Assessment of Reservoir Sedimentation using Remotely Sensed and Ground Observation Data (The Case of Legedadi Reservoir, Ethiopia)
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Date
2021-07
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Addis Ababa University
Abstract
Reservoir sedimentation is one of the issues that need to be addressed in water resources management. Sediment deposition in reservoirs for water system, hydroelectric power control, and urban water supply, reduces their capacity, service life, water quality and requires expensive operations for removal and treatment. Lack of normal and less cumbersome methods for assessment of sedimentation ranges and available potential poses undertaking for the sustainable administration of reservoirs. The conventional methods for quantification of sediment such as inflow- outflow and hydrographic survey methods are clumsy, expensive and time consuming. Hence, there is a need for simple methods, which requires less time and economical. The remote sensing is incredibly useful, economical and reliable tool for conducting such surveys and monitoring sedimentation in reservoir.
This study examines to assess Legedadi reservoir sedimentation by using remotely sensed data. Satellite imageries have been employed for the water spread area, which was used for calculating sedimentation rate. This research put together the geographical information system (GIS), Envi software, and DEM to assess the reservoir sedimentation by using remote sensing data.
The result indicated that the current 2019/20 capacity of the Legedadi reservoir estimated using remote sensing techniques becomes 34.87Mm3 at an elevation of 2465.13m a.m.s.l and the original capacity (using hydrographic survey) was 40.8 Mm3 at the same level, the loss in reservoir gross capacity due to sediment deposition for the period of 41 years of reservoir since 1979 to 2020 was determined to be 5.93 Mm3 which convert to 14.53 % gross capacity loss or showing annual storage loss due to sedimentation deposition is found to be 0.35% loss between elevation 2465.13 and 2457.46 m a.m.s.l. Accordingly, the annual rate of sedimentation using remote sensing was found to be 0.145Mm3/year. Those values are found to be in close correspondence with results obtained from the hydrographic survey. LULC change and domination of cultivated land indicate a significant impact on reservoir sedimentation.
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Keywords
Remote sensing, reservoir sedimentation rate, Storage capacity, Reservoir, hydrographic survey