Forest hydrology function of the Miyun Reservoir watershed:A case study of Beizhuang small watershed

This paper presents the effects of forest to the hydrological characteristics with three scales,including the runoff section,the natural slope runoff sites,and the watershed.The results show that:in the experimental watershed,annual runoff coefficient was 43.12% in 2004 and 10.43% in 2005 while sediment yields was zero.Runoff coefficient had significant correlation with rainfall and there was a relation of a conic curve.Comparing the natural slope runoff sites in the forest land and non-forest land,the maximum value of annual runoff coefficient in the forest land was 0.72 in 2003,while one in the non-forest land was 0.97 in 2004.The sediment modulus of natural slope runoff in the forest land significantly dropped.Sediment subduction in the forest land was 18.7% in 2004 and 77.3% in 2005.The order of runoff amount was Castanea mollissina>Robinia pseudoacacia>Pinus tabulaeformis in the runoff plot of different trees.By sampling inspection on water quality of watershed,the results show that most indexes of water quality achieved the national standards of Ⅰ class,while over-leveled indexes were total N content and total P content.In general,with the increasing the forest coverage in the watershed,the function of flood control,water retention,sediment reduction,and improvement of water quality could be strengthened obviously.