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Modeling Pollutant Routing in Runoff in Agricultural Watersheds: A Mixed Approach

Author(s): Maria Jose Polo; Raquel Gomez-Beas; Eva Contreras; Cristina Aguilar; Javier Herrero; Agustin Millares; Miguel A. Losada; Raquel Gomez-Beas

Linked Author(s): Agustín Millares, María José Polo Gómez, Miguel A. Losada

Keywords: Pollutant routing; Herbicide in runoff; GIS model; Watershed modeling; Surface water quality

Abstract: Pollutant routing modeling in agricultural watersheds requires both an accurate hydrological modeling and a water quality monitoring network that captures all the significant sources of variability. However, the latter is often lacking in many areas and the use of complex models usually involves too many parameters, which increases the model uncertainty and makes it impractical to apply. This work proposes a simple parametric approach to model pollutant transfer from soil to runoff and its routing throughout the watershed, based on a GIS physically based hydrological model, and applies it to herbicide routing in two agricultural watersheds in southern Spain. The results show the good performance of this mixed approach to simulate the herbicide daily loads at a control point located upstream a reservoir in the first watershed, where specific sampling work was done to monitor herbicide concentration, with a global error around 11% on a daily basis and 6% for the whole study period (a hydrological year). The applicability of the model under the usually available datasets was confirmed from the results in the second watershed, with higher surface and where no specific sampling was performed and just monthly public dataset were used. The distributed character of the model allows the mapping of the contribution to the pollutant loads within the watershed, and made it possible to identify the most active areas in herbicide transfer to runoff, where mitigation actions should be concentrated. The model constitutes a useful basis to develop further tools for assessing soil and crop management practices in relation to water quality issues.


Year: 2013

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