Kızılırmak havzasının kuraklık risk değerlendirmesi

In this study, it is aimed to calculate the standardized precipitation index (SPI), which is one of the meteorological drought indexes, which is the first stage, by using the data obtained from 39 meteorological precipitation observation stations in the Kızılırmak Basin. Monthly total precipitation data were used and the drought index was calculated. Drought data were determined according to 1-3 and 12-month time periods of each station. Univariate marginal distributions of drought duration and drought severity data obtained separately for each station were determined as Lognormal, Gamma, Exp, Weibull, Normal and Logistic distributions. Each was determined according to the results of KS, CvM, AD, AIC, BIC and MLE tests.. Drought parameters were determined in accordance with these distributions and CDF graphs were prepared for the drought duration and drought severity of the most appropriate distribution. To determine the optimal multivariate copula function using R-studio software, ten copula families (Gaussian, Student-t, Clayton, Gumbel, Frank, Joe, BB1, BB6, BB7 and BB8) were determined by MLE, AIC and BIC methods. The close relationship between Kendall-Tau value and upper tail dependence was taken into account when determining the copula family. After defining the multivariate copula family, graphs were created for each station and each time period. Finally, the common return times of drought parameters (drought duration and drought severity) were calculated and separate tables were created for all stations according to 1-3 and 12- month time intervals.