Calculation of seasonal agricultural grey water footprint in monsoon region based on river reference conditions

Grey water footprint accounting is of great significance to water resources management. The two important parameters of grey water footprint accounting, the natural background concentration of pollutants and the pollutant export coefficient, have obvious seasonal differences in the monsoon region, while the possible sea-sonal differences of grey water footprint in the monsoon region had been less considered in the previous research of grey water footprint accounting. This paper calculated the seasonal agricultural grey water footprint of Zhangjiakou City in North China by taking the river reference condition of total phosphorus as its natural background concentration and considering the seasonal difference of river reference condition of total phos-phorus and the pollutant export coefficient. The results showed that the agricultural grey water footprint calculated with the reference condition of total phosphorus as the natural background concentration were 1.60 and 1.38 times of that calculated with zero as the natural background concentration in the rainy season and dry season, respectively. Due to the seasonal difference in the proportion of pollutants entering the river and the reference condition of total phosphorus, the agricultural grey water footprint showed obvious seasonal differ-ences. The agricultural grey water footprint in rainy season was 11.73 times higher than that in dry season. In the composition of agricultural grey water footprint in Zhangjiakou from 2003 to 2018, the grey water footprint of livestock and poultry accounted for a large proportion. Districts and counties with relatively large agricultural grey water footprint in Zhangjiakou were concentrated in the south and north of Zhangjiakou, mainly including Zhuolu, Huailai, Yuxian, Xuanhua and Zhangbei; The districts and counties with relatively small agricultural grey water footprint were mainly located in the urban area of Zhangjiakou, including Qiaodong District, Qiaoxi District and Xiahuayuan District. This paper could clarify the seasonal difference of agricultural grey water footprint accounting in monsoon region and promote the development of grey water footprint accounting methods.