Since water cycle begins with the formation of moisture in the atmosphere (climatic) before runoff flows (hydrologic) in rivers due to rainfall, the linkages between hydrologic and climatic data are based on complex physical processes that are difficult to conceptualize. Although many studies have attempted to explore the mechanisms and characteristics of hydro-climatic processes, their linearity has been less well considered, meaning that a detailed understanding of these processes and their interactions remains limited. Identification of the relationships between hydrologic and climatic variables is very important for many hydrologic applications such as prediction of missing records, analysis of climate change impacts, and estimation of hydrologic responses of ungauged basins. Observed meteorological and stream-flow data is initially used for the understanding of hydrological processes and thus for modeling these processes in order to estimate the stream-flow of a watershed. Statistical approaches have long been used in analyzing the relationships between hydrologic and climatic systems.