lacunaires voire absentes, ces incertitudes sont encore plus importantes, et le besoin de les réduire devient incontournable. Cette thèse s'intéresse à des méthodes simples et robustes qui peuvent apporter de l'information pertinente pour quantifier les incertitudes de prévision dans les bassins versants non jaugés. Le but est d'étudier la meilleure stratégie pour chercher l'information dans les bassins jaugés "donneurs", et pour la transférer vers le site non jaugé. Nous étudions les besoins pour mettre en place un modèle de simulation pluie-débit et pour effectuer une mise à jour du modèle de prévision en temps réel. Ces deux composantes de la prévision sont ainsi découplées dans notre approche. Cette thèse s'appuie sur une large base de données constituée d'environ 1000 bassins versants français, dont un jeu clé de 211 bassins versants qui permet la validation des approches développées. Elle s'appuie également sur une archive d'environ 4,5 années de prévisions d'ensemble de pluies, utilisées en forçage à la modélisation hydrologique journalière. La démarche adoptée consiste à intégrer les scenarios de transfert de l'information régionale disponible et les scenarios de la prévision météorologique d'ensemble dans un système de prévision orienté vers les bassins versants non jaugés. L'approche de prévision d'ensemble est ainsi généralisée à ce cas particulier de la prévision hydrologique. A travers plusieurs scénarios de débits futurs, nous cherchons à quantifier les incertitudes de prévisions dans les sites cibles non jaugés. Pour évaluer les différents scénarios des prévisions hydrologiques émis, un cadre de diagnostic d'évaluation des principales qualités d'un système de prévision d'ensemble, comprenant plusieurs critères numériques et graphiques, a été mis en place. Dans cette thèse, une attention particulière est prêtée aux attributs "fiabilité" et "précision" des prévisions. Nous proposons ainsi un nouveau critère graphique, nommé diagramme de précision d'ensemble. Ce critère permet notamment de mettre en valeur la qualité des prévisions qui ne sont pas forcément fiables, mais qui sont précises. Les résultats obtenus ont mis en évidence que la fiabilité des prévisions peut être améliorée sur un bassin versant non jaugé par l'utilisation de plusieurs jeux de paramètres issus des bassins versants voisins. Si la variabilité apportée par le voisinage géographique influe sur la dispersion des membres, et augmente ainsi la fiabilité des prévisions, la prise en compte des caractéristiques physiques, principalement de la surface des bassins versants, est apparue comme une alternative intéressante, influençant positivement aussi l'attribut précision des prévisions sur le site cible. De plus, il a été montré que la précision des prévisions d'ensemble sur le site non jaugé est améliorée par l'intermédiaire du transfert des bassins versants jaugés vers le site cible des corrections faites lors de la mise à jour sur les bassins voisins (mise à jour caractérisée ici par l'assimilation de la dernière observation de débit dans le modèle hydrologique, avant l'instant de prévision). Les différentes mesures de performance ont montré que la meilleure option pour améliorer la précision des prévisions serait de considérer les corrections effectuées sur le bassin le plus proche à chaque pas de temps de prévision. Le krigeage a également donné des résultats satisfaisants, marqués en plus par l'influence positive sur l'attribut fiabilité des prévisions. / Flood forecasting is a complex hydrological task: there are numerous uncertainties in the hydrological modelling process, in the determination of the initial catchment conditions before launching the forecast, and in the evolution of future weather conditions. In ungauged catchments, where streamflow observations are incomplete or absent, these uncertainties are even greater, and the need to reduce them becomes essential.This thesis focuses on simple and robust methods that can provide relevant information to quantify the uncertainty in ungauged catchments. The aim is to study the best strategy to search for information in gauged "donors" basins and to transfer it to the ungauged site. We investigate what information is needed to set up a rainfall-runoff model and to perform forecast updating in real time. These two components of a flood forecasting system are thus decoupled in our approach.This thesis is based on a large database of about 1000 French catchments, which includes a key set of 211 catchments that are used to validate the developed approaches. It also relies on an archive of about 4.5 years of ensemble forecasts of rainfall, which are used for hydrological modelling on a daily time step. The methodology adopted here integrates the scenarios of regional transfer of information and the scenarios of weather forecasting together in a forecasting system for ungauged basins. The approach of ensemble forecasting is thus generalised to this particular case of hydrological forecasting. Using several scenarios of future flows, we seek to quantify the predictive uncertainty in ungauged sites.To evaluate the flow forecast scenarios of the hydrological ensemble prediction system, a diagnostic framework with several numerical and graphical criteria is developed. Special attention is paid to the attributes of "reliability" and "accuracy" of the forecasts. We propose a new graphic criterion, named "diagram of ensemble accuracy". This criterion allows to highlight the quality of forecasts that are not necessarily reliable, but are accurate.The results show that forecast reliability in ungauged sites can be improved by using several sets of parameters from neighbour catchments. If on the one hand the variability brought by the information from the geographical proximity influences the spread of the ensemble forecasts, and thus improves forecast reliability, on the other hand taking into account the physical characteristics of the catchments, especially the surface, emerged as an interesting alternative, as it positively influences also the accuracy of the forecasts at the ungauged site.It is also shown that the accuracy of ensemble forecasts at ungauged sites can be improved with the transfer of updating information from gauged neighbour catchments (forecasting updating is here characterized by the assimilation of the last discharge observation in the hydrological model before the time of forecast). The updating information transferred to the ungauged site is the correction applied to the routing reservoir of the hydrological model. Different measures of forecast performance showed that the best option to improve forecast accuracy is to consider the corrections made at the closest gauged site. Kriging also gave satisfactory results, with additionally a positive impact also on the reliability of the ensemble flow forecasts.

A crescente preocupação com o meio ambiente pressiona a sociedade como um todo para a uma mudança rumo a hábitos mais sustentáveis. No setor produtivo, o impulso se dá pelo desenvolvimento de técnicas mais eficientes de produção, embasados em pesquisas e experimentos de campo. No setor florestal, além da preocupação com a técnicas de manejo e com o solo, o principal recurso a ser preservado é a água. Por meio do monitoramento de rios em bacias hidrográficas, séries históricas são coletadas, possibilitando o uso da teoria de séries temporais para ajuste de modelos pela metodologia Box e Jenkins. Em casos de monitoramentos de microbacias pareadas, existe a possibilidade de se comparar séries temporais, como descrito no presente trabalho. Em duas microbacias pareadas localizadas na região centro-leste do estado do Paraná, em uma fazenda no município de Telêmaco Borba, dados correspondendo a duas séries temporais distintas de vazão específica foram coletados. Devido a presença de falhas nos conjuntos de dados, uma metodologia para imputação foi utilizada de duas maneiras diferentes, possibilitando a posterior comparação das duas séries temporais pela metodologia de séries temporais. De acordo com os resultados, verifica-se que ambas as séries são diferentes tanto para o teste de comparação das funções de autocorrelação, quanto para o teste de comparação de séries temporais proposto por Silva, Ferreira e Sáfadi (2000). Portanto, segundo a caracterização dos estudos em microbacias pareadas, pode-se constatar que o manejo florestal empregado nos dois locais influenciam de forma diferente no comportamento da variável avaliada. / The growing concern for the enviroment presses society as a whole for a change towards sustainable habits. Regarding the production systems, more efficient production techniques based on research and field experiments are needed. As for forestry, besides the concern with management techniques and with soil preparation, the main resource to be preserved is water. Time series are collected by monitoring rivers in drainage basins, making possible the use of time series theory for fitting models based on Box and Jenkins methodology. When studying paired drainage basins, it is possible to compare time series, as described in this work. Two time series consisting of specific flow data were collected in a farm situated in the municipality of Telêmaco Borba, Eastern Paraná state, in two paired drainage basins. Because there were missing data, imputation techniques were used, making it possible to compare the two time series. Results showed that the time series are different for the comparison of the autocorrelation test and the time series comparison test proposed by Silva, Ferreira e Sáfadi (2000). Therefore, according to studies involving paired drainage basins, different forest management techniques influence differently the behavior of the response variable in the different drainage basins.

<p>Attention to participatory watershed management is increasing across the developing world<em> </em>as<em> </em>soil erosion continues to degrade agricultural land; reservoirs and irrigation infrastructure are clogged with sediment. The realization of the importance of watersheds is crucial for sustainable utilization especially in developing countries where rural livelihoods and economies are highly dependant on the exploitation of natural resources. The Lake Victoria basin is characterized by high population pressures, low productive subsistence agriculture, poor farming methods, loss of soil fertility and deforestation due to demand of fuel wood and charcoal, timber and building materials that are posing serious threat to watersheds. High population density in the basin also means new needs emerge too fast to which rural societies cannot respond in time leading to more area expansion for agricultural land. In spite of positive efforts under the Lake Victoria Basin Commission, there remains a huge gap between policy and institutional framework development at the top level and the actual implementation of actions on the ground to prevent land degradation, soil erosion and decrease sediment load. The study focused on Kagera and Nyando catchments of Lake Victoria Basin and aiming to establish if there exist and the extent to which participatory watershed management has been implemented on the ground to decrease land degradation and sediment load. It therefore provides an insight into watershed management in the Kagera and Nyando catchments by illustrating the link between policy formulation and actual implementation and enforcement.</p>

Several studies in high-latitude catchments have demonstrated the importance of near-stream riparian zones as hydrogeochemical hotspots with a substantial influence on stream chemistry. An adequate representation of the spatial variability of riparian-zone processes and characteristics is the key for modeling spatio-temporal variations of stream-water quality. This thesis contributes to current knowledge by refining landscape-analysis techniques to describe riparian zones and by introducing a conceptual framework to quantify solute exports from riparian zones. The utility of the suggested concepts is evaluated based on an extensive set of hydrometric and chemical data comprising measurements of streamflow, groundwater levels, soil-water chemistry and stream chemistry. Standard routines to analyze digital elevation models that are offered by current geographical information systems have been of very limited use for deriving hydrologically meaningful terrain indices for riparian zones. A model-based approach for hydrological landscape analysis is outlined, which, by explicitly simulating groundwater levels, allows better predictions of saturated areas compared to standard routines. Moreover, a novel algorithm is presented for distinguishing between left and right stream sides, which is a fundamental prerequisite for characterizing riparian zones through landscape analysis. The new algorithm was used to derive terrain indices from a high-resolution LiDAR digital elevation model. By combining these terrain indices with detailed hydrogeochemical measurements from a riparian observatory, it was possible to upscale the measured attributes and to subsequently characterize the variation of total organic-carbon exports from riparian zones in a boreal catchment in Northern Sweden. Riparian zones were recognized as highly heterogeneous landscape elements. Organic-rich riparian zones were found to be hotspots influencing temporal trends in stream-water organic carbon while spatial variations of organic carbon in streams were attributed to the arrangement of organic-poor and organic-rich riparian zones along the streams. These insights were integrated into a parsimonious modeling approach. An analytical solution of the model equations is presented, which provides a physical basis for commonly used power-law streamflow-load relations. / At the time of doctoral defense, the following papers were unpublished and had a status as follows: Paper 2: In press; Paper 4: Manuscript. / Swedish Research Council (VR, grant no. 2005-4289)

Attention to participatory watershed management is increasing across the developing world as soil erosion continues to degrade agricultural land; reservoirs and irrigation infrastructure are clogged with sediment. The realization of the importance of watersheds is crucial for sustainable utilization especially in developing countries where rural livelihoods and economies are highly dependant on the exploitation of natural resources. The Lake Victoria basin is characterized by high population pressures, low productive subsistence agriculture, poor farming methods, loss of soil fertility and deforestation due to demand of fuel wood and charcoal, timber and building materials that are posing serious threat to watersheds. High population density in the basin also means new needs emerge too fast to which rural societies cannot respond in time leading to more area expansion for agricultural land. In spite of positive efforts under the Lake Victoria Basin Commission, there remains a huge gap between policy and institutional framework development at the top level and the actual implementation of actions on the ground to prevent land degradation, soil erosion and decrease sediment load. The study focused on Kagera and Nyando catchments of Lake Victoria Basin and aiming to establish if there exist and the extent to which participatory watershed management has been implemented on the ground to decrease land degradation and sediment load. It therefore provides an insight into watershed management in the Kagera and Nyando catchments by illustrating the link between policy formulation and actual implementation and enforcement.