Abstract:
Evaluating and selecting improved and efficient irrigation water management practices are
essential for enhancement of project or farm profitability by increasing the water productivity.
However, in Tendaho large scale Irrigation scheme there is no a sound evaluation studies in the
last few years. Therefore, this study was carried out to evaluate irrigation water management of
Tendaho large scale irrigation scheme in the lower Awash River basin of Ethiopia, for
improving overall irrigation water management, distribution and delivery in the scheme. The
study also assessed basic procedures used to support sustainable irrigation water management
practices. Primary data were collected through field measurements and survey, and secondary
data were gathered from different sources. Disturbed and undisturbed Soil samples were
collected from selected irrigation blocks within the irrigation scheme. Soil moisture,
fieldcapacity, permanent wilting point and bulk density were analyzed in Tendaho Sugar Factory
Research Center laboratory. Infiltration capacity was estimated using double ring inflitro-meter
and the basic/constant infiltration rate was 0.4cm/hr. For determining and evaluating the
performance of Tendaho large scale scheme, irrigation water performance evaluation
parameters like adequacy, efficiency, equity and dependability were estimated. The discharges
were measured using current flow meter at main canal, three primary, six secondary and twelve
tertiary canals. The crop water requirement was estimated by CROPWAT-8 software. The results
show that the overall Efficiency and Equity of water distribution of the system are not good and
the adequacy of water distribution and dependability of the water supplied in the system is rated
as good. The average Water surface elevation ratios at head, middle and tail reaches of the
canal during the monitoring period were generally less than one, thus they show that the canal
has a sedimentation/siltation problem. The result of Effectiveness of infrastructure shows, 18%
of the structures were destroyed. So, this is signal for the need of maintenance or rehabilitation
of canal structures. The result of Sustainability of irrigated area show that, currently from the
total irrigable land of 25,000ha which was prepared for sugarcane production only about
9660ha was irrigated which means about 38% of the total prepared irrigable land. This is
because of great social problems that are lack of trust on the project from the pastorals side, due
to design and construction problems of canal, land leveling problem and different other
problems accounted for minimized of irrigated land. Generally, for the long term sustainability,
water distribution equity, reliability and water saving; continuous monitoring, maintenance and
improvement measures are required