No description available.

Anthropogenic activities including urbanization, rapid industrialization, deforestation and burning of fossil fuels are broadly agreed on as primary causes for ongoing climate change. Scientists agree that climate change over the next century will continue to impact water resources with serious implications including storm surge flooding and a sea level rise projected for North America. To date, the majority of climate change studies conducted across the globe have been for large-sized watersheds; more attention is required to assess the impact of climate change on smaller watersheds, which can help to better frame sustainable water management strategies. In the first of three studies described in this dissertation, trends in annual precipitation and air-temperature across the Commonwealth of Kentucky were evaluated using the non-parametric Mann-Kendall test considering meteorological time series data from 84 weather stations. Results indicated that while annual precipitation and mean annual temperature have been stable for most of Kentucky over the period 1950-2010, there is evidence of increases (averages of 4.1 mm/year increase in annual precipitation and 0.01 °C/year in mean annual temperature) along the borders of the Kentucky. Considered in its totality, available information indicates that climate change will occur – indeed, it is occurring – and while much of the state might not clearly indicate it at present, Kentucky will almost certainly not be exempt from its effects. Spatial analysis of the trend results indicated that eastern part of the state, which is characterized by relatively high elevations, has been experiencing decreasing trends in precipitation. In the second study, trends and variability of seven extreme precipitation indices (total precipitation on wet days, PRCPTOT; maximum length of dry and wet periods, CDD and CWD, respectively; number of days with precipitation depth ≥20 mm, R20mm; maximum five-day precipitation depth, RX5day; simple daily precipitation intensity, SDII; and standardized precipitation index, SPI were analyzed for the Kentucky River Basin for both baseline period of 1986-2015 and the late-century time frame of 2070-2099. For the baseline period, the majority of the indices demonstrated increasing trends; however, statistically significant trends were found for only ~11% of station-index combinations of the 16 weather stations considered. Projected magnitudes for PRCPTOT, CDD, CWD, RX5day and SPI, indices associated with the macroweather regime, demonstrated general consistency with trends previously identified and indicated modest increases in PRCPTOT and CWD, slight decreases in CDD, mixed results for RX5day, and increased non-drought years in the late century relative to the baseline period. The study’s findings indicate that future conditions might be characterized by more rainy days but fewer large rainfall events; this might lead to a scenario of increased average annual rainfall but, at the same time, increased water scarcity during times of maximum demand. In the third and final study, the potential impact of climate change on hydrologic processes and droughts over the Kentucky River basin was studied using the watershed model Soil and Water Assessment Tool (SWAT). The SWAT model was successfully calibrated and validated and then forced with forecasted precipitation and temperature outputs from a suite of CMIP5 global climate model (GCMs) corresponding to two different representative concentration pathways (RCP 4.5 and 8.5) for two time periods: 2036-2065 and 2070-2099, referred to as mid-century and late-century, respectively. Climate projections indicate that there will be modest increases in average annual precipitation and temperature in the future compared to the baseline (1976-2005) period. Monthly variations of water yield and surface runoff demonstrated an increasing trend in spring and autumn, while winter months are projected as having decreasing trends. In general, maximum drought length is expected to increase, while drought intensity might decrease under future climatic conditions. Hydrological droughts (reflective of water availability), however, are predicted to be less intense but more persistent than meteorological droughts (which are more reflective of only meteorological variables). Results of this study could be helpful for preparing any climate change adaptation plan to ensure sustainable water resources in the Kentucky River Basin.

Temporary streams and their dynamics have often been largely overseen in hydrological research and there is relatively little knowledge about how the occurrence of flow in these streams varies temporally and spatially. Temporary streams are important from a hydro- logical perspective because they affect water quantity and quality in downstream peren- nial reaches, and from an ecological perspective because they provide habitat to unique species. In order to gain knowledge about these important streams, this maser thesis was conducted, within the Msc program in Water and Environmental Engineering at Uppsala University and the Swedish University of Agricultural Sciences, in collaboration with the Hydrology and Climate group at the University of Zurich. In this study, the temporal and spatial variation of the temporary streams in a small pre-Alpine catchment in Switzerland were investigated, both in terms of the presence of flowing water and stream chemistry. The 20 ha Studibach catchment is typical for the pre-Alpine area, with frequent precipi- tation. The streams in the lower part of the Studibach catchment were mapped in the field during September 2020. The temporal and spatial variations of the presence of flow and stream chemistry within the stream network was investigated in September and October 2020 during varying weather conditions. During ten field campaigns the flow state of the streams was classified and the Electrical Conductivity (EC) of the streams was mea- sured approximately every 20 meter. The findings from the field campaigns were related to topographic indices, in particular the Topographic Wetness Index (TWI) and Upslope Accumulated Area (A), in order to see how topography influenced the presence of stream- flow and stream EC. The results show a high temporal and spatial variation in both stream chemistry and streamflow. The active network length expanded by a factor of two in re- sponse to precipitation events. The stream EC also had a large spatial variation, and the streams in the southeast part of the catchment had a higher EC than the other streams. This spatial variation is expected to reflect the large variability in groundwater EC within the catchment. The spatial variation of the streamflow demonstrated a difference between the north-middle and the south part of the catchment, where the south part responded quicker to events and drained and retracted faster after the event. The findings also indicate that topographic indices can predict the occurrence of flow in the stream network, with sites with higher topographic index values having a higher probability of flowing water in the stream. Topography also influences the stream chemistry. The variation in stream chem- istry was smaller for sites with higher values for the topographic indices, something that can be explained by the Representative Elementary Area (REA) concept, because sites with higher topographic index values are located further downstream and water at these locations is a mixture of the smaller streams that feed these streams. / Temporära bäckar och dess dynamik har länge varit förbisedda inom hydrologisk forskn- ing, och en djupgående kunskap rörande temporära och rumsliga variationer saknas. Tem- porära bäckar är viktiga utifrån ett hydrologisk perspektiv eftersom de påverkar både kvantitet och kvalitet på vattnet nedströms, och från ett ekologiskt perspektiv eftersom de bidrar med habitat till unika arter. Detta examensarbete har genomförts för att öka kunskapen kring dynamiken i dessa temporära nätverk. Examensarbetet genomfördes inom Civilingenjörsprogrammet i Miljö och Vattenteknik vid Uppsala Universitet och Sveriges Lantbruksuniversitet, i ett samarbete med Hydrologi- och Klimatgruppen vid University of Zurich. Studien har undersökt temporära och rumsliga variationer i ett tem- porärt bäcknätverk med avseende på flöden och kemin i vattnet, i ett mindre pre-alpint avrinningsområde i centrala Schweiz. Bäckarna i den nedre delen av avrinningsområdet Studibach karterades i fält för hand med karta och kompass under september 2020. Avrin- ningsområdet är på 20 ha och räknas som typiskt för ett pre-Alpint område, med frekvent nederbörd. Tio fältkampanjer genomfördes där temporära och rumsliga variationer un- dersöktes genom klassificering av flöden och mätningar av Elektrisk Konduktivitet (EC) i bäckarna ungefär var 20e meter, under september och oktober 2020 i varierande väder- förhållanden. Resultaten från fältkampanjerna relaterades till de topografiska indexen Topographic Wetness Index (TWI) och Upslope Accumulated Area (A) för att undersöka hur topografin påverkar flöden och bäckkemin. Studien kom fram till att bäckarna i den nedre delen av Studibach visar både en temporär och en rumslig variation för både flöde och bäckkemi. De aktiva bäckarna i nätverket visade på en expansion med en faktor två som svar på nederbörd. En rumslig variation för flödet påträffades även mellan den södra och nord-centrala delen av nätverket där den södra svarade snabbare mot event och även drogs ihop snabbare. Kemin i bäckvattnet visade på en stor rumslig variation, med högt EC i den sydöstra delen av avrinningsområdet, vilket förmodas bero på den stora rumsliga variationen av EC i grundvattnet. Resultaten visar även på att topografiska index kan till viss del förutspå flöden i bäckarna, där platser med högre topografiska index har högre sannolikhet att det flödar i bäcken. Topografin påverkar även bäckkemin. Variationen i bäckkemin var mindre för platser med högre topografiska index, vilket kan förklaras med Representative Elementary Area (REA) konceptet, eftersom platser med högre to- pogragiska index värden återfinns längre nedströms och vattnet på dessa platser är en blandning av de mindre bäckarna som tillför vattnet till de större.

No description available.

Within the frame work of the International Water Research Alliance Saxony (IWAS), project “Middle East” a complex integrated water management system is developed and tested in the project region of Middle East (Oman and Saudi-Arabia). Hence, new solutions for a sustainable management of the scarce water resources in (semi-) arid regions are explored within IWAS in the sultanate of Oman on which this study work is carried out. Rainfall runoff models are established to estimate the “water yield” of the catchments in the project region. Modeling is a very important tool that enables hydrologists to make more comprehensive use of rainfall time series. Rainfall-runoff modeling is also useful for water resources assessment as these models can generate a long representative time series of stream flow volumes from which water supply schemes can be designed (D.A. Hughes, 1995). Therefore, this study project mainly focuses on the following main tasks such as data analysis, data processing and statistical evaluation; Model selection and model setup; Model adaptation test and verification. As part of the common modeling protocol, sensitivity analysis of a Rainfall-Runoff Modeling Toolbox (RRMT) is carried out in this study with the aim to identify sensitive model parameters. RRMT has been developed in order to produce parsimonious, lumped model structures with a high level of parameter identifiability. Such identifiability is crucial if relationships between the model parameters representing the system and catchment characteristics are to be established. RRMT is a modular framework that allows its user to implement different model structures to find a suitable balance between model performance and parameter identifiability. The study is carried out in the upper catchment part of Wadi Ma’wil (gauge near to Afi’), Batinah Region of the Sultanate of Oman. Arid and semi-arid zones are characterized by rainfall which is highly variable in space, time, quantity and duration (Noy-Meir, 1973). The Sultanate of Oman is characterized by hyper-arid (<100 mm rainfall), through the arid (100–250 mm rainfall) and semi-arid (250–500 mm rainfall) environments that are experienced in different parts of the country. Furthermore, arid areas have distinctive hydrological features substantially different from those of humid areas. The high temporal and spatial distribution of the rainfall, flash floods, absence of base flow, sparsity of plant cover, high transmission losses, high amounts of evaporation and evapotranspiration and the general climatologies are examples of such differences.:Acknowledgments i Abstract ii List of Figures and Photos v List of Tables and Plots v 1. Description of Study Area 1 1.1 General characteristics of arid regions 1 1.2 Study area (Batinah Region and Ma’awil catchment of gauge ‘Afi’) 2 1.2.1 Overview of Study area 2 1.2.2 Wadi Ma’awil and Gauge near to Afi’ 3 2. Data Processing and Evaluation 6 2.1 Rainfall data 6 2.1.1 Monthly and Annual Mean Rainfall Analyses 6 2.1.2 Estimation of Missing Precipitation Data 6 2.1.3 Annual and monthly average rainfall 6 2.2 Runoff data 9 2.2.1Rainfall-Runoff events – Processing and Analysis 9 2.2.2 Wadi Ma’awil Runoff Analysis 9 2.3 Areal Precipitation 11 2.3.1 Area 11 2.3.2 Summary of Calculated Results of Mean Annual Areal Precipitation 12 2.4 Evapotranspiration 13 2.4.1 Evaporation and Potential Evapotranspiration 13 2.4.2 Calculation of Evapotranspiration by FAO Penman-Monteith Equation 13 2.4.3 Sample Calculation for Daily ET using FAO Penman-Monteith Equation 14 2.4.4 Comparisons of Evapotranspiration Calculation Results 16 3. Rainfall-Runoff Modeling 16 3.1 Modeling approach – selection of modules 16 3.1.1 Basic Principle 16 3.1.2 Classification of models 16 3.1.3 Modeling Process 17 3.2 Rainfall-Runoff Modeling Toolbox 19 3.2.1 Introduction 19 3.2.2 Data Needs and Model Structure 20 3.3 Provision of input data 20 3.4 Calibration and Validation 20 3.4.1 Model Calibration and Validation 21 3.5 Sensitivity Analysis 22 3.6 Discussions of Results 23 3.6.1 Optimization Modules 23 3.6.2 Soil Moisture Accounting (SMA) Modules 24 3.6.3 Routing (R) Modules 25 3.6.4 The objective functions 26 3.6.5 Visualization Modules Results 27 3.7 Conclusions and Recommendations 35 3.7.1 Conclusions 35 3.7.2 Limitations and Recommendations 35 References 37 Appendix 38 Appendix A: Daily extraterrestrial radiation (Ra) for different latitudes for the 15th day of the month 38 Appendix B: Mean daylight hours (N) for different latitudes for the 15th of the month 38 Annexes 39 Annex - A: Mean Rainfall for the Gauge Afi’ from 1995 – 2005 39 Annex A-1: Annual Mean Rainfall for Gauge Afi’ for the time period 1995-2005 39 Annex A-2: Monthly Mean Rainfall for Gauge Afi’ for the time period 1995-2005 39 Annex A-3: Monthly Mean Rainfall for each Rain Gauge within the Wadi Ma’awil Catchment area for the time period 1995-2005 40 Annex - B: Rainfall - Runoff events for the Gauge Afi’ 41 Annex B-1: Annual Rainfall Vs Runoff events for the Gauge Afi’ from 1995 – 2005 42 Annex B-2: Monthly Rainfall Vs Runoff events for the Gauge Afi’ from 1995 – 2005 44 Annex B-3: Daily Rainfall Vs Runoff events for the Gauge Afi’ sample graphs with the time period from 1995to 2005 46

The work deal with the measurement, processing and analysis of Q/h characteristics of the sluice chamber in the wastewater treatment plant on a physical hydraulic model in the conditions of influencing the overflow phenomenon by the groundwater level. Based on the achieved results, a measuring system has been projected in the area of the sluice chamber to measure the flow and flow rate of lightened water into the Svratka river. The measurements on the model were performed in the premises of the Laboratory of water Management Research of the Institute of Water Structures of the Faculty of Civil Engineering of Brno University of Technology by the author of this work. The results of the diploma thesis is a flow chart describing the calculation procedure used to determine the immediate flow, on the basis of which a new software of the evaluation unit of the measuring system was realized.

No description available.

Evapotranspiration ET is a dominant Earth System process that couples the water and energy cycles at the earth surface. The pressure of global environmental changes foster the broad scientific aim to understand impacts of climate and land-use on evapotranspiration under transient conditions. In this work, the spatial scale of river catchments is addressed through data analysis of hydrological and meteorological archives with ET classically derived through water balance closure. Through a synthesis of various catchments with different climatic forcings and hydrological conditions, the core objectives of this thesis are: - Did environmental changes in the past, such as climatic- or land-use and land cover (LULC) changes, result in detectable non-stationary changes in the hydro-climate time series? - How can the impacts of climatic- from LULC changes on the hydroclimatology of catchments be separated? - What are the factors that control the sensitivity of ET and streamflow to external changes? These research questions are addressed for the climatic scales of long-term annual averages and seasonal conditions which characterise the hydroclimatology of river catchments. Illustrated by a rich hydro-climatic archive condensed for 27 small to medium sized river catchments in Saxony, a method is proposed to analyse the seasonal features of river flow allowing to detect shifting seasons in snow affected river basins in the last 90 years. Observations of snow depth at these same times lead to the conclusion, that changes in the annual cycle of air temperature have a large influence on the timing of the freeze-thaw in late winter and early spring. This causes large changes in storage of water in the snow pack, which leads to profound changes of the river regime, particularly affecting the river flow in the following months. A model-based data analysis, based on the fundamental principles of water and energy conservation for long-term average conditions, is proposed for the prediction of ET and streamflow, as well as the separation of climate related impacts from impacts resulting from changes in basin conditions. The framework was tested on a large data set of river catchments in the continental US and is shown to be consistent with other methods proposed in the literature. The observed past changes highlight that (i) changes in climate, such as precipitation or evaporative demand, result in changes of the partitioning within the water and energy balance, (ii) the aridity of the climate and to a lesser degree basin conditions determine the sensitivity to external changes, (iii) these controlling factors influence the direction of LULC change impacts, which in some cases can be larger than climate impacts. This work provides evidence, that changes in climatic and land cover conditions can lead to transient hydrological behaviours and make stationary assumptions invalid. Hence, past changes present the opportunity for model testing and thereby deriving fundamental laws and concepts at the scale of interest, which are not affected by changes in the boundary conditions.:Kurzfassung Abstract List of Manuscripts Symbols and abbreviations List of Symbols List of abbreviations 1 Introduction 1.1 Motivation and relevance 1.1.1 Scientific importance of evapotranspiration 1.1.2 Pressure of human driven changes 1.1.3 Practical importance of evapotranspiration 1.2 Scope 1.2.1 Focus on the catchment scale 1.2.2 Changes in the hydroclimatology of river catchments 1.2.3 Hydro-climate data analysis 1.3 Objectives and research questions 1.3.1 Shifting seasons in hydrology 1.3.2 Long-term annual average changes of evapotranspiration and streamflow 1.3.3 Methodological requirements 1.4 Structure of the thesis 2 Long term variability of the annual hydrological regime 2.1 Introduction 2.1.1 Motivation 2.1.2 Seasonal changes in hydrologic records 2.1.3 Regional climate in Saxony 2.1.4 Objective and structure 2.2 Methods 2.2.1 Annual periodic signal extraction 2.2.2 The runoff ratio and its annual phase 2.2.3 Descriptive circular statistics 2.2.4 Detection of nonstationarities, trends and change points 2.3 Data 2.4.1 Estimation and variability of the timing of the runoff ratio 2.4.2 Temporal variability of the timing 2.4.3 Does temperature explain trends in seasonality of runoff ratio? 2.4.4 Trend analysis in snow dominated basins 2.4.5 Uncertainty and significance of the results 2.5 Conclusions 2.A Preparation of basin input data 2.A.1 Precipitation 2.A.2 Temperature and snow depth data 3 Evaluation of water-energy balance frameworks 3.1 Introduction 3.2 Theory 3.2.1 Coupled water and energy balance 3.2.2 The ecohydrologic framework for change attribution 3.2.3 Applying the climate change hypothesis to predict changes in basin evapo transpiration and streamflow 3.2.4 Derivation of climatic sensitivity using the CCUW hypothesis 3.2.5 The Budyko hypothesis and derived sensitivities 3.3 Sensitivity analysis 3.3.1 Mapping of the Budyko functions into UW space 3.3.2 Mapping CCUW into Budyko space 3.3.3 Climatic sensitivity of basin evapotranspiration and streamflow 3.3.4 Climate-vegetation feedback effects 3.4 Application: three case studies 3.4.1 Mississippi River Basin (MRB) 3.4.2 Headwaters of the Yellow River Basin (HYRB) 3.4.3 Murray-Darling River Basin (MDB) 3.5 Conclusions 3.5.1 Potentials and limitations 3.5.2 Insights on the catchment parameter 3.5.3 Validation 3.5.4 Perspectives 3.A Derivation of the climate change direction 4 Climate sensitivity of streamflow over the continental United States 4.1 Introduction 4.1.1 Motivation 4.1.2 Hydro-climate of the continental US 4.1.3 Aims and research questions 4.2 Methods 4.2.1 Ecohydrological concept to separate impacts of climate and basin changes 4.2.2 Streamflow change prediction based on a coupled water-energy balance framework 4.2.3 Streamflow change prediction based on the Budyko hypothesis 4.2.4 Statistical classification of potential climate and basin change impacts 4.3 Data 4.4 Results and discussion 4.4.1 Hydro-climate conditions in the US 4.4.2 Climate sensitivity of streamflow 4.4.3 Assessment of observed and predicted changes in streamflow 4.4.4 Uncertainty discussion 4.5 Conclusions 4.A Mathematical derivations for the Mezentsev function 5 Summary and conclusions 5.1 Shifting seasons in hydrology 5.1.1 Major findings 5.1.2 Socio-economic and political relevance 5.1.3 Limitations and possible directions for further research 5.2 Long-term annual changes in ET and streamflow 5.2.1 Major findings 5.2.2 Socio-economic and political relevance 5.2.3 Limitations and further research 5.3 General conclusions and outlook 5.3.1 Regional and temporal limits and validity 5.3.2 Hydrological records carry signals of climate and land use change 5.3.3 Statistical significance of past changes 5.3.4 Improvements in assessing ET 5.3.5 Remote sensing 5.3.6 Learning from the past to predict the future? Bibliography Danksagung Erklärung / Die Verdunstung ist ein maßgeblicher Prozess innerhalb des Klimasystems der Erde, welche den Wasserkreislauf mit dem Energiehaushalt der Erde verbindet. Eine zentrale wissenschaftliche Herausforderung ist, zu verstehen, wie die regionale Wasserverfügbarkeit durch Änderungen des Klimas oder der physiographischen Eigenschaften der Landoberfläche beeinflusst wird. Mittels einer integrierten Datenanalyse von vorhandenen langjährigen Archiven hydroklimatischer Zeitreihen werden die folgenden wissenschaftlichen Fragestellungen dieser Dissertation diskutiert: - Haben beobachtete Änderungen der Landoberfläche und des Klimas zu nachweisbaren, instationären hydroklimatischen Änderungen geführt? - Lassen sich die hydroklimatischen Auswirkungen von Klimaänderungen und Änderungen der Landoberfläche voneinander unterscheiden? - Welche Faktoren beeinflussen die Sensitivität von Abfluss und Verdunstung auf Veränderungen der klimatischen und physiographischen Randbedingungen? Hierbei fokussiert sich die Arbeit auf Änderungen im langjährige Mittel und im Jahresgang von hydroklimatischen Variablen auf der räumlichen Skala von Flusseinzugsgebieten. Zur Untersuchung des hydrologischen Regimes wurde ein harmonischer Filter angewandt, der es erlaubt, die Eintrittszeit des Jahresgangs (Phase) zu quantifizieren. Diese klimatologische Kenngröße wurde für eine Vielzahl von Einzugsgebieten in Sachsen untersucht, wobei sich vor allem für die Gebiete in den Kammlagen des Erzgebirges signifikante Veränderungen ergaben. Es konnte gezeigt werden, dass die signifikante Phasenverschiebung der Temperatur seit Ende der 1980er Jahre zu einer verfrühten Schneeschmelze und dadurch zu einem Rückgang des Abflusses bis in die Sommermonate hinein geführt hat. Desweiteren wurde eine modellbasierte Datenanalyse entwickelt, welche auf Massen- und Energieerhalt von Einzugsgebieten im langjährigen Mittel beruht. Das entwickelte Konzept erlaubt es, Auswirkungen von Klimaänderungen von anderen Effekten, welche z.B. durch Landnutzungsänderungen bedingt sind, abzugrenzen und zu quantifizieren. Die Ergebnisse einer Sensitivitätsanalyse dieses Konzeptes sowie die Anwendung auf einen umfangreichen hydroklimatischen Datensatz der USA zeigen: (i) Veränderungen im Wasser- oder Energiedargebot beeinflussen auch die Aufteilung der Wasser- und Energieflüsse. (ii) Die Aridität des Klimas und nachgeordnet die physiographischen Faktoren bestimmen die Sensitivität von Verdunstung und Abfluss. (iii) Beide Faktoren beeinflussen die Stärke und Richtung der Auswirkungen von physiographischen Änderungen. (iv) Anthropogene Veränderungen der Landoberfläche führten zum Teil zu stärkeren Auswirkungen als klimatisch bedingte Änderungen. Zusammenfassend zeigt sich, dass Änderungen von Landnutzung und Klima zu Verschiebungen im Wasserhaushalt führen können und damit auch die Annahme von Stationarität verletzen. Hydroklimatische Veränderungen bieten aber auch eine Gelegenheit zum Testen von Theorien und Modellen, um somit die grundlegenden Zusammenhänge zu erkennen, welche nicht durch Änderungen der Randbedingungen hinfällig werden.:Kurzfassung Abstract List of Manuscripts Symbols and abbreviations List of Symbols List of abbreviations 1 Introduction 1.1 Motivation and relevance 1.1.1 Scientific importance of evapotranspiration 1.1.2 Pressure of human driven changes 1.1.3 Practical importance of evapotranspiration 1.2 Scope 1.2.1 Focus on the catchment scale 1.2.2 Changes in the hydroclimatology of river catchments 1.2.3 Hydro-climate data analysis 1.3 Objectives and research questions 1.3.1 Shifting seasons in hydrology 1.3.2 Long-term annual average changes of evapotranspiration and streamflow 1.3.3 Methodological requirements 1.4 Structure of the thesis 2 Long term variability of the annual hydrological regime 2.1 Introduction 2.1.1 Motivation 2.1.2 Seasonal changes in hydrologic records 2.1.3 Regional climate in Saxony 2.1.4 Objective and structure 2.2 Methods 2.2.1 Annual periodic signal extraction 2.2.2 The runoff ratio and its annual phase 2.2.3 Descriptive circular statistics 2.2.4 Detection of nonstationarities, trends and change points 2.3 Data 2.4.1 Estimation and variability of the timing of the runoff ratio 2.4.2 Temporal variability of the timing 2.4.3 Does temperature explain trends in seasonality of runoff ratio? 2.4.4 Trend analysis in snow dominated basins 2.4.5 Uncertainty and significance of the results 2.5 Conclusions 2.A Preparation of basin input data 2.A.1 Precipitation 2.A.2 Temperature and snow depth data 3 Evaluation of water-energy balance frameworks 3.1 Introduction 3.2 Theory 3.2.1 Coupled water and energy balance 3.2.2 The ecohydrologic framework for change attribution 3.2.3 Applying the climate change hypothesis to predict changes in basin evapo transpiration and streamflow 3.2.4 Derivation of climatic sensitivity using the CCUW hypothesis 3.2.5 The Budyko hypothesis and derived sensitivities 3.3 Sensitivity analysis 3.3.1 Mapping of the Budyko functions into UW space 3.3.2 Mapping CCUW into Budyko space 3.3.3 Climatic sensitivity of basin evapotranspiration and streamflow 3.3.4 Climate-vegetation feedback effects 3.4 Application: three case studies 3.4.1 Mississippi River Basin (MRB) 3.4.2 Headwaters of the Yellow River Basin (HYRB) 3.4.3 Murray-Darling River Basin (MDB) 3.5 Conclusions 3.5.1 Potentials and limitations 3.5.2 Insights on the catchment parameter 3.5.3 Validation 3.5.4 Perspectives 3.A Derivation of the climate change direction 4 Climate sensitivity of streamflow over the continental United States 4.1 Introduction 4.1.1 Motivation 4.1.2 Hydro-climate of the continental US 4.1.3 Aims and research questions 4.2 Methods 4.2.1 Ecohydrological concept to separate impacts of climate and basin changes 4.2.2 Streamflow change prediction based on a coupled water-energy balance framework 4.2.3 Streamflow change prediction based on the Budyko hypothesis 4.2.4 Statistical classification of potential climate and basin change impacts 4.3 Data 4.4 Results and discussion 4.4.1 Hydro-climate conditions in the US 4.4.2 Climate sensitivity of streamflow 4.4.3 Assessment of observed and predicted changes in streamflow 4.4.4 Uncertainty discussion 4.5 Conclusions 4.A Mathematical derivations for the Mezentsev function 5 Summary and conclusions 5.1 Shifting seasons in hydrology 5.1.1 Major findings 5.1.2 Socio-economic and political relevance 5.1.3 Limitations and possible directions for further research 5.2 Long-term annual changes in ET and streamflow 5.2.1 Major findings 5.2.2 Socio-economic and political relevance 5.2.3 Limitations and further research 5.3 General conclusions and outlook 5.3.1 Regional and temporal limits and validity 5.3.2 Hydrological records carry signals of climate and land use change 5.3.3 Statistical significance of past changes 5.3.4 Improvements in assessing ET 5.3.5 Remote sensing 5.3.6 Learning from the past to predict the future? Bibliography Danksagung Erklärung

Climate models are essential for generating future climate projections. However, due to simplifications, the models can produce systematic differences between output and reality, which is referred to as model bias. Bias adjustment methods aim to reduce this error, which is important for making future projections more reliable. Here, the suitability of four different bias adjustment methods was tested: distribution-based (Distribution Scaling (DS), Quantile Delta Mapping (QDM)) and non-distribution- based methods (Copula, Multivariate Bias Correction (MBCn)), of which each one univariate and one multivariate approach. The methods were assessed on climate future projections together with a non bias adjusted data set, focusing on their impacts on hydrological modelling simulations. For this, 16 hydrological signatures were analysed and categorized into: 1) water balance and flow dynamics, 2) seasonal behaviour of the flow, 3) low flow characteristics and 4) high flow characteristics. The assessment was carried out based on 50 catchments in Sweden, 10 climate models and one hydrological model. Most noticeable differences were observed between distribution-based and non-distribution-based methods, rather than between univariate and multivariate methods. Bias adjustment methods introduce half as much variation as climate models, catchments contribute substantially more to the projected signatures. Specific hydrological signatures differed regionally, such as changes in the average spring streamflow magnitude and greater bias adjustment variations in low- and high-flow frequencies, compared to varia- tions among catchments, suggesting a shift in the frequency of extreme streamflow events in the future. The choice of bias adjustment method impacted ’High flow characteristics’ the strongest. The Copula method deviated in the trend analysis by utilizing an existing trend. This research prompts further exploration of variation between current and projected future climate, or the inclusion of other variables that might impact projections, to determine the necessity of the methods. / Vi befinner oss i en tid av klimatförändringar. Det blir mer och mer synligt och klimatet kommer förändras i närtid och långt fram i tiden. Men hur exakt kommer det vara i slutet av detta århundrade? För att förutspå det, används klimatmodeller. Dock kan klimatmodeller bara ge en uppskattning om hur det kommer se ut, eftersom de måste förenkla jordsystem och klimat genom simplifieringar och antaganden, för att kunna beräkna projektionen. Det betyder att klimatprojektioner är ingen särskilt exakt förutsägelse. För att projicera framtidens vattenföring i en förändrande klimat, behöver an först modellera framtidens klimat och ut ur det modellera framtidens hydrologiska processer genom hydrologiska modeller. Kombinationer av flera modelltyper kallas modellkedja. För att projicera framtidens klimat, behövs en hel modell-kedja som består av klimatmodeller och hydrologiska modeller. Ju fler delar en modell-kedjan består av, desto osäkrare blir projektionen. Osäkerheten kallas systematiskt och slumpmässigt fel, kort bias. För att förbättra projektionen kan man inkluderar en så kallat bias korrektions metod, vars syfte är att minska biasen med en massa ekvationer och underliggande algoritmer. Det finns flera olika metoder, baserade på olika algoritmer, som beroende på algoritmernas innehåll är mer eller mindre komplicerad.  Jag undersökte i det här projektet, om det gör en skillnad, vilket bias korrektur metod man använder för att förbättra sitt klimat projektion. Det kan, t.ex. vara intressant att veta, när man måste bestämma sig mellan olika bias korrektur metoder som innehåller olika nivåer av komplexitet som användaren måste förstå sig på för att beräkna och korrigerar dataset som är utdatan från klimatmodellerna. För att testa det, tog jag ett existerande stort dataset (bestående av 4 olika bias korrektur metoder och ett dataset som inte var bias korrigerad, med 10 stycken klimatprojektioner för 50 avrinningsområden jämt utspridda över hela Sverige). För att kunna ge en omfattande överblick av framtidens klimat, beräknade jag flera, så kallade hydrologiska signaturer av vattenföringens karakteristik. De signaturer testades statistiskt för att visar avvikande och liknande betedde.  Metoder som korrigerar systematiskt fel betog sig ganska lika varandra, dock introducerades ungefär hälften så mycket variation som hos de 10 testade klimatmodeller, däremot introducerade de 50 flodbäcken mycket mer variation än bias korrektur metoderna, förutom vissa undantag. Jämförelsen föreslår en förändring i vårflöde och ett betydligt skifte i extremflöden i framtiden, jämfört med dagens flöde i älvarna. Det syns att det som blivit påverkat mest av från valet av bias korrektur metoder är kategorin "hög flod drag".  Det här projektet är bara en liten del av en större forskning, och det finns mycket kvar att studera. I framtidens forskning skulle det vara intressant att jämföra skillnaden mellan dagens avloppet och i framtiden och hur stor skillnaden är, jämfört med styrkan av variationen mellan de testade bias korrektur metoder. Därmed kunde man minska forskningsgapet ytterligare, och göra ett noggrant konstaterande i samband med olika bias korrektur metoder och om valets betydelse.

The economic and social losses of environmental disasters are increasingly higher. Floods are a main concern in many locations around the world. Preventive actions are urgent and necessary. This doctoral thesis addresses topics related to hydro-meteorological risks and water resources management. Its aim is to cope with hydrological risks and water resources management through a flooding risk index, complex watershed modeling, different calibration techniques, and ensemble streamflow forecasting. Specific assumptions and research questions are defined in each chapter of the thesis, and are mostly related to the 12,600 km2 Piracicaba watershed, in Southeast, Brazil. Chapter one has general introductions and explains how the thesis is organized. Chapter two brings an assessment and mapping of flooding risks. Chapter three reviews the watershed modelling topic, through applications of a selected watershed model (the Soil and Water Assessment Tool - SWAT) in Brazil. Chapter four proposes a good practice methodology for calibration of watershed models for different time-steps with available data, having hydrology as main focus. Chapter five explores different methodologies for calibrating hydrological models, using two optimization algorithms and with a multi-site and single site approaches to evaluate related changes in performance. Chapter six has complex watershed modeling for sub-daily time-step, with an automatic hourly calibration module that was included in SWAT-CUP and the application of these models to forecast ensemble streamflow and with a data assimilation approach with optimization to improve the quality of the forecasts. Chapter seven has overall conclusions and chapter eight has a summarized list of other activities developed during the doctoral process. Overall we believe the methodologies and results for the Piracicaba watershed are very good. And that they can be replicated in other watersheds in Brazil and around the world. The proposed mapping assessments of flooding vulnerability and risks can be applied for the entire Brazil, and could be used as a tool in water resources management and planning. The watershed model (SWAT) used on this doctoral thesis also proved to be a versatile and robust model, with several good example applications in Brazil, and in particular for the Piracicaba case study. The step by step calibration methodology, as well as the different calibrations performed can help other modelers on choosing where and how to calibrate their own models. For hourly application, this work is pioneer, in area scale and model used. The results for ensemble flow forecasting and data assimilation show a little of what can be performed with this kind of application, and that it can be a potential tool for real time applications in streamflow forecasting and early warning systems. We believe the lessons learnt in this thesis can improve and aid modeler and water resources managers worldwide. / Os prejuízos econômicos e sociais de desastres ambientais têm sido maiores. Inundações são uma das principais preocupações ao redor do mundo. Ações preventivas são urgentes e necessárias. Esta tese de doutorado aborda temas relacionados à gestão dos recursos hídricos e de riscos hidro-meteorológicos. Possui o objetivo de lidar com riscos hidrológicos através de índices de risco a inundações, modelagem complexa de bacias hidrográficas, diferentes técnicas de calibração, e previsão de vazões por conjunto. Pressupostos e objetivos específicos são definidos em cada capítulo da tese, e são na sua maioria relacionados à bacia hidrográfica do Rio Piracicaba (12.600 km2), Sudeste do Brasil. O Capítulo um traz as introduções gerais e explica a organização da tese. O capítulo dois desenvolve mapeamento de riscos a inundações. O capítulo três revisa o tópico de modelagem de bacias hidrográficas, através de aplicações de um modelo selecionado (Soil and Water Assessment Tool - SWAT) no Brasil. O quarto capítulo propõe uma metodologia de boas práticas para a calibração de modelos de bacias hidrográficas utilizando dados disponíveis, com foco principal na hidrologia. O capítulo cinco explora diferentes metodologias de calibração, utilizando dois algoritmos de otimização e abordagens de calibração em um local e demais locais para avaliar alterações relacionadas ao desempenho da modelagem. O capítulo seis trabalha com modelagem sub-diária, com um módulo de calibração horária automática, que foi incluído no SWAT-CUP, e aplicação destes modelos para previsão de vazões por conjunto e assimilação de dados com otimização, para melhorar a qualidade das previsões. O sétimo capítulo traz as conclusões gerais da tese e oitavo capítulo apresenta uma lista resumida de outras atividades desenvolvidas durante o doutorado. Acreditamos que as metodologias e resultados para a bacia hidrográfica Piracicaba são muito bons. E que podem ser replicados em outras bacias hidrográficas no Brasil e ao redor do mundo. O mapeamento de vulnerabilidade e riscos de inundação propostos pode ser aplicados para todo o Brasil, além de possuir potencial como uma ferramenta de planejamento. O modelo utilizado (SWAT) também provou ser versátil e robusto, com vários bons exemplos de aplicações no Brasil, e em especial para a Bacia do Piracicaba. A metodologia sistemática para calibração, bem como as diferentes calibrações executadas podem auxiliar outros modeladores a escolherem como calibrar seus próprios modelos. Este trabalho é pioneiro no tipo de aplicação horária apresentada. Os resultados de previsão por conjunto de vazões e de assimilação de dados mostram o potencial da metodologia para sistemas de previsão de vazões em tempo real e em sistemas de alerta antecipado. Nós acreditamos que as lições aprendidas nesta tese podem auxiliar modeladores e gestores de recursos hídricos ao redor do mundo.