A groundwater crisis is going on in the North China Plain (NCP), due to the excessive water consumption of the traditional winter wheat (WW)/summer maize (SM) double cropping system (two harvests in one year). In order to improve the water use efficiency in this particular cropping system and to evaluate the sustainability of water usage in Chinese agroecosystems, two field experiments were conducted from October 2004 to September 2006 at two sites of the North China Plain. The field experiments included four treatments: (1) farmers' practice (FP) with two harvests in one year (WW/SM rotation), (2) FP with reduced input (RI) of water and nitrogen (WW/SM rotation), (3) three harvests in two years (TW, 1st year: WW/SM; 2nd year: spring maize), and (4) continuous spring-maize monoculture (CS) with one harvest per year (spring maize). In the treatments RI, TW and CS, the amount and timing of irrigation and nitrogen fertilization was optimized using TDR based soil moisture measurements and the Nmin-method, respectively. Data showed that the utilization efficiency of irrigation water can be improved by optimizing soil water management compared to the traditional water management (FP). However, the groundwater net consumption required for RI still surpassed 300Â mmÂ yr-1. Both FP and RI, still overused groundwater resources. The groundwater consumption in the continuous spring maize (CS) was on average 139Â mmÂ yr-1. Therefore, the CS system can show the potential to use groundwater sustainably in the long term. Water usage of the TW treatment was in between the water usage of the other treatments. The grain yields in the double cropping systems (FP and RI) were higher than that in the two other systems (TW and CS). But the CS treatment showed the higher WUE than others.