Modelling pesticide leaching under climate change: parameter vs. climate input uncertainty

Abstract

The assessment of climate change impacts on the risk for pesticide leaching needs careful consideration of different sources of uncertainty. We investigated the uncertainty related to climate scenario input and its importance relative to parameter uncertainty of the pesticide leaching model. The pesticide fate model MACRO was calibrated against a comprehensive one-year field data set for a well-structured clay soil in south-west Sweden. We obtained an ensemble of 56 acceptable parameter sets that represented the parameter uncertainty. Nine different climate model projections of the regional climate model RCA3 were available as driven by different combinations of global climate models (GCM), greenhouse gas emission scenarios and initial states of the GCM. The future time series of weather data used to drive the MACRO-model were generated by scaling a reference climate data set (1970–1999) for an important agricultural production area in south-west Sweden based on monthly change factors for 2070–2099. 30 yr simulations were performed for different combinations of pesticide properties and application seasons. Our analysis showed that both the magnitude and the direction of predicted change in pesticide leaching from present to future depended strongly on the particular climate scenario. The effect of parameter uncertainty was of major importance for simulating absolute pesticide losses, whereas the climate uncertainty was relatively more important for predictions of changes of pesticide losses from present to future. The climate uncertainty should be accounted for by applying an ensemble of different climate scenarios. The aggregated ensemble prediction based on both acceptable parameterizations and different climate scenarios could provide robust probabilistic estimates of future pesticide losses and assessments of changes in pesticide leaching risks

SWAT hydrologic model parameter uncertainty and its implications for hydroclimatic projections in snowmelt-dependent watersheds

“…In fact, quantification of this model uncertainty has been investigated extensively in recent years for several different hydrologic models (Chen et al, 2011b;Poulin et al, 2011;Steffens et al, 2014). These studies suggest that multiple hydrologic models with multiple calibration sets should be considered when making management decisions.…”

Direct and indirect effects of climate change on herbicide leaching — A regional scale assessment in Sweden

“…Fowler et al, 2007). We followed the approach and reasoning described in Steffens et al (2014). The change factors were derived by comparing the projected present and future climate periods for each member of the ensemble of climate scenarios.…”

“…Most of these studies only considered the potential direct impacts of climate change. Bloomfield et al (2006), Beulke et al (2007), as well as Steffens et al (2013Steffens et al ( , 2014 hypothesized that the indirect effects of climate change might be more significant for future pesticide losses than direct effects, but to our knowledge only a few studies have explicitly attempted to quantify such effects. Kattwinkel et al (2011) assessed the effects of climate change on the exposure of surface water to agricultural insecticides and concluded that the combined effect is likely to be stronger than the direct or indirect effects of climate change (i.e.…”

“…Beulke et al (2007) performed a modelling study assessing the effects of climate change on the transport to groundwater and surface water of several different representative pesticides. Steffens et al (2013Steffens et al ( , 2014 demonstrated the effect of model structural, parameter and climate uncertainty on predictions of pesticide losses to tile drains from a heavy clay soil under present and future climate conditions. Ahmadi et al (2014) modelled changes in atrazine losses to surface water via surface run-off at the watershed scale for a large ensemble of climate model projections.…”

Bioavailability in Biodegradation and Function of Herbicides

“…Soil retentive processes and biodegradation kinetics are key parameters in predicting offsite transport of herbicides [1,2]. Sorptive and physical entrapment processes interact with highly compartmentalized tortuous pore space to impose limitations on the availability of herbicides to the plants they are designed to kill, as well as the microorganisms required for biodegradation [3,4].…”