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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
11

Grey Optimization For Uncertainty Modeling In Water Resources Systems

Karmakar, Subhankar 06 1900 (has links)
In this study, methodologies for modeling grey uncertainty in water resources systems are developed, specifically for the problems in two identified areas in water resources: waste load allocation in streams and floodplain planning. A water resources system is associated with some degree of uncertainty, due to randomness of hydrologic and hydraulic parameters, imprecision and subjectivity in management goals, inappropriateness in model selection, inexactness of different input parameters for inadequacy of data, etc. Uncertainty due to randomness of input parameters could be modeled by the probabilistic models, when probability distributions of the parameters may be estimated. Uncertainties due to imprecision in the management problem may be addressed by the fuzzy decision models. In addition, some parameters in any water resources problems need to be addressed as grey parameters, due to inadequate data for an accurate estimation but with known extreme bounds of the parameter values. Such inexactness or grey uncertainty in the model parameters can be addressed by the inexact or grey optimization models, representing the parameters as interval grey numbers. The research study presented in this thesis deals with the development of grey and fuzzy optimization models, and the combination of the two for water resources systems decision-making. Three grey fuzzy optimization models for waste load allocation, namely (i) Grey Fuzzy Waste Load Allocation Model (GFWLAM), (ii) two-phase GFWLAM and (iii) multiobjective GFWLAM, and a Grey Integer Programming (GIP) model for floodplain planning, are developed in this study. The Grey Fuzzy Waste Load Allocation Model (GFWLAM) for water quality management of river system addresses uncertainty in the membership functions for imprecisely stated management goals of the Pollution Control Agency (PCA) and dischargers. To address the imprecision in fixing the boundaries of membership functions (also known as membership parameters), the membership functions themselves are treated as imprecise in the model and the membership parameters are expressed as interval grey numbers. The conflict between the fuzzy goals of PCA and dischargers is modeled using the concept of fuzzy decision, but because of treating the membership parameters as interval grey numbers, in the present study, the notion of ‘fuzzy decision’ is extended to the notion of ‘grey fuzzy decision’. A terminology ‘grey fuzzy decision’ is used to represent the fuzzy decision resulting from the imprecise membership functions. The model provides flexibility for PCA and dischargers to specify their aspirations independently, as the membership parameters for membership functions are interval grey numbers in place of a deterministic real number. In the solution, optimal fractional removal levels of the pollutants are obtained in the form of interval grey numbers. This enhances the flexibility and applicability in decision-making, as the decision-maker gets a range of optimal solutions for fixing the final decision scheme considering technical and economic feasibility of the pollutant treatment levels. The methodology is demonstrated with the case studies of a hypothetical river system and the Tunga-Bhadra river system in Karnataka, India. Formulation of GFWLAM is based on the approach for solving fuzzy multiple objective optimization problem using max-min as the operator, which usually may not result in a unique solution. The two-phase GFWLAM captures all the alternative optimal solutions of the GFWLAM. The solution technique in the Phase 1 of two-phase GFWLAM is the same as that of GFWLAM. The Phase 2 maximizes upper bounds and minimizes lower bounds of decision variables, keeping the optimal value of goal fulfillment level same as obtained in the Phase 1. The two-phase GFWLAM gives the unique, widest, intervals of the optimal fractional removal levels of pollutant corresponding to the optimal value of goal fulfillment level. The solution increases the widths of interval-valued fractional removal levels of pollutants by capturing all the alternative optimal solutions and thus enhances the flexibility and applicability in decision-making. The model is applied to the case study of Tunga-Bhadra river system, which shows the existence of multiple solutions when the GFWLAM is applied to the same case study. The width of the interval of optimal fractional removal level plays an important role in the GFWLAM, as more width in the fractional removals implies a wider choice to the decision-makers and more applicability in decision-making. The multiobjective GFWLAM maximizes the width of the interval-valued fractional removal levels for providing a latitude in decision-making and minimizes the width of goal fulfillment level for reducing the system uncertainty. The multiobjective GFWLAM gives a new methodology to get a satisfactory deterministic equivalent of a grey fuzzy optimization problem, using the concept of acceptability index for a meaningful ranking between two partially or fully overlapping intervals. The resulting multiobjective optimization model is solved by fuzzy multiobjective optimization technique. The consistency of the solution is verified by solving the problem with fuzzy goal programming technique. The multiobjective GFWLAM avoids intermediate submodels unlike GFWLAM, so that the solution from a single deterministic equivalent of the GFWLAM adequately covers all possible situations. Although the solutions obtained from multiobjective GFWLAM provide more flexibility than those of the GFWLAM, its application is limited to grey fuzzy goals expressed by linear imprecise membership functions only, whereas GFWLAM has the capability to solve the model with any monotonic nonlinear imprecise membership functions also. The methodology is demonstrated with the case studies of a hypothetical river system and the Tunga-Bhadra river system in Karnataka, India. The Grey Integer Programming (GIP) model for floodplain planning is based on the floodplain planning model developed by Lund (2002), to identify an optimal mix of flood damage reduction options with probabilistic flood descriptions. The model demonstrates how the uncertainty of various input parameters in a floodplain planning problem can be modeled using interval grey numbers in the optimization model. The GIP model for floodplain planning does not replace a post-optimality analysis (e.g., sensitivity analysis, dual theory, parametric programming, etc.), but it provides additional information for interpretation of the optimal solutions. The results obtained from GIP model confirm that the GIP is a useful technique for interpretation of the solutions particularly when a number of potential feasible measures are available in a large scale floodplain planning problem. Though the present study does not directly compare the GIP technique with sensitivity analysis, the results indicate that the rigor and extent of post-optimality analyses may be reduced with the use of GIP for a large scale floodplain planning problem. Application of the GIP model is demonstrated with the hypothetical example as presented in Lund (2002).
12

Mejora de la gestión del recurso hídrico mediante la incorporación de indicadores de regímenes ecológicos en el análisis de sistemas de recursos hídricos

Pardo Loaiza, Jesús 09 March 2023 (has links)
Tesis por compendio / [ES] El agua constituye un recurso esencial cuya disponibilidad limitada y su creciente demanda hace que sea considerado como un elemento de gran valor desde diversos puntos de vista (ambiental, biológico, social, económico, etc.). El mantenimiento de condiciones favorables que permitan un equilibrio medioambiental adecuado es una de las metas de una adecuada planificación y gestión de recursos hídricos. Una de las acciones principales para la preservación de la biodiversidad de las cuencas consiste en la implementación de caudales ecológicos. Para ello, es importante poder contar con herramientas adecuadas que permitan cuantificar los efectos de los cauda-les ecológicos sobre las actividades socioeconómicas y el medio ambiental. Esta tesis tiene como objetivo proponer metodologías para la obtención y análisis de indicadores que permitan la optimización de regímenes de caudales ecológicos en sistemas de recursos hídricos complejos. Estas metodologías posibilitan evaluar los efectos de los caudales ecológicos en la alteración hidrológica, la alteración del hábitat, las garantías de las demandas, y la explotación del recurso hídrico. Esta tesis doctoral se estructura como un compendio de tres artículos científicos publicados en revistas del primer y segundo cuartil del Journal Citation Reports. En el primer artículo se define una metodología para el análisis de la alteración hidrológica en sistemas altamente regulados para diferentes escenarios de caudales ecológicos, apoyada en la utilización de modelos de simulación de la gestión de sistemas de recursos hídricos, y la posterior estimación y agrupación de indicadores de alteración hidrológica. Dicha metodología ha sido aplicada en la parte española de la Demarcación Hidrográfica del Duero. El segundo artículo plantea una metodología para la obtención de un indicador de alteración del hábitat en cuencas reguladas, mediante la aplicación conjunta de un modelo de simulación de la gestión de cuencas y un modelo de estimación de series temporales de hábitat de las especies acuáticas presentes en la zona de estudio. La metodología se aplica en el sistema de explotación del Órbigo, perteneciente a la Demarcación Hidrográfica del Duero. Las series temporales de hábitat fueron obtenidas y analizadas para diferentes escenarios de regímenes de caudales ecológicos, evaluando sus efectos en la alteración del hábitat y las garantías de las demandas. El tercer artículo propone una metodología para evaluar la variación temporal y espacial del índice de explotación del recurso hídrico (WEI+) en cuencas reguladas. Esta metodología, que fue aplicada en la cuenca del río del Órbigo, permite analizar los efectos de los regímenes de caudales eco-lógicos en el estrés hídrico de los distintos tramos de rio de una cuenca regulada. El enfoque propuesto para reducir la escala espacial del índice de explotación del recurso hídrico es también es útil para identificar las mejores fuentes de agua en las cuencas fluviales para satisfacer futuras demandas de agua y/o restricciones ambientales. Finalmente, a partir de la información obtenida de estas metodologías, se realiza un análisis conjunto de todos estos parámetros para las diferentes alternativas de caudal ecológicos planteadas. Para ello, se evalúan de manera conjunta indicadores globales de alteración hidrológica, alteración de hábitat, déficits de las demandas y estrés hídrico. Estos indicadores globales facilitan, tanto a los gestores como a los usuarios del agua, el análisis de estrategias de planificación y gestión de recursos hídricos. / [CA] L'aigua constitueix un recurs essencial la disponibilitat limitada del qual i la seua creixent demanda fa que siga considerat com un element de gran valor des de diversos punts de vista (ambiental, biològic, social, econòmic, etc.). El manteniment de condicions favorables que permeten un equilibri mediambiental adequat és una de les metes d'una adequada planificació i gestió de recursos hídrics. Una de les accions principals per a la preservació de la biodiversitat de les conques consisteix en la implementació de cabals ecològics. Per a això, és important poder comptar amb eines adequades que permeten quantificar els efectes dels cabals ecològics sobre les activitats socioeconòmiques i el mitjà ambiental. Aquesta tesi té com a objectiu proposar metodologies per a l'obtenció i anàlisi d'indicadors que permeten l'optimització de règims de cabals ecològics en sistemes de recursos hídrics complexos. Aquestes metodologies possibiliten avaluar els efectes dels cabals ecològics en l'alteració hidrològica, l'alteració de l'hàbitat, les garanties de les demandes, i l'explotació del recurs hídric. Aquesta tesi doctoral s'estructura com un compendi de tres articles científics publicats en revistes del primer i segon quartil del Journal Citation Reports. En el primer article es defineix una metodologia per a l'anàlisi de l'alteració hidrològica en sistemes altament regulats per a diferents escenaris de cabals ecològics, recolzada en la utilització de models de simulació de la gestió de sistemes de recursos hídrics, i la posterior estimació i agrupació d'indicadors d'alteració hidrològica. Aquesta metodologia ha sigut aplicada en la part espanyola de la Demarcació Hidrogràfica del Duero. El segon article planteja una metodologia per a l'obtenció d'un indicador d'alteració de l'hàbitat en conques regulades, mitjançant l'aplicació conjunta d'un model de simulació de la gestió de conques i un model d'estimació de sèries temporals d'hàbitat de les espècies aquàtiques presents en la zona d'estudi. La metodologia s'aplica en el sistema d'explotació del Órbigo, pertanyent a la Demarcació Hidrogràfica del Duero. Les sèries temporals d'hàbitat van ser obtingudes i analitzades per a diferents escenaris de règims de cabals ecològics, avaluant els seus efectes en l'alteració de l'hàbitat i les garanties de les demandes. El tercer article proposa una metodologia per a avaluar la variació temporal i espacial de l'índex d'explotació del recurs hídric (WEI+) en conques regulades. Aquesta metodologia, que va ser aplicada en la conca del riu del Órbigo, permet analitzar els efectes dels règims de cabals ecològics en l'estrés hídric dels diferents trams de va riure d'una conca regulada. L'enfocament proposat per a reduir l'escala espacial de l'índex d'explotació del recurs hídric és també és útil per a identificar les millors fonts d'aigua en les conques fluvials per a satisfer futures demandes d'aigua i/o restriccions ambientals. Finalment, a partir de la informació obtinguda d'aquestes metodologies, es realitza una anàlisi conjunta de tots aquests paràmetres per a les diferents alternatives de cabal ecològics plantejades. Per a això, s'avaluen de manera conjunta indicadors globals d'alteració hidrològica, alteració d'hàbitat, dèficits de les demandes i estrés hídric. Aquests indicadors globals faciliten, tant als gestors com als usuaris de l'aigua, l'anàlisi d'estratègies de planificació i gestió de recursos hídrics. / [EN] Water is an essential resource whose limited availability and growing demand means that it is considered an element of great value from various points of view (environmental, biological, social, economic, etc.). The maintenance of favourable conditions that allow an adequate environmental balance is one of the goals of water resources planning and management. One of the main actions for the preservation of the basin biodiversity in the implementation of environmental flows. To this end, it is important to have adequate tools that allow assessing the effects of environmental flows on socioeconomic activities and the environment. This thesis aims to propose methodologies for assessing and analysing indicators that allow the optimization of ecological flow regimes in complex water resource systems. These methodologies enable evaluating the effects of ecological flows on hydrological alteration, habitat alteration, reliability of water demands, and water resources exploitation. This doctoral thesis is structured as a compendium of three research papers published in journals indexed in the first and second quartiles of the Journal Citation Reports. In the first paper, a methodology for the analysis of hydrological alteration in highly regulated systems for different scenarios of ecological flows is pro-posed. The methodology is endorsed using models for the management of water resource systems, and the subsequent computation and grouping of indicators of hydrological alteration. This methodology was applied to the Spanish part of the Duero Water District. The second paper proposes a methodology for assessing an indicator of habitat alteration in regulated basins through the joint application of a basin management simulation model and a model to estimate habitat time series of the aquatic species present in the study zone. The methodology is applied to the Órbigo exploitation system, which belongs to the Duero Water District. Habitat time series were obtained and analysed for different environmental flow regime scenario, and the effects of this environmental flows on habitat alteration and water demand reliability were assessed. The third paper proposes a methodology to evaluate the temporal and spatial variation of the water exploitation index (WEI+) in regulated basins. This methodology, which was applied in the Órbigo river basin, allows ana-lysing the effects of ecological flow regimes on water stress in the different river sections of a regulated basin. The proposed approach to reduce the spatial scale of the water exploitation index is also helpful to identify the best water sources in river basins to meet future water demands and/or higher values of environmental restrictions. Finally, based on the information obtained through the application of these methodologies, a joint analysis of all these parameters was carried out for the different proposed environmental flow alternatives. To this end, global indicators of hydrological alteration, habitat alteration, water demand deficits and water stress are jointly evaluated. These global indicators help water managers and users to analyse strategies of water resources planning and management. / The authors thank the Spanish Ministry of Science and Innovation (MCIN) and Spanish Research Agency (AEI) for the financial support MCIN/AEI/10.13039/501100011033 to RESPHIRA project (PID2019- 106322RB-I00). RB was partly funded by MCIN/AEI /10.13039/501100011033 through Juan de la Cierva program (IJC2019-038848-I). Funding for open ac- cess charge: CRUE-Universitat Politècnica de València. The authors also thank three anonymous reviewers for their suggestions to improve this work. / Pardo Loaiza, J. (2023). Mejora de la gestión del recurso hídrico mediante la incorporación de indicadores de regímenes ecológicos en el análisis de sistemas de recursos hídricos [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/192461 / Compendio

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