Performance assessment of irrigation schemes network is very essential in taking different water management strategies. However, the performance of Mychew irrigation scheme was not assessed and hence, this research was undertaken to assess the hydraulic performance of Mychew small scale irrigation scheme. Moreover, identification of the cause and effect for mal-functionality of irrigation structures was also another objective of this study. Hence, comprehensive field observations, measurements and focus group discussions were held to investigate hydraulic performance and cause & effect of failed hydraulic structures. Simple descriptive statistics was employed for analysis of the collected data from focus group discussions and observations. Eight performance indicators were used to assess the performance of this irrigation scheme. Several factors such as sedimentation, design problem, damage of sluice gates, abstraction of irrigation water by unwanted plants has been identified for mal-functionality of different structures. There were problems in irrigation adequacy (0.75) and equity (0.28) of irrigation water was categorized as poor, while good and fair for dependability (0.08) and irrigation efficiency (0.79), respectively. The average water surface elevation ratio, delivery performance ratio, and delivery duration ratio of the main canal during the monitoring period was less than one, greater than 5% , and 150%, respectively. The highest sediment accumulation was observed at head and middle reaches of the irrigation scheme than the tail reaches. Generally, there were a number of irrigation structures which have mal-functioned in this irrigation scheme. Now it needs sustainable solution to improve performance of the irrigation scheme. Hence, it was recommended that water should be fairly distributed spatially and temporally. Moreover, capacity building and awareness creation of concerned bodies holds the key to bring a difference in irrigation water management in this irrigation scheme.

Keywords: Mychew, small scale irrigation scheme, hydraulic performance, irrigation structures, small scale irrigation schemes