Application of HEC-HMS Model for Runoff Simulation

Abstract

Hydrologic modelling involves formulating the mathematical models to represent the hydrologic processes such as, precipitation, snowmelt, interception, evapotranspiration, infiltration, sub-surface flow, and surface flow, as well as the interaction between them. Hydrologic modeling can be challenging because it involves highly nonlinear processes, complex interactions and high spatial variability’s at basin scale. Physically based hydrologic models are based on known scientific principles of energy and water fluxes whereas, conceptual models are based on conceptual storages and model parameters that require calibration, or they are moisture accounting models without explicitly considering energy fluxes, and so they mimic physical processes in a simplified manner. Focus on the physically based distributed hydrologic modelling started in order to minimize or overcome the deficiencies of the conceptual models. In physically based hydrologic modelling the hydrologic process of water movement are modeled either by the finite difference approximation of the partial differential equation representing the mass, momentum and energy balance or by empirical equations. Typically the primary components of hydrologic cycle related to the land phase are taken into consideration. These are: interception, snowmelt, evapotranspiration, sub-surface runoff, groundwater flow, surface runoff and channel routing. Physically based hydrologic models can be fully distributed where a river basin is discretized as a rectangular grid mesh, or be semi-distributed when the basin is divided into limited number of sub basins based on the terrain features and the drainage network. Study and simulation of a watershed has been done using HEC-HMS. The Silsako watershed located in Guwahati city has been modelled and the peak simulated discharge obtained at the outlet of the watershed is 6793815.6 m3.