Best management practices (BMPs) are the most effective and practicable means to control nonpoint source (NPS) pollution at desired levels. Models are valuable tools to assess their effectiveness. Watershed managers need to choose appropriate and effective modelling methods for a given set of conditions. This paper considered state-of-the-art modelling strategies for the assessment of agricultural BMPs. Typical watershed models and specific models were analyzed in detail. Further improvements, including simplified tools, model integration, and incorporation of climate change and uncertainty analysis were also explored. This paper indicated that modelling methods are strictly scale dependent, both spatially and temporally. Despite current achievements, there is still room for future research, such as broadening the range of the pollutants considered, introducing more local BMPs, improving the representation of the functionality of BMPs, and gathering monitoring date for validation of modelled results. There is also a trend towards agricultural decision support systems (DSSs) for assessing agricultural BMPs, in which models of different scales are seamlessly integrated to bridge the scale and data gaps. This review will assist readers in model selection and development, especially those readers concerned about NPS pollution and water quality control.

Pesticides applied worldwide to meet food demand is recognized as a key threat to the Sustainable Development Goals (SDGs) set by the United Nations. Studies on pesticide risks employ different ingredients, methods or specific environments, which makes it difficult to quantify the scale of the problem. Furthermore, the complex influences and hotspots of long-term pesticide usage remain unclear. Herein, we present a national-scale study of four typical pesticides in China, the world’s largest pesticide user. The spatiotemporal changes in legacy and risk of pesticides over 30 years were analyzed using a modified fugacity model approach coupled with comprehensive ingredient database. Pesticide risk in mainland China might last until 2075 due to the previous legacy, although the usage has declined since 2014. The use of target pesticides was estimated as 2.38 × 10⁵ tonnes in 2017, and about 6.59 × 10³ tonnes discharged into the ocean from major basins. Risk areas expanded from 47% in 1991 to 79% in 2017, with 30% at high risk. Of the risk areas, 31% were highly populated while 3% had high biodiversity. 7% of mainland China suffered from both limited water resource and high pesticide risk. It is shown that the improper substitution with lower toxicity pesticides would make the proportion of high-risk regions unexpectedly increased from 18% to 44% due to the longer half-lives of the alternatives. Pesticides pose risks to environmental and human health, and the tailored assessment tool will be vital in contributing towards future pesticide management and meeting sustainability targets in China.