Based on the measured data of 44 years from hydrometric station,this paper conducts a quanti-tative analysis on the rainfall-runoff relationship in Qianshan watershed with the method of self-contrast. Based on the classification map of vegetation coverage,the typical years of 1987,1999 and 2007 are se-lected to study the impact of forest vegetation change in Qianshan watershed on water conservation capaci-ty. Comparing the data of 2007 and 1987,the results show that the percentage of low vegetation coverage area decreased by 56% ;the percentage of medium vegetation coverage increased by 12% ,high vegetation 24% ;the average annual rainfall decreased by 52% ,and the average annual runoff 69% . Therefore,we can draw a conclusion that the growth of the vegetation coverage can help cut the runoff and the runoff co-efficient dramatically and improve the flood control ability of the watershed,which enhances the water conservation capacity of the forest.%采用流域自身对比法，利用潜山流域水文站实测的44 a 降雨量-径流量数据，定量分析了该流域降雨量-径流量变化关系。选择1987年、1999年和2007年3个典型年份，结合植被覆盖度分级图，定量分析研究了大别山地区潜山流域森林植被变化对该区域森林水源涵养关系的影响。研究发现，2007年低植被覆盖区比1987年减少56%，中植被覆盖区比1987年增加12%，高植被覆盖区比1987年增加24%，2007年平均降雨量较1987年减少52%，而平均径流量较1987年减少69%，表明森林覆盖率提高能减少径流，显著降低径流系数，增强流域抗洪能力，使得森林水源涵养能力得到提升。
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