Estimation of Reservoirs Sedimentation Using Bathymetry Survey: Case Study on Three Koga Night Storage Reservoirs

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Addis Ababa University


Reservoir sedimentation is a serious problem that affects the life of reservoirs. Because it reduces the original capacity of the reservoir significantly which in turn affects irrigation, hydropower and drinking water supply activities. This study was conducted in koga night storage reservoirs in Amhara region Upper Blue Nile basin with the objectives of estimating reservoirs sedimentation and life of koga night storage reservoirs using bathymetric survey. To estimate reservoirs sediment deposition, comparison of initial reservoirs capacity and present capacity. The later obtained by bathymetry survey developing of TIN surface and analyzing volume of reservoirs using ArcGIS 10.4.Sedimentation reduced reservoirs capacity from initial value (design storage) of 32294, 36902 and 36296m in 2012 to 27054, 27722 and 27441m 3 3 in 2020 for the Tagel, Adbra and Teleta NSR respectively. The result showed that oga night storage reservoirs have lost on the average 16.2, 24.8 and 24.4% of their capacity, respectively due to sedimentation in 8 years of operation period. Average rate of sedimentation was estimated to be 655, 1147.5and1106.9 m /year with 2.1, 3.1 and 3.04% annual rate of loss for Tagel, Adbra and Teleta NSRs, respectively. Based on bathymetry survey result, the sedimentation rates in live storage zones are found to be 655, 1147.5and1106.9 m 3 /years. At the current rate of sedimentation the storage of the Tagel,Adbra and Teleta NSR will be completely lost by sedimentation in 49, 32 and 32 years respectively.



Koga night storage reservoirs, Reservoir sedimentation, Bathymetry