Analysis of the Relationship between Vegetable Virtual Water Trade and Saltwater Intrusion in Shouguang City, China

Shouguang City is located in north-central of Shandong, distributing the piedmont plain and coastal plain from the south to north. This area, as a vegetable base in northern China, not only meets local needs but also has a large number of vegetables exported to domestic and foreign countries in the form of virtual water. The vegetable production in this area mainly depends on groundwater exploitation, which causes saltwater intrusion problems. This study establishes the linear model of virtual water and vegetable production, irrigation water consumption, total population, per capita vegetable sales volume, and the purchase amount of vegetable trade. The output of vegetable virtual water from 1980 to 2012 is calculated. 3.79 billion kg of vegetables were exported in the form of virtual water with a volume of 145 million m(3) in 2012, accounted for 78% of the average annual groundwater resources in the region. The vegetable trade development in Shouguang City from 1980 to 2002 can be divided into two stages: bare land vegetable cultivation in 1980-1990 and greenhouse vegetable cultivation in 1991-2002. The correlations among the annual virtual water output volume of vegetable trade, annual groundwater cumulative storage, groundwater depth at the center of depression area, and saltwater intrusion area are established and analyzed. In the first stage, for every 10 million m(3) of vegetable virtual water was transferred, the salt water intrusion area in this area increased by 13.8 km(2); in the second stage, the saltwater intrusion area increased correspondingly by 5 km(2). The influence of saltwater intrusion on adjusting crop-planting structure is also analyzed to achieve the purpose of effectively alleviating the ecological and environmental problems in the area.