A simple time-stepping strategy for coupled river-aquifer systems

RODRÍGUEZ LB; VIONNET CA

Buenos Aires, Argentina

Congreso; 4th World Congress on Computational Mechanics; 1998

IACM – International Association on Computational Mechanics

In this work some numerical solutions based on a finite element discretization of the depth-averaged Boussinesq equation for ground-water flow and the kinematic wave approximation for open channel flow are presented. This problem belongs to a class of coupled problems in which different physics occur in different domains. An additional difficulty is given by the fact that both components are characterized by vastly different time scales. Using a simple known exact solution it is shown how the fast time scale effects, representative of the river behavior, are concentrated along a narrow region close to it, while the slow time phenomenon produces a solution that is smooth over most of the domain. Then, a time-stepping strategy is developed for the numerical solutions of the coupled problem based on those physical properties of the system rather than on numerical considerations. It is shown that this is indeed the appropriate staggered stepping procedure that better reflects the competing physical mechanisms of the coupled system. The comparison with field data shows the versatility of the approach.