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Titre : Seyhan ve Çoruh akarsu havzalarında kuraklık analizi / Drought analysis in Seyhan and Çoruh river basins

Auteur : ÖZÇELİK Nur Banu

Université de soutenance : İstanbul Teknik Üniversitesi

Grade : Master Thesis 2021

Résumé partiel
Drought is one of the major natural hazards that occur all over the world. There are many definitions of drought ; one of the most common, drought, is the period when the amount of water in a region is less than the amount of water available at normal times, regardless of the climatic conditions of that region. Due to the accelerated climate shifts and anthropogenic activities, drought affects more people worldwide. Turkey is mainly located in a semi-arid climatic zone. Therefore it may face the risk of drought frequently. Its effects have begun to appear in our daily lives and bring economic, social, and environmental consequences. Therefore, studies on the analysis of drought and its future severity have gained more importance. The main purpose of this study is to analyze drought in Seyhan and Çoruh river basins and predict future drought intensity. In this study, drought analyses were carried out with mean monthly streamflow data from gauging stations. The current gauging stations were used and operated by the General Directorate of State Hydraulic Works. From both river basins were chosen 7 stations with and we studied 14 stations. In terms of the data length effects, we have investigated short and long-term streamflow periods. All stations were performed for 20 years by Streamflow Drought Index. After that, we investigated station number E1801 in the Seyhan river basin for 75 years and station number E1805 in the Seyhan river basin for 72 years by Streamflow Drought Index. In the Çoruh river basin, we have examined station number E2304 for 48 years and station number E2326 station for 47 years. For calculation of Streamflow Drought Index, continuous series is necessary. For this purpose, linear regression analyses were performed for missing months and years. The missing data in the four stations were obtained by looking at the highest correlation coefficient between other stations. After that, we determined the best fit distributions. For the mean monthly streamflow data, the series investigated the drought level for the 1 month, 3 months, 6 months, 9 months, and 12 months periods using the Streamflow Drought Index (SDI). The drought degree has been classified based on Streamflow Drought Index results. For each time scale, we examined dry and wet periods. Based on the outcome, severe and extreme drought was investigated between 2007-2008 for 7 stations in the Seyhan river basin. For all stations in the Seyhan river basin, in 2001 and 2005, it was observed to vary between moderate and severe drought. In the Çoruh river basin, mild to moderate drought was observed at stations number D23A26 and D23A32 in 2000, 2001, and 2002, while intense and extreme drought was seen at the other 5 stations. At this stage, based on the Streamflow Drought Index classification, the probability of the level of the drought was calculated. In addition, with this calculation was examined the effect of data length on the result. Station number E1801 (in the Seyhan river basin) determined the 20-year and 75-year streamflow drought index results and compared them. SDI-1, SDI-3, SDI-6, SDI-9, and SDI-12, the percentage of wet and mild, moderate, severe, extreme drought levels for each period were determined. Furthermore, we calculated the probabilities of the 48-year and 20-year Streamflow Drought Index results in the station number E2304 located in Çoruh river basin.

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