Remote-sensing based indices such as Normalized Difference Vegetation Index have yielded valuable information about plant health. As the availability of water is one of the factors that controls plant's response to their environment, it is possible to indirectly studythe hydrology of an area via vegetation indices. Hence the thesis work used this tool to characterize the potential shifts in vegetation cover within and between years in Kilombero river catchment in Tanzania and make connection to the hydrology in the area. Separate time series analyses conducted on data pertaining to NDVI values and the areal coverage variability of arbitrarily defined NDVI-classes. The former data was extracted from a naturally vegetated wetland in the middle of the catchment while the latter from the topographically defined areas of the catchment. Results from the analyses showed that bothdatasets are sensitive to the seasonal rainfall while at inter-annual scale the areal coverage variability displayed significant correlations with past precipitation. Meanwhile the relatively higher sensitivity of the lowland area‟s NDVI to precipitation conforms to the initial assumption which emphasizes the importance of the wetland sub-catchment codenamed 1KB17 in describing Kilombero‟s hydrology. But the datasets show weak trends and it was not possible to make accurate future predictions on the hydrological conditions in the area. Meteorological distortions like clouds and environmental processes such as climate patterns or disturbances might have caused the problem in trend detection. Further studies needed to shed more light on the connection between land cover and hydrologic response in Kilombero.

This thesis aimed to study how different actors perform hydrological observations in Sweden. Target groups for the study were institutions that regularly measure water stage and river discharge, including water councils, water- and wastewater departments in municipalities, water authorities and hydropower companies. After the identification of the different actors, the study investigated how, where and why they perform hydrological observations as well as the way actors perceive the accuracy of these measurements. Information was collected through interviews and the development of a number of questionnaires. A total of 447 actors were contacted and 260 replied. The majority of them, 209, answered that they do not perform any hydrological measurements while the remaining 51 answered that they measure water stage. One of the main reasons for measuring is that many actors are facing water-rights court ruling. There were also several actors that stated that they perform hydrological measurements to make sure that the water body where water from wastewater treatment plants and storm water is emitted has sufficient water stage for environmental concerns. The hydropower companies replied that they, in addition to maintaining a water-rights court ruling, used water stage data to control the functioning of the plant. They also calculate river discharge based on production, floodgate position and stage. There were also seven municipalities, which stated that they had implemented a flood-monitoring model and that water stage data were used as input to the model. These municipalities and two other actors stated that they measure discharge or use a stage-discharge relationship (rating curve) to derive discharge data. However, in some cases, control measurements were lacking. Most actors used pressure sensors to measure stage. Their perceived levels of accuracy varied from ± 1 mm to ± 5 cm. Only five actors stated that they level their instruments regularly, which is a precondition for maintaining a correct data series. The results are useful for SMHI’s continued review of their hydrological network, although continued attempts to receive answers from all contacted actors would provide a more complete overview of hydrological observations. A study that thoroughly investigates how actors perceive the accuracy of their measurements would also give further knowledge in this field. / Examensarbetet syftade till att undersöka hur olika aktörer genomför hydrologiska mätningar i Sverige. Målgrupper för studien var aktörer vars verksamhet innefattar mätningar av vattenföring och vattenstånd. De målgrupper som identifierades var vattenråd, kommunala VA-avdelningar, vattenmyndigheter och vattenkraftbolag. När aktörerna identifierats undersöktes hur, var och varför aktörerna mäter samt hur de uppfattar noggrannheter i sina mätningar. Informationen samlades in genom frågeformulär och intervjuer. Totalt kontaktades 447 aktörer varav 260 svarade på frågorna som ställdes. Majoriteten, 209 aktörer svarade att de inte utför några hydrologiska mätningar medan resterande svarande att de mäter vattenstånd. Den anledning som flest aktörer gav till att de mäter var att de har en vattendom. Det var även flera aktörer som mätte för att försäkra sig om att recipienter för dagvatten och avloppsreningsverk hade tillräckligt högt vattenstånd för utsläpp. Vattenkraftproducenterna svarade att de, utöver att de har vattendomar, använder vattenståndsdata för att reglera kraftverken. De beräknade också vattenföringen utifrån lucköppningsgrad, vattenstånd och producerad effekt. Det var även sju kommuner som svarade att de hade implementerat modeller för översvämningsövervakning och använde vattenståndsmätningar som indata i prognosmodellerna. Dessa kommuner och två ytterligare aktörer svarade att de mäter vattenföring eller använder avbördningskurvor men i flera fall är kontrollmätningar av vattenföringen bristande. De flesta aktörerna använde tryckgivare för att mäta vattenståndet och de gav noggrannhetsintervall mellan ± 1 mm och ± 5 cm. Endast fem aktörer uppgav att de avväger mätinstrumentet vilket är en förutsättning för att upprätthålla en korrekt mätserie. Resultaten är användbar information i SMHIs utvärdering av sitt nätverk av hydrologiska mätstationer, dock skulle fortsatta försök att få svar från samtliga kontaktade aktörer ge en mer heltäckande bild av hydrologiska mätningar utförda av de olika målgrupperna. Det vore även intressant med en studie som går djupare in på hur noggrannhet uppskattas och uppfattas av de olika aktörerna.

This focuses on hydrological transport in shallow catchments with topography-driven flow paths. The thesis gives new insight to kinematic pathway models for estimation of tracer discharge at the catchment outlet. A semi-analytical methodology is presented for transient travel time and age distributions referred to as "kinematic pathway approach“(KPA) that accounts for dispersion at two levels of morphological and macro-dispersion. Macro-dispersion and morphological dispersion components are reflected in KPA by assuming an effective Péclet number and topographically driven pathway length distributions, respectively. The kinematic measure of the transport, defined as a characteristic velocity of water flow through the catchment is obtained from the overall water balance in the catchment. To include transformation process in its simplest form of linear decay/degradation a framework is presented that solves one-dimensional reactive transport with numerically simulated travel times as the independent variable. The proposed KPA and coupled transport framework for quantifying tracer discharge at the shallow catchment outlet are applied to two selected catchments in Sweden. KPA is applied to modeling of a 23-year long chloride data series for the Kringlan catchment whereas the implantation of the framework for quantifying natural attenuation is illustrated for the Forsmark catchment. Numerical simulations of Forsmark catchment advective travel times are obtained by means of particle tracking using the fully-integrated flow model MIKE SHE. The KPA is found to provide reasonable estimates of tracer discharge distribution when considering the transport controlled by hillslope processes associated with short topographically driven flow paths to adjacent discharge zones, e.g. rivers and lakes. Simulated natural attenuation for Forsmark is also estimated well provided that the pathway length distribution is skewed toward short pathway lengths. This fact is indicative of the controlling impact of topography on flow path length and travel time distributions in shallow catchments. Our work has shown that the pathway (Lagrangian) methodologies are promising as predictive tools for hydrological transport. / <p>QC 20170928</p>

Abstract Water resources management calls for methods to simultaneously manage groundwater (GW) and surface water (SW) systems. These have traditionally been considered separate units of the hydrological cycle, which has led to oversimplification of exchange processes at the GW-SW interface. This thesis studied GW hydrology and the previously unrecognised connection of the Rokua esker aquifer with lakes and streams in the area, with the aim of identifying reasons for lake water level variability and eutrophication in the Rokua esker. GW-SW interactions in the aquifer were first studied with field methods. Seepage meter measurements showed substantial spatial variability in GW-lake interaction, whereas transient variability was more modest, although present and related to the surrounding aquifer. Environmental tracers suggested that water exchange occurs in all lakes in the area, but is of varying magnitude in different lakes. Finally, GW-SW interaction was studied in peatland catchments, where drainage channels in the peat soil presumably increased groundwater outflow from the aquifer. Amount and rate of GW recharge were then estimated with a simulation approach developed explicitly to account for the physical characteristics of the Rokua esker aquifer. This produced a spatially and temporally distributed recharge estimate, which was validated by independent field techniques. The results highlighted the impact of canopy characteristics, and thereby forestry management, on GW recharge. The data collected and the new understanding of site hydrology obtained were refined into a fully integrated surface-subsurface flow model of the Rokua aquifer. Simulation results compared favourably to field observations of GW, lake levels and stream discharge. A major finding was of good agreement between simulated and observed GW inflow to lakes in terms of discharge locations and total influx. This thesis demonstrates the importance of using multiple methods to gain a comprehensive understanding of esker aquifer hydrology with interconnected lakes and streams. Importantly, site-specific information on the reasons for water table variability and the trophic status of Rokua lakes, which is causing local concern, is provided. As the main outcome, various field and modelling methods were tested, refined and shown to be suitable for integrated GW and SW resource management in esker aquifers. / Tiivistelmä Vesivarojen hallinnassa tarvitaan menetelmiä pohja- ja pintaveden kokonaisvaltaiseen huomioimiseen. Pohja- ja pintavesiä tarkastellaan usein erillisinä osina hydrologista kiertoa, mikä on johtanut niiden välisten virtausprosessien yksinkertaistamiseen. Tässä työssä selvitettiin Rokuan pohjavesiesiintymän hydrologiaa ja hydraulista yhteyttä alueella oleviin järviin ja puroihin. Tutkimuksessa pyrittiin osaltaan selvittämään syitä harjualueen järvien pinnanvaihteluun ja veden laatuongelmiin. Kenttätutkimuksissa todettiin voimakasta alueellista vaihtelua järven ja pohjaveden vuorovaikutuksessa. Pohjaveden suotautumisen ajallinen vaihtelu puolestaan oli vähäisempää, mutta havaittavissa, ja kytköksissä järveä ympäröivän pohjavesipinnan vaihteluihin. Merkkiaineet vesinäytteistä viittasivat vastaavan vuorovaikutuksen olevan läsnä myös muissa alueen järvissä, mutta suotautuvan pohjaveden määrän vaihtelevan järvittäin. Turvemailla tehdyt mittaukset osoittivat pohjaveden purkautuvan ojaverkostoon ja ojituksen mahdollisesti lisäävän ulosvirtaamaa pohjavesiesiintymästä. Pohjaveden muodostumismäärää ja -nopeutta tutkittiin numeerisella mallinnuksella, joka kehitettiin huomioimaan harjualueelle ominaiset fysikaaliset tekijät. Mallinnus tuotti arvion ajallisesti ja alueellisesti vaihtelevasta pohjaveden muodostumisesta, joka varmennettiin kenttämittauksilla. Tuloksissa korostui kasvillisuuden, ja sitä kautta metsähakkuiden, vaikutus pohjaveden muodostumismääriin. Hydrologiasta kerätyn aineiston ja kehittyneen prosessiymmärryksen avulla Rokuan harjualueesta muodostettiin täysin integroitu numeerinen pohjavesi-pintavesi virtausmalli. Mallinnustulokset vastasivat mittauksia pohjaveden ja järvien pinnantasoista sekä purovirtaamista. Työn merkittävin tulos oli, että mallinnetut pohjaveden purkautumiskohdat ja purkautumismäärät alueen järviin vastasivat kenttähavaintoja. Tämä työ havainnollisti, että ymmärtääkseen pohjaveden ja siitä riippuvaisten järvien ja purojen vuorovaikutusta harjualueella on käytettävä monipuolisia tutkimusmenetelmiä. Työ toi lisätietoa Rokuan harjualueen vesiongelmien syihin selittäen järvien vedenpinnan vaihtelua ja vedenlaatua pohjavesihydrologialla. Väitöstyön tärkein anti oli erilaisten kenttä- ja mallinnus-menetelmien soveltaminen, kehittäminen ja hyödylliseksi havaitseminen harjualueiden kokonaisvaltaisessa pinta- ja pohjavesien hallinnassa.

I Sverige finns det en brist på studier angående hydrologisk torka trots att det existerar problem med torka idag. Hydrologisk torka kan ha allvarliga konsekvenser på både naturen och samhället när det kommer till vattentillgång, växt -och djurliv och jordbruk. Av den anledningen är det viktigt att studier görs som undersöker allvarligheten i den hydrologiska torkan i Sverige för att få en bättre förståelse. I den här studien användes ett månadsvis Q95 värde som ett tröskelvärde med ett minimum av fem dagar i följd under tröskelvärdet för att definiera hydrologisk torka. Metoden applicerades på fem avrinningsområden in Sverige med data som sträckte sig mellan 1961- 2010. Resultatet från studien visade på att hydrologisk torka var speciellt framträdande under v issa år. Dessa år verkade vara kopplade till varandra under två till tre år i följd. De visade även ofta liknande månader och antal dagar under tröskelvärdet. Andra studier gjorda över de Nordiska länderna visade på liknande resultat. Metoden överensstämde även till en stor del av historisk torka i Sverige. För att kunna ge en större och komplett bild av hydrologisk torka diskuterades några möjliga metoder. Nederbörd, snö, strömflöde, evapotranspiration och grundvatten skulle behöva räknas med för en mer pr ecis studie. Standardiserade index kan täcka de mesta av de olika delarna, men för att få mera specifika förlustvärden så skulle även en tröskelnivå metod behöva implementeras i studien / In Sweden there is a lack of studies on the topic of hydrological drought even though it exist present problems of drought. Hydrological drought can have severe effects on both nature and society regarding water supply, animal life and agriculture. It is important to investigate the severity of hydrological drought in Sweden to get a better understanding of this phenomenon and its affects. To define hydrological drought this study used a Q95 monthly threshold with a minimum of 5 consecutive days below the threshold. This method was used on five catchments in Sweden with data ranging from 1961 -2010. The result from the study showed that hydrological drought was very prominent in some year s. These years seemed to be often linked together in two to three consecutive years. They often had similar amount of days and months below the threshold. Other studies over the Nordic countries showed similar results. The method also gave a result that to a certain degree showed droughts that coincided with historical records of drought in Sweden. This gave a positive feedback of the index accuracy. To get a broader picture of how hydrological drought propagates in Sweden some possible choices were discuss ed. Precipitation, snow, streamflow, evapotranspiration and groundwater would need to be covered for a more precise study. Standardized indices have most of spectrum covered, but it would be suggested to implement the threshold level method as well to get accurate deficits.

L’urbanisation a de multiples impacts sur les processus hydrologiques. A l’échelle du bassin versant, ces impacts sont difficiles à quantifier et les résultats de la littérature sur ce sujet sont assez disparates. L’objectif de cette thèse est d’analyser conjointement l’évolution de l’urbanisation et l’évolution des écoulements des bassins versants. La détection et la quantification des changements d’écoulement potentiellement liés à l’urbanisation des bassins nécessitent de distinguer les changements de débits liés à l’urbanisation de ceux liés à d’autres facteurs de variabilité hydrologique, tels que le climat. Ceci soulève plusieurs questions liées notamment à la relation entre la variabilité du climat et celle de la réponse hydrologique des bassins, et aussi à la détermination d’une mesure de l’urbanisation utile pour l’hydrologie. Pour répondre à ces questions, plusieurs approches ont été testées : 1) Nous avons analysé la fiabilité d’un modèle hydrologique pour simuler l’impact de l’urbanisation. Pour cela, nous avons utilisé la technique des bassins versants appariés : un bassin versant urbanisé proche d’un autre bassin versant non-urbanisé servant de témoin permet d’évaluer l’impact de l’urbanisation sur la réponse hydrologique des bassins. 2) Nous nous sommes également intéressés à la caractérisation de l’urbanisation par des mesures de structure du paysage urbain, en complément de mesures plus classiques (imperméabilité et fraction de surface urbaine). 3) Nous avons ensuite étudié les variables qui expliquent le mieux chaque variable hydrologique de bassin (module et débits caractéristiques de crue et d’étiage. 4) Nous avons enfin utilisé un modèle hydrologique permettant de synthétiser le comportement du bassin versant au cours e son urbanisation.Les résultats ont montré que l’approche par modélisation hydrologique permettait de quantifier d’une façon satisfaisante l’impact du changement d’occupation du sol. Cette approche par modélisation donne des résultats proches de celle par bassins appariés. La thèse met également en évidence que l'impact de l'urbanisation sur la réponse hydrologique du bassin versant reste difficile à généraliser. En effet, une majorité de bassins versants urbains ne présente pas de tendance significative sur les caractéristiques hydrologiques analysées (débits caractéristiques de crue et d’étiage). Enfin, les caractéristiques de fragmentation du paysage urbain fournissent des éléments complémentaires aux mesures plus classiques de l’urbanisation. / Urbanization and population concentration are suspected of having multiple impacts on the catchment’s hydrologic response. It is difficult to synthetize the results from the numerous case studies related to the impact of urbanization on catchment’s hydrologic response. The main objective of this study is to compare the flow changes detected by urbanization. The change flow quantification is impacted simultaneously by climate variability and urbanization, which makes it difficult to distinguish the causal effects of change. To cope with this climate confusing effect and determination a useful measure of urbanization for catchment hydrological response several approach have been tested: 1) We are looking for changes in the hydrological signal time-series in urbanizing catchments and then identifying repeatedly model parameters on successive time periods. The conceptual modelling (top-down) approach was used to calibrate model on the urbanized catchments and simulated the non-urban condition. 2) In addition to traditional urban measures (total impervious area) the urban area were characterized by landscape metrics, which enable analyzing the patterns of historical urban growth. 3) We combine a hydrological model, catchments characteristics and landscape metrics to quantify the explaining variables for the hydrologic response change. 4) We were used the hydrological model to evaluate the catchment behavior over time. Results confirmed that the hydrological model is useful to quantify the impact of land use change. The results show the good agreement between conceptual modelling approaches and the paired catchments approaches change detections.The impact of urbanization on the catchment hydrological response remains difficult to generalize. The most of catchment show the no significant trend on hydrological response over the study. However, results confirmed that the urban fragmentation and landscape metrics provide additional elements compared to the total impervious study.

Les environnements montagneux sont un lieu privilégié d'échange d'eau et d'énergie. Les rivières de montagne alimentent en eau 40% de la population mondiale et sont sujettes à une pression démographique et climatique important. Dans ce contexte, la compréhension des processus météorologiques, hydrologiques et hydrogéologiques est fondamentale pour la gestion globale de la ressource en eau. L'étude, présentée dans ce manuscrit de thèse, se positionne au sein des environnements montagneux où l'hydrologie est influencée par le couvert neigeux saisonnier et par les glaciers, et propose une approche de modélisation interdisciplinaire afin d'améliorer la compréhension des processus en jeu.Aujourd'hui, si les modèles sont capables de simuler le débit sur les rivières de montagnes jaugées sous influence nivale et glaciaire, un certain nombre d'incertitudes persistent quant à l'utilisation de tels modèles hors de leur conditions de validation (en réponse à un climat différent ou sur un domaine non-jaugé). La principale source d'incertitude est liée au manque de connaissance des précipitations en montagne, dont la mesure est rare et incertaine. C'est pourtant la principale composante du bilan hydrologique. A cet égard, nous proposons d'exploiter l'information fournie par la géométrie du couvert neigeux et des glaciers, en tant que “pluviomètres géants” à l'échelle de ces réservoirs, dans un modèle hydrologique à réservoirs conceptuels reposant sur la notion de bassin versant.L'information, hydrologique, nivale et glaciaire est évaluée dans un cadre de calibration multi-objectifs. Les résultats montrent que, dans cette configuration, la validation conjointe du modèle hydrologique par le débit journalier, le bilan de masse glaciaire annuel et la hauteur de neige locale journalier permet de réduire fortement l'incertitude sur le forçage météorologique journalier et d'améliorer la robustesse du modèle. Ce résultat préliminaire nous a permis de reconstruire, en conséquence, le bilan de masse local annuel à l'échelle des glaciers.Par ailleurs, la représentation des glaciers au sein d'un modèle hydrologique pose un certain nombre de défis, surtout dans la perspective de simuler les processus hydrologiques à l'échelle pluri-annuelle. En particulier, la prise en compte de l'évolution de la géométrie des glaciers au sein d'un modèle hydrologique est balbutiante. A cet égard, nous proposons, dans cette étude, des axes d'amélioration de la représentation des glaciers au sein d'un modèle hydrologique par un angle d'investigation géomorphologique. Cette approche a permis d'élaborer un modèle probabiliste permettant de décrire les surfaces englacées au sein d'un bassin versant selon une courbe de niveau. / Mountainous environments are a privileged place of water and energy exchange. Mountainous rivers feed about 40% of the world population and are subjected to climate change and a growing demography. In this context, the comprehension of meteorological, hydrological and hydrogeological processes is essential for a better overall management of water resource. This PhD study is focused squarely on the mountainous environments where hydrology is influenced by snow cover and glaciers, and introduces a multidisciplinary modeling approach in order to improve our comprehension of the process involved.Today, hydrological models are able to simulate gauged mountainous river streamflows under the influence of snow and glaciers but some uncertainties remain when applying such models out of their calibration phase (for instance in response to a different climate or on a ungauged basin). The main uncertainty source is the lack of knowledge of mountainous precipitations, whose measure is sparse and uncertain. It remains the principal component of the hydrological budget though. In this study, we suggest using the meteorological information provided by snow cover and glaciers as “giant pluviometers” to their reservoir scales, with a conceptual reservoir model associated with the concept of watershed.The information provided by hydrology processes, snow and glaciers is assessed in a multi-objective calibration phase. Results show that, in this configuration, the joint validation of the hydrological model by daily streamflow, annual mass balance and daily local snow depth reduces significantly the uncertainty on the meteorological forcing and improves the model robustness. This preliminary result has motivated, consequently, the local annual mass balance of the glaciers.Also, the representation of glaciers in a hydrological model raises a certain amount of issues, especially in the perspective of simulation long-term hydrological processes. In particular, the consideration of the evolution of the glacier geometry is at an early stage. To this end, we propose, in this study, ways of improvements for the representation of glaciers from a geomorphological perspective. This approach allowed us to build a probabilistic model able to describe the glaciated surfaces within a watershed according to a given topographic contour line.

abstract: The National Oceanic and Atmospheric Administration (NOAA)’s National Water Model (NWM) will provide the next generation of operational streamflow forecasts at different lead times across United States using the Weather Research and Forecasting (WRF)-Hydro hydrologic system. These forecasts are crucial for flood protection agencies and water utilities, including the Salt River Project (SRP). The main goal of this study is to calibrate WRF-Hydro in the Oak Creek Basin (OCB; ~820 km2), an unregulated mountain sub-watershed of the Salt and Verde River basins in Central Arizona, whose water resources are managed by SRP and crucial for the Phoenix Metropolitan area. As in the NWM, WRF-Hydro was set up at 1-km (250-m) resolution for the computation of the rainfall-runoff (routing) processes. Model forcings were obtained by bias correcting meteorological data from the North American Land Data Assimilation System-2 (NLDAS-2). A manual calibration approach was designed that targets, in sequence, the sets of model parameters controlling four main processes responsible for streamflow and flood generation in the OCB. After a first calibration effort, it was found that WRF-Hydro is able to simulate runoff generated after snowmelt and baseflow, as well as magnitude and timing of flood peaks due to winter storms. However, the model underestimates the magnitude of flood peaks caused by summer thunderstorms, likely because these storms are not captured by NLDAS-2. To circumvent this, a seasonal modification of soil parameters was adopted. When doing so, acceptable model performances were obtained during calibration (2008-2011) and validation (2012-2017) periods (NSE > 0.62 and RMSE = ~2.5 m3/s at the daily time scale). The process-based calibration strategy utilized in this work provides a new approach to identify areas of structural improvement for WRF-Hydro and the NWM. / Dissertation/Thesis / Masters Thesis Civil, Environmental and Sustainable Engineering 2020

In February of 2014 NASA has launched the core observatory of The Global Precipitation Measurement Mission (GPM). Since then, the mission has been providing a wealth of observation data collected by the core observatory along with other satellites belonging to the mission space constellation. One of the most important data products that GPM provides is the Level 4 (L4) rainfall data product called Integrated Multi-satellitE Retrievals for GPM (IMERG). IMERG is constructed using the raw data collected by the Microwave (MW) sensors on board the constellation satellites along with the Infrared (IR) sensors on board geostationary satellites and the advance Dual-frequency Precipitation Radar (DPR) on board the GPM core satellite. The IMERG product is available globally for all interested researchers to use. In this dissertation, I focus on the applicability of IMERG in hydrologic applications, and specifically in flood peak modeling. In order to conduct a comprehensive evaluation of IMERG that is oriented towards hydrologic modeling. I have explored multiple hydrologic models which can be used to produce stream flow estimates using IMERG without the need of parameter calibration based on the model’s inputs. The calibration free capability is essential since model parameter calibration obscures the effect of the errors associated with the rainfall input on the estimated discharges, which in turn will limit our understanding about the distribution of the errors in IMERG over space and time. The two hydrologic models we used in this study are both physically based distributed models and were setup over the domain of the state of Iowa which is located in the United States’ Midwest. I also explored the performance of one of the hydrologic models’ component, which is the runoff-routing component, in order to estimate an additional portion of the errors in the discharge estimates that is not attributed to the model’s input but rather to the hydrologic model itself. A significant portion of my dissertation is concerned with identifying and using accurate methods to evaluate both IMERG and the hydrologic models’ outputs in a hydrologic context that is useful for flood modeling. Several studies have evaluated other satellite rainfall products using methods that vary in complexity. Some studies used the simplest methods of evaluation, such as, mean aerial differences and standard deviation of the differences (additive or multiplicative) compared to a benchmark rainfall product. This is done without taking the spatial dependency of the errors in space into consideration. Other studies modeled the spatial dependency (correlation) between the errors in the rainfall product, however, using Euclidean distance based approaches that do not account for the hydrologic basins’ shape and size. Nevertheless, it is important to realize that hydrologic models will eventually aggregate the rainfall values, along with the errors associated with them, through a stream network that is dichotomous in nature and does not comply with Euclidean distance. Thus, we employed a stream based evaluation framework, called the Spatial Stream Network (SSN) approaches, to characterize the errors in IMERG taking into account the stream distances and the stream connectivity information between evaluation sites. Although previously used in applications such as modeling water temperatures and pollutant transport, to the best of my knowledge this approach has not been used in rainfall product evaluation before this study. The SSN analysis of IMERG allowed me to answer the question, “What is the proper basin scale which is capable of filtering out the correlated errors in IMERG by accumulating the rainfall values through the stream network?” Finally, in order to add value to the current methods of evaluating model simulated stream flows. I proposed a time based evaluation that is capable of detecting peaks in both the observed and simulated flows and estimating the lag time of the simulated peaks. Typically, previous studies have used simple skill scores such as Root Mean Squared Errors (RMSE), correlation coefficient, and Nash-Sutcliff Efficiency (NSE) to evaluate hydrograph performance as a whole, or the difference in time to peak which involves primitive peak detection method (e.g., a moving or a defined time window). In this dissertation I propose a Continuous Wavelet Transform (CWT) based method to evaluate the peak times and shapes produced by the hydrologic model. The method is based on filtering the frequencies in the hydrograph by treating it as a signal and detecting sharp features in both the observed and time series and the phase difference between them. We also emphasized on the importance of the choice of wavelet shape used in the evaluation, and how different wavelet shapes can affect the inference about the time series.

Orientador: Luiz Fernando Rolim de Almeida / Resumo: Orquídeas epífitas estão expostas a diferentes microclimas, que são caracterizados pela alta irradiância imposta ao dossel e baixa irradiância em plantas situadas no sub-bosque. Além disso, este grupo de plantas frequentemente lida com a restrição hídrica. Na produção comercial, o estabelecimento de orquídeas é em quase sua totalidade limitada pela distribuição e intensidade destes mesmos fatores disponibilizados em casas de vegetação. Gomesa flexuosa Sims e Oncidium sphacelatum Lindley pertencem à subtribo Oncidiinae, e quando hibridizadas dão origem a O. ‘Aloha’ (uma orquídea CAM facultativa e importante híbrida comercial). O objetivo deste estudo foi elucidar a performance fotossintética e as estratégias de balanço hídrico de G. flexuosa e O. sphacelatum sob condições de estresse hídrico e luminoso, focando tanto nas diferenças interespecíficas como nas funções dos diferentes órgãos em um mesmo indivíduo. Para isso, analisamos trocas gasosas, fluorescência da clorofila a, quantificação de lipoperóxidos, discriminação isotópica, acidez titulável, conteúdo relativo de água e potencial hídrico em tecidos foliares, de pseudobulbos e raízes, em diferentes tratamentos envolvendo restrição hídrica e variação luminosa. Depois de restrição hídrica por 60 dias, G. flexuosa apresentou conversão de metabolismo C3 para CAM, o que deu subsídios para uma melhor performance das trocas gasosas, fluorescência da clorofila a, mecanismo de fotoproteção e relações hídricas. Quando submetida a ... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Epiphyte orchids are exposed to different microclimates, which are characterized by high irradiance imposed on the canopy and low irradiance in plants located on the understory. In addition, this group of plants frequently deals with water restriction. In commercial production, the distribution and intensity of these same factors inside the greenhouses also limit the orchids establishment. Gomesa flexuosa Sims and Oncidium sphacelatum Lindley are Oncidiinae species and when hybridized, it gave origin to O. ‘Aloha’ (a facultative CAM orchid and na important commercial hybrid). The aim of this study was to elucidate the photosynthetic performance and the water balance strategies of G. flexuosa and O. sphacelatum under water and light stress conditions, focusing on an interspecific diferences as well as on different organs functions in the same individual. For that, we analyzed the gas exchange, chlorophyll a fluorescence, lipoperoxides quantification, isotopic discrimination, titratable acidity, water relative content and water potential of leaf, pseudobulb and root tissues in different treatments involving water restriction and light variation. After 60 days of water restriction, G. flexuosa converted the photosynthetic metabolism from C3 to CAM, which provided a better performance on gas exchanges, chlorophyll a fluorescence, photoprotection mechanism and water relations. When G. flexuosa was submitted to two events of water restriction, it showed a capacity to store informat... (Complete abstract click electronic access below) / Doutor