<![CDATA[Abstract The development of irrigation infrastructure in Indonesia is an absolute prerequisite for ensuring national food security; however, challenges such as damage to the weir crest often hinder agricultural productivity. This study aims to design the rehabilitation of the Ngeprih Weir in Ponorogo Regency to re-optimize its function in raising water levels and supplying irrigation needs. The research methodology includes hydrological analysis to determine the design flood discharge and hydraulic analysis to establish the technical dimensions of the weir. Rainfall data for the 2015-2024 period from the Slahung and Ngrayun Stations were processed using the Gumbel distribution, which was subsequently validated using Chi-Square and Smirnov-Kolmogorov tests. The design flood discharge calculation was performed using the Nakayasu Synthetic Unit Hydrograph (SUH) method. The hydrological analysis results indicate that the design rainfall for a 100-year return period (R100) is 205,55 mm, with a design flood discharge (Q100) of 43,60 m³/s. Technically, the Ngeprih Weir is designed using a rounded crest type at an elevation of +154,43, with a weir height of 1,88 meters and a total width of 27 meters. To dissipate flow energy, a submerged bucket type stilling basin was selected, considering the riverbed characteristics consisting of boulders. Based on stability analysis, the weir structure is declared safe against overturning, sliding, eccentricity, and soil bearing capacity under various water level conditions.]]>
