Integrating a water tracer model into WRF-Hydro for characterizing the effect of lateral flow in hydrologic simulations

Such lateral flow is fundamental at catchment scales and becomes crucial for finer-scale land models. To test the effect of incorporating lateral flow toward three-dimensional representations of hydrological processes in the next generation land models, we integrate a water tracer model into the WRF-Hydro framework to track water movement from precipitation to discharge and evapotranspiration.

This hydrologic-tracer integrated system allows us to identify the key mechanisms by which lateral flow affects the flow paths and transit times in WRF-Hydro. By comparing modeling experiments with and without lateral routing in two contrasting catchments, we determine the impacts of lateral flow on the transit times of precipitation event-water. Results show that with limited hydrologic connectivity, lateral flow extends the transit times by reducing (increasing) event-water drainage loss (accumulation) in ridges (valleys) and allowing reinfiltration of infiltration-excess flow, which is missing in most land models.