Modelling pesticide fate with GLEAMS

Abstract

The pesticide component of GLEAMS (Groundwater Loading Effects of Agricultural Management Systems) model was developed to evaluate the complex interrelationships among pesticide and soil properties, management alternatives, and climate using long-term simulations. GLEAMS resulted from an enhancement of the CREAMS model to allow simulation of pesticide transport within and through the plant root zone in addition to transport in surface runoff from field-sized areas. The pesticide submodel is operated with daily inputs from the hydrology and soil erosion sub-models. Pesticide input parameters are required to specify application rates, dates and methods and the properties of the chemical. Outputs are pesticide concentrations and mass in runoff water and attached to transported sediments, pesticide mass leached below the root zone, and pesticide distribution with depth in the root zone. Multiple applications of up to 10 different pesticides can be simulated simultaneously for periods of up to 50 years. The model also considers pesticide metabolites produced by sequential first-order reactions and plant uptake of pesticides. Application methods simulated may be soil surface application, soil incorporation, soil injection, foliar application, or through irrigation water. Values for pesticide soil half-life, foliar half-life, foliar wash-off potential, solubility, and Koc (sorption coefficient for soil carbon) may be obtained from the internal data base or supplied by the user if more specific information is available.