Irrigation development has been identified as an important tool to stimulate economic growth and ru ralrndeve lopment, and is co nsidered as a cornerstone of food security and poverty reduction in Ethiopia. Whilerna lot of effort is being exerted towards irrigation development, little attempt is being made toward thernSllstainability of already constructed schemes. This study is an attempt to show whether alreadyrnconstructed scheme is sustainable or not, in the case of Ned hi Gelan Sedi SS I scheme in Eastern OromiarnRegion, Deder Di strict, which was selected purpos ive ly. Therefore, the major concern of this study is tornidentify Sllstainability of the scheme from socio-cultural, environmental, physical, fin ancial, insti tuti onalrnand community empowerment aspect .To realize these objectives, structured househo ld surveyrnquestionnaires, semi-structured interviews, group discussions, fi eld observations and literature were used.rnFor household survey questi onnaires a total of 88 sampled households were randomly selected.rnPhys ical stability, efficiency of the scheme, environmental protection, productivity, equity, coll ectivernaction system resilience and re levance are those categories ' that a re se lected to ind icate practices underrnwhich we will feel confident that the system should continue to exi st and to function, at least for timespanrnof20-30 years. Categories are further expressed by arou nd 36 indicators. By using the computed Vesrnor No response of the sampled household, rated scale of each category was calculated from rated scale ofrnindicators. Finally, average va lue of all categories was taken to be the sustainability index of the scheme.rnThe study indicates that, the approach of intervent ion was not palt icipatory. The communities did notrnparticipate during study and construction period and no handing over of the project to the community.rnElected committees were not representative of all vill ages, and at this ti m~ water distribution, massrnmobil ization for maintenance and confl ict resolutions were handled by traditi onal water leader Malaqarnthat are limited in their own vill age. Equali ty in water distribut ion is non-existence. Even if IF AD did therndemonstration, the resu lt was not sati sfactory. Land scarcity is number one problem in the area. Siltationrnof head work and damage of col umn of flume is also a seri es issue that needs immediate solut ion.rnWatershed management must be practiced in the area. 92 percent of sampled households are not paid andrnwill ing to pay operation and maintenance costs, water fee costs and project recovery costs, which showrnweakness of financial viabil ity of the proj ect.rnAs a resul t, the key fi ndi ngs of the study reveal that the sustai nability index of the scheme was 1.31 whichrnshows value approach to unsustainable condition, an outcome of lack of equitable resource distri bution,rnwhich create lack of co llective action towards the scheme sustainabili ty issues, especially for operationrnand maintenances that harm stabi lity of the physical capital by minimizing the efficiency of the scheme,rncoupled with low protective action of the environment, aggravate the problem and fi nally systems are nornlonger to deli ver their benefit and the people are also no longer to devote necessary efforts to keyrnactivities and sustainabili ty of the system become under questi on even for this generation.rnThe supports from IFAD would have been more rewarding, if it is coupled with improvement of therncondition of physical stabili ty of the scheme with maintenance and establ ishment of representative WUA.rnMoreover, to improve the economic and environmental sustainability of small scale-i rrigation schemes,rnin stitutional support (input supply, output marketing and cred it serv ices), trai ning of farmers on improvedrncrop and water management issues, regu lar supervision and monito ring of scheme activ ities are crucial.