Elidar earth fill dam is located near Elidar town, Afar Region, North East Ethiopia. Elidar earth fill dam was designed to harvest 2.56 MCM of water from a catchment area of about 130 km 2 to introduce a modern irrigation practice downstream of the dam and to fulfill livestock water demand. The dam was planned for irrigation, livestock, and domestic water supply purpose. However, the dam performs under capacity and does not give service yet as a result of the high-water loss. The main objective of this study is to focus on the cause of failures of Elidar earth fill dam. Primary and secondary data were collected from the study area and design documents. The analysis was conducted using the GEO-STUDIO model to analyze the seepage flux, slope stability by using soil laboratory result to gate soil characteristics, metrological data to get evaporation. The amount of Seepage losses through the dam body and foundation based on the design document was 6.05*10 -4 m3/sec and seepage estimated based on laboratory test data SEEP/W software model done was 2.24 *10 -4 m3 /sec. The design document indicated that the critical upstream and downstream slopes of the dam are safe for possible loading and operation cases. But laboratory test data result at steady state was 1.168 it indicated that the critical downstream slope of the dam was not safe for the possible loading condition. Based on the result of the study cut-off, dawn stream berm, toe drain, and upstream impervious blanket were recommended. Key word: Evaporation; Failure; Seepage; Slope Stability.