“…As early as 1951, Hurst () demonstrated that the annual run‐off record from the Nile River displayed a long‐term persistence (self‐similar), and he developed the “Hurst exponent” to characterize the long‐term persistence. Subsequently, long‐term persistence has been recognized in many time series, such as economic (Muchnik, Bunde, & Havlin, ), climatic (Orun & KoçAk, ), and water quality (Shi, Liu, Huang, Zhang, & Su, ) data sets. Calculation methods for the Hurst exponent include detrended fluctuation analysis (DFA) (Onderka et al, ), wavelet transforms (Simonsen, Hansen, & Nes, ), and rescaled range analysis (Nnaji, ).…”