Efficient and realistic modelling of individual runoff events in ecohydrological systems

The different temporal scales of surface flow and vegetation growth represent a major challenge when simulating the dynamics of ecohydrological systems. The much faster surface flow is therefore commonly simplified by treating it as stationary and linearizing the equations. While the simplified equations can be solved efficiently, they do not resolve individual runoff events. However, the sequence of events can be relevant for the dynamics of dryland vegetation. The nonlinear flow during individual precipitation events can be resolved by employing more sophisticated numerical methods, such as adaptive-time stepping and implicit time-integration. However, this requires the iterative solution of a sequence of discrete linear systems at each time step. This is complicated by asymmetry of the discrete system, originating from the advection of the flow. Here, we explore strategies for the efficient simulation of the nonlinear flow during individual precipitation events when modelling vegetation dynamics over centuries.