Assessment of sedimentation capacity in Rantambe Reservoir using acoustic methods

Abstract

Reservoir sedimentation is a major problem for dam safety, water security and productivity. So, regular monitoring and assessment of sedimentation rate performances are paramount. Rantambe reservoir with an initial gross capacity of 21 MCM, constructed under Mahaweli Development Scheme is a multipurpose reservoir used for power generation (52 MW) and flood controlling. However, due to excess sedimentation through Uma Oya, the capacity of the reservoir is affected and therefore compromised the dam safety and water security. In this study, the sedimentation characteristics were assessed using acoustic methods for identifying the performance of reservoir sediment management measures. Hence, Sub-bottom profiler with 10 kHz and 3.5 kHz transducers were used as the main acoustic instrument to determine the height of the water column, the layering of the reservoir bed and the sedimentation pattern. Results show 1.93 MCM as the reservoir's existing volume and due to excessive sedimentation in the mouth of Uma Oya exceeding the dead storage level at the dam thus significantly decreasing the water depth limiting the reservoir capacity.