Nowadays significant tones of sediment are transported from upland watershed and accumulated to the downstream storage reservoirs and lakes every year. Reviewed literatures indicate that storage dam reservoirs are highly threatened by sedimentation problem. According to ICOLD 1988 and other recent studies the world average annual loss of reservoir capacity exceeds 1% because of sedimentation problem. Moreover, past studies conducted in the Blue Nile Basin Reservoirs shows the rate of soil erosion, land degradation and downstream reservoir sedimentation is alarmingly increasing. This research focuses on study area of Aguat-wuha storage dam reservoir located in South-Wollo Beshilo Sub-basin of Blue Nile Basin. Relatively little or no studies have been conducted in the Beshilo sub basin. Even if the Aguat-wuha storage dam reservoir became functional since 2018 rainy season, its sedimentation over 5 year service was not investigated and quantified yet. In this study we have employed the bathometric differencing technique in conjunction shore area bed elevation extraction there by applying spectral water indices from high resolution sentinel-2 satellite image. Bathometric differencing technique is done by DEM & TIN these are digital Terrain Models DEM differencing & TIN analysis gives us the spatially distributed depth of sedimentation and volume respectively while as shore area bed elevation extraction is extract reservoir area by method NDWI using cloud free Sentinel-2 Image of 10m resolutions in date to reservoir water level recorded use to developing the post filling 2022 Reservoir Capacity. Both the sediment depth and sediment volume spatial distribution shows that the shallower sediment accumulation depths are relatively located in the vicinity of less-gorge reservoir area, whereas the maximum sediment depths are found in the more gorge portion of reservoir mostly closer to Dam axis .The maximum sediment depth of 4.75m is found near dam outlet closer to Dam axis indicted that clay and finer sandy loam incoming sediment simply run in more gorge area near dam axis since the steeper slope is found near the tail of reservoir. The research findings show that both the bathymetric DEM differencing and capacity curve difference between the prefilling (2018) and post filling (2022) results the total deposited sediment is estimated 68109.25m3 (6.81 ha.m) in a period of 5 years. This implies the annual sedimentation rate of Aguat-wuha reservoir is estimated to be 13621.85 m3/year or 1.362 ha-m/year. At Normal Pool Level 2874, the reservoir storage capacity decrease from 82.109 ha-m to 75.3ha-m.Engineering This corresponds to 8.2% of reservoir capacity loss over a period of 5 years. Annually the storage capacity loss of Aguat-wuha reservoir is about 1.6% which is greater than the global average reservoir loss rate (1%). In addition to this, the specific sediment yield of reservoir watershed was approximated based on computed sedimentation volume (68109.25 m3) and reservoir trap efficiency of 93.4%. Beside to this the specific sediment yield of Aguat-wuha reservoir watershed estimated 21.3 ton/ha/year. This is much greater than the Global and African averages of 15 and 10 ton/ha/year respectively. The useful life of reservoir design dead storage 4 years’ service for feature and 5 year service for past therefor total function of dead storage is 9 years from 30 years design dead storage for worst senior’s .So, the Aguatwuha reservoir sediment management is needed before the dam ceases its functions. It also indicates the Aguat-wuha watershed had a significant watershed degradation and it is accelerating the sedimentation rate of Aguat-wuha reservoir. Keywords: Reservoir, sedimentation, Bathymetric survey, Remote sensing.