温室农业雨水集蓄利用工程规模优化

为了优化蓄水池最佳工程规模，该文通过构建雨水集蓄利用工程规模优化原理和方法，即工程效益最优法，并以北京某温室农业雨水集蓄利用工程为例对该方法进行了论证。研究结果表明地区日降雨规律以及集雨窖的规模对工程的集雨效率有很大影响，在降雨量、汇流总面积确定的情况下，集雨窖规模越大，可收集的雨量越多，但单位容积可收集的雨量随之减少；工程成本效益分析表明，设计日降雨量为25～40 mm时，工程总效益/费用比值较高，全年可收集雨量与温室农业年用水量基本相当；在工程寿命期内，现有规模下的效益成本比值远低于最优规模时的效益成本比值。因此，适当降低集雨窖的规模可提高工程的经济性。该文论证的雨水集蓄利用工程规模优化方法能够为雨水工程的设计和应用提供理论依据和实践指导。

Scale optimization of greenhouse agricultural rainwater harvesting and utilization project

Rainwater harvesting project by agricultural greenhouse could provide reliable water source for urban agriculture around water scarce cities. However, guiding theory of optimal size for water storage pool is absent. It will lower the efficiency and benefit of rainwater harvesting project. To provide water for agriculture and enhance economic feasibility of rainwater harvesting project, principle and methodology for optimizing storage pool was developed in this paper. Research on existing agricultural rainwater harvesting project showed that rainwater harvesting efficiency was influenced by difference of daily rainfall and size of storage pool. In the case of certain rainfall and catchment area, the amount of rainwater harvested increases with increasing of storage pool. But the amount by unit volume of storage pool decreased. Cost-benefit analysis showed that the ratio of benefit to cost of the project was relatively high when design daily rainfall is around 25-40 mm. And rainwater harvested could almost meet water need. A case study showed, in normal year, the actual rainwater harvesting rate was slightly lower than the designed rainwater harvesting rate due to temporal distribution of rainfall and agricultural water use. And the ratio of benefit to cost was far lower than that of the project at optimal scale. Thus properly reduction of size of the storage pool could improve the economy of the project. The methodology can provide theory and practical guidance for agricultural rainwater harvesting project.