从水量平衡看洞庭湖周边丘岗区农业生态建设

EVALUATION OF AGRO-ECOLOGICAL CONSTRUCTION IN THE AREA AROUND DONGTING LAKE BY WATER EQUILIBRIUM

水平衡是生态系统生态建设的基本依据。通过对环洞庭湖丘岗地区坡地(垫面)、集雨区(微流域)两个层次上的定位观测,初步探明水平衡状况为:水资源呈季节性配置,有季节性富余(8～19旬311.3mm)与季节性亏缺(23～27旬134.7mm)。但雨水总量丰沛,可维持生态系统各个尺度上的水量平衡;可利用的集雨水量为最大灌溉水需求量的2.41倍。天降雨水大约只有76％产生派生资源参与系统水分循环,其余部分主要以径流形式溢泄入下游水域。这一过程使该地区每年流失或向洞庭湖水域输送水131×10~8m^3、泥沙16.4×10~4m^3、养分(N、P、K)0.89×10~4t。影响水平衡的主要因子是:集雨的有限性和局限性,与坡地生态系统的构建。因此,本地区水平衡生态建设要注重集雨水利建设,强化雨水人为资源化过程。坡地构建农林复合生态系统,合理地设计雨水自然资源化比重。

Water equilibrium is the basis for the ecological construction of ecosystems. The water equilibrium status has been preliminarily ascertained by location observation on two levels, sloping land and catchment area, in the hilly area around Dongting Lake. The results are given as follows: the water resources show seasonal distribution with a seasonal surplus of 311.3 mm from the middle ten days of March to the first ten days of July and a seasonal shortage of 134.7 mm from the first ten days of August to the last ten days of September, but total rainfall is rich and can maintain water equilibrium at each level of the eco-system. The utilizable rain water is 2.41 times as much as the maximum requirement of irrigation, about 76% of precipitation produces derivative resources to participate in water cycling in the system and the other part overflows to lower water area mainly in the form of runoff, 131×108 m3 of water,16.4×104 m3 of silt and 0.89×104 t of nutrient (N.P.K) in the area bleeds or are transported into Dongting Lake by the course each year. The main factors affecting water equilibrium are limitations of rainfall collection and the construction of ecosystems of sloping land.Therefore,for the ecological construction of water equilibrium in the area special attention needs to be paid to the construction of water conservancy project for rainfall collection, and the course of artificial resourcing of rain water and agro-forest multi-ecosystems in sloping land and rational designing the proportion of the natural resourcing of rain water.