- 1Institute of Environmental Assessment and Water Research (IDAEA)-CSIC, Barcelona, Spain (pilar.llorens@idaea.csic.es)
- 2Catalan Water Agency, Barcelona, Spain
- 3University of Nevada, Las Vegas, USA
Ecohydrological studies frequently use the stable isotopic composition of precipitation as a natural tracer. In wooded areas, understanding how the precipitation isotopic composition is modified as it passes through the canopy is therefore key to accurate ecohydrological assessments. This work presents a model to estimate the isotopic composition of throughfall at a detailed time-step, based on the dynamics of rainfall isotopic composition and meteorological conditions during rainfall events. The model couples the Rutter (1971) rainfall interception model with the Gonfiantini (1986) equation, the latter is used to estimate the stable isotopic composition of open water bodies subject to evaporation.
The model was tested and validated using intra-event volumes (5 min intervals) and isotopic compositions (131 samples, sampled each 5-mm of rainfall) from 25 rainfall/throughfall events in a Scots pine forest at the Vallcebre Research Catchments (South-Eastern Pyrenees, Spain).
The results demonstrate the model's ability to predict both throughfall volumes and the isotopic compositions across a range of precipitation events with marked differences in precipitation volumes (9 to 72 mm), mean intensities (0.6 to 29 mmh-1), meteorological conditions, and different intra-event dynamics of the rainfall isotopic composition. An excellent correlation was found between observed and predicted throughfall volumes, with 84% of the events having a Kling-Gupta efficiency greater than 0.65. In addition, the model accurately predicted the observed throughfall isotopic signature (for δ18O, r2=0.98, p<0.05). At the intra-event scale, observed and predicted throughfall isotopic signatures were not statistically different. However, the isotopic shift between throughfall and rainfall was somewhat higher for the observed throughfall compared to model results, with 84% and 76% of the throughfall observed and predicted samples, respectively, more enriched than rainfall.
How to cite: Llorens, P., Cayuela, C., Pinos, J., Latron, J., and Gallart, F.: Modelling the changes in the isotopic composition of water routing through the forest canopy, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8408, https://doi.org/10.5194/egusphere-egu25-8408, 2025.
