The Saba watershed is the main water source for irrigation areas downstream of the Saba river. The Titab Reservoir was built to be able to meet the continuity of irrigation water supply, especially during the dry season. This study aims to analyze the fulfillment of irrigation water requirements provided by the Titab reservoir. The study began by collecting data first, in the form of primary and secondary data. Primary data is used to see the existing conditions. Secondary data is used for irrigation requirements analysis and simulation. The secondary data used for manual calculations are 15 daily rainfall data, 15 daily measured discharge, and climate data for 10 years from 2006-2016. The output of these data is the need for irrigation water, the potential evaporation, and the discharge reliability used for the simulation. The simulation was carried out using the RIBASIM 7.01.24 program by entering the calculated data and the existing reservoir data. The simulation results show that the irrigation water needs supplied in each irrigation area are not sufficient according to the plan and the reservoir reliability value is low, namely 57.35%.