A deterministic-empirical model of the effect of the capillary fringe on near-stream area runoff .2. Testing and application

The testing and application of HECNAR, a deterministic-empirical model that can account for the hydrologic effect of the capillary fringe on the near-stream area runoff, was carried out in several steps. The model was tested against the response of a laboratory model which resembled a near-stream saturated region of a cross-section, and the results of a field experiment. In each case, the simulated flow components were compared with the separated hydrograph components using a conservative tracer and the predictions of an unsaturated-saturated numerical model. The results were in reasonably good agreement. The model was then applied to a mine tailings site and the predictions were compared with numerical simulations, measured streamflows and the components of the stream hydrograph separated using O-18 as a conservative tracer. The predictions of HECNAR and the numerical. model were in good agreement, as were the trends of the simulated and the measured hydrographs. However, some discrepancies existed between the measured and the simulated flows. This study shows that HECNAR is computer efficient and has a relatively modest input requirement. Incorporation of the model into a larger-scale and more comprehensive watershed model could provide a valuable tool to quantify total flows and runoff source components to the stream, in watersheds in humid environments.