Οptimum volumetric computation of fluvial sediment deposits in reservoirs by comparative analysis of different hydrographic survey methodologies

Abstract

Reservoir sedimentation studies provide a useful tool for the determination of the actual sedimentation rate and the computation of the real useful life of the reservoir. This task is often carried out with a full hydrographic survey of the reservoir, which feeds data to a Digital Terrain Model (DTM) of the reservoir’s invert. In other regions of the world, this task is alternatively accomplished with the range lines surveying technique, which is less accurate but is less expensive and copious and therefore suitable for developing countries and large scale reservoir systems. This paper examines these two different approaches of the volumetric computation of the sediment deposits at Kremasta reservoir, Western Greece. The volume of the deposited sediment for the Agrafiotis segment of the reservoir was calculated from the DTM survey and was accepted as the true sediment volume. The accuracy of the range line technique was tested against the DTM survey using five different sets of range lines. The results show a considerable underestimation of the sediment volume for all the sets of range lines. The underestimation is more evident when the range lines are sparse and it is shown that beyond a certain number of range lines there is no improvement of the overall estimation.