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
compare the hydraulic performance of the two small-scale irrigation schemes mainly
using comparative analysis of hydraulic performance indicators. The existing hydraulic
structures were identified and evaluated their functionality and for malfunctioned
structures the cause and effect of the problem was investigated through field observation
and focus group discussions. On top of this, the hydraulic performance of the irrigation
schemes were practically assessed using Parshall flume and 90 degree V-notch
instruments spatially and temporally. 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. As
a result of this, all flow control gates of the offtake in T.Tsalit irrigation schemes has
already stolen and no flow control gates was constructed in Mychew and consequently,
farmers are using stone and mud for controlling of water flow which further adds
siltation to the canals. According to the irrigation performance standards, there was no
any problem in irrigation adequacy, equity, dependability and efficiency of irrigation
water in T.Tsalit irrigation schemes. However in Mychew, the adequacy and equity of
irrigation water was categorized as poor, while good and fair for dependability and
irrigation efficiency 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 due to many different reasons and 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.
