基于植被生态需水的区域水资源结构调整

通过确定泾河流域各类植被生态需水定额,再利用面积定额法计算生态需水量,对植被需水量、需水结构和单位面积需水量进行分析.结论如下:林地适宜生态需水量为341 773.23×104 m3,草地需水569 705.99万m3,农作物需水740 543.20万m3.其中农作物以小麦、玉米、各种谷物、蔬菜瓜果类需水最多.作物需水占植被总需水量的近一半,但作物生态效益远远小于林地和草地,其中还有一部分耕地为坡耕地.泾河流域不同的林、草、农作物比例和农作物种植结构,使得各县植被单位面积需水量和农作物单位面积需水量差异很大.前者的最大值在泾阳县,为5 339 m3/hm2,最小值在环县,为2 082 m3/hm2,平均值为3 081m3/hm2 ;后者的最大值在泾阳县,为5 682 m3/hm2,最小值在定边县,为4 022 m3/hm2,平均值为4 583m3/hm2.基于以上计算与分析,提出泾河流域水资源调整的对策为:以系统论为指导,实现生态环境与经济的协调发展;通过调整农作物、林地、草地种植结构和调整农作物内部结构是实现水资源合理配置重要一环,退耕还林还草,尤其是增加草地种植比例,提高林地、草地的覆盖度,是改善泾河流域生态环境的根本出路;多角度实施农业节水;树立流域系统协调发展观念,完善流域综合管理机制;进一步完善与解决相关科学问题.

Structure adjustment of regional water resources based on ecological water requirement of vegetation——A case study in Jinghe Watershed

Jinghe river is one of the ten major rivers of the Yellow River,and a main stream in the losse plateau.It consists of 31 administrative counties in Ningxia Hui Autonomous Region,Gansu and Shaanxi Province. Now Jinghe Watershed is confronting with the restriction and threat because of water resource scarcity and environments exacerbation.Vegetation consists of forest, grass and crops. Water requirement structure of vegetation partly reflexes water use structure,and structure of ecological and economy benefit.After studying the quota of every kind of vegetation,with quota-area method,we analyzed vegetation ecological water requirement,vegetation ecological water requirement structure and vegetation ecological water requirement per unit.Our study conclusions are as follows: the suitable ecological water requirement of the forests in Jinghe watershed is 341 773.23×10⁴ m³, the ecological water requirement of the grass is 569 705.99×10⁴ m³,and the ecological water requirement of the crops is 740 543.20×10⁴ m³. The wheat,maize,corns and vegetables in Jinghe watershed require more water than any other crop.The crop ecological water requirement is nearly half of total vegetation ecological water requirement,however,the ecological benefit of crops is far less than that of forest and grass.This calculation is under the hypothesis that water requirement quotas of most vegetation in one County are equal to that in another County.The 31 counties have different vegetation structures,which results in large difference in vegetation water requirements per hectare and in crop water requirements per hectare at county level.The highest of vegetation water requirements per hectare,5 339 m³/hm²,is in Jingyang County; the lowest,2 082 m³/hm², is in Huan County;the average is 3 081 m³/hm². The highest of,5 682 m³/hm², is in Jing-yang County;the lowest,4 022 m³/hm²,is in Ding-bian county;the average is 4 583 m³/hm².Based on these calculation and analysis,the countermeasures suggested for high-efficiency use of water and land resources are: to adjust vegetation structure and crops structure to realize water resource optimal allocation,especially to increase grass through grain for green;to develop water-saving agriculture;to perfect water integrated management mechanism to balance man and nature at watershed system level;further to resolve relative scientific problems.