Effective values of rainfall for irrigation management of sugarcane in Goiana, Pernambuco, Brazil

Abstract

The objective of this work was to estimate the decendium effective rainfall to Goiana City (North Forest Zone), Pernambuco, Brazil, which has a great representation in the sugarcane industry of the State, aiming at helping the irrigation management and the rational use of water. The rainfall database used had a temporal scale from January 1981 to December 2009. The daily rainfall was grouped in a 10 days period and was adjusted to the Gamma probability density function so the probable rainfall could be obtained from 75 and 90% levels of probability. The effective rainfall was estimated by the methodologies of FAO, USDA and Fixed Percentage (PF), through the CROPWAT software. It was observed that the effective rainfall is affected by the seasonality of the rainfall regime in the region where the city is placed. In El-Niño years the USDA and 80% PF methods were considered the best, in years of hot waters in the south Tropical Atlantic the most appropriate methodology is the 20% FP, whilst the method proposed by FAO or 50% PF is more indicated for regular years.