Applicability of the complementary relationship of evapotranspiration for heterogeneous vegetation cover at boundary and plot scales

Abstract

Study region

Two boundary-scale watersheds (Yangjiagou and Dongzhuanggou) and three typical vegetation plots [a single plantation, a mixed plantation, and a natural grassland] in the Loess Plateau.

Study focus

The performance of different Generalized Complementary Relationships (four versions of GCR) in simulating actual evapotranspiration (ET_a) at boundary (∼1 km²) and plot scales (much less than 1 km²) remains unclear, particularly under heterogeneous vegetation cover. Furthermore, the feasibility of using GCR directly to obtain accurate net ET_a (ET_an, the sum of soil evaporation and plant transpiration) through parameter calibration is investigated. The influence of timescale and vegetation diversity is also discussed.

New hydrological insights for the region

Dynamic Scaling of the GCR could achieve high accuracy at boundary-scale watersheds (NSE=0.78) and different vegetation plots (NSE=0.79), indicating the universality and stability of the GCR, in line with the conclusions of previous large-scale studies. Reducing the timescale will decrease the GCR's simulation performance for both ET_a and ET_an. Interestingly, as vegetation heterogeneity increased, GCR's performance improved when simulating ET_a but decreased when simulating ET_an. Furthermore, using GCR to obtain ET_an directly may generate bias near extreme points at a weekly timescale but becomes feasible at longer timescales. This study expanded recognition of GCR's performance under varying spatiotemporal scales and provided evidence for the possibility of simulating evapotranspiration components by the method.