Performance assessment of upgraded spillway–case study

Though all the aspects concerning hydrology, geology, topography and operational needs are taken into accounted while designing a spillway, eventually some spillways of existing dams need upgradation. Upgradation for the purpose of increasing the storage of the reservoir involves raising of the reservoir level above the normal operating level and this would result in additional submergence of land on the upstream. Upgradation in the gated spillways, necessitating the provision of piers, the full reservoir level (FRL), is required to be raised. The New Umtru Project is one of these projects. It is proposed to be upgraded by providing gates to the existing overflow spillway to utilize the flows optimally. Hydraulic model studies of the proposed modifications were conducted on 1:30 scale 2D sectional model at Central Water and Power Research Station (CWPRS) for evolving the optimum design of spillway and energy dissipator. It was observed from the studies that the original design of spillway and energy dissipator was required to be revised. Hence, improvement in the performance of the spillway after these modifications and other recommendations from the model studies are described in the paper. The present paper also describes the numerical simulation for upgraded spillway using computational fluid dynamics (CFD). © 2018 Indian Society for Hydraulics.