Research on climate change evidenced by comparative studies of different river catchments in Kenya and in the Central African Republic (CAR) consists to analyze the inter-annual and spatio-temporal variability of hydro-rainfall resources, their dynamics according to changes occurring in their modes and in terms of climatic extreme events. Climatic and extreme phenomena evolution (droughts, low-water levels, floods, violent storms) is a major concern in the younger past where aridification of climate was recognized since the 1970s (Olivry, 1987; Olivry et al., 1998; Laraque et al., 1998; Paturel et al., 1998; Servat et al., 1999; Ardoin-Bardin, 2004). Thus, short and long term hydrological periods and their variability would insinuate modifications in water ‘behavior’ according to different climatic types (Nguimalet, 2009). The periods of variability display rainfall and runoff and other hydrological data resources gathered.