Browsing by Subject "STANDARDIZED PRECIPITATION INDEX"

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    A NOVEL APPROACH FOR DROUGHT CHARACTERIZATION BASED ON PERFORMANCE-ORIENTED SPI: AN ILLUSTRATIVE CASE OF SOUTHEASTERN ANATOLIA REGION, TURKEY
    (CORVINUS UNIV BUDAPEST) Yilmaz, B
    Drought is a main water-related natural hazard due to its features, sensitivities and effects to all sectors. According to climate change scenarios, drought hazards are expected to be more devastating, especially in arid and semi-arid regions. Drought characterization is essential to be aware of expected negative effects of droughts as well as to devise water management plans including possible mitigation measures. To this end, many drought indices have been developed for drought analysis, one of which is the Standardized Precipitation Index (SPI) that is widely used worldwide. In this study, a new drought index is proposed, namely the Drought Power Index (DPI), based on the SPI with orientation by reliability-resilience-vulnerability (RRV) concept. The use of the RRV approach with the SPI time series empowers the drought characterization by considering the frequency of drought event, drought recovery period as well as the severity of droughts-once a drought has occurred. Since the drought is identified as an unfavorable phenomenon, the DPI ranges from 0 to 1 where the higher values indicate higher drought devastating features (probability, duration and extremity of drought) and vice versa. The proposed approach is illustrated with reference to the Southeastern Anatolia Region, Turkey. The long-term (1970-2017) monthly precipitation data of eight meteorological stations under the operation of General Directorate of Meteorological Services of Ministry of Forestry and Water Affairs are used in the study. The 12-month SPI time series, which were later used for calculations of DPI, were obtained by the use of SPI_SL_6 software. The study revealed that there has been an increasing trend in DPI values in the basin, especially after 1993. It is concluded that the DPI is a valuable indicator for (i) spatially and temporally evaluating the drought characteristics, (ii) analysing meteorological, agricultural and hydrological drought severity with its coherent capability with SPI, (iii) ranking the regions in accordance with the drought vulnerability conditions.
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    ANALYSIS OF HYDROLOGICAL DROUGHT TRENDS IN THE GAP REGION (SOUTHEASTERN TURKEY) BY MANN-KENDALL TEST AND INNOVATIVE SEN METHOD
    (CORVINUS UNIV BUDAPEST) Yilmaz, B
    The analysis of drought trends plays a significant role in the efficient water resource management, especially in arid and semi-arid regions. Assessing the drought trends by drought indices, of which the Standardized Precipitation Index (SPI) is the most popular, is a reasonable way, because the drought indices measure the climatic anomalies through their severity, duration and frequency. In this study, the possible hydrological drought trends in the GAP region (Southeastern Turkey) were investigated by the use of 12- and 24-month SPI series. The SPI series were determined by 48-year-long (1970-2017) monthly precipitation data monitored at nine selected stations (Mardin, Adiyaman, Batman, Diyarbakir, Siirt, Sirnak, Gaziantep, Kilis and Sanhurfa) in the GAP region. In the analyses, a recent graphical trend detection method entitled Innovative Sen Metod (ISM) and Mann-Kendall trend test (MK) were used. The ISM has non-parametric basis without any restrictive assumption, moreover, its application is rather simple when compared with the other trend identification methods. The ability to identify the trends of low, medium and high values of a series is the innovative side of the ISM. Since the significance test is a crucial factor to identify the possible trends scientifically, the results were statistical tested at the 0.05 significance level in the methods. The ISM and MK test both revealed that, Mardin is the most vulnerable province in the region, due to the significant decreasing trend, which determined by 12-month and 24-month SPI values. Sanhurfa, Kilis, Siirt, Diyarbakir and Batman are second order drone prone provinces. In accordance with the results of the ISM, there is an increasing trend in normal and wet conditions in Gaziantep, Sirnak and Adiyaman. Specifically, the results highlight that the central of the GAP region has a tendency toward the heavier droughts in the future. It is also concluded that the ISM is a valuable tool with its simplicity as well as the inherent properties to deduce qualitative information.