02 Fakultät Bau- und Umweltingenieurwissenschaften
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Item Open Access Large-scale high head pico hydropower potential assessment(Stuttgart : Eigenverlag des Instituts für Wasser- und Umweltsystemmodellierung der Universität Stuttgart, 2018) Schröder, Hans Christoph; Wieprecht, Silke (Prof. Dr.-Ing.)Due to a lack of site-related information, Pico hydropower (PHP) has hardly been a projectable resource so far. This is particularly true for large area PHP potential information that could open a perspective to increase the size of development projects by aggregating individual PHP installations. The present work is extending the capabilities of GIS based hydropower potential assessment into the PHP domain through a GIS based PHP potential assessment procedure that facilitates the discrimination of areas without high head PHP potential against areas with PHP potential and against areas with so called “favorable PHP potential”. The basic unit of the spatial output is determined by the underlying PHP potential definition of this work: a standardized PHP installation and the required hydraulic source, together called standard unit, are located on an area of one square kilometer. The gradation of the output is a consequence of the verification techniques. Several large area PHP potential field assessment methods, based on contemplative analysis techniques, are developed in this work. Field assessments were conducted in Yunnan Province/China, Costa Rica, Ecuador and Sri Lanka. The aim for all field assessments is to get a comprehensive view on the PHP potential distribution of the entire country/province. Application of the GIS based PHP potential assessment procedure is aimed at the global tropical and subtropical regions.Item Open Access Porosity and permeability alterations in processes of biomineralization in porous media - microfluidic investigations and their interpretation(Stuttgart : Eigenverlag des Instituts für Wasser- und Umweltsystemmodellierung der Universität Stuttgart, 2022) Weinhardt, Felix; Class, Holger (apl. Prof. Dr.-Ing)Motivation: Biomineralization refers to microbially induced processes resulting in mineral formations. In addition to complex biomineral structures frequently formed by marine organisms, like corals or mussels, microbial activities may also indirectly induce mineralization. A famous example is the formation of stromatolites, which result from biofilm activities that locally alter the chemical and physical properties of the environment in favor of carbonate precipitation. Recently, biomineralization gained attention as an engineering application. Especially with the background of global warming and the objective to reduce CO2 emissions, biomineralization offers an innovative and sustainable alternative to the usage of conventional Portland cement, whose production currently contributes significantly to global CO2 emissions. The most widely used method of biomineralization in engineering applications, is ureolytic calcium carbonate precipitation, which relies on the hydrolysis of urea and the subsequent precipitation of calcium carbonate. The hydrolysis of urea at moderate temperatures is relatively slow and therefore needs to be catalyzed by the enzyme urease to be practical for applications. Urease can be extracted from plants, for example from ground jack beans, and the process is consequently referred to as enzyme-induced calcium carbonate precipitation (ECIP). Another method is microbially induced calcium carbonate precipitation (MICP), which uses ureolytic bacteria that produce the enzyme in situ. EICP and MICP applications allow for producing various construction materials, stabilizing soils, or creating hydraulic barriers in the subsurface. The latter can be used, for example, to remediate leakages at the top layer of gas storage reservoirs, or to contain contaminant plumes in aquifers. Especially when remediating leakages in the subsurface, the most crucial parameter to be controlled is its intrinsic permeability. A valuable tool for predicting and planning field applications is the use of numerical simulation at the scale of representative elementary volumes (REV). For that, the considered domain is subdivided into several REV’s, which do not resolve the pore space in detail, but represent it by averaged parameters, such as the porosity and permeability. The porosity describes the ratio of the pore space to the considered bulk volume, and the permeability quantifies the ease of fluid flow through a porous medium. A change in porosity generally also affects permeability. Therefore, for REV-scale simulations, constitutive relationships are utilized to describe permeability as a function of porosity. There are several porosity-permeability relationships in the literature, such as the Kozeny-Carman relationship, Verma-Pruess, or simple power-law relationships. These constitutive relationships can describe individual states but usually do not include the underlying processes. Different boundary conditions during biomineralization may influence the course of porosity-permeability relationships. However, these relationships have not yet been adequately addressed. Pore-scale simulations are, in principle, very well suited to investigate pore space changes and their effects on permeability systematically. However, these simulations also rely on simplifications and assumptions. Therefore, it is essential to conduct experimental studies to investigate the complex processes during calcium carbonate precipitation in detail at the pore scale. Recent studies have shown that microfluidic methods are particularly suitable for this purpose. However, previous microfluidic studies have not explicitly addressed the impact of biomineralization on hydraulic effects. Therefore, this work aims to identify relevant phenomena at the pore scale to conclude on the REV-scale parameters, porosity and permeability, and their relationship. Contributions: This work comprises three publications. First, a suitable microfluidic setup and workflow were developed in Weinhardt et al. [2021a] to study pore space changes and the associated hydraulic effects reliably. This paper illustrated the benefits and insights of combining optical microscopy and micro X-ray computed tomography (micro XRCT) with hydraulic measurements in microfluidic chips. The elaborated workflow allowed for quantitative analysis of the evolution of calcium carbonate precipitates in terms of their size, shape, and spatial distribution. At the same time, their influence on differential pressure could be observed as a measure of flow resistance. Consequently, porosity and permeability changes could be determined. Along with this paper, we published two data sets [Weinhardt et al., 2021b, Vahid Dastjerdi et al., 2021] and set the basis for two other publications. In the second publication [von Wolff et al., 2021], the simulation results of a pore-scale numerical model, developed by Lars von Wolff, were compared to the experimental data of the first paper [Weinhardt et al., 2021b]. We observed a good agreement between the experimental data and the model results. The numerical studies complemented the experimental observations in allowing for accurate analysis of crystal growth as a function of local velocity profiles. In particular, we observed that crystal aggregates tend to grow toward the upstream side, where the supply of reaction products is higher than on the downstream side. Crystal growth during biomineralization under continuous inflow is thus strongly dependent on the locally varying velocities in a porous medium. In the third publication [Weinhardt et al., 2022a], we conducted further microfluidic experiments based on the experimental setup and workflow of the first contribution and published another data set [Weinhardt et al., 2022b]. We used microfluidic cells with a different, more realistic pore structure and investigated the influence of different injection strategies. We found that the development of preferential flow paths during EICP application may depend on the given boundary conditions. Constant inflow rates can lead to the development of preferential flow paths and keep them open. Gradually reduced inflow rates can mitigate this effect. In addition, we concluded that the coexistence of multiple calcium carbonate polymorphs and their transformations could influence the temporal evolution of porosity-permeability relationships.Item Open Access Fluid-phase transitions in a multiphasic model of CO2 sequestration into deep aquifers : a fully coupled analysis of transport phenomena and solid deformation(Stuttgart : Institut für Mechanik (Bauwesen), Lehrstuhl für Kontinuumsmechanik, Universität Stuttgart, 2017) Häberle, Kai; Ehlers, Wolfgang (Prof. Dr.-Ing. Dr. h. c.)Item Open Access Long-term lumped projections of groundwater balances in the face of limited data(Stuttgart : Eigenverlag des Instituts für Wasser- und Umweltsystemmodellierung der Universität Stuttgart, 2024) Ejaz, Fahad; Nowak, Wolfgang (Prof. Dr.-Ing.)Item Open Access Stochastic and hydrological modelling for climate change prediction in the Lima region, Peru(2015) Chamorro Chávez, Alejandro; Bárdossy, András (Prof. Dr. rer. nat. Dr.-Ing.)Climate change has been an important field of research in the past years and certainly is a major concern in the present time. It involves a broad spectrum of subjects and significant different time scales, ranging from decades to thousands or millions of years. Generally speaking, in a climate change scenario a change in the pattern, average or extreme conditions of some variables is observed, and this can be due to many different causes as changing processes in the earth, human activities or extra terrestrial induced factors. This study concentrates on the influences on the climate due to human activities and focuses on the hydrological response to these influences or changes as a primarily goal, for the next few decades. The main motivation is the vulnerability and scarcity of the water availability in the capital of Peru, Lima, and how the area under study will respond to a change in the climate. An important focus of analysis in order to reduce the uncertainty in the predictions is the errors that appears when modeling a given variable or set of variables. This issue is addressed first in regionalization of precipitation and second in the calibration of hydrological models in which a robust parameter estimation is performed. In the first issue concerning to regionalization, External Drift Kriging is applied. In this part of the work the results of regionalization are analyzed with focus on the errors and systematic errors which appear during the modeling. The main goal here is the reduction of these errors through some proposed transformations. Here, three approaches are suggested, namely smoothing of the digital elevation model (DEM) considering a symmetric area, power transformation and smoothing considering a non symmetric area. The second issue concerning the uncertainty in the estimations (discharge) was addressed two-fold, namely by optimizing the objective function by means of a heuristic optimization procedure based on Monte Carlo simulation, and by means of a robust parameter estimation (ROPE) algorithm developed quite recently by Bárdossy and Singh, which in general terms can be used as a general multivariate optimization procedure. The algorithm offers a way of finding a set of “good” parameter vectors, which among other characteristics, are transferable in time. The final result comprises an ensemble of estimations for expected discharge variations accounting for the uncertainty in parameterization and processes description in the models. In this study HVB and HYMOD models are used. The assessment of the impact of climate change in precipitation and temperature is carried out by a statistical downscaling procedure based on a quantil-quantil transformation. Here the information given by the Global Climate Models (GCMs) outputs are transferred to the local scale. Two different GCMs and three scenarios are used in this step. This permitted the definition of a range for the expected future variations for temperature and precipitation. The last chapter of the study addresses the assessment of the discharge in the short term. The goal here is to “infer” the outcome of a random variable (discharge) in the next time step by taking information from past observations (previous steps). As we can regard the observations (time series) as a realization generated from a stochastic process, we can address this issue from a stochastic point of view. The task is addressed first by considering some of the existing autoregressive models (AR process), and second by considering a Copula-based autoregressive model. In order to perform the Copula-based autoregressive model, a given time series (modelled discharge) was transformed into three vectors representing the same original time series but shifted in time. A three dimensional Copula was then fitted to the univariate distributions. For this, a Gaussian model as well as a Beta kernel model expressed in terms of the Beta function was considered.Item Open Access Microbial stabilization of lotic fine sediments(Stuttgart : Eigenverlag des Instituts für Wasser- und Umweltsystemmodellierung der Universität Stuttgart, 2018) Schmidt, Holger; Wieprecht, Silke (Prof. Dr.-Ing.)The microbial stabilization of fine sediments constitutes an essential ecosystem function with great ecological and economic implications e.g. in the context of reservoir and waterway management. Although this process is well researched in intertidal mudflats, there is still a major lack of knowledge for lotic systems. To perform fundamental research in this field and to account for the associated very high level of complexity, expertise of natural and engineering science was combined in an interdisciplinary approach. A highly sophisticated mesocosm setup was designed and constructed to guarantee fully controllable and reproducible natural-like boundary conditions during biofilm formation. The overall aim of the performed studies in this doctoral thesis was a comprehensive investigation of all relevant parameters of the cultivated biofilms, such as the microbial biomass, the produced extracellular polymeric substances (EPS), and the composition of the microbial community as well as the stability of the biofilm. This extensive approach should allow the identification of functional key parameters of the biofilm as well as essential interactions and their impact on the overall biofilm ecosystem and resulting biostabilization. In a series of long-term experiments, different influencing factors on biofilm development and corresponding biostabilization were assessed. The first potential impact factor that was analyzed was the experimental setup itself. Furthermore, the influence of the seasonal changes of the microbial community in the utilized river water and the effects of different levels of bed shear stress and illumination intensity were assessed. The results of these different experiments provided essential new insights into the process of biostabilization of lotic fine sediments. Firstly, the reliability of the used experimental setup could be proven, as no significant differences could be detected in biofilm formation and biostabilization comparing different mesocosm sections. The fact that very similar biofilms were developing when the boundary conditions were identical was a crucial prerequisite for any further investigations. In addition, the relevance of biostabilization in lotic systems, which was doubted for a long time, could be proven. However, freshwater and brackish habitat can be very different (e.g. in terms of nutrient availability). This was exemplarily indicated by significantly lower microbial biomass in the analyzed freshwater biofilms compared to biofilms from well-studied intertidal mudflats. Moreover, the very complex interplays between bacteria and diatoms in the biofilm matrix were underlined which led to a focus on this subject during further subsequent studies via an extensive genetic and microscopic profiling. Secondly, the important role of EPS during biostabilization could be demonstrated, whereby the significance of extracellular proteins, such as adhesives produced by sessile diatoms, was suggested. This observation may extend the current EPS research which focusses on extracellular carbohydrates due to their high quantitative fraction in the EPS matrix. Furthermore, the interactions between the microbes, the extracellular matrix and the overall stability of the biofilm system appeared to be much more complex than formerly assumed. Thirdly, the importance of the microbial community in the biofilm system could be elucidated. Even though a high correlation between mere microbial biomass and biostabilization could be detected, especially the seasonality experiments emphasized the impact of the life style of key players among the diatoms. These insights could be extended during the experiments analyzing the different levels of abiotic boundary conditions, where differently stable biofilms were clearly dominated by different assemblages of dominant bacteria. These observations constitute very important new insights into microbial biostabilization as a direct correlation between microbial ecology and the overall, actually measurable ecosystem function of the biofilm could be shown for the first time. Concluding, the insights into the fundamental principles of biostabilization gathered during this thesis can be seen as important steps for further fundamental research. The construction of a reliable unique setup is complete, the reproducible biofilm cultivation in this setup is verified and first investigations of different driving factors during biostabilization were performed. These analyses paved the way for further studies to analyze currently hardly assessed boundary conditions and deeper assessments in order to generate a sound database for future modelling approaches of the dynamics of microbially stabilized lotic fine sediments.Item Open Access Entwicklung eines ökologisch-ökonomischen Vernetzungsmodells für Wasserkraftanlagen und Mehrzweckspeicher(Stuttgart : Eigenverlag des Instituts für Wasser- und Umweltsystemmodellierung der Universität Stuttgart, 2018) Fenrich, Eva Katrin; Wieprecht, Silke (Prof. Dr.-Ing.)Die Bereitstellung von Frischwasser für die Bewässerung, Trink- und Brauchwasser sowie umweltfreundlich produzierter elektrischer Energie ist eine der wichtigsten Grundlagen für die Entwicklung einer Region oder eines Landes. Viele unterschiedliche Nutzungsansprüche auf begrenzte Ressourcen sind zu beachten und abzuwägen. Die vernetzten Versorgungsrisiken im Nexus „Wasser, Energie, Nahrung“ sind gleichermaßen eine große Herausforderung für Politik und Ingenieure. Wasserkraft stellt eine saubere, CO2-neutrale, regenerative Energiequelle dar. Jedoch sind aufgrund der Veränderung des Abflussregimes und der Querverbauung der Gewässer große Auswirkungen auf die lokale Ökologie zu erwarten. Diese Auswirkungen auf die lokale oder auch globale Flussökologie bedingen, dass bei der Planung von Wasserkraftanlagen und Mehrzweckspeichern auf ein komplexes System an Einflüssen eingegangen werden muss. Die Wechselwirkungen zwischen den unterschiedlichen Nutzungsarten einerseits und der Fluss- und Auenökologie andererseits müssen in ihrer Gesamtheit erfasst werden. Aufgrund der langen Lebensdauer der Anlagen ist es notwendig sehr eingehend die Auswirkungen eines Projekts in allen Bau- und Betriebsphasen zu untersuchen, da es sich hierbei nicht um kurzfristige Eingriffe, von denen sich das natürliche Gewässer wieder erholen kann, handelt. Ebenso ist es bei Wasserkraftanlagen und Mehrzweckspeichern, wie bei allen großen Infrastrukturmaßnahmen wichtig, dass Entscheidungsträger die Möglichkeit bekommen, übersichtlich Einblicke in die Wirkungszusammenhänge zu gewinnen und Projektvarianten zu vergleichen. Dies ist insbesondere auch dann relevant, wenn verschiedene Interessengruppen oder Projektpartner eine Einigung über die Weiterverfolgung bestimmter Projektvarianten erzielen sollen. Ausgehend von der vorgestellten Problematik wird eine ganzheitliche qualitative und quantitative Bewertung von Wasserkraftanlagen und Mehrzweckspeichern sowohl für die Planung als auch für den Betrieb vorgestellt. Hierzu wurde ein Bilanzierungsmodell entwickelt, das auf Grundlage Leontief'scher Input-Output-Analyse als Entscheidungsunterstützung für Projektentscheidungen beim Neubau und der Erneuerung von Anlagen dienen kann. Die Input-Output-Analyse, ein Verfahren der empirischen Wirtschaftsforschung, das für volkswirtschaftliche Analysen eingesetzt wird, ist ein geeignetes Werkzeug, um Verflechtungen zwischen verschiedenen Aspekten eines Systems zu beschreiben. Durch die Möglichkeit, Stoff- und Wirtschaftsströme in unterschiedlichen Einheiten miteinander zu verknüpfen, eignet sich die Input-Output-Analyse sehr gut zur Modellierung komplexer vernetzter Strukturen. Zunächst wurden qualitative Modelle für die jeweiligen Anlagentypen aufgestellt und anschließend an die Bedingungen des betrachteten Projekts angepasst. Hierzu wurden die Systemgrenzen festgelegt und bestimmt, welche Nutzungsarten zum aktuellen Betrachtungszeitraum relevant sind. Mit Hilfe von Input-Output-Graphen werden die Gesamtsysteme anschaulich dargestellt. Traditionell stehen die Knoten des Graphen für die Sektoren einer Volkswirtschaft und die Kanten stellen die jeweiligen Verflechtungen dar. Produkte eines Sektors einer Volkswirtschaft werden zur Produktion von Gütern und Dienstleitungen anderer Sektoren benötigt. Die Richtung der jeweiligen Kante des Graphen stellt eine Lieferbeziehung dar. Bei der Bewertung von Wasserkraftanlagen und Mehrzweckspeichern werden an Stelle von Sektoren einzelne Aspekte innerhalb des Projektes, wie beispielsweise die Trinkwassergewinnung oder die Erzeugung elektrischer Energie, sowie als Primärinputs natürliche Ressourcen betrachtet. Die Input-Output-Graphen können anschließend teilweise mit Hilfe graphentheoretischer Überlegungen vereinfacht werden. Beispielsweise können Teilgraphen zusammengefasst oder zirkuläre Abhängigkeiten aufgedeckt werden. Von besonderem Interesse sind häufig die indirekten Lieferbeziehungen zwischen Sektoren, die zunächst nicht direkt ersichtlich sind, im Input-Output-Modell aufgrund der Darstellung als Systemgraph jedoch deutlich erkennbar werden. Ein wichtiger Grund, qualitative Modelle zu erstellen, kann unter anderem auch sein, verschiedene Projekte oder Projektvarianten zunächst aufgrund ihrer Struktur zu vergleichen, oder um schon vorhandene Projekte unterschiedlicher Größe als Grundlage für die Datenbeschaffung neu geplanter Projekte zu nutzen. Dieses qualitative Modell wird jeweils für eine bestimmte Anlagengröße und Nutzungsart quantifiziert und anschließend werden iterativ Nutzungs-Szenarien evaluiert. Bei Bedarf kann als abschließende Untersuchung das so entwickelte Input-Output-Modell als Grundlage einer linearen Optimierung verwendet werden. Quantitative Gesamtmodelle und lineare Optimierungsmodelle sind jeweils stark abhängig von den betrachteten Projektvarianten. Durch eine vernetzte Formulierung ökonomischer und ökologischer Fragestellungen wird eine quantitative Bewertung der gegenseitigen Beeinflussung ermittelt. Anhand von Fallstudien wurde die Anwendbarkeit der zuvor erarbeiteten Methodik auf verschiedene Anlagentypen und -größen verifiziert und das Modell weiterentwickelt. Um die grundsätzliche Anwendbarkeit der Input-Output-Analyse auf Wasserkraftanlagen und Mehrzweckspeicher zu untersuchen, wurde zunächst ein sehr einfaches schwach vernetztes System eines Ausleitungskraftwerks an der Drau in Österreich untersucht. Hierbei wurde vor allem auf die Vernetzung von Wasserdargebot, energetischer Nutzung und Flussökologie eingegangen. Die Integration von Bewässerung und Landnutzungsparametern in einem Input-Output-Modell wurde anhand eines Bewässerungssystems in Venezuela untersucht. Hierbei werden vor allem auch sozioökonomische Aspekte mit integriert. In einer weiteren Fallstudie wurde ein Ausleitungskraftwerk an der unteren Argen mit gleichzeitiger Wasserentnahme zur Bewässerung untersucht. Als sehr stark vernetztes System wird das Kandadji-Projekt am Niger, ein typisches Mehrzweckspeicher-Projekt mit Bewässerung, Wasserkraft und Trinkwassergewinnung, betrachtet. Schließlich wird, um die Bandbreite der Anwendbarkeit des entwickelten Modells darzustellen, eine Fallstudie für ein Gezeitenkraftwerk zusammen mit einer Landnutzungs-Wassergütemodellierung im Küstenbereich erstellt. Die verschiedenen Fallstudien geben einen Überblick über die Bandbreite der Anwendungsbereiche des hier entwickelten Modells. Deutlich zu erkennen ist, dass qualitative Modelle und auch quantifizierte Teilmodelle jeweils übertragbar auf andere Projekte und Projektvarianten sein können. Damit wurde Ingenieuren und Entscheidungsträgern ein wertvolles Werkzeug in die Hand gegeben, um die Auswirkungen von Wasserkraftanlagen und Mehrzweckspeichern in allen Planungs- und Betriebsphasen zu bewerten.Item Open Access Development, mapping and validation of resilience and vulnerability indicators across spatial scales for climate related hazards(2021) Feldmeyer, Daniel; Jörn, Birkmann (Prof. Dr.-Ing.)Item Open Access Impacts of the existing water allocation scheme on the Limarí watershed : Chile, an integrative approach(2015) Kretschmer, Nicole; Bárdossy, András (Prof. Dr. rer. nat. Dr.-Ing. )The research is motivated by an interest in evaluating the special Chilean water management framework, relating to the 1981 Water Code legislation, introduced by the military government. This law mainly strengthened private property rights and increased private autonomy in water use. In particular, it is of interest to assess the impacts of this legislation in the context of the current highly stressed water availability situation in central and northern Chile, combined with intensive and increasing agricultural demands. The reason to look at this region first is to test a catchment with a more or less vivid water market. The purpose of this research is to investigate the influence of water rights on water management practices under the present situation as well as changing situations. Here changing situation refer on one hand to improvement and extension of infrastructure, on the other hand to different use of the water in magnitude and further time and space. The latter one mainly based on the water market. The main objective of this study is to investigate if the proposed WRAP Modelling System (Water Rights Analysis Package) which is used in the whole state of Texas, is able to model the consequences of the allocation scheme in the present, as well changing situations, incorporating the Chilean legal framework, here especially the allocation according to water rights. The main changes are subject to i. new legislation to incorporate in the allocation of water resources ii. further development, like new reservoirs in the upstream sub-catchments, iii. water right transfers as well as iv. different operation policies WRAP was chosen to investigate the impacts of the water management practices. It combines detailed information describing water resource development, management, allocation and use with natural river system hydrology represented by naturalized streamflows, assuming that the hydrological pattern of a catchment stays the same in the future (Wurbs, 2011). Beside the development of the spatial configuration of the system, which has been defined as a set of control points (CP) that represent pertinent sites in the river basin, geospatial data, time series data, census data, operational data sheets of the organisations as well as information and data about the water rights of each stakeholder have been statistically and spatially pre-processed in order to be able to estimate agricultural water demand, understand the legal system in general and of the basin under study in particulary. Further information of the Food and Agricultural Organisation (FAO), monitored data of the National Water Authority (DGA), elaborated data of the National Centre of Natural Resources (CIREN) and historical and actual regional as well as local studies were consulted to elaborate all the needed information to model the system. With this information and preprocessed data the WRAP modelling system was implemented, to quantify the impacts of decision making and its consequences on the whole system. Model results include water supply reliabilities (including reliability indices) as well as flow and storage frequency statistics developed from the simulation results representing long-term probabilities or percent-of-time estimates. Furthermore shortage metrics have been developed by the model and evaluated for each scenario. The model includes the following frequency statistics for concisely summarizing modelling results: (a) volume and period reliability tables for water supply diversion, (b) frequency tables for naturalized, regulated and unappropriated flows, reservoir storage volumes, as well as instream flow shortages and (c) reservoir storage-reliability tables. After all the different scenario simulations and analysis of the results it can be stated that the WRAP modelling system is applicable for the questions under study based on the legal Chilean water management framework. Flexibility is provided for adaption of a broad range of modelling approaches. A huge variety of management records can be combined in many different ways to be able to model any application. Ingenuity is required from the modeller to achieve the incorporation of sometimes quite complex allocation rules, apply different target options, demands, administrate a variety of users and include new developments within a multiple and multipurpose reservoir-river management system. Although some simplification of the independent sub-catchments was necessary, the achieved results show that the consequences of allocation decisions, including water transfer and future development are simulated in a satisfactory manner and can therefore be much better understood. The model system is adequate to serve as a basis for decision making within the chilean legal framework.Item Open Access Assessing dynamics of rural-urban linkages and their influence on rural vulnerability to extreme flood events : case study of three rural farming communities in Punjab, Pakistan(2021) Jamshed, Ali; Birkmann, Jörn (Prof. Dr.-Ing. habil.)Although rural areas and cities are intrinsically linked, the vulnerability of rural households and communities to hazards or extreme weather and climatic events is often assessed without considering their relationships to cities. These linkages are important due to interdependencies between rural and urban areas for socio-economic and physical growth. Moreover, extreme events can lead to dramatic shifts in societal processes, disrupt rural-urban linkages, and affect rural vulnerability; these matters need to be investigated. Considering these gaps in knowledge, this study aims to conceptualise and understand rural vulnerability with respect to the dynamics of rural-urban linkages in the case of flooding, with a special focus on spatial factors like city size and proximity to the city. To do so, a mixed methods approach was adopted in this research. Still, the present study is largely based on quantitative techniques. First, the current literature on rural-urban linkages, vulnerability and factors that influence them was critically reviewed, and a unified framework was proposed to connect the elements of rural-urban linkages and flood vulnerability. The framework was designed to examine changes in rural-urban linkages and the subsequent impact on rural vulnerability to flooding. For empirical research, three case studies (Darya Khan, Muzaffargarh, and Multan) were selected in the Punjab province of Pakistan. A multistage, mixed methods sampling approach was applied to derive 325 samples. Secondary data, observations and a focus group discussion deepened understanding of the topic. The household survey, using a structured questionnaire, was administered to collect information from the required sample, comprised of a flood-affected rural population surrounding three different-sized cities and at varied proximity. The data were analysed using descriptive statistics (frequency analysis, cross-tabulation) and inferential statistics (correlation, regression, chi-square, the Mann-Witney U test). Moreover, an index-based approach was developed to obtain the composite values of the three components of vulnerability: (1) exposure, (2) susceptibility and (3) capacity. The findings show that flooding severely affects rural households both directly and indirectly. The ramifications have led to several changes among rural households; most notably, they have modified how they earn a living and their relationship with the nearest major city. Floods have shifted the flow of people, information, finances, goods, and services between rural and urban areas. The research indicates that rural-urban linkages are altered in that flooding both increases and decreases rural households’ dependence on cities in different ways. These outcomes are largely driven by socio-economic, spatial, and flood-related factors. In terms of vulnerability, first, the findings signal that rural populations surrounding smaller cities are less exposed, but more vulnerable, as compared to rural households that surround larger cities. This is because rural populations adjoining larger cities are better able to deal with flood hazards due to stronger linkages. Secondly, the results confirmed that distance to the city influences the vulnerability of surrounding farming households. Rural farming households located close to cities are less vulnerable, mainly due to a better transfer of services and facilities from cities, which has made such households more educated, informed, financially strong and more closely connected, with easier access to public and private institutions. Thus, city size and proximity to the city modify linkages that further impact the flood vulnerability of the rural population. Lastly, changes in linkages made by rural households following a flood influence their overall vulnerability differently; increasing linkages with the city after a flood reduce their vulnerability, while decreasing linkages with the city exacerbate it. These changes in linkages are used to adapt to future floods and affect rural households’ vulnerability both positively and negatively. Hence, the dynamics of linkages and rural households’ exchanges with cities are crucial to reducing their vulnerability to future flood hazards. This study paves the way for regional planners and disaster managers to establish synergies between them for devising integrated flood management and development strategies that strengthen linkages, mitigate disparities and curtail vulnerability.