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İstanbul Teknik Üniversitesi (2012)

Statistical Analysis Of Low Flow In Climate Change

BAŞKAYA AYTEKĐN Ayşen

Titre : Statistical Analysis Of Low Flow In Climate Change

İklim Değişikliğinde Düşük Akımların İstatistik Analizi

Auteur : BAŞKAYA AYTEKĐN Ayşen

Université de soutenance : İstanbul Teknik Üniversitesi

Grade : Doctor of Philosophy (PhD) 2012

Résumé
Water resources are under the threat of pollution which is caused by population growth as well as global warming. Climate change has received growing attention due to its effects on social and economic environments. Climate is a major factor which controls the hydrological cycle. The most important affect of climate change on hydrological variables is deterioration of stationarity property of these variables. If measured low flow-rates are non-stationary, modelling the statistical characteristics of non-stationarity, estimating them and predicting them for the life cycle of the water structure must be done. In the classical frequency analysis approach for low flow-rates, the most suitable probabilty distribution is calculated for observed series with the assumption that stationarity and obsesrvations are independent. Applicability of frequency analysis must be queried when these assumptions are not valid. Thus, new techniques must be developed to be able to take non-stationarity into account for low flow-rate series and assumption of independency should be used just as preliminary approach. Taking into account the change in amount of water with time and the change in statistical characteristics of low flow-rate series at non-stationarity in time is decisive in life time and economics of projected project. In this study, developed methods for non-stationary low flow-rates frequency analysis have been presented. Separation of trend from the time series, estimation of parameters and quantiles in non-stationary low flow-rate series with time are given for two parameters lognormal (LN2), Weibull (W2) and power distributions. Return period concept for non-stationary low flow-rate series and determination of risk for a certain period of time are discussed as well.

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