Climatic changes play an important role on agricultural production. Their impacts on agricultural sciences are significantly different form one region to another. There are many factors on the impact of climate change in farmlands. SPI (Standardized Precipitation Index) is one of the drought indices. SPI values show similar variation in relatively drought periods and different amounts of precipitation. The main aim of this study is to understand different factors and their role at different scales with wavelet analysis of long-term precipitation and the SPI data. All data is being evaluated under the catchment basin area. Data records cover Big Menderes Catchment area at Aegean Region in Turkey between 1960 and 2015. The results of this study underline in general small scale influences have more important role in all selected stations. Spatial variation of entropy at watershed basin has been associated with micro, meso or large scale influences. In general, gradually increasing trends of drought and wet conditions are resulted in small scale factors.