A computer simulation of the effects of differing crop types on the water balance of small catchments over long time periods

A multilayer crop model is used to simulate the interception and evaporation of rainfall as well as transpiration loss for a pine canopy. A considerable improvement, in terms of physical realism, over the Rutter (Rutter et al. 1971) model appears to have been achieved and the results generally agree with experimental work. Simulation runs on synthetic meteorological data indicate that the Rutter model substantially underestimates the interception loss from low intensity rainstorms. the multilayer pine model, MANTA, is run with a year's data and the results compared with those from an equivalent unilayer pine and also a grass model. the results show that MANTA predicts a 20% increase in interception loss over the Rutter model estimate and that over the year the interception loss from grass is one quarter of that from pine.