Agricultural groundwater footprint of the major cropping system in the North China Plain: A case study of Wuqiao County, Hebei Province

As a newly developed concept and research method for water footprint studies in recent years, groundwater footprint (GF) could be used to evaluate potential use of renewable groundwater to increase agricultural production or in combination with water footprint and virtual water calculations. The GF method was used to analyze the groundwater resources utilization in agriculture and to assess the environmental impacts in wheat-maize crop rotation system at Wuqiao Experiment Station-a traditional region where wheat-maize crop rotation is practiced in the North China Plain. This study was based on the latest developments in theories and methods of GF in combination with agricultural practices. In addition, GFs of crops were calculated at county scale, and the impact of the different crops on GF analyzed for Wuqiao County in Hebei Province. The results showed that since 1949, GF of winter wheat was higher than that of summer maize, with respective mean values of 89.02 km² and 29.84 km² for Wuqiao County. Also based on the trend of change, GF of winter wheat and summer maize had an increasing trend of fluctuation. In terms of GF stress index (GF per unit area, GF/A_aq) for the crops, winter wheat basically had a moderate stress (0.1 < GF/A_aq < 1) and the stress index for summer maize was less (0.01 < GF/A_aq < 0.1) for most the years, which increased for recent years. Thus if reasonable measures were not taken to control cultivation, GF would increase and have a significant impact on the balance of water circulation in regional environmental system in the coming years. This would put considerable pressure on groundwater resources to meet water needs of crops in Wuqiao County. The research suggested that to reduce groundwater pressure and ensure effective restoration of groundwater resources, the traditional wheat-maize cropping system could be adjusted through the cultivation of peanut and potato, whose GFs were 2.08×10^-7 km²·m^-2 and 1.94×10^-7 km²·m^-2, around 40% and 58% less than that of winter wheat. Thus through the exploration of GF, cropping structure in Wuqiao County could be adjusted or the area of crop rotation between low water-consumption crops and staple grain crops could be increased to enhance the use of water-saving technologies and improvement of water-saving measures. The study showed that GF analysis had the potential for application in agricultural research. It was concluded that in future, basic GF research should be enhanced and GF parameter database construction at various scales and for various crops were required to provide a solid basis for research on sustainable use of groundwater resources and the development of sound government policies.