Determination of decadal climatic cycles in runoff fluctuation of a hydrologic unit

A group of 60 runoff and 15 precipitation time series, all belonging to a hydrological unit in Southwest Mexico, in the Pacific watershed was analyzed. The internal homogeneity of the time series was tested and completed for the calculation period using suitable statistical methods. Three homogeneous regions were defined in the studied zone through correlation matrices. The climatic decadal cycles were determined with the help of the integrated differences curves. The anthropogenic impact on the runoffs was estimated through the homogeneity curves. The length of the cycles were ranged from 30 to 40 years. The structure of the decadal cycles permitted the estimation of the duration of deficiency, abundance, and normality runoff periods in each region.