A DETERMINISTIC-EMPIRICAL MODEL OF THE EFFECT OF THE CAPILLARY-FRINGEON 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 mo del was tested against the response of a laboratory model which resemb led a near-stream saturated region of a cross-section, and the results of a field experiment. In each case, the simulated flow components we re compared with the separated hydrograph components using a conservat ive tracer and the predictions of an unsaturated-saturated numerical m odel. The results were in reasonably good agreement. The model was the n applied to a mine tailings site and the predictions were compared wi th numerical simulations, measured streamflows and the components of t he stream hydrograph separated using O-18 as a conservative tracer. Th e predictions of HECNAR and the numerical. model were in good agreemen t, as were the trends of the simulated and the measured hydrographs. H owever, some discrepancies existed between the measured and the simula ted 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.