Reservoir sedimentation is a severe problem around the world, as it reduces the original capacity of the reservoir significantly which affects the irrigation, hydropower and drinking water supply activities. This study was conducted in Maiambelay reservoir in North Western Zone of Tigray region with the objectives of estimating reservoir sedimentation and useful life of Maiambelay reservoir using Bathymetric survey method. The research put together the Revised Universal Soil Loss Equation (RUSLE) model to identify the soil erosion hotspot area. To estimate reservoir sediment deposition, comparison of reservoir capacity on two periods one before dam construction and the other from bathymetry survey was applied by developing TIN surface and analyzing volume of reservoir using ArcGIS 10.1.The result showed that Maiambelay reservoir has lost 10.27% of its capacity due to sedimentation in 7 years operation period. The average rate of sedimentation is estimated to be 108560.2 m3/y with1.46% annual rate of loss. The study indicated that the sedimentation rates in dead storage and live storage zones are 39714.28 m3/y and 68857.15 m3/y respectively this shows that the dead storage and live storage zones have been losing 31.23 % and 7.40% of their storage capacity respectively after 7years of operation. Based on bathymetry survey result the sediment yield and specific sediment yield of the watershed are 126796.28tyr-1 and 4661.62tkm-2yr-1 respectively. At the current rate of sedimentation the dead storage of the reservoir will be lost by sedimentation in 15 years.