Copula-based bivariate drought severity and duration frequency analysis considering spatial–temporal variability in the Ceyhan Basin, Turkey

In recent times, copula families have been mostly employed in bivariate drought duration and severity. Archimedean copulas are mainly used conveniently among various potential for hydrologic design water resource management. this study, events defined by standard precipitation index (SPI3 time series) series 24-gauge stations Ceyhan Basin Turkey considering different elevation levels (high, average, low). Both severity tested their dependence with Mann–Kendall Spearman Rho trend test at a 0.05 significant level. While Gamma Weibull perform better than the other distributions average elevation, Log-normal found to fit DD DS most located low high elevations, respectively. The best is construct joint distribution function. influence of upper tail dependencies select appropriate Gumbel BB1 often regarded as series, After acquiring copula, return periods modeled each station. Finally, risk categories (mild, moderate, severe, extreme drought), spatial risk-return period constructed. High risks observed middle part basin based on TDS T′DS under mild categories. Apart from using univariate frequency analysis, analysis performed model theory which great importance hydrology