Simulation of Flows at Tehri Dam during Various Storm Events using HEC-HMS

Reliable prediction of storm runoff from rainfall and snowmelt are important for flood hazard mitigation and resilience. In this study, the HEC-HMS software of U.S. Army Corps of engineers was used to simulate the flows at Tehri Dam during various storm events. The Tehri dam is the 4th highest dam in the world in earth and rock fill category. The catchment area of Tehri dam is 7293 km², out of which 2042 km² is covered with permanent snow. Eight storm events from monsoon of 2016–2017 and two events from monsoon of 2018 have been selected for calibration and validation respectively. Model parameters were calibrated and performance of the model was evaluated by comparing the six hourly flows at Tehri dam. Maximum and minimum nash and Sutcliff efficiency (nSE) for 8 events during calibration were 90.7% and 72.6% respectively. While during the validation of two monsoon events of 2018 the nSE were 85.3% and 85.1%. Model performs satisfactorily to reproduce the runoff induced from rainfall as well as snowmelt. The paper discusses delineation of sub-catchments, selection of storm events, sensitivity analysis, calibration of parameters and validation of six hourly flows at Tehri dam.