Effects of Forest on the Average Annual Runoff
It is still an argumentative question today that the forest increses, or decreases the average annual runoff. In this paper, a new analysis method of the formative cause of this question is advanced by using water balance principle based on the analysis of mechanism of precipitation and evaportranspiration and the observed data. Form the analysis it is concluded that the forest will decrease the average annual runoff due to silvicultural treatment. The quantity of decreased runoff is more in the small area of silviculture, approximately equal to the increased evaportranspiration of the forest, and less in the large area of silviculture, but no less than 35% of the increased evaportranspiration in China. And in the hot-humid region in South China, the average annual runoff decreases more than in the cold-arid region in North China.