环洞庭湖丘岗地区是我国南方丘陵农林复合生态系统的典型板块。雨水资源对生态系统水环境、水平衡具有不可替代性。生态系统水环境要素的定位观测和小流域水平衡监测研究表明:该地区雨水资源呈季节性配置,系统水平衡过程有明显盈(季节性水富余311.3mm)、亏(季节性水亏缺134.7mm)现象。本地区自然降雨大约有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;雨水侵蚀使该地区每年流失或向洞庭湖水域输送水1.31×1010m3、泥沙1.64×106m3、养分(N、P、K)0.89×104t。集雨利用是本地区农业雨水管理的基本形式,据研究估测,可利用的集雨水量为现今农业可用地灌溉水需求量的2.41倍;可集雨水量和农业集雨需求量的比值与系统尺度有关。影响生态系统水平衡和农业集雨利用有两大因子,即人工蓄调雨水的局限性和坡地生态系统构建。因此,雨水资源的生态管理重在坡地系统构建———地表植被植物群落的组配和土壤生产力持续性保护。

The hilly area around Dongting Lake is a typical agro-forest multi-ecosystem in the hilly area of southern China.Rainfall resources are indispensable to water environment and water equilibrium in the ecosystem.Locational observations on water environment factors in the ecosystem and monitoring and research on water equilibrium in the small watershed were carried out.Results showed that the rainfall resources were rich in the region.But with the differences in seasonal allocation of rainfall,both surplus and deficiency occurs in the process of water balancing in the system.The seasonal surplus water was311.3mm,and the deficiency was134.7mm in the average year.About 76%of precipitation belonged to derivative resources for water cycle,and the remaining amount overflowed to downstream water area in the form of runoff.Some 1.31×10 10 m 3 of water,1.64×10 6 m 3 of silt and0.89×10 4 t of nutrients(N,P,K)in the area are lost or transported into Dongting Lake in the process of rainfall erosion each year.Thus rainwater conservancy is the basic form of the rainwater management .The utilizable rainwater is2.41times as much as the maximum requirement of irrigation water for the existing farmland at present,and the ratio of utilizable rainwater to requirement is related to ecosystem scale.The main factors affecting water equilibrium and water use efficiency are limitations of rainfall conservancy project and the construction of sloping land ecosystems,especially the construction of agro-forest multi-ecosystem.It contains the planting patterns of vegetation community and sustainable conservation of soil productivity.