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La compréhension du cycle de l'eau d'une région où les ressources en eau sont limitées est fondamentale pour assurer une gestion durable de celles-ci, c'est le cas de Galápagos. Cette thèse présente la première étude intégrée du fonctionnement hydrogéologique des aquifères perché de l'île San Cristóbal. Pour ce faire, une approche pluridisciplinaire, fondée sur la mise en place d'un site expérimental sur le bassin versant de Cerro Gato (CG), a été conduite. Pour quantifier les entrées d'eau dans le système hydrologique une approche canopée-transfert hydrique du sol a été utilise. La recharge est principalement affectée par l'altitude en raison de l'effet orographique sur les gradients de pluie et d'évapotranspiration. Néanmoins, à haute altitude, la différence est principalement associée à la couverture végétale en raison de l'apport additionnel fourni par l'interception du brouillard sous la forêt. Une analyse hydrologique montre que les pertes des bassins versants situés à haute-altitude deviennent les entrées d'eau souterraine des bassins versants situés à moyenne altitude (comme CG). Les données du méthode électromagnétique héliportée SkyTEM permettent définir l'extension du bassin hydrogéologique de CG qui est plus grande que le bassin hydrologique. Des approches précédemment décrites, découlent un modèle conceptuel des sources de CG. Ainsi, les eaux souterraines de ces sources sont issues d'un aquifère perché qui s'est formé à la faveur d'une fine couche peu perméable. Ce modèle est testé par simulations numériques qui montrent cette plausibilité. Cette thèse fournit les fondements scientifiques d'une gestion durable des ressources en eau. / The understanding of the hydrogeological functioning in regions such as San Cristobal Island (Galapagos), where water is limited, is fundamental for a suitable management of its resources. This work is the first study of this type on high-level aquifers in San Cristobal using a multi-disciplinary approach, based in the implementation of an experimental site and modeling strategies. For this purpose, a hydrological network was installed in Cerro Gato (CG) and surrounding watersheds. Inputs to the watershed are estimated using the joint modeling of a canopy and soil water transfer. Recharge rates are mainly affected by altitude in mid-elevation watersheds, whereas land cover is the main controlling factor at high-elevation watersheds because of the additional input of fog interception in forests. A hydrological analysis shows that losses from the high-elevation basins become groundwater inputs in the mid-elevation basins, while others have inputs from watersheds at the same altitude, such as CG. The detailed geometry of its hydrogeological watershed is obtained from the dataset of a high resolution AEM SkyTEM survey, which confirms the assumption that its hydrogeological watershed is bigger than its hydrological one. Results from these approaches allow proposing a hydrogeological conceptual model for the springs of CG, where the groundwater flow of springs is fed by a perched aquifer suspended by a low permeability thin layer. This model is tested with numerical simulations, which confirm the plausibility of the existence of a perched aquifer. This thesis provides scientific basis for an effective water management strategy.

O modelo Soil and Water Assessment Tool (SWAT) tem sido utilizado para avaliar os impactos do uso e manejo da terra nos recursos hídricos, sedimentos e agroquímicos em diversas escalas e condições ambientais em todo o mundo. Entretanto, pelo fato de ter sido desenvolvido em centros de pesquisa norte-americanos, alguns parâmetros e rotinas de simulação não refletem adequadamente determinados processos de bacias localizadas em regiões tropicais. Nesse sentido, o presente trabalho visou aprimorar a modelagem hidrológica do SWAT através da revisão e modificação de processos relacionados à simulação da evapotranspiração. Os procedimentos propostos incluíram a alteração das rotinas de dormência vegetal no código fonte do modelo e a modificação dos cronogramas de operações de manejo e parâmetros do banco de dados de crescimento das plantas, visando reproduzir com maior precisão o ciclo das culturas em bacias tropicais. As modificações foram testadas em cinco bacias localizadas no Estado de São Paulo, com áreas entre 42 e 5.959 km², sendo comparados os resultados obtidos antes e depois da implementação das mesmas. Com as alterações, a análise do balanço hídrico anual evidenciou um aumento nos valores de evapotranspiração de cerca de 61% nas bacias, aproximando-se dos totais anuais de evapotranspiração calculados através de métodos empíricos, bem como houve redução significativa do escoamento superficial. Verificou-se uma melhoria da simulação de vazão em todas as bacias, sendo obtidos valores superiores para o Coeficiente de Eficiência de Nash-Sutcliffe (NSE) quando comparados à simulação sem as alterações. A calibração e validação foram realizadas com base na simulação modificada, sendo obtidos valores de NSE mensais entre 0,71 e 0,93 na calibração e 0,53 e 0,88 na validação, enquanto os valores diários de NSE situaram-se entre 0,51 e 0,82 na calibração e 0,38 e 0,83 na validação. A calibração a partir de uma simulação na qual as distorções dos processos hidrológicos da bacia estivessem previamente minimizadas resultou em bons resultados sem alteração excessiva dos parâmetros, indicando uma simulação hidrológica de melhor consistência. / The Soil and Water Assessment Tool (SWAT) has been used to predict the impact of land management practices on water, sediment, and agricultural chemical yields in a wide range of scales and environmental conditions across the globe. However, originally developed in the United States, some parameters and routines are unrealistic for simulating in tropical watersheds. In this sense, this work aims to improve the hydrologic modeling of SWAT model by reviewing and modifying parameters and routines related to evapotranspiration process. In order to adequately represent crop growth in tropical basins, the proposed procedures included changes in dormancy routines of SWAT source code and modifications of scheduled management operations and plant growth database parameters. These modifications were tested in five different basins at São Paulo State, Brazil, with areas ranging from 42 to 5959 km², by comparing the results before and after their implementation. Annual water balance analysis showed an increase in evapotranspiration about 61% for basins, approaching the total annual evapotranspiration estimated by empirical methods. Hence, it was observed that surface runoff and base flow components showed a decrease. The modifications resulted in improved flow simulation for all basins, showing better Nash-Sutcliffe Efficiency Coefficient (NSE) values compared to the unchanged simulation. Calibration and validation processes used the modified simulation database, being achieved monthly NSE between 0.71 – 0.73 at calibration and 0.53 – 0.88 at validation, while daily NSE were 0.51 – 0.82 at calibration and 0.38 – 0.83 at validation. Overall, minimizing distortions in hydrological processes at pre-calibration step resulted in good estimations without excessive modification of parameters at calibration, attesting a consistent hydrological modeling for the basins analyzed.

Nos últimos anos tem aumentado o interesse no uso do pinhão-manso (Jatropha curcas L.) como fonte de óleo para a produção de biodiesel. No entanto, o conhecimento atualmente disponível sobre o consumo hídrico desta cultura é escasso e constitui um dos principais fatores limitantes no seu uso como alternativa agroenergética. Somado a isso, acredita-se que o aumento da produção de biodiesel no mundo irá aumentar a pressão sobre os recursos hídricos, o que torna necessário utilizar a água na agricultura da forma mais eficiente possível. Assim, este estudo teve como objetivo construir seis lisímetros de pesagem direta que serão utilizados para estudar o consumo hídrico do pinhão-manso irrigado por pivô central, gotejamento e sem irrigação. Esses lisímetros foram calibrados e testados quanto a sua sensibilidade a temperatura do ar e vento. Além disso, comparou-se a influência do uso de duas células de carga diferentes na qualidade dos mesmos. Na área de cada tratamento foram instalados dois lisímetros, sendo um utilizando células de carga ALFA® e outro HBM®. Cada lisímetro foi constituído por tanques de aço carbono de 1,955 m de raio interno (12 m2) e 1,3 m de profundidade útil. Estes foram circundados por paredes de concreto, possuíam sistema de drenagem e se encontravam diretamente apoiados sobre três células de carga. Ambos os modelos das células apresentavam capacidade nominal de 10.000 kg, sendo a capacidade combinada do lisímetro de 30.000 kg. Os lisímetros foram calibrados adicionando e, depois, retirando 1.000 kg de massa dos mesmos. Os dados foram usados para ajustar um modelo de regressão linear entre a massa acumulada e a média do sinal de saída das três células de carga. No teste de sensibilidade à temperatura, a massa dos lisímetros foi monitorada por até dois dias consecutivos, sob condição de massa constante e com proteção para não haver interferência do vento. Os dados foram comparados com a temperatura registrada na estação meteorológica e, também, com a temperatura medida pelo datalogger e um termohigrômetro, os quais foram instalados no fosso dos lisímetros. Para a avaliação da sensibilidade ao vento, foram construídos protótipos de árvores usando tubos de PVC e lonas de ráfia. Em cada lisímetro instalou-se uma árvore e, sob condição de massa constante, a massa dos mesmos foi monitorada por seis dias consecutivos. Os dados obtidos foram comparados com a velocidade do vento medida na estação meteorológica. Todos os lisímetros construídos neste estudo apresentaram qualidade suficiente para serem usados na determinação da evapotranspiração em escala horária e diária. Nos lisímetros ALFA®, a resolução final das medidas foi de 0,0013 mm, sendo realizadas com boa precisão, apresentando histerese e baixa acurácia (erro padrão entre 0,27 e 1,04 mm). Os lisímetros HBM® apresentaram resolução final de 0,00088 mm, boa precisão, pouca ou nenhuma histerese e alta acurácia (erro padrão entre 0,03 e 0,1 mm). Todos os lisímetros demonstraram não sofrer influência da temperatura e do vento na determinação da evapotranspiração, embora, em ambos, ALFA® e HBM®, a precisão das medidas foi reduzida linearmente com o aumento da velocidade do vento. / Recently, there is an increasing interest in using physic nut (Jatropha curcas L.) as a source of oil for biodiesel production. However, currently knowledge regarding its crop water requirement is scarce and constitutes one of the main gaps that limit its use as an agroenergy alternative. In addition, there is a general agreement that an increase in biodiesel production worldwide will bring additional pressure to water resources, what provokes to use water in agriculture in a more efficient way. So, this study had as objective to construct six direct weighing lysimeter that will be used to study the water use of physic nut conducted under sprinkler and drip irrigation, and without irrigation. These lysimeters were calibrated and tested for its sensibility to air temperature and wind. Furthermore, there was also compared the influence of using two different load cells on their quality. Two lysimeters were installed for each treatment, one using ALFA® load cells and other using HBM®. Each lysimeter was constituted by a steel tank with 1.955 m inner radius (12 m2) and 1.3 m of usable depth. They were encompassed by concrete walls, have a drainage system and were directly supported by three load cells. Both load cell models has a nominal capacity of 10,000 kg, with a lysimeter summed capacity of 30,000 kg. Lysimeters calibration procedure was done by adding and, after it, removing 1,000 kg of mass from then. Data were used to fit a linear regression model between the accumulated mass and the mean output value of the three load cells. For testing the sensibility to temperature, lysimeters mass were monitored till two consecutive days, under constant mass and with a barrier for protecting against wind interference. Data were compared to the temperature measured by the weather station and, also, by that measured by a datalogger and a thermohygrometer, which were installed inside the lysimeters pit. For testing to wind sensibility, there were constructed some trees prototypes using PVC pipes and raffia tarpaulin. One tree was installed on each lysimeter and, under constant mass, lysimeters mass were monitored during six consecutive days. Data were compared to the wind velocity, as measured by the weather station. All the six lysimeters constructed in this study presented adequate quality to be used for the determination of evapotranspiration on hourly and daily basis. For ALFA® lysimeters, the final measurement resolution was 0.0013 mm, being obtained with good precision, hysteresis, and low accuracy (standard error of 0.27 to 1.04 mm). HBM® lysimeters presented a final resolution of 0.00088 mm, good precision, few or no hysteresis, and high accuracy (standard error between 0.03 and 0.1 mm). All lysimeters proved to be not influenced by air temperature and wind on the determination of evapotranspiration, in spite of, in both, ALFA® and HBM® lysimeters, their measurement precision was linearly reduced with an increase in wind velocity.

Miscanthus Giganteus is a rapidly growing perennial grass utilizing C4 photosynthesis that is a promising candidate as a raw resource for “second generation” biofuel production. This study seeks to determine the long-term sustainability, from a water balance perspective, of cultivating this plant in different climate zones. CoupModel, a model for the soil-plant-atmosphere system, is utilized to model M. Giganteus and simulate its cultivation over a 30-year period at four sites in Europe, each representing a different climate zone. A future climate scenario building on historical climate data together with projections for monthly changes in temperature and precipitation, as modeled by the HadCM3 global climate model in the A2 emission scenario, is then created and used for another simulation at each site. The growth, yields, and water balances in each simulation are analyzed and compared. The highest yields and water use efficiencies are achieved in the warmest climates, but the most sustainable zones when taking water balance into account are the more humid ones. The humid continental, Dfb, zone and the humid subtropical, Cfa, zone are determined to be sustainable in the long-term for cultivation of M. Giganteus. / Miscanthus Giganteus är ett snabbväxande perennt gräs med C4-fotosyntes samt en lovande kandidat som resurs i tillverkandet av andra generationens biobränslen. Denna studie syftar till att bestämma den långsiktiga hållbarheten av odling av denna växt i olika klimatzoner ur ett vattenbalansperspektiv. CoupModel, en datamodell som simulerar systemet “jord-planta-atmosfär”, används för att simulera M. Giganteus och dess tillväxt över en 30-årsperiod för fyra platser i Europa vilka alla representerar en klimatzon. Ett framtida klimatscenario som bygger på historisk klimatdata tillsammans med projektioner för framtida månatliga förändringar i temperatur och nederbörd, framtaget av HadCM3 för IPCC:s utsläppsscenario A2, tas sedan fram och används för att göra ytterligare en simulering för varje plats. Plantans tillväxt, skörd och vattenbalans för varje simulation analyseras och jämförs. De högsta skördarna och högst vattenanvändningseffektivitet uppnås i de varmaste klimaten, men de mest hållbara zonerna för odling av M. Giganteus när vattenbalansen tas hänsyn till är zonerna med mest nederbörd. Dfb-zonen, med fuktigt inlandsklimat, och Cfa-zonen med fuktigt subtropiskt klimat bedöms vara långsiktigt hållbara för odling av M. Giganteus.

Water resources in hard rock terrain are difficult to characterize due to heterogeneity and anisotropy in the fracture network, low porosities and limited recharge volumes available during the summer season. Three methods were developed and evaluated in order to assist in water supply planning. A groundwater resources potential index was estimated using multivariate statistics, where physical and geological variables were classified using Analysis of Variance and Fisher's Least Significant Difference tests according to their effect on hydraulic properties. Principal component analysis was used to assign weights to the different classed variables. Classes and weights were used to produce an index referred to as groundwater resources potential (GRP), which correlated significantly with well data. Nearly 80% of the wells with less than median specific capacity values also had GRP values at those locations of zero or lower. Non-stationary variance was observed in specific capacity sub-samples taken from the Geological Survey of Sweden's well archive, despite homogeneous geology and topography. Spatial statistical analyses showed that spatial correlations were weak in well archive samples, implying that regional approximations based on sparse point data are highly error prone. Kinematic porosity estimated using superficial fracture measurements correlated significantly with well archive data. However, low correlation coefficients indicated that well data is likely not a suitable method for predicting water supply characteristics. This approach is an efficient method which shows promise in preliminary estimations of groundwater storage in heterogenic terrains. A groundwater balance model which describes seasonal groundwater storage changes was created in order to better approximate the groundwater situation often found in Swedish urbanized and semi-urbanized hard rock terrains. The model was based on a water budget approach at the pixel scale, and allows for approximation of well extraction which is not uniformly distributed in space. The model showed that in specific regions groundwater extraction may lead to severe decreases in groundwater level, where these impacts may not otherwise be expected. Dry season modelling with 10% increased evapotranspiration showed that in several areas groundwater reservoir depletion may be influenced by more than 50%. / <p>QC 20140331</p>

How do additional data of the same and/or different type contribute to reducing model parameter and predictive uncertainties? This was the question addressed with two models – the HBV hydrological water balance model and the ICBM soil carbon balance model – that were used to investigate the usefulness of the Generalized Likelihood Uncertainty Estimation (GLUE) method for calibrations and uncertainty analyses.  The GLUE method is based on threshold screening of Monte Carlo simulations using so-called informal likelihood measures and subjective acceptance criterion. This method is highly appropriate for model calibrations when errors are dominated by epistemic rather than stochastic uncertainties.  The informative value of data for model calibrations was investigated with numerous calibrations aimed at conditioning posterior parameter distributions and boundaries on model predictions.  The key results demonstrated examples of: 1) redundant information in daily time series of hydrological data; 2) diminishing returns in the value of continued time series data collections of the same type; 3) the potential value of additional data of a different type; 4) a means to effectively incorporate fuzzy information in model calibrations; and 5) the robustness of estimated parameter uncertainty for portability of a soil carbon model between and tropical climate zones.  The key to obtaining these insights lied in the methods of uncertainty analysis used to produce them.  A paradigm for selecting between formal and informal likelihood measures in uncertainty analysis is presented and discussed for future use within a context of climate related environmental modeling. / QC 20110414

This study provides a long-term understanding of the impact of climate varia-bility and land use on seasonal water balance conditions for sustainable agricul-ture development, hydropower generation and ecosystem stability in the Lower Rufiji Basin. The severity of soil drought, extreme flooding and salinity intru-sion in the lower Rufiji floodplains are currently increasing smallholder poverty and enhance the sensitivity on the natural wetlands for shifting farming and livestock pastures. The CoupModel and SWAT hydrological model were ap-plied to assess and compare the impact of climate variability on the water bal-ance. The monthly river discharge was used for calibrating and validating the runoff at the Stiegler's Gorge. The simulated results for water balance compo-nents at Stiegler's Gorge showed 55% of accumulated precipitation is lost through evapotranspiration and 42 % is river runoffs for downstream agricul-ture and ecosystem services. The evaluation of the models simulation perfor-mance and posterior distribution of parameter behavioral value indicates the (GLUE) calibration method in the CoupModel agreed satisfactory with the Bayesian calibration (BC). The minimal variance in the Bayesian Calibration posterior parameter distribution was observed in the parameter for regulating water uptake from (CritThresholDry) and soil moisture availability for soil evaporation(PsiRs_ip). The SWAT simulation showed that south of the central floodplains has high risk of soil drought. The overall assessment implies that drought and river runoff dynamics in the LRB is affected by upstream land use activities. The strategies for building smallholder resilience towards climate change and land use impact requires collective and coordinated water manage-ment actions powered by individual, institutional, financial and technological adaptation.

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As the main component of terrestrial energy and water balance, evapotranspiration (ET) moves a large amount of water and energy in the form of latent heat flux from bare soil and vegetated surfaces into the atmosphere. Despite the development of many methods and equations through past decades, accurate ET estimation is still a challenging task, especially for the Red River Valley of the North (RRV) that has limited updated information on ET either for landscape or agricultural water management. The overall objective of first study was to evaluate the ASCE-EWRI reference ET (ETo) method by developing an accurate crop coefficient (Kc) using an eddy covariance (EC) system over an unirrigated turfgrass site. The results showed that with mean ETgrass/ETo ratio as 0.96 for the entire growing seasons of turfgrass, the ASCE-EWRI ETo method is valid for guiding the turfgrass irrigation management in cold climate conditions. In a Controlled drainage with subirrigation (CD+SI) field, an EC system was used to measure and quantify energy flux components along with soil water content (SWC) and water table depth (WTD) measurements during four corn growing. This study showed that the subsurface drainage along with the CD + SI system can be used for optimal water management with an improvement of 26.7% and 6.6% of corn yield during wet and dry year, respectively. For the final task, ET was measured using EC, Bowen ratio system (BREB), and soil water balance (SWB) method during the corn growing season. The comparison of the EC and the BREB system illustrated the advantages of using the residual method to close the energy balance closure of EC. Among the different time approaches for SWB method, ET by the SWB method using the average soil water contents between 24:00 to 2:00 time period showed non-significant differences (alpha = 0.05) compared to the BREB system during the observation periods. / USDA National Institute of Food and Agriculture project / USDA NCR SARE project / ND Soybean Council / ND Water Resources Research Institute / ND Agricultural Experimental Station / USDA Hatch project / NASA ROSES Project