Two-dimensional physically based finite element runoff model for small agricultural watersheds: I. Model development

Soil erosion by water is the root cause of ecological degradation in the Shiwalik foothills of Northern India. Simulation of runoff and its component processes is a pre-requisite to develop the management strategies to tackle the problem, Successfully. A two-dimensional physically based distributed numerical model. ROMO2D has been developed to simulate runoff from small agricultural watersheds oil an event basis. The model employs the 2-D Richards equation with sink term to simulate infiltration and soil moisture dynamics in the vadoze zone under variable rainfall conditions, and 2-D Saint-Venant equations under the kinematic wave approximation along, with Manning's equation as the stage-discharge equation for runoff routing The various flow-governing equations have been solved numerically by employing a Galerkin finite element method for spatial discretization using quadrilateral elements and finite difference techniques for temporal Solutions. The ROMO2D computer program has been developed as a class-based program, coded in C++ in such a way that with minor modifications, the model can be used to simulate runoff on a continuous basis. The model writes Output For a runoff hydrograph of each storm. Model development is described in this paper and the results of model testing and field application are to be presented ill a subsequent paper. Copyright (C) 2008 John Wiley & Sons, Ltd.