| Abstract:
Precipitation is one of the most important meteorological criteria whose quantity significantly varies throughout the earth. One of the methods to study precipitation trends in the past and present is the analysis of time series in different time scales. In this study, time series analysis was used for modeling and forecasting the average annual precipitation in Shiraz. Accordingly, the annual precipitation data in Shiraz were collected in the time interval 1951-2010. The results of this study indicated that 2. 5, 5, 10, 12 and 20-year cycles cover in the study area and the third Compatible with a return period of 20-years and variance about 12 percent was dominanted in the study area. In the end, to make sure of the trend in the past and also forecasting the future precipitation, the ARIMA modeling was used. Finally, by trial and error in the ARIMA patterns family, a final pattern called M4(0, 1, 1) CON was selected as the optimum pattern in terms of statistical criteria. This pattern has suggested a 1. 44 mm decline in precipitation until the year 2020. According to the results (the decreasing annual precipitation) and according to the climate change as a main topic, a comprehensive planning for the management of water resources unavoidable in Fars province and Shiraz city.
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