Probable rainfall contribution to coffee water demand in Uberlândia, Minas Gerais state, Brazil

Abstract

The occurrence, distribution of rainfall and the knowledge of crop water demand are essentials to irrigation planning. Thus, the determination of probable rainfall can contribute substantially to suitable irrigation projects. This work aimed to determine the probable rainfall for Uberlândia, Minas Gerais state, Brazil, in order to evaluate its contribution to coffee water demand. Daily precipitation data from 1975 to 2010 were summed in a 30-day period (monthly) and applied to Gamma distribution. The probable rainfall was estimated to different probability levels (%): 40, 45, 55, 65, 75, 85, and 95. With 75% of probability of exceedance (considered suitable to irrigation purposes) the probable rainfall in Uberlândia overcomes the coffee evapotranspiration only in December and January, suggesting a supplementary irrigation for vegetative growth and fructification periods (from October to April-May). During the entire dry-season the probable rainfall does not overcome the coffee evapotranspiration.