在森林地之地表径流端赖截留量、蒸发散量及土壤吸收渗透量之多寡而决定 ,有剩余量才会产生。根据文献报告指出 ,截留量随降雨强度增而增加后 ,又随着减少 ,同时与树种、林相有关 ,针叶树比阔叶树截留量多 ,多层树冠之截留量亦多。蒸发散量亦是与树种、林相有关 ,郁蔽度大者蒸发散量少 ,因为郁蔽度大着通风不良、日照减少、温度降低。土壤吸收渗透量与树种、林相亦有关系 ,因为树种之根系型态不尽相同 ,枯枝落叶量多寡 ,郁蔽度大小皆会有影响 ,土壤孔隙率受根系多少而变化 ,有机质含量大则吸水能力强 ,增加水分渗透机会 ,植物种类引诱动物活动 ,也会增加土壤孔隙 ,导致土壤水吸收与渗透量增加。由于森林与水文循环关系密切 ,森林之林相、主要树种、树龄在水文循环过程中均扮演极重要之角色 ,所以森林内之施业 ,诸如伐木作业、开辟林道、造林、林相改良、林相变更、工程施工、开矿采石等活动对森林集水区水文会有明显变化。本省气候特殊 ,雨量集中 ,干湿分明 ,洪患与干旱灾害是本省最大隐忧 ,若能经由不同之林业经营方式来影响森林集水区水文变化 ,提高森林涵养水源、净化水质、调解水量与保安固土 ,灾害降低至最小 ,将森林功效发挥至最大 ;规划水文站网 ,做好气象、水文观测工作 ,一定是必要条件 Surface runoff in the forest land depends on the amount of interception, evapotranspiration and soil uptake and quantity of the decision, the remaining amount will be generated. According to the literature report, the interception amount increases with the increase of rainfall intensity, and then decreases with the increase of rainfall intensity. At the same time, it is related to tree species and forest facies. Evapotranspiration is also related to tree species, forest phase, the larger the degree of evapotranspiration less evapotranspiration, because the degree of depression with poor ventilation, sunshine reduction, temperature decreases. The amount of soil infiltration and permeability and tree species, forest phase also has a relationship, because the tree species of different root patterns, the amount of litter, the degree of depression will have an impact on soil porosity by the number of changes in the root, large organic matter content Strong water absorption, increase the chance of water penetration, plant species to lure animal activity, will also increase soil porosity, resulting in increased soil water absorption and infiltration. Because of the close relationship between forest and hydrological cycle, the forest phase, main tree species and age of the forest play an extremely important role in the hydrological cycle. Therefore, the construction within the forest, such as logging operations, opening up forest roads, afforestation, forest facilitation, forest facies changes, Construction, mining and quarrying have significantly changed the hydrology of the forest catchment. The province’s special climate, rainfall, wet and dry, floods and drought disaster is the province’s biggest worry if the different forestry management can affect the hydrological changes in forest catchment, improve water conservation forest, water purification, mediation of water and security Solid earth and disaster to a minimum, to maximize the effectiveness of the forest; planning hydrological network, doing meteorological and hydrological observations, must be a necessary condition