Δ18OLW is nearly always less enriched than Δ18Oe, meaning that leaf water is not a well-mixed pool undergoing evaporative enrichment, so two models were developed to explain Δ18OLW based on its isotopic sources: the two-pool model (Eqn. 1) and the Péclet effect model (Roden & Ehleringer 1999; Barbour & Farquhar 2000; Helliker & Ehleringer 2000; Gan et al. 2003; Barbour 2007). The Péclet effect model, instead of the fraction of water contributed by the sites of evaporation (α in Eqn. 3) being fixed, it was modified to be dependent on the Péclet number (P; Eqn. 7). The Péclet number