This study had the aim to evaluate a regionalization system of supplemental irrigation demand for the main irrigated crops in the State of Minas Gerais. The performance of the socalled IRGNET system was evaluated by assessment of the accumulated supplemental irrigation demand for Minas Gerais during the year of 1999, for two planting dates, for bean (dry) crop. The water demand was calculated by the IRGNET system and by a climatic method proposed by Camargo (1971). The total volume of water used for irrigation of bean with all potential irrigated area of Minas Gerais was estimated for two planting dates. The estimated reference crop evapotranspiration for Viçosa, Minas Gerais, was also compared for the year of 1999, calculated by means of the soil water balance, Class A pan evaporation and the Penman-Monteith method. It was observed that the accumulated supplemental irrigation demand was higher than the estimates calculated by the climatic model suggested by Camargo (1971). The total water volume for the irrigation of bean crop in the State of Minas Gerais was 611,720,830 m³ for the planting period of 1st May, while 686,660,480 m³ were found for the cultivation period of 15th September. The Class A pan evaporation method underestimated the reference crop evapotranspiration by 7.6%.
supplemental irrigation; water balance; geographic information system; internet
