Evolving a Methodology for Assessing Pesticide Pressure on Water Bodies under Data Scarce Conditions: A Case Study on the Marmara Basin in Türkiye

In this study, current pesticide use was determined on the basis of active substances (ASs) in each water body in the Marmara Basin, which is the most crowded region of Türkiye and where agriculture is intensive. The risks of detected pesticide ASs were then categorized in terms of usage amount, water body monitoring results, and hazardous characteristics. At the same time, a system was proposed for determining pesticide use on an AS basis, based on the product planted in districts that do not have detailed information on AS use. Finally, a methodology for assessing pesticide pressure on water bodies was developed by utilizing pesticide risk based on the determined AS types under data scarcity conditions. The topic undertaken is current and extremely important in the era of food safety, and is related to growing pressure on water, on one hand, and human health and quality of food products, on the other. Data based on ASs are hard to record and store, particularly in developing countries; therefore, a data inventory was initially realized in the study as an essential step towards an assessment procedure. The easy-to-use pesticide pressure determination methodology was developed and applied to the Marmara Basin of Türkiye, ensuring compliance with the Water framework Directive (WFD) and EU Green Deal. Constraints experienced during the application of the developed methodology are put forth with the intention of providing utilizable information to those international scientists who will be interested in practicing it in the future. Therefore, transposition of the methodology to other basins in different countries will be possible. According to 2021 data, 0.04–8.83 kg/ha pesticide and 173 pesticide active substances were used in the basin. ASs were prioritized over four criteria based on the amount of use, hazardous properties, and monitoring results. Consequently, 52 active substances were determined and included in the risk group. Taking these criteria into consideration, all the 276 agricultural water bodies in the basin were revealed to be under pesticide pressure.