2.2.3 Water balance at the field scale
In the case of a small intensively instrumented experimental study area,
such as the studied field, it may be possible to solve the complete
water balance for hydrological research purpose (Ward and Robinson,
2000). The aim of the water balance in this study is to improve the
knowledge of hydrological processes at the field scale.
A water balance was calculated using daily time step as follows:
\(S=P-RET-D-I\) (Equation 2)
where ΔS is the variation of soil water storage in the horizon LA and
S1, P is the rainfall, RET is the real evapotranspiration, D is the
drainage factor, i.e. sum of surface and subsurface runoff and I is the
infiltration from S1 to S2. All the terms are in millimeters. The RET
was estimated from the PET and from the crop growth coefficient. The
crop growth coefficient was estimated using degree-day and growth stages
relation.