Abstract:
Hillslopes are the dominant landscape components
where incoming precipitation becomes groundwater, streamflow
or atmospheric water vapor. However, directly observing
flux partitioning in the soil is almost impossible. Hydrological
hillslope models are therefore being used to investigate
the processes involved. Here we report on a modeling
experiment using the Catchment Modeling Framework
(CMF) where measured stable water isotopes in vertical
soil profiles along a tropical mountainous grassland hillslope
transect are traced through the model to resolve potential
mixing processes. CMF simulates advective transport of
stable water isotopes 18O and 2H based on the Richards equation
within a fully distributed 2-D representation of the hillslope.
The model successfully replicates the observed temporal
pattern of soil water isotope profiles (R2 0.84 and Nash–
Sutcliffe efficiency (NSE) 0.42). Predicted flows are in good
agreement with previous studies. We highlight the importance
of groundwater recharge and shallow lateral subsurface
flow, accounting for 50 and 16% of the total flow leaving the
system, respectively. Surface runoff is negligible despite the
steep slopes in the Ecuadorian study region.
