COMPARATIVE PERFORMANCES ANALYSIS OF TWO SMALL-SCALE IRRIGATION SCHEMES: CASE OF TAHTAY TSALIT AND MYCHEW, TIGRAY, ETHIOPIA

Abstract

Assessment of irrigation performances is very essential in taking different water management strategies. However, the performance of Tahtay Tsalit and Mychew irrigation schemes were not assessed yet and hence, this research was undertaken to investigate and compare the performance of the two small-scale irrigation schemes. Moreover, identification of the cause and effect for malfunctionality of irrigation structures was also another objective of this study. Hence, comprehensive field observations and focus group discussions was held to investigate the cause and effect of failed hydraulic structures. Moreover, field measurements on canal dimensions and water flow measurements were undertaken at selected sampling points. Simple descriptive statistics was employed for analysis of the data collected from group discussions and observations. However, hydraulic performance indicators were used to evaluate the performance of the two irrigation schemes. Several factors such as flooding, sedimentation, design problem, damage of sluice gates, abstraction of irrigation water by unwanted plants has been identified in both schemes for malfunctionality of different structures. There was no any problem in irrigation adequacy, equity, dependability and efficiency of irrigation water in Tahtay Tsalit irrigation schemes. However in Mychew, the 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. For both irrigation schemes, 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 schemes than the tail reaches for both irrigation schemes. Generally, in both irrigation schemes there were a number of irrigation structures which were malfunctioned. Now needs sustainable solution to improve the performance of the irrigation schemes. Hence, it was recommended that Water should be fairly distributed spatially and temporally particularly at Mychew irrigation scheme. Moreover, capacity building and awareness creation to concerned bodies holds the key to bring a difference in irrigation water management in both irrigation schemes.