Forecasting climate processes makes available appropriate tools to managers at different fields, given these projections, they should design future policies in order to optimize costs and maximize productivity features. Precipitation forecast is very important for various purposes as, flood, drought, catchment management, agriculture, etc. The main aim of this study is to investigate changes in the time of precipitation using time models in the study area and forecasting these elements as well as studying drought and wet years for water management. In this study, three models, namely Box Jenkins, Decomposition and Healt Winterz models were used for the period 1977 to 2010 in Shiraz station and finally, regarding the comparison of error between the three methods, the Box Jenkins approach was chose as was the most appropriate method for forecast and then the monthly and seasonal precipitation forecast from 2010-2013 years have been investigated. Studying annual rainfall of this station using Hiem and Koutil Tables, it was found that Shiraz pre-province have been in drought period 20 years out of 33 years with 51.51% weak drought and 9% severe drought and these droughts have been occurred especially in these years. The recent drought has had an impact on lakes and underground water sources and causes a shortage of water and declining groundwater for agriculture.
