Along with the population growth rate of Barru Regency, Soppeng Riaja Sub-district, which experienced an increase in expansion, so that the lands that were previously irrigation service areas/agricultural areas changed their functions as residential land, ponds and the existence of a railroad project. This study aims to determine how much irrigation water needs due to changes in irrigation area and whether there is sufficient water availability by using irrigation areas. The evapotranspiration analysis calculation method used is the FAO Modified Penman method. For the calculation of the average rainfall analysis using a minimum halfmonth rainfall by means of Algebraic Average while for the analysis of water availability using the F. J Mock method. From the results of the calculation of irrigation water needs by setting different planting schedules will provide different water requirements, so the maximum irrigation water needs are obtained for each alternative. I is 2.64 L/second/ha, alternative II is 2.30 L/second/ha and alternative III is 2.46 L/second/ha. The value of the smallest maximum irrigation water requirement was obtained, namely 2.30 L/second/ha in the second period of October. Based on the water balance calculation in Kiru-kiru DI, the water deficit occurred in September period 2 and October period 1 because the water demand was greater than the mainstay discharge.

Keywords : Irrigation Water Needs, Mainstay Discharge, Irrigation Area.