Staff Research Highlight - Development of a fully integrated hydrological fate and transport model for plant protection products: incorporating groundwater, tile drainage, and runoff
Callaghan, M. V., Frey, S. K., Miller, K., Hwang, H.-T., Zolfaghari, R., Hammel, K., Berg, S. J., & Sudicky, E. A. (2024). Development of a fully integrated hydrological fate and transport model for plant protection products: incorporating groundwater, tile drainage, and runoff. Frontiers in Environmental Science, 12. https://doi.org/10.3389/fenvs.2024.1505480
“HGS is a flexible fully integrated GW–SW and chemical fate and transport model that supports many conceptualizations of hydrological settings using physically realistic boundary conditions and contaminant source geometries; as such, it is not solely a PPP transport model but a modeling platform well-suited to PPP fate and transport modeling.”
Fig. 1. Cross section through the HGS tile drain model for the FOCUS surface water D4 scenario, (A) showing model geometry, layering, and (B) boundary conditions (BCs).
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We’re pleased to highlight this research co-authored by Reza Zolfaghari and Klaus Hammel, as well as Aquanty’s Michael V. Callaghan, Steven K. Frey, Steven J. Berg, Killian Miller, Hyoun-Tae Hwang, and Edward A. Sudicky. This research investigates how the integrated hydrological modelling of plant protection products (PPPs) such as pesticides can provide a more comprehensive understanding of their environmental behavior across groundwater, surface water, and tile drainage systems.
Fig 7. Cross section through the FOCUS surface water D4 scenario, as implemented in HGS with a potato crop, showing simulated Test Substance I concentrations within the porous media (micropore) domain in μg L−1 on 21 August 1985 with the water table position (black line). The tile drain position is indicated with a black circle. The depth scale is approximate.
PPPs play a crucial role in modern agriculture, but the implications of their release to the environment, particularly concerning groundwater and surface water quality, remain a significant concern. While many existing models focus on isolated pathways, such as groundwater leaching or surface runoff, this study addresses the need for an integrated approach by using HydroGeoSphere (HGS) to simulate the coupled interactions of PPP fate and transport across these systems.
The study evaluates how PPPs migrate through agricultural landscapes, with a combined focus on leaching to groundwater, transport to tile drainage systems, and runoff generation. Using HGS, a sophisticated modelling platform known for its ability to simulate fully integrated surface water and groundwater interactions, researchers enhanced the model’s capabilities to include processes like nonlinear adsorption, temperature- and moisture-dependent degradation, and root uptake of solutes. This enabled them to capture the interconnected hydrological processes that govern PPP behavior, providing a more accurate representation of how these chemicals move through different pathways under variable conditions.
Through a series of comparisons of HGS model outputs to regulator accepted one-dimensional models, including PEARL, PELMO, and PRZM, and the widely applied HYDRUS model, the research demonstrated HGS's ability to provide accurate results for predicting PPP leaching to groundwater, transport to tile drains and runoff generation.
It is known that one-dimensional models often underestimate the complexity of PPP dynamics, particularly in systems with significant surface-subsurface interactions. This research highlights the importance of adopting integrated three-dimensional modelling approaches like HGS to evaluate PPP behavior comprehensively. It offers valuable insights for policymakers and agricultural stakeholders, emphasizing the need to consider the combined effects of groundwater, surface water, and tile drainage systems in regulatory assessments. By identifying critical pathways and vulnerabilities, the study contributes to developing more effective management strategies to mitigate the environmental risks associated with PPPs.
Abstract:
Plant protection products (PPPs) such as pesticides and herbicides are experiencing increased use worldwide. In the context of PPP authorization and registration, water exposure assessments (drinking water and aquatic exposure) use numerical modeling to simulate relevant hydrological processes and exposure pathways. A common practice for estimating PPP leaching to groundwater, PPP loading onto surface water via tile drainage, or PPP transport via runoff utilizes multiple one-dimensional models, each representing a separate exposure pathway. Separate analysis of individual exposure pathways can result in disparate assumptions being made that represent relative worst-case scenarios for each pathway, rather than an integrated reasonable worst-case scenario for all pathways.