The USEPA Office of Pesticide Programs (OPP) estimates pesticide concentrations in drinking water and aquatic environments using fate and transport models combined with water monitoring analysis. OPP is developing the Spatial Aquatic Model (SAM) as a higher-tier refinement to estimate spatial and temporal patterns of pesticide concentrations as a function of chemical properties, environmental factors, and crop use for actual water bodies within use regions. An initial alpha version of SAM focused on pesticide runoff in a dominantly corn-soybean-small grains agricultural setting at the HUC-12 scale. Recent updates in the beta version calculate daily pesticide concentrations in water based on daily runoff, sediment transport, and pesticide mass loads aggregated across the entire watershed area. SAM uses a time-of-travel approach to account for differences in the time it takes pesticide loads from the upper end of a larger watershed to reach the outlet, compared to pesticide loads from fields near the outlet. Here we will introduce a cloud-based beta version of SAM, discuss the model improvements and limitations, and present comparisons of SAM streamflow outputs with empirical streamflow monitoring data for a variety of watersheds.

Spatial aquatic model (SAM) for spatially-explicit pesticide exposure: Overview and hydrology evaluation

ACS Fall 2021

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