Frequency analysis of low flow series from Çekerek Stream Basin

Kuraklık analizleri çalışmalarında en uygun olasılık dağılımının seçimi minimum akım istatistikleri açısından önemlidir. Bu çalışmanın amacı, Çekerek çayındaki üç akım gözlem istasyonunda ölçülen 7-günlük minimum akım serilerinin frekans analizi için uygun olasılık dağılımının çıkarılmasıdır. En düşük 7-günlük akım serileri her yılın 7-günlük periyotları için günlük akım dalaşından oluşturuldu. 7-günlük akım, ardışık 7 günlük periyot içinde ölçülen en düşük akımdır. Seçilen olasılık dağılımlarının parametrelerinin tahmininde L-moment tekniği kullanıldı. Olasılık dağılımların performanslarını karşılaştırmak için MADI ve MSDI indisleri kullanıldı. Araştırma sonuçlara göre, en iyi performans genelleştirilmiş pareto (GPA) dağılımıyla elde edildi. Negatif değerler üreten dağılımlar elimine edildi. Gringorten formülünden elde edilen olasılık seviyelerine bağlı olarak pozitif değerler üreten dağılımlardan tahmin edilen akımlar (loğ pearson 3 hariç) % 75 den daha büyük olasılık seviyeleri için gerçek minimum akım değerlerini oldukça iyi temsil etmektedir. GPA dağılımına bağlı olarak 10 yıllık tekrarlanma aralığına sahip (Û7,ıo) istatistikler, 1424, 1409 ve 1404 numaralı akım gözlem istasyonları için 0.29,1.27 ve 2.11 m3/s olarak tahmin edildi.

Çekerek Havzası minimum akım serilerinin frekans analizi

The most true selection probability distribution is important to describe the low flow statistics for the studies related to drought analysis. The aim of this study is to derive appropriate probability distributions for frequency analysis of 7-day annual low flows at three gauging stations of the Çekerek Stream. The lowest 7-day flow series were constituted from daily flow data for 7-day periods of each year. A minimum 7-day flow is the lowest flow that occurred within a 7-consecutive day period. L-moment technique was used to predict the parameters of the selected distributions. Two goodness of fit indices, including MADI and MSDI, were used to compare the performances of the probability distributions for fitting. According to results, the best performance was obtained for generalized pareto (GPA) distribution. The distributions produced negative values were discarded. The predicted low flows obtained from the distributions that produced positive values (except Log Pearson type three) for empirical probability levels (Gringorten formula) sufficiently represent the actual low flows for probability levels higher than 75%. The statistics having reoccurrence interval of ten years (O?,™) based on GPA distribution were predicted as 0.29, 1.27 and 2.11 m3/s for gauging stations 1424,1409 and 1404, respectively.

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