River networks and groundwater flow: a simultaneous solution of a coupled system

Coupled hydrologic modeling of surface and subsurface systems are necessary to obtain a better understanding of hydrologic pathways in a watershed. In early studies, the coupling is achieved by linking the two systems through an iterative process in which convergence of parameters linking the two domains are defined as the criteria for an acceptable solution. In this study, we propose a new approach based on the simultaneous solution of coupled channel and groundwater flow systems. The proposed method is based on the idea of solving a single global matrix at once rather than solving separate matrices for each flow domain while improving the solution iteratively. The proposed solution technique is implemented by coupling a one-dimensional channel network flow model that uses the complete form of the St Venant equation with a two-dimensional vertically averaged groundwater flow model. The proposed approach provides a more efficient solution strategy for the coupled flow problem and demonstrates an effective process of integrating the two hydrologic systems.