L’agrivoltaïque, association sur une même surface d’une production agricole et d’une production d’énergie d’origine photovoltaïque, apparait aujourd’hui comme une solution innovante pour atténuer les effets du changement climatique, notamment sur le secteur agricole. Déjà imaginé en 1982, les premières expérimentations débutées à Montpellier (France) en 2010 ont montré la pertinence de cette association à travers un maintien des rendements sous certaines conditions, une meilleure efficience d’utilisation du sol ainsi qu’une diminution de la consommation en eau des cultures sous ombrage. Suite à ces travaux pionniers réalisés sous des panneaux photovoltaïques à inclinaison fixe, l’utilisation de panneaux dynamiques à inclinaison variable est apparue nécessaire pour réduire l’hétérogénéité du rayonnement disponible pour la culture mais aussi, adapter la stratégie d’ombrage aux besoins radiatifs de la culture au cours de son développement.La présente thèse avait pour objectif de caractériser et de modéliser l’impact de la présence de panneaux solaires sur le bilan hydrique d’une culture conduite sous dispositif agrivoltaïque dynamique en vue d’optimiser la stratégie d’irrigation et le pilotage de l’inclinaison des panneaux. Les expérimentations menées sur une culture de laitues ont mis en évidence l’intérêt de panneaux dynamiques afin de réduire les hétérogénéités radiatives. Le développement d’un modèle de redistribution des pluies par les panneaux photovoltaïques a permis la mise en œuvre d’une stratégie de pilotage de l’inclinaison en temps réel a permis d’homogénéiser les cumuls observés au sol. L’adaptation d’un modèle de bilan hydrique et de développement de culture par l’ajout d’un module décrivant la dynamique stomatique sous ombrage fluctuant a permis de décrire la consommation en eau de la culture et son développement sous différentes stratégies de pilotage de l’ombrage. Enfin, différentes stratégies de pilotage de l’inclinaison des panneaux photovoltaïque ont pu être simulées et évaluées à l’aide d’un indicateur globale intégrant l’efficience d’utilisation du sol, la productivité de l’eau, le décalage de maturité et les sources d’hétérogénéités pouvant affecter la production de laitues. / Agrivoltaism, defined as the association on the same land of agricultural and photovoltaic energy production, appears as an innovating concept to dampen some of the effects of climate change, in the agricultural sector. Although the concept was already imagined in 1982, the first experimentations started in 2010 at Montpellier (France) and showed the relevance of this combination by the maintenance of crop yield under certain conditions, the increase of land use efficiency and a reduction of water consumption for the tested crops. Following this pioneering work done under fixed (but not horizontal) photovoltaic panels, the use of "dynamic" panels, i.e. panels with a variable tilting angle, appears necessary to reduce the spatial heterogeneity of the transmitted radiation but also to adapt the shading strategy to the radiation amount required for crop growth.This thesis aims to characterize and to model the impact of the photovoltaic panels on the water budget of the cultivated plot and to progress towards the optimization of irrigation strategies in such systems controlled by the variations in time of the tilting angle of the panels. Experimentations conduced on lettuces showed the benefits of "dynamic" photovoltaic panels to reduce the radiative heterogeneity. Accounting for rain redistribution by the solar panels permits the implementation of a real time strategy to reduce rainfall heterogeneity on the ground surface. The derivation of a water budget and crop development model which describes the dynamics of stomatal conductance under fluctuating shading allows a better simulation of water consumption and crop development for different shading strategies. Finally, various strategies for the piloting of the solar panels could be tested and evaluated by a new, global index combining land use efficiency, water productivity, maturity delays and heterogeneities (in rain and radiation) which can impact production.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The El Nino Southern Oscillation (ENSO) is a large-scale phenomenon that impacts weather and climate worldwide, including Southern and Northeast Brazil. Soil water is a major factor that affects interannual crop production in Rio Grande do Sul State. Other factor that may affect crop yield is the possible climate change. Human activities have been blamed to increase the CO2 concentration of the Earth s Atmosphere. Earth temperature may increase in response to increasing CO2 concentration. The Impact of the projected climate change on soil water and agroecossystems yield is an important and relevant issue both from a scientific and political viewpoint. The objective of this study was to simulate wheat, maize and soybean yields, and the fraction of transpirable soil water (FTSW) and link its interannual variability to ENSO and under climate change scenarios at Santa Maria, RS. Soil water and crop yield were simulated with models available in the literature. Air temperature and rainfall were modified to create climate change scenarios. The results showed that neutral years are the years of the largest risk to production of wheat, maize and soybean. During La Niña years the trend of water deficit is not clear and El Niño years are associated with years with greater FTSW. The increase in temperature, expected to decreases wheat and maize yields more than soybean yield. / O El Niño Oscilação Sul (ENOS) é um fenômeno de grande escala que afeta o tempo e o clima em diversos locais do Globo Terrestre, incluindo o Brasil, especialmente as regiões Sul e Nordeste brasileiro. A água disponível no solo para os cultivos é um importante fator de variabilidade interanual da produção agrícola no Estado do Rio Grande do Sul. Outro fator que poderá influenciar o rendimento das culturas é a possível mudança climática. A concentração de CO2 da atmosfera terrestre está aumentando devido às atividades humanas, assim, a temperatura média do ar do Planeta poderá aumentar nos próximos anos devido ao efeito estufa do CO2 atmosférico. O impacto de uma possível mudança climática sobre a água disponível e o rendimento em agroecossistemas é um assunto de interesse científico e político. O objetivo deste estudo foi simular a fração de água disponível no solo e sua conseqüência sobre o rendimento de trigo, milho e soja, associando sua variabilidade interanual com o fenômeno ENOS e, em diferentes cenários climáticos para Santa Maria, RS. Para a simulação foi utilizado o cenário meteorológico atual (1969-2003) e, criados cenários de mudança climática com diferentes aumentos de temperatura do ar com e sem aumento de precipitação pluviométrica para os próximos 100 anos. Os resultados mostraram que anos neutros constituem anos de maior risco para as culturas do trigo, milho e soja. Para anos de La Niña a tendência de défice hídrico não foi tão clara. Anos de El Niño, normalmente, estão associados a maior disponibilidade hídrica para as plantas. Se o aquecimento global se confirmar, espera-se que o rendimento de grãos de trigo e milho seja mais afetado do que a soja.

No description available.

Stormwater bioretention cells (BRCs) are a variety of green stormwater infrastructure with the potential to restore pre-urban water balance, provided they can be tailored to infiltrate and evapotranspire (i.e., harvest) urban runoff in proportions consistent with pre-urban hydrologic conditions. This paper evaluates their capacity to do so, focusing on evapotranspirative harvest, which is relatively understudied, and the capacity of CSR (Competitve, Stress-tolerant, and Ruderal) functional type to serve as an overarching framework characterizing the water use strategy of BRC plants. The goal is to determine if harvest (and therefore the ratio of urban runoff infiltrated to harvested; the I:H ratio) might be fine-tuned to meet pre-urban values in BRCs through informed manipulation of plant community composition. This study focuses on 3 critical plant water use traits, the turgor loss point, the point of incipient water stress, and maximum stomatal conductance. A global plant traits meta-analysis identified degree of plant competitiveness and stress tolerance as significant determinants of all three water use traits, with stem type (woody vs herbaceous) also being significant, but only for turgor loss point. Based on these results, six water use scenarios appropriate for plants with different CSR type/stem type combinations were developed. BRC plants spanning the range of CSR types necessary to actionize these scenarios were determined to be available in eight major climate zones of the coterminous US, suggesting that regulating plant water use in BRCs using CSR is likely feasible. Hydraulic simulations (Hydrus 1D) were conducted for each scenario in all eight climate zones and revealed significant differences in evapotranspirative harvest and I:H ratios in simulated BRCs. Competitive woody plants had the highest evapotranspiration and lowest I:H ratios; 1.5-1.8 times more evapotranspiration and a 1.6-2 times lower I:H ratio than stress tolerant herbaceous plants, on average, across climate zones. Despite these significant differences, no simulated BRC in any climate zone was capable of reproducing pre-urban I:H ratios, regardless of plant type. More water was infiltrated than harvested in all scenarios and climates with the inverse being true for all pre-urban conditions. This suggests that absent additional sources of harvest (e.g., use of BRC water for nonpotable purposes such as toilet flushing and outdoor irrigation, or adoption of novel BRC designs that promote lateral exfiltration, stimulating "extra" evapotranspiration from nearby landscapes), BRCs will be unable to restore pre-urban water balance on their own. If true, then using BRCs in combination with other green technologies (particularly those biased towards harvest), may be the best path forward for balancing urban water budgets. / Master of Science / Stormwater bioretention cells (BRCs) are a variety of green infrastructure designed to manage urban stormwater flows that can dramatically reduce the amount of stormwater that is rapidly (and unnaturally) conveyed from paved surfaces to ecosystems. Their ability to recreate natural flow conditions is dependent on them balancing rates of infiltration – slowly filtering water down to the water table – and evapotranspiration – letting plants capture and transpire water. This paper evaluates the extent to which different plant functional types (competitive, stress tolerant, and ruderal (weedy)) can be used to regulate this balance, bringing urban hydrologic conditions closer to pre-urban ones. Competitiveness and stress tolerance were found to significantly influence plant water use traits, as was plant stem type (woody vs herbaceous) to a lesser extent (i.e., managing water budgets using CSR functional type is theoretically possible). Published BRC vegetation guidelines in 8 major US climate zones were found to include both competitive and stress tolerant species (i.e., the range of functional types required to regulate BRC water balance exists, suggesting it is feasible). Finally, hydraulic simulations conducted under six plant water use scenarios (reflecting different CSR types and stem types) revealed significant differences in the ratio of water infiltrated to evapotranspired by BRCs (i.e., changing plant functional types can meaningfully influence BRC water balance). This said, the magnitude of this effect may be insufficient to return urban catchments to a pre-urban state. All BRCs infiltrated too much water in our simulations suggesting that absent additional sources of harvest (for instance., use of BRC water for nonpotable purposes such as toilet flushing or outdoor irrigation), BRCs will be unable to restore pre-urban water balance on their own. If true, then using BRCs in combination with other green technologies (particularly those biased towards harvest), may be the best path forward for balancing urban water budgets.

In den letzten zwei Jahrzehnten wurden in Sumatra (Indonesien) große Regenwaldflächen für den Anbau von Kautschuk- und Palmölplantagen zerstört. Dies zeigt sich in der Abnahme Waldfläche in dieser Region um 36% zwischen 1990-2010. Eine solch schnelle Landnutzungsänderung hat Auswirkungen auf die Umwelt: Es ist davon auszugehen, dass die Zerstörung von Regenwald und die Etablierung von Kautschuk- und Palmölplantagen aufgrund von Einflüssen auf die Bodenoberfläche, Veränderungen von Streufall, Nährstoffverfügbarkeit und Management in den Plantagen zu erhöhter Nährstoffauswaschung und einer verminderten Nährstoffretentionseffizienz führt. Diese Arbeit stellt zwei Studien vor, die sich mit den Auswirkungen der Regenwaldzerstörung - und der einhergehenden Kultivierung von Kautschuk und Ölpalmenbäumen - auf Nährstoffauswaschung und Nährstoffretentionseffizienz beschäftigt. Außerdem untersucht sie Unterschiede in der Nährstoffauswaschung zwischen gedüngten und mit Palmwedeln bedeckten Bereichen in Palmölplantagen. Beide Studien wurden in zwei Landschaften der Provinz Jambi (Sumatra, Indonesien) mit stark verwitterten Acrisol-Böden durchgeführt, die sich in der Bodenart unterscheiden (lehm- bzw. tonhaltiger Acrisol). Die Nährstoffauswaschung im Boden wurde mit Saugkerzen-Lysimetern gemessen, die in 1,5m Tiefe im Boden installiert wurden. Beprobt wurde von Februar bis Dezember 2013 zweiwöchentlich bis monatlich. Die erste Studie beschäftigt sich mit der Nährstoffauswaschung und Nährstoffretentionseffizienz im Boden vierer verschiedener Landnutzungsarten. Dabei handelt es sich um die zwei Referenznutzungsformen Tieflandregenwald sowie Sekundärwald durchsetzt mit Kautschukbäumen, als auch um die veränderten Landnutzungsformen kleinbäuerlicher Kautschuk- und Ölpalmplantagen. Jede Landnutzung, ausgenommen der Palmölplantagen mit drei Wiederholungen, wurde durch vier Wiederholungsflächen innerhalb jeder Landschaft repräsentiert. Somit wurde die Studie auf insgesamt 30 Flächen durchgeführt. Die Ergebnisse zeigen für den lehmigen Acrisol-Boden der Referenzflächen eine höhere Auswaschung und eine niedrigere N-Retentionseffizienz für Stickstoff (N) und basische Kationen, verglichen mit dem tonigen Acrisol-Boden bestanden. In den Palmölplantagen zeigte sich, dass Düngung und Kalkung zu erhöhter Auswaschung von gelöstem N, gelöstem organischen Kohlenstoff (DOC) und basischen Kationen führte, sowie zu einer geringeren Retentionseffizienz von N und basischen Kationen im Boden. In den ungedüngten Kautschukplantagen dagegen waren die Auswaschungsverluste von gelöstem N, DOC und basischen Kationen geringer als in den Palmölplantagen. Zusammenfassend zeigten die Ergebnisse, dass Nährstoffverluste und Nährstoffretentionseffizienz in Kautschuk- und Palmölplantagen auf stark verwitterten Acrisolen primär von Tongehalt und Management abhängen. In der zweiten Studie wurde die Nährstoffauswaschung in den gedüngten und mit Palmwedeln bedeckten Bereichen in Palmölplantagen von Kleinbauern in lehm- bzw. tonhaltigen Acrisolen gemessen. Die Ergebnisse zeigten höhere Auswaschverluste (d.h. N, basische Kationen, Gesamt-Aluminium, Gesamt-Mangan, Gesamt-Schwefel und Chlor) in den gedüngten Bereichen als in den mit Palmwedeln bedeckten Bereichen aufgrund der Frequenz des Mineraldünger- und Kalkeinsatzes. Auf Landschaftsebene wurden die höheren Bodennährstoffvorräte und eine niedrigere Nährstoffauswaschung im Ton-Acrisol im Vergleich zum Lehm-Acrisol sowohl in den gedüngten als auch in den mit Palmwedeln bedeckten Bereichen durch die höhere Nährstoffretention (als Ergebnis höheren Tongehaltes) verursacht. Die Kombination von Nährstoffauswaschung und Nährstoffeintrag (d.h. Gesamtniederschlag und Dünger) mit zusätzlichen Informationen über den Nährstoffaustrag durch die Ernte, geben uns umfassendere Informationen über die Veränderungen im partiellen Nährstoffhaushalt von N, Phosphor (P), und basischen Kationen bei Waldumwandlung zu Palmöl- und Kautschukplantagen. Gedüngte Palmölplantagen hatten aufgrund der hohen jährlichen Nährstoffauswaschung und des Ernteexports das niedrigste jährliche Teilbudget an N, Kalzium (Ca) und Magnesium (Mg). Dennoch verringerten die hohen negativen Teilbudgets von N, Ca und Mg in den Palmölplantagen nicht deren Vorräte in 1m Bodentiefe verglichen mit den anderen Landnutzungsformen - außer für austauschbares Mg im Lehm-Acrisol. Obwohl ungedüngte Kautschukplantagen geringere Auswaschung zeigen als der Wald (z.B. für P), führte der Ernteexport zu einem geringeren jährlichen P-Teilbudget. Insgesamt implizieren die Ergebnisse der beiden Studien folgende verbesserte Managementverfahren für diese hochverwitterten Böden: eine Synchronisation der Düngermenge mit der Pflanzenaufnahme sowie eine Anpassung der Düngungshӓufigkeit.

Seit mehr als 100 Jahren wird Oberflächenwasser mit verschiedenen Verfahren versickert, wobei sich dessen Qualität stark verbessert. Sie finden zunehmend weltweit Anwendung, um eine zuverlässige Versorgung mit sauberem Trinkwasser zu gewährleisten. Solche Verfahren erfordern nur einen geringen technischen Aufwand. Während bei der Versicherung mit Schluckbrunnen und bei künstlichen Infiltrationsbecken das Wasser noch gepumpt und oft auch vorgereinigt werden muss, reduziert die Nutzung eines natürlichen Gewässers den Aufwand nochmals. Am Beispiel eines Untersuchungsgebiets am Tegeler See in Berlin werden die hydraulischen Prozesse modelliert. Die regionale, instationäre und 3-dimensionale Modellierung eines langen Zeitraums zeigt, dass die bisher verwendeten linearen Ansätze zur Beschreibung der Durchlässigkeit der Kolmationsschicht sowohl die infiltrierten Wassermengen als auch die Infiltrationsprozesse nur unzureichend wiedergeben. Grundwasserpiegelschwankungen werden stärker als bisher angenommen gedämpft. Als Folge dieser Wasserspiegelschwankungen wird die Bodenluft in der ungesättigten Bodenzone ausgetauscht und Sauerstoff eingetragen. Auf diese Weise erhöht sich die Durchlässigkeit der Kolmationsschicht um mindestens eine Größenordnung. Auf Grundlage dieser Ergebnisse wurden eine instationäre Wasserbilanz aufgestellt und die Uferfiltratanteile bestimmt. Die genaue lokale Lage eines Grundwasserstauers wird mit Hilfe eines neu entwickelten inversen Modellkonzeptes bestimmt. Er wird mit räumlich verteilten Pilot Points und Überparameterisierung unter Nebenbedingungen kalibriert. Die Zielgröße sind Piezometerhöhenschwankungen. Kreuzvalidierung bestätigt, dass die Lage des Grundwasserstauers präzise bestimmt wird. Diese hat einen entscheidenden Einfluss auf das räumliche Strömungsfeld und liefert neue Anhaltspunkte zur Genese des Tegeler Sees. Ein Transportmodell liefert lediglich mit den hydraulisch kalibrierten Parametern eine genaue Anpassung der Durchbruchskurven von Chlorid, 18O und Temperatur. Dies kann als Vorhersage angesehen werden und zeigt die Güte des Modells. Es konnte gezeigt werden, dass der Sauerstoffeintrag die Redoxprozesse in der Infiltrationszone dominiert. In Kombination mit der Lage des Grundwasserstauers können so auch zuvor widersprüchliche und lokale geochemische Verhältnisse schlüssig interpretiert werden. Es wird eine Theorie entwickelt, die erklärt, wie die vertikale Schichtung von oxidiertem und reduziertem Wasser zu starker Verockerung der Brunnen führt. / Several kinds of managed aquifer recharge techniques provide very good purification of surface water since more than 100 years. In order to maintain a reliable supply of clean water, they are becoming increasingly popular all over the world. These methods require low technical effort. At Aquifer Storage and Recovery and ponded infiltration the recharged amounts are technically controlled. The infiltration water has to be pumped and often pretreated. At bank filtration this is dispensable, the approach, of using existing surface water bodies is even more consequent. Exemplarily, at a test site at Lake Tegel, Berlin, Germany, the hydraulic processes are modelled. By means of 3D long term regional and transient hydraulic modelling it was detected that the existing approaches for determining the leakance induce large errors in the water balance and describe the infiltration zone insufficiently. The leakance could be identified to be triggered by the groundwater table, causing air exchange and intrusion of atmospheric oxygen, which reduces clogging by altered redox conditions by at least one order of magnitude. This causes that changes of the groundwater table are mitigated much more than previously assumed. Taking these findings into account, a transient water balance is determined and bank filtration ratios are quantified. A new inverse modelling concept has been developed and applied to a 3D short term local and transient hydraulic model. It comprises spatially distributed pilot points and overparameterisation constrained by regularisation and calibration to head differences. Significance of the results is demonstrated by cross validation. With this approach the spatial distribution of an aquitard have been identified with high precision. The highly transient and heterogeneous flow conditions are specified and a new viewpoint on the geologic formation of Lake Tegel is obtained. The good fit of modelled and observed breakthrough curves of 18O, chloride and temperature by just using transferred parameters obtained with the previous hydraulic methods, show the very good model performance and predictive capabilities. The intrusion of atmospheric oxygen into the unsaturated zone is identified to be the principal redox determining factor during infiltration. Previously inconsistent and also local geochemical conditions are identified to be determined by interaction of infiltration processes with the spatial extent of the aquitard. A theory for chemical clogging of abstraction wells is developed, identifying the strong vertical redox zoning as principal factor of influence.

The San Joaquin Valley is part of the Great Central Valley of California, a major agricultural centre and food supplier for the United States. This area has significant water management concerns given the very high water demand for an increasing state population and for intense irrigation in a hot, temperate to semi-arid climate where the overall rate of evapotranspiration (ET) is high, and the overall rate of precipitation is low. Irrigation heavily relies upon groundwater and surface water extractions. Through the historical and current concerns of regional water resources reliability, land surface subsidence, water quality issues, and the health of ecosystems, a need for regional-scale water resource management and planning has developed. The physically-based surface-subsurface HydroGeoSphere (HGS) model is used to examine the regional-scale hydrologic budget of a large portion of the San Joaquin Valley. The objective of this investigation is to develop a steady-state groundwater-surface water model of the San Joaquin Valley representative of predevelopment hydrologic conditions. The groundwater-surface water system has undergone drastic changes since the employment of groundwater and surface water extractions for irrigation and mining, and is still responding to past and present stresses. The only certain stable initial condition must therefore be that of the natural system. The model input parameters were constrained by all relevant available hydrologic data. The model was not calibrated to subsurface hydraulic heads or river flows. However, the model does provide a fair match between simulated and actual estimated water table elevations. Historic river flow estimates were not used to calibrate the model, because data consistent with that collected by Hall (1886) and representative of the natural system were not available. For this investigation, water enters through precipitation and the inflow of major rivers only. The subsurface domain is bounded by no-flow boundaries, and groundwater is therefore only able to exit the subsurface through discharge to surface water features or through ET. Surface water is only able to exit the model through discharge via the San Joaquin River and through ET. Average river inflows circa 1878 to 1884 documented by Hall (1886) were applied where the rivers enter into the valley. The spatially variable average rate of precipitation (years 1971 to 2000) from a PRISM dataset was applied to the top of the model. The spatially variable long term average potential ET rates from the California Department of Water Resources (DWR) et al. (1999) were applied to the top of the model. Averaged overland flow parameters and vegetation factors needed to calculate actual ET were specified at the top of the model based on literature values and the 1874 spatial distribution of natural vegetation provided by California State University at Chico et al. (2003). Hydrogeological data including hydraulic conductivities, porosities, specific storage, and unsaturated zone properties are based on literature values from other relevant studies. The resulting steady state model is therefore characterized by historical long term average data assumed to be representative (as close as possible) of the flow system circa 1848. Results indicate that the natural hydrologic setting of the San Joaquin Valley is a complex one. Complex hydrologic processes, including significant groundwater-surface water interaction along the major rivers and within wetland areas formed by flooded surface water, as well as ET and impacted root zone processes were identified in the model domain. Identification and simulation of the complex recharge and discharge relationships in the model domain sheds insight into the hydrologic nature of some historic natural wetlands. Evapotranspiration is a very significant sink of both surface water and groundwater (44.8 % of the water balance input), and has a major impact on hydrologic processes in the root zone. The presence and path of the major rivers in the domain are well defined in the model output and agree well with their actual locations. The model simulates gaining and losing reaches of the major rivers, replicating the historic recharge-discharge relationship documented by others. The general location, formation, and hydrologic processes of some significant wetlands simulated by the model have a fair agreement with historical records. As mentioned above, there is also a fair match between simulated and actual estimated water table elevations. Successful simulation of the complex hydrologic processes and features that characterize the predevelopment hydrologic conditions of the San Joaquin Valley and that resolve the water balance of the natural system underscores the importance and necessity of using an integrated model. This steady state model should serve as a reasonable initial condition for future transient runs that bring the model up to current hydrologic conditions capable of estimating present and future water budgets.

The San Joaquin Valley is part of the Great Central Valley of California, a major agricultural centre and food supplier for the United States. This area has significant water management concerns given the very high water demand for an increasing state population and for intense irrigation in a hot, temperate to semi-arid climate where the overall rate of evapotranspiration (ET) is high, and the overall rate of precipitation is low. Irrigation heavily relies upon groundwater and surface water extractions. Through the historical and current concerns of regional water resources reliability, land surface subsidence, water quality issues, and the health of ecosystems, a need for regional-scale water resource management and planning has developed. The physically-based surface-subsurface HydroGeoSphere (HGS) model is used to examine the regional-scale hydrologic budget of a large portion of the San Joaquin Valley. The objective of this investigation is to develop a steady-state groundwater-surface water model of the San Joaquin Valley representative of predevelopment hydrologic conditions. The groundwater-surface water system has undergone drastic changes since the employment of groundwater and surface water extractions for irrigation and mining, and is still responding to past and present stresses. The only certain stable initial condition must therefore be that of the natural system. The model input parameters were constrained by all relevant available hydrologic data. The model was not calibrated to subsurface hydraulic heads or river flows. However, the model does provide a fair match between simulated and actual estimated water table elevations. Historic river flow estimates were not used to calibrate the model, because data consistent with that collected by Hall (1886) and representative of the natural system were not available. For this investigation, water enters through precipitation and the inflow of major rivers only. The subsurface domain is bounded by no-flow boundaries, and groundwater is therefore only able to exit the subsurface through discharge to surface water features or through ET. Surface water is only able to exit the model through discharge via the San Joaquin River and through ET. Average river inflows circa 1878 to 1884 documented by Hall (1886) were applied where the rivers enter into the valley. The spatially variable average rate of precipitation (years 1971 to 2000) from a PRISM dataset was applied to the top of the model. The spatially variable long term average potential ET rates from the California Department of Water Resources (DWR) et al. (1999) were applied to the top of the model. Averaged overland flow parameters and vegetation factors needed to calculate actual ET were specified at the top of the model based on literature values and the 1874 spatial distribution of natural vegetation provided by California State University at Chico et al. (2003). Hydrogeological data including hydraulic conductivities, porosities, specific storage, and unsaturated zone properties are based on literature values from other relevant studies. The resulting steady state model is therefore characterized by historical long term average data assumed to be representative (as close as possible) of the flow system circa 1848. Results indicate that the natural hydrologic setting of the San Joaquin Valley is a complex one. Complex hydrologic processes, including significant groundwater-surface water interaction along the major rivers and within wetland areas formed by flooded surface water, as well as ET and impacted root zone processes were identified in the model domain. Identification and simulation of the complex recharge and discharge relationships in the model domain sheds insight into the hydrologic nature of some historic natural wetlands. Evapotranspiration is a very significant sink of both surface water and groundwater (44.8 % of the water balance input), and has a major impact on hydrologic processes in the root zone. The presence and path of the major rivers in the domain are well defined in the model output and agree well with their actual locations. The model simulates gaining and losing reaches of the major rivers, replicating the historic recharge-discharge relationship documented by others. The general location, formation, and hydrologic processes of some significant wetlands simulated by the model have a fair agreement with historical records. As mentioned above, there is also a fair match between simulated and actual estimated water table elevations. Successful simulation of the complex hydrologic processes and features that characterize the predevelopment hydrologic conditions of the San Joaquin Valley and that resolve the water balance of the natural system underscores the importance and necessity of using an integrated model. This steady state model should serve as a reasonable initial condition for future transient runs that bring the model up to current hydrologic conditions capable of estimating present and future water budgets.

Le bassin versant du fleuve Niger est directement influencé par les fluctuations de la mousson africaine, qui impactent les ressources en eau et entraînent des évènements extrêmes tels que des inondations ou des sécheresses. En retour, les forts taux d'évaporation observés dans le Delta intérieur du Niger, large région annuellement inondée, impactent le climat, au moins à l'échelle régionale. Une meilleure compréhension des processus hydrodynamiques de ce bassin ne peut cependant être obtenue sans un réseau d'observations ayant une couverture spatiale et temporelle suffisante. La mission SWOT fournira des cartes 2D de hauteurs et pente des eaux de surface avec une résolution encore jamais atteinte en altimétrie (50 à 100 mètres). Cette thèse s'inscrit dans le cadre de la phase de préparation à la mission SWOT et se propose d'offrir des perspectives d'utilisation de ces données satellites pour l'amélioration des modèles d'hydrologie globale. Dans un premier temps, le modèle hydrologique du CNRM, ISBA-TRIP, incluant un schéma d'inondations et un réservoir simple d'aquifères ajouté durant cette thèse est évalué sur le bassin du Niger à l'aide de multiples observations in-situ et satellites. L'étude montre que le modèle simule de façon cohérente l'évolution des eaux de surface, des zones inondées, et les anomalies de stock d'eau sur le bassin. Ensuite, un schéma d'assimilation de données est mis en place afin d'optimiser un des paramètres clés en hydrologie, le coefficient de Manning. Ce coefficient, décrivant la propriété du sol à 'retenir' les flux d'eau, influence fortement la dynamique des eaux de surface, et notamment les hauteurs d'eau et le débit. L'assimilation des données SWOT est appliquée dans le cadre d'une expérience jumelle, qui consiste à considérer une simulation de référence, appelée 'vérité', de laquelle sont issues les observations virtuelles de hauteur d'eau SWOT. L'étude montre que l'assimilation des hauteurs d'eau SWOT permet l'optimisation du coefficient de Manning, distribué spatialement, malgré l'hypothèse d'équifinalité. Les hauteurs d'eau et les débits sont considérablement améliorés, et on obtient une meilleure simulation des anomalies de stocks d'eau sur le bassin ainsi que des zones inondées sur le Delta intérieur du Niger (occurrence, intensité). Enfin, le potentiel des données SWOT pour améliorer les prévisions hydrologiques sur des périodes plus longues que celle de la phase d'assimilation est mis en évidence. / The hydrologic and hydrodynamic processes of the Niger basin are largely influenced by the West African monsoon variabilty. In the last 3 decades these variations have resulted in an increase of extreme events such as floods and droughts. Retrospectively, the climate might be impacted by the evaporation fluxes from the inner Delta flooded region, at least regionally. A better understanding of the Niger basin water cycle is a crucial issue for water resources management but requires observation datasets with a large spatial and temporal coverage. The SWOT satellite mission will provide 2D global maps of water level and slope at an unprecedented resolution (50 to 100 meters). Within the framework of the preparation of the SWOT mission, this thesis aims at proposing a SWOT data assimilation strategy for the improvement of global scale hydrological models. First, the ISBA-TRIP hydrological model from CNRM is evaluated over the Niger basin. This model includes an inundation scheme and simple aquifer reservoir. The model diagnostics are compared to an extensive set of in-situ and satellite observations. According to its relative simple physics, the model is able to simulate in a realistic manner, the continental water dynamics : discharge, water levels, floods, total water storage variations. Sensitivity tests are also performed to determine the most sensitve ISBA-TRIP parameters. Among them, the Manning coefficient has a key role in the flow dynamics but its estimation is difficult and usually based on geomorphologic relationships. The second part of this work consists in setting up a SWOT data assimilation strategy for the optimization of the ISBA-TRIP parameters. Since the SWOT observations are not available yet and also to assess the skills of the assimilation method, the study is carried out in the framework of an Observing System Simulation Experiment (OSSE). The corrected parameter is the Manning coefficient, spatially distributed over the river. The assimilation allows a good improvement of the relative bias of discharge and water level over the river. The Manning coefficient is also globally improved and tends to an optimal value. Moreover, the water storage anomalies and flooded fraction are also better simulated. Finally, the study shows that the method is useful for hydrological forecasting over longer time periods than those of the calibration.

Water BudgetThis chapter documents the hydrologic analysis of a watershed within the Windy Ridge mega-landslide of Central Utah to (1) create a water budget and (2) place a quantitative limit on the magnitude of climatic changes documented by Shurtliff et al. (2017) and Hudson et al. (2019). (1) A water budget was calculated over the last four years using instrumentation and weather stations both within and surrounding the watershed, In terms of precipitation input, 85% is released by the evapotranspiration of the Pinyon-Juniper forest, 4% discharges as surface water from the base of the watershed, and 11 % infiltrates the groundwater system. This infiltration rate is slightly lower than the 15% suggested by Maxey-Eakin method (Maxey and Eakin, 1949), likely due to the less permeable, clay-rich sediment. (2) Previous studies performed on Garden Basin Cattail (GBC) Fen at the base of its watershed suggest swings from pond-like to wetland environments (Shurtliff et al, 2017; Hudson et al, 2019). This study estimated precipitation values necessary to create standing water (pond) environments. Changes in annual precipitation, as well as input from North American monsoon (NAM), may cause these environmental changes. Each of these cases were examined. Trends in piezometer measurements compared to mean annual precipitation indicated that ‰¥ 644 mm of annual precipitation are required to sustain a wet (perennial standing water) environment. The change from wetland to pond conditions may depend on seasonal trends in precipitation. This study suggests an increase of 150-300 mm of precipitation in late summer (NAM) may be connected to perennially wet conditions. The higher annual precipitation values, largely accomplished by NAM fluctuations, caused a transition from wetland to pond (Hudson et al., 2019; Shurtliff et al., 2017). Chapter 2: Core AnalysisChapter 2 further documents the watershed's historical environmental and climate record by analyzing sediment and topography surrounding GBC fen, adding to the works of Shurtliff et al. (2019) and Hudson et al. (2019). A core was extracted from GBC fen at the base of the watershed and the sediment analyzed in terms of color, texture, environmental scanning electron microscope (ESEM) imaging, RockEval pyrolysis, and 14C ages. These results were then compared to pre-existing pollen and diatom proxies completed on a previous core by Shurtliff et al. (2019). This study suggests climatic variation, along with basin fill processes, was the driver of environmental change in GBC fen (Garden Basin watershed). Climate proxies show the basic trend from a particularly wet period (12-9 ka BP) of more stagnant or deeper water, to a much dryer period of much shallower water levels (9-3 ka BP), followed by a rebound in moisture levels, especially in the past few hundred years. Although climate was the driver of transitions within GBC2 core, a pollen record of sustained shallow water plants and MASW (Park et al., 1999) survey may suggest beaver activity.