Türkiye'de iklim değişikliğinin yıllık nehir akımları üzerindeki etkisinin iklim elastikiyeti metodu ile incelenmesi
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Tarih
2021
Yazarlar
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Yayıncı
Kırıkkale Üniversitesi
Erişim Hakkı
info:eu-repo/semantics/openAccess
Özet
Son yıllarda, tüm dünyada giderek daha belirgin hale gelen iklim değişikliğinin nehir akımları üzerindeki etkilerinin araştırılması, havza ölçeğinde su bütçesi açısından önemli bir hidrolojik problem olarak karşımıza çıkmaktadır. Bu çalışma, Türkiye genelinde doğal akarsu akımlarının (Q) yağış (P), potansiyel evapotranspirasyon (Ep) ve kuraklık indeksindeki değişimlere karşı tepkisini araştırmak amacıyla gerçekleştirilmiştir. Bu amaçla, 25 adet nehir havzası içerisinde baraj etkisinde olmayan farklı büyüklükte ve yeterli hidrometeorolojik veriye sahip toplam 376 adet alt havza tespit edilmiştir. Bunlardan 30 yıl ve daha fazla akım verisine sahip olan 146 adet alt havzanın yıllık ortalama verilerindeki uzun süreli zamansal eğilimlerini belirlemek için Mann-Kendall trend testi uygulanmıştır. Daha sonra, bütün alt havzalarda yıllık ortalama akımların yağış, Ep ve kuraklık indeksine olan hassasiyeti Schaake (1990) tarafından önerilen iklim elastikiyeti metodu ile değerlendirilmiştir. Trend analizine tabi tutulan alt havzaların birçoğunda akış değerlerinde azalma eğilimleri olduğu saptanmıştır. Sonuçlara göre, Türkiye'nin belirli bölgelerinde akış verilerinde %5 ve daha az anlamlılık düzeyinde istatistiksel olarak anlamlı eğilimlere sahip nispeten az sayıda alt havza bulunmaktadır. Çalışmada göz önüne alınan alt havzalarda iklim elastikiyeti metodu ile hesaplanan, akışın yağış hassasiyeti katsayısı (?p) ve Ep hassasiyeti katsayısının (?Ep) ortalama değerleri sırasıyla 1,55 ve -0,55 olarak elde edilmiştir. Buna göre; Türkiye genelinde yağışta meydana gelecek %10'luk bir artışın (azalışın) akışta ortalama %15,5'lik bir artışa (azalışa), öte taraftan Ep'deki %10'luk bir artışın (azalışın) ise akışta ortalama %5,5'lik bir azalışa (artışa) neden olacağı anlaşılmaktadır. Burada ?p'nin ortalama değerinin ??Ep?'nin ortalama değerinden daha büyük olması, Türkiye genelinde akışın P'ye olan hassasiyetinin Ep'ye göre daha fazla olduğunu göstermektedir. Diğer taraftan, alt havzalarda akışın kuraklık indeksi hassasiyet katsayısı (?Ø) ortalama değeri -1,66 olarak hesaplanmış olup bu değer kuraklık indeksinde %10'luk bir artışın akışta ortalama %16,6'lık bir azalışa neden olacağını ifade etmektedir. Bunlara ilave olarak, alt havzalara ait akışın iklim değişikliği hassasiyeti katsayıları (?p, ??Ep? ve ??Ø?) ile akış katsayısı (Q/P) arasında doğrusal olmayan ters bağıntılar olduğu ve dolayısıyla alt havzalarda akıştaki azalma ile akışın iklimsel değişikliğe olan hassasiyetinin artacağı görülmüştür. Son olarak, Türkiye genelinde yüksek kotlardan alçak kotlara doğru gidildikçe ?p, ??Ep? ve ??Ø? değerlerinde göreceli bir artış olduğu tespit edilmiş olup alt havzalarda alçak kotlarda akışın iklim değişimlerine karşı hassasiyetinin nispeten daha fazla olduğu anlaşılmıştır.
In recent years, assessing the effects of climate change, which has become more pronounced all over the world, on river flows has emerged as an important hydrological problem in terms of water budget at the basin scale. This study was conducted to investigate the response of natural streamflows (Q) to the changes in precipitation (P), potential evapotranspiration (Ep) and drought index throughout Turkey. For this purpose, 376 sub-basins under no dam effect with different sizes and sufficient hydrometeorological data were identified within 25 river basins. The Mann-Kendall trend test was applied to determine the long-term temporal trends in the annual average flows of 146 sub-basins, which have 30 years or more data. Then, the sensitivity of annual average flows in all sub-basins to precipitation, Ep and drought index was evaluated by the climate elasticity method proposed by Schaake (1990). In most of the sub-basins subjected to trend analysis, it has been determined that there are decreasing trends in flow values. According to the results, relatively few sub-basins with statistically significant trends at 5% and less significance levels in flow data are located in certain regions of Turkey. In the sub-basins considered in the study, the average values of precipitation sensitivity coefficient (?p) and Ep sensitivity coefficient (?Ep) of the flow calculated by the climate elasticity method were obtained as 1.55 and -0.55, respectively. Therefore, it is observed that a 10% increase (decrease) in precipitation would lead to an average increase (decrease) of 15.5% in streamflow while a 10% increase (decrease) in Ep would yield an average decrease (increase) of 5.5% in streamflow across the study area. Here, the fact that the average value of ?p is greater than the average value of ??Ep? indicates that the sensitivity of streamflow to P in the study area is higher than that of Ep. On the orther hand, the average value of sensitivity coefficient of streamflow to drought index (?Ø) was determined as -1.66, which means that a 10% increase in the drought index will result in an average decrease of 16.6% in streamflow within the study area. Additionally, it has been observed that there is a nonlinear inverse correlation between the climate change sensitivity coefficients (i.e., ?p, ??Ep? and ??Ø?) and the flow coefficient (Q/P) values of the sub-basins indicating that the decrease in streamflow would increase the sensitivity of streamflow to climatic variability. Finally, it was generally determined that there exist relative increases in ?p, ??Ep? and ??Ø? values from high to low elevations throughout Turkey revealing that the sensitivity of streamflow to climate changes seems to be relatively higher at low elevations.
In recent years, assessing the effects of climate change, which has become more pronounced all over the world, on river flows has emerged as an important hydrological problem in terms of water budget at the basin scale. This study was conducted to investigate the response of natural streamflows (Q) to the changes in precipitation (P), potential evapotranspiration (Ep) and drought index throughout Turkey. For this purpose, 376 sub-basins under no dam effect with different sizes and sufficient hydrometeorological data were identified within 25 river basins. The Mann-Kendall trend test was applied to determine the long-term temporal trends in the annual average flows of 146 sub-basins, which have 30 years or more data. Then, the sensitivity of annual average flows in all sub-basins to precipitation, Ep and drought index was evaluated by the climate elasticity method proposed by Schaake (1990). In most of the sub-basins subjected to trend analysis, it has been determined that there are decreasing trends in flow values. According to the results, relatively few sub-basins with statistically significant trends at 5% and less significance levels in flow data are located in certain regions of Turkey. In the sub-basins considered in the study, the average values of precipitation sensitivity coefficient (?p) and Ep sensitivity coefficient (?Ep) of the flow calculated by the climate elasticity method were obtained as 1.55 and -0.55, respectively. Therefore, it is observed that a 10% increase (decrease) in precipitation would lead to an average increase (decrease) of 15.5% in streamflow while a 10% increase (decrease) in Ep would yield an average decrease (increase) of 5.5% in streamflow across the study area. Here, the fact that the average value of ?p is greater than the average value of ??Ep? indicates that the sensitivity of streamflow to P in the study area is higher than that of Ep. On the orther hand, the average value of sensitivity coefficient of streamflow to drought index (?Ø) was determined as -1.66, which means that a 10% increase in the drought index will result in an average decrease of 16.6% in streamflow within the study area. Additionally, it has been observed that there is a nonlinear inverse correlation between the climate change sensitivity coefficients (i.e., ?p, ??Ep? and ??Ø?) and the flow coefficient (Q/P) values of the sub-basins indicating that the decrease in streamflow would increase the sensitivity of streamflow to climatic variability. Finally, it was generally determined that there exist relative increases in ?p, ??Ep? and ??Ø? values from high to low elevations throughout Turkey revealing that the sensitivity of streamflow to climate changes seems to be relatively higher at low elevations.
Açıklama
Fen Bilimleri Enstitüsü, İnşaat Mühendisliği Ana Bilim Dalı
Anahtar Kelimeler
İnşaat Mühendisliği, Civil Engineering
