| Based on case study in Shunyi County, regional water resource balance and the crop characteristics of water usage were studied through onsite experiment and typical household survey. On the ground of analyses above, the way of water saving was probed at the end of the paper.Firstly, water resource balance was studied at the level of region, cropping system and crops. As a fact, there is about 85 million m3 of water in short every year in Shunyi county. 190~220 million m3 of water was used in cropping system every year. Through the study of crop water requirement and the rainfall utilization efficiency, the main crops can be grouped at three levels: 1. the crops requiring much irrigation, including rice, winter wheat, clover and cotton; 2. the ones requiring little irrigation including most of the crops planted in summer and other crops such as jowar and millet; 3. the others needing average irrigation.Secondly, many crop water parameters, including ETa, WUE and water sensitive parameters etc., were studied through onsite experiment, typical household survey and other methods. By analyzing crop water usage characteristics, we concluded: 1. about ETa: the amout of pear water consumption was highest (750.2mm), however, the watermelon planted in greenhouse consumed only 266.5mm; 2. about WUE: clover WUE (20.9~21.2 kg/ hm2.mm)was higher than other field crops (5.3~13.9 kg/ hm2.mm). Most fruit trees WUE were from 51.5 kg/ hm2.mm to 67.51 kg/ hm2.mm. The cabbage WUE (204.4kg/ hm2.mm) was highest in all the vegetables, instead frijole WUE was only 28.8kg/ hm2.mm and less than other vegetables.Lastly, this paper estimated the potential of water saving: 1. by reducing the abundant irrigation, about 0.4-0.5 million m3 water can be saved; 2. 10 percent irrigation can be saved by deficit irrigation with the yield decreasing below 5 percent; 3. about another 10 percent irrigation water can be saved by using high effective irrigation facility.
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