Dominant controls on pesticide transport from tile to catchment scale: Lessons from a minimalist model

Abstract

[1] This paper proposes a minimalist modeling approach for characterizing pesticide concentrations in runoff from agricultural catchments across spatial scales. The model proposed is of an intermediate level of complexity between traditional chromatographic separation models and the more complex dual-domain models. Parsimony in the model is achieved by assuming stationarity of catchment travel time distributions and by coupling a dual-domain source zone model that describes near-surface pesticide dynamics with the mass response function (MRF) approach, which describes catchment-scale solute transport. The model is evaluated by comparing predicted atrazine concentrations with measured values over a 5 yr period at two spatial scales (tile drain: 3-5 ha; river station: 69 km 2 ) within an intensively managed agricultural catchment in Illinois, United States. Pesticide dynamics within the source zone provided the strongest control on leaching. Two parameters were calibrated at the tile scale, G, which describes partitioning in the dualdomain surficial source zone, and k e , which describes the mass transfer rate constant between the two domains. The initial peak of concentration was found to be sensitive to G, while the later peaks were sensitive to k e . The calibrated parameters at the tile stations were used to predict atrazine dynamics at the river station. Prediction errors are examined and related to the lack of detailed information about anthropogenic forcings across scales (e.g., land-use or soil/crop management practices).

Comparison of performance of tile drainage routines in SWAT 2009 and 2012 in an extensively tile-drained watershed in the Midwest

“…Eighty-five percent of the watershed area is in eastern Vermilion County, 13 % of the watershed is in Champaign County, and 2 % of the watershed is in Edgar County. The LVR watershed consists of flat topography, with elevations ranging from 235 m in the headwaters to 174 m at the watershed outlet and with an average slope reaching at most 1 % (Zanardo et al, 2012). The long-term (1991)(1992)(1993)(1994)(1995)(1996)(1997)(1998)(1999)(2000) average annual precipitation for the watershed is 990 mm yr −1 (Kalita et al, 2006).…”

“…Ninety percent of the LVR watershed is agricultural land used for corn and soybean production, and the remainder consists of grassland, forest land, roadways, and farmsteads (Kalita et al, 2006). Annual area planted with soy- (Zanardo et al, 2012;Keefer, 2003), and the dominant hydrologic soil groups are B and C. The LVR watershed is a typical tile-drained watershed in Illinois. Water quantity and quality data for this watershed are available from a long-term (1991)(1992)(1993)(1994)(1995)(1996)(1997)(1998)(1999)(2000)(2001)(2002)(2003) monitoring project through which data were collected from several subsurface stations, surface stations, river stations and wetland sites in the watershed (Mitchell et al, 2003;Kalita et al, 2006).…”

“…Daily tile flow, surface runoff, nitrate load in tile flow, surface runoff, streamflow, and sediment load in surface runoff and streamflow were aggregated into monthly data and adopted in this study for model calibration and validation (Table 1). Other stations were not considered due to the quality of their data (Zanardo et al, 2012). Corn and soy-bean planting, harvest, and tillage practice data were collected from landowners (Table 1).…”

“…For instance, the Little Vermilion River (LVR) watershed, an extensively tile-drained watershed in Illinois, has altered hydrology from an extensive subsurface drainage system network (Zanardo et al, 2012). Lal et al (1989) studied tillage-caused alterations in water balance and sediment transport for a corn-soybean rotation in Ohio, and the results demonstrated that the percentages of annual precipitation drained by tiles in plowed conditions and on no-till plots are 33 to 58 % and 28 to 59 %, respectively.…”

Spatial and Temporal Variability in Pesticide Exposure Downstream of a Heavily Irrigated Cropping Area: Application of Different Monitoring Techniques

“…This irrigation 421 paddock runoff (and associated pesticide losses) is transported through a network of drains 422 which ultimately discharge into Barratta Creek introducing flow into a normally ephemeral 423 system and explains why pesticide concentrations in Barratta Creek increase prior to the 424 onset of wet season rains [17][18][19] . Several studies have shown that the dominant mechanism 425 driving the amount of pesticide lost from croplands relates to surface runoff following 426 rainfall as well as the timing of pesticide application [52][53] . In contrast, the design of the water 427 supply and discharge network of the Burdekin Water Supply Scheme means that irrigation 428 runoff within the Barratta Creek catchment drives the prolonged and elevated pesticide 429 ecological threshold values 40 for freshwater (Table 4) and/or estuarine systems (Table 5).…”