Using Gleams to Select Environmental Windows for Herbicide Application in Forests’

Observed herbicide runoff and groundwater data from a pine-release herbicide application study near Gainesville, Florida were used to validate the GLEAMS model hydrology and pesticide component for forest application. The study revealed that model simulations agreed relatively well with the field data for the one-year study. Following validation, a modified version of GLEAMS was applied using a 50.year climatic record to determine the periods (windows) for least water quality degradation within the Forest Service’s recommended application window for best vegetation control. The pesticide component of GLEAMS was modified to simulate up to 245 pesticides simultaneously. Four herbicides commonly used in the region Lo conrroi competing vegetation were represented in the model study. Within the application windows for each herbicide, the best application dates, or “environmental” windows were determined to minimize environmental effecfects for each location. Results of the simulation study are tabulated in the paper for use in the forest industry.