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Drift Modeling

Spray drift of agrochemicals into aquatic systems is one form of transport that has spatial variability. The physical processes governing spray drift include distance, wind speed, droplet size, and intervening vegetation among others. Properties of the receiving water body can also be used to estimate concentrations based on regulatory assumptions.

Waterborne uses a variety of methods to model spray drift of agrochemicals applied to crops including AgDrift, GIS incorporated in drift models, or the sophisticated spatial Drift Modeling Tool that we developed.

AgDRIFT

Several regulatory tools exist to estimate drift deposition and final water body concentration, including AgDRIFT (developed by the Spray Drift Task Force) and the drift calculator developed by FOCUS (FOrum for Co-ordination of pesticide fate models and their USe). These models were developed from the results of extensive field trials and will generate a deposition rate and concentration based on inputs such as crop type, distance, and application method (boom, aerial, etc.) for regulatory purposes.

Incorporating Spatial Components

Factors such as wind speed and distance from crop to water vary across a landscape, as well as temporally. To be protective, regulatory agencies use an assumed conservative wind speed that will not be exceeded in the majority of situations. Measurements of distance from crop to water can be generated very effectively using GIS and geospatial data. These measurements, coupled with drift regression equations from regulatory models, generate drift rates and ultimately concentrations for thousands of water bodies in an agricultural landscape. Wind direction is also incorporated such that concentration distributions are generated for only a single wind direction at one time (rather than assuming the wind blows from all directions onto the water body at once).