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İstanbul Teknik Üniversitesi (2019)

Flow duration curve model for ungauged intermittent rivers

BURGAN Halil İbrahim

Titre : Flow duration curve model for ungauged intermittent rivers

Akım ölçümü olmayan kuruyan akarsular için debi süreklilik çizgisi modeli

Auteur : BURGAN Halil İbrahim

Université de soutenance : İstanbul Teknik Üniversitesi

Grade : Doctor of Philosophy (PhD) 2019

Résumé partiel
A flow duration curve is used to determine the discharge of a certain time percentage (quantile) in hydrological basins. It can simply be obtained by sorting the observed streamflow time series in the ascending order and plotting it against its corresponding duration. In a gauged basin, it is obtained by sorting the observed flow from the largest to the smallest, and plotting against the corresponding exceedance probability. At ungauged basins where no data exists the need for developing empirical methods emerges. Flow duration curves are useful tools for characterizing hydrological regimes and flow variability. They are widely used in the determination of the upper extreme events (floods) as well as in the calculation of low-flow characteristics of streams. The urban storm water modelling, environmental flow allocation and the determination of hydropower potential and water availability at ungauged sites are all performed by using flow duration curves. Flow duration curve-related studies started as early as the first half of the 20th century for producing weekly flow duration curves. Due to the importance of water resources, flow duration curves have always been studied in the water-related development and planning projects for which extensive hydrological engineering practice is needed. Therefore, there are quite high number of studies in the literature based on a wide range of methodologies such as regression equations, probabilistic and empirical approaches, analytical and statistical methods, and soft computational techniques applied at individual gauging stations or used at regional scale. Flow duration curve models were established using regression equations based on morphological characteristics such as drainage area and elevation of the hydrological basin. Flow duration curve at ungauged basins were estimated by regression equations between the mean flow and the drainage area, and precipitation over the hydrological basin. Probability distribution functions have also widely been used in the flow duration curve literature as well as the analytical and statistical methods. Recently, soft computational techniques such as artificial neural networks, gene expression programming and geostatistical methods have also been applicable extensively in the flow duration curve literature. Not all hydrological basins are properly gauged. Therefore, regional flow duration curves have been studied for many cases aiming at transferring information at gauged sites to ungauged sites. In regional flow duration curves, morphological characteristics of the hydrological basin are used solely or they are combined with the parameter of the probability distribution function. For the ungauged basins, regression equations using the drainage area as an input has always been valuable. Methodologies used for the flow duration curves of ungauged basins consider also the dominant landscape and climate characteristics and also the karstic and non-karstic structure of the hydrological basin. A regional model for the estimation of the dimensionless flow duration curve in sites with no or limited data has a higher importance due to the generalization ability of the dimensionless flow duration curve.

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