The aim of this study was to determine the threshold value of the agricultural areas under the dual constraints of the total amount of water intaking and the total amount of water consumption, which is an important value for the healthy development in agriculture of the areas short of water resource similar to the suburbs of Beijing. Firstly, the constraint value of the total amount of agricultural water consumption and the constraint value of the total amount of the water intaking for irrigation in Daxing District, Beijing was analyzed. Then, the changing trends of the agricultural water consumption by adopting the measures such as the optimization of the irrigation schedules and the adjustment of planting structure had been studied. Finally, based on the recommended scenarios of planting structure adjustment, the threshold value for agricultural areas under the constraint of total amount of water consumption was studied. The results showed that: 1) Optimizing the irrigation schedules could significantly reduce the agricultural water consumption and irrigation amount, which enabled the regional water consumption in agriculture to be lower than the constraint value of the total water consumption and enabled the total amount of water intaking for agricultural irrigation to be lower than the actual average level for many years, but the total amount of water intaking for agricultural irrigation was still higher than the constraint value; 2) In Daxing District, the planting areas for the open-field vegetables and winter wheat with higher water consumption were decreased. Then, the planting areas for the summer maize with less irrigation amount and lower water consumption were increased. Meanwhile, the areas for facility agriculture with higher efficiency of agricultural water were developed. Based on these, the constraint values of the total amount of water intaking for agricultural irrigation and the total amount of the water consumption could be met and the requirements to stabilize the grain yields and increase the output of vegetables as prescribed in the Development Planning of Urban Modern Agriculture for the Period of Beijing "12th Five-Year" could be fulfilled; 3) The threshold value to meet the agricultural area under the constraint value of the total amount of water intaking for agricultural irrigation was 4.60×104-7.42×104 hm2, and that to meet the agricultural areas under the constraint value of the total water consumption was 6.72×104-9.48×104 hm2. By synergistically using the agricultural water control measures of adjusting the planting structure and optimizing the irrigation schedules, the threshold value was 7.42×104 hm2; 4) In the case that the total amount of water consumption kept unchanged, with the development of facility agriculture areas, the development areas of traditional agriculture had been reduced, but the areas threshold values of the facility agriculture and traditional agriculture did not align perfectly due to the differences in the constraint values of the total amount of water consumption. In order to maintain the sustainable and efficient utilization of regional water resources, to ensure the healthy development of regional agriculture, it was bound to adopt the water-saving measures such as the optimization of irrigation schedules and the adjustment of planting structure both to control the threshold value for agricultural areas within a reasonable range, so that the total amount of the regional agricultural water consumption would not break through the constraint value of the total amount of water intaking for agricultural irrigation and the constraint value of the total water consumption. The study provides an effective method for regional water amount control in areas short of water resources.%该文以农业耗水总量及灌溉取水总量为约束条件,采用优化灌溉制度和种植结构调整措施下京郊农业发展面积阈值.结果表明:1)采用优化灌溉制度措施能显著降低研究区农业耗水量与灌溉量,使区域农业耗水总量低于耗水总量控制指标及其使农业灌溉量取水总量低于其多年实际平均水平,但是农业灌溉取水总量仍超过其控制指标;2)在北京市大兴区减少耗水量高的露地蔬菜与冬小麦的种植面积,增加灌溉量少且耗水较低的夏玉米种植面积,同时进一步发展农业用水效率较高的设施农业面积,能够满足农业灌溉取水总量与耗水量总量控制指标,且符合国家规划稳定粮食产量与提高蔬菜产量的要求;3)满足灌溉取水总量控制下农业发展面积阈值为4.60×104~7.42×104hm2,而满足耗水总量控制下农业发展面积阈值为6.72×104~9.48×104hm2,而同时满足2种约束条件下农业发展面积阈值为7.42×104hm2;4)在维持用水总量不变情况下,随着设施农业发展面积扩大,传统农业发展面积相应减少,但因用水总量约束值差异设施农业与传统农业的发展阈值并不完全一致.可见,为维持区域水资源持续高效利用,确保区域农业健康发展,势必采用优化灌溉制度与种植结构调整等节水措施,控制农业发展阈值在合理范围内,才能使区域农业用水总量不能突破灌溉取水总量与耗水总量的控制指标.研究对类似京郊资源性缺水地区农业健康发展具有重要参考价值.
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