Cd. Brown et Jm. Hollis, SWAT - A SEMIEMPIRICAL MODEL TO PREDICT CONCENTRATIONS OF PESTICIDES ENTERING SURFACE WATERS FROM AGRICULTURAL LAND, Pesticide science, 47(1), 1996, pp. 41-50
A semi-empirical model called SWAT has been developed to predict conce
ntrations of agriculturally applied pesticides moving to surface water
s, an aspect which is not well described by current models for pestici
de fate. The model is based upon a direct hydrological link establishe
d between soil type and the amount of water moving rapidly to streams
in response to rainfall. Attenuation factors describe the decrease in
concentrations of pesticide between field application and loss in wate
r moving from the site into surface waters. Evaluation of model predic
tions against available field data from three sites and four soil type
s in England shows that SWAT is capable of predicting the transient pe
ak concentrations of a wide range of pesticides during rapid water mov
ement to streams in response to rainfall. Predicted concentrations wer
e too great when rainfall initiated water movement to streams very soo
n after pesticide application, particularly for the more mobile pestic
ides, and some predictions for pesticides sorbed very strongly to soil
were relatively poor. Almost all of the predicted concentrations were
within one order of magnitude of measured values.