Plant growth is a very important contributor to hydrologic budgeting through the evapotranspiration effects. Manual
descriptions are input for the plant growth based on local knowledge of average growth descriptions for major crops
(Wild, 1988). Methods used by other models such as "crop coefficient curves" or plant growth estimation routines
based on plant and environment parameters are generally less accurate or more difficult to define. This approach
has proven easy to apply, and sufficiently accurate to achieve expected hydrologic accuracies.
The annual crop growth is described by three annual distributions of plant canopy, greenness, and rooting depth. A
fourth curve, yield susceptibility, defines the relative impact of accumulative crop water stress on grain yields when
correlated with observed grain yields. For simulations involving nitrogen budgets, the annual nitrogen uptake
distribution is included in the crop definitions. Crops growing over the end of the calendar year require two years of
definitions. Multiple year crop rotations are developed by selecting a cropping sequence in the “management”
screen.