Identifying pesticides critical source areas in a Mediterranean river basin using the SWAT model

The use of pesticides in agriculture has been constantly debated. On the one hand, chemicals such as pesticides can contribute to increasing food production with the same cultivated surface areas; on the other hand, their excessive use represents a threat for soil and water quality. Sampling campaigns are an important aspect to be considered while carrying out studies on pollutants such as pesticides. However, field activities are expensive and time consuming and may represent limited spatial areas. Hence, in this context, eco-hydrological models are increasingly being used to assess pesticide concentration, fate and transport processes. This work aims to assess the suitability of the Soil and Water Assessment Tool (SWAT) in simulating pesticide loss in the Canale d’Aiedda river basin (S-E Italy). A sampling campaign was carried out twice a month for the year 2021 in a river section. Copper was detected in the totality of samples. SWAT was calibrated for hydrology (2017-2019) at daily scale and for Copper using discrete data. Results showed a good performance for both hydrology and Copper calibration (R2 0.72, NSE 0.71, PBIAS +5.1 and R2 0.70, NSE 0.67, PBIAS +13.5, respectively). The maximum concentration value of Copper was detected in June (6.2 µg/l, observed; 5.3 µg/l, simulated). Further studies and new monitoring programs are needed to implement mitigation measures and adequately analyse their cost effectiveness.