The incorporation of a reliability analysis in the design of hydraulic structures can provide insights into management strategies that may consider potential failure modes, uncertainties, and corresponding risks. This study evaluates the reliability of water supply channels (applicable to channels in design or existing) using the reliability theory based upon field observations, specifically two failure modes observed in channels in the Maragheh-Bonab plain of Iran. Failure Mode 1 occurs when the main channel cannot pass the design flow. Failure Mode 2 occurs when the intake from the main channel is not responsive to the design flow. The formulation established the performance function based on the safety margin and load/resistance, where the mean-value first-order second-moment method approximated the mean and variance of the performance functions. The formulation was implemented in the water supply channels of the Maragheh-Bonab plain, northwest of Iran. The results of Mode 1 confirmed high reliability values in most channels, which compliments economic optimization efforts. A conclusion from this study highlights a safety issue is that although the channels are conservatively designed, the Failure mode 2 can still occur where water overflows the main channel. This study also provides a practical guide for the design or analysis of canals by providing reliability curves as a function of the distance between the regulator gate and the intake channel. These curves can assist with locating or relocating intake channels and show an inverse relation between reliability and the distance.
