Irrigation plays a very important role in increasing agricultural yields to maintain national food security and improve the welfare of the Manatuto people in Timor-Leste. The purpose of this study is to determine the cropping pattern that can be applied effectively in the area. In order to plan an optimal cropping pattern, analysis of climatic and topographic data is very important to obtain information on evapotranspiration, effective rainfall, and irrigation water requirements. To determine effective rainfall, 10 years of data were used to obtain rainfall values at the research site. Meanwhile, the Blaney-Criddle method is used in the calculation of evapotranspiration. Through this analysis, an attempt was made to find the right time to start planting by assessing the required irrigation water requirements. The simulation results showed that the Laclo irrigation system was not able to meet the required water needs every month of the year. In further analysis, the K values obtained in alternatives 1 to 5 showed significant differences each month. The first alternative has the highest average K value, which is 0.51. Therefore, the first alternative was selected for land preparation in January first.