Catchment rainfall-runoff and stable isotope tracer response were modeled using a lumped conceptual model that integrates the unit hydrograph and isotope hydrograph separation methodologies. The model was applied across eight nested catchments (7 to 147 ha) for four rainstorms collected between summer and fall in 2001–2002, generating 23 usable rainstorm datasets. Monte Carlo simulations were run for four model structures of varying complexity and evaluated using a Generalized Likelihood Uncertainty Estimation approach. We found that a model of intermediate complexity was adequate to model all catchment-storm pairs. Relationships between the parameters of the best model and catchment and storm characteristics were sought. We found that the fraction of effective rainfall routed as event water was correlated to rainstorm size but insensitive to catchment size, indicating that it is controlled by environmental conditions such as storm intensity and size. The mean transit time of event water decreased with increasing rainstorm size, indicating increased connectivity during larger rainstorms. Finally a correlation was found between the mean transit time of event water and catchment size suggesting that the time it takes for event water to be transferred to the stream is directly related to catchment size, particularly for catchments greater than 30 ha (see figure below).  

Publications

34. *Crampe E., Segura, C., Jones, JA. 2021. Fifty years of runoff response to conversion of old-growth forest to planted forest in the H.J. Andrews Forest, Oregon, USA. Hydrological Processes,https://doi.org/10.1002/hyp.14168.

28. Segura, C., Bladon, K., Hatten, J., Jones, J., and Hale, C.. 2020. Long-term effects of forest harvesting on summer low flow deficits in the Coast Range of Oregon. Journal of Hydrology 585 (2020) 124749.

22. Mosquera G., Segura C, Crespo P. 2018.Flow Partitioning Modelling Using High-Resolution Water Stable Isotopes and Electrical Conductivity. Water 2018, 10 (7), 904; https://doi.org/10.3390/w10070904.

5.  Segura C, James A, Lazzati D, Roulet NT.  2012.  Scaling relationships for event water contributions and transit times in small-forested catchments in Eastern Quebec. Water Resources Research 48, W07502, doi:10.1029/2012WR011890.