Reservoir sedimentation is a serious problem that affects the life of reservoirs. Because itrnreduces the original capacity of the reservoir significantly which in turn affects irrigation,rnhydropower and drinking water supply activities. This study was conducted in koga nightrnstorage reservoirs in Amhara region Upper Blue Nile basin with the objectives ofrnestimating reservoirs sedimentation and life of koga night storage reservoirs usingrnbathymetric survey. rnTo estimate reservoirs sediment deposition, comparison of initial reservoirs capacity andrnpresent capacity. The later obtained by bathymetry survey developing of TIN surface andrnanalyzing volume of reservoirs using ArcGIS 10.4.Sedimentation reduced reservoirsrncapacity from initial value (design storage) of 32294, 36902 and 36296mrn in 2012 torn27054, 27722 and 27441mrn3rn3rn in 2020 for the Tagel, Adbra and Teleta NSR respectively. rnThe result showed that oga night storage reservoirs have lost on the average 16.2, 24.8 andrn24.4% of their capacity, respectively due to sedimentation in 8 years of operation period. rnAverage rate of sedimentation was estimated to be 655, 1147.5and1106.9 mrn/year with 2.1,rn3.1 and 3.04% annual rate of loss for Tagel, Adbra and Teleta NSRs, respectively. Basedrnon bathymetry survey result, the sedimentation rates in live storage zones are found to bern655, 1147.5and1106.9 mrn3rn/years. At the current rate of sedimentation the storage of thernTagel,Adbra and Teleta NSR will be completely lost by sedimentation in 49, 32 and 32 rnyears respectively.