Jv. Soares et Ac. Almeida, Modeling the water balance and soil water fluxes in a fast growing Eucalyptus plantation in Brazil, J HYDROL, 253(1-4), 2001, pp. 130-147
A five-layered water balance model, with water movement between layers alon
g hydraulic gradients, was developed and parameterized for a eucalypt plant
ation (Eucalyptus grandis Hill ex. Maiden hybrids) in Brazil. Available soi
l water controls stomatal conductance and hence transpiration, which is cal
culated by the Penman-Monteith equation. The model accounts for changes in
the depths of the water table. Calculations are supported by measurements:
the test period was from October 1995 to September 1996 in a 9-year-old pla
ntation in an experimental catchment in eastern Brazil. Total transpiration
for the year was 1116 mm, with 151 mm intercepted and re-evaporated and an
other 78 mm soil surface evaporation, giving evapotranspiration of 1345 mm
compared to rainfall of 1396 mm. The water balance was closed by net flow b
elow the root zone of about 25 mm and an increase in water storage (in the
first layer) of 24 mm. The model also estimated a transpiration deficit (di
fference between the potential and current transpiration) of 125 mm for the
period. Upward flux from the water table was around 82 mm and piezometric
measurements showed 2.5 m recession of the water table for the same period.
The upward flux into the root zone was about I mm day(-1) at the end of a
long dry season; that kept the water storage in that zone to about 15% of c
apacity and helped prevent complete stomatal closure.
Comparison between estimated water storage and measurements confirmed that
this model is a very promising tool for calculating water use by plantation
s. It can also provide water balance information and information about stom
atal conductance for growth prediction models. (C) 2001 Elsevier Science B.
V. All rights reserved.