Field management of a drinking water reservoir basin based on the investigation of multiple agricultural nonpoint source pollution indicators in north China

Agricultural nonpoint source (NPS) pollution has become one of the major contributors to water quality degradation. It is of great significance to identify the spatial-temporal distribution and output characteristics of agricultural NPS pollution, and to explore the mitigation methods in typical watersheds, such as drinking water source area. In this study, taking the Miyun Reservoir watershed in China as the study area, the primary drinking water source in Beijing, the distribution patterns and output characteristics of agricultural NPS pollution were investigated and several field management methods were proposed, based on field experiments and a questionnaire survey. The results showed that different land use types had a significant influence on the distribution patterns of agricultural NPS pollutants, especially on the soil N content. Concurrently, soil NPS pollutant contents under different vegetation had significant temporal dynamics. The correlations between the NPS pollutant contents in the runoff and soil varied significantly with land use types. Significant correlations were observed for cropland and economic forest. Furthermore, there were significant differences for the agricultural activities and environmental consciousness of the local residents. Based on the results of the field experiments and the questionnaire survey, land use types, rainfall characteristics and agricultural activities were identified as the major factors affecting outputs of agricultural NPS pollution. Certain best management practices should be taken at the field scale to control the agricultural NPS pollution in the upstream of the Miyun Reservoir watershed.