A Hydrological Modeling Framework for Defining Achievable Performance Standards for Pesticides

Abstract

This paper proposes a hydrological modeling framework to define achievable performance standards (APSs) for pesticides that could be attained after implementation of recommended management actions, agricultural practices, and available technologies (i.e., beneficial management practices [BMPs]). An integrated hydrological modeling system, Gestion Intégrée des Bassins versants à l'aide d'un Système Informatisé, was used to quantify APSs for six Canadian watersheds for eight pesticides: atrazine, carbofuran, dicamba, glyphosate, MCPB, MCPA, metolachlor, and 2,4-D. Outputs from simulation runs to predict pesticide concentration under current conditions and in response to implementation of two types of beneficial management practices (reduced pesticide application rate and 1- to 10-m-wide edge-of-field and/or riparian buffer strips, implemented singly or in combination) showed that APS values for scenarios with BMPs were less than those for current conditions. Moreover, APS values at the outlet of watersheds were usually less than ecological thresholds of good condition, when available. Upstream river reaches were at greater risk of having concentrations above a given ecological thresholds because of limited stream flows and overland loads of pesticides. Our integrated approach of "hydrological modeling-APS estimation-ecotoxicological significance" provides the most effective interpretation possible, for management and education purposes, of the potential biological impact of predicted pesticide concentrations in rivers.

Integrated assessment of climate change impact on surface runoff contamination by pesticides

“…This application occurs in summer, when intense and highly, spatially variable, convective events are frequent. Table 5 shows the mean transported pesticide loads in surface runoff Overall, mean annual pesticide loads transported correspond to less than 1% of the total mass of AI applied, which is comparable to other surface runoff loads reported in the literature (Wauchope 1978;Bloomfield et al 2006;Rousseau et al 2012). The loads transported in proportion of mass applied per treatment can be larger when considering shorter timeframes (e.g., daily).…”

Ammonia Stripping of Biologically Treated Liquid Manure

“…Achievable Performance Standards are intended to identify water chemistry improvements that could be realized through the implementation of various scenarios of alternative land management practices, including BMPs. Rousseau et al (2012) present a novel approach for defi ning APS for pesticides that could be attained following implementation of recommended BMPs. Pesticides, including herbicides, insecticides, and fungicides, are widely used in agriculture.…”

“…In many locales, however, current in-stream pesticide concentrations are greater than IPS. Rousseau et al (2012) applied an integrated hydrological modeling system (Gestion Intégrée des Bassins versants à l'aide d'un Système Informatisé, GIBSI) to defi ne pesticide concentrations for six Canadian watersheds modeled under diff erent scenarios: the reference (or current) situation and at least one of three BMP scenarios (addition of riparian buff er strip; reduction in pesticide application; riparian buff er strip + reduced pesticide application). For each watershed and each scenario, a cumulative distribution function curve was developed for a given pesticide based on results from about 30 model simulations using diff erent weather data and random dates of pesticide application.…”

“…Th e modeling approaches applied by both Rousseau et al (2012) and Yang et al (2012) lend themselves to use by farmers or decision makers to assist with BMP selection. In the case of the approach developed by Rousseau et al (2012), watershed maps are generated that show APS values for a specifi c pesticide and the likelihood of exceeding its IPS for a given river segment and scenario (current or choice of BMPs).…”

“…In the case of the approach developed by Rousseau et al (2012), watershed maps are generated that show APS values for a specifi c pesticide and the likelihood of exceeding its IPS for a given river segment and scenario (current or choice of BMPs). Yang et al (2012) produced charts that show the mean, maximum, and minimum load reductions predicted to occur in response to BMP application.…”